COMPARATIVE STUDIES OF THE SUGAR AND MINERAL CONTENTS OF INDUSTRIALLY PROCESSED FRUIT JUICES

ABSTRACT

The sugar and mineral levels of industrially processed fruit juices (mainly 100% and 50% fruit juices) sold to consumers in Enugu state, Nigeria were determined and compared with that of freshly prepared fruit juices. The liquid nature as well as the versatility of juice has increased the ease with which fruit juices can be altered with sugar, contaminants, water or inferior juices by unethical suppliers. This research was performed to address the potential concern that industrially processed fruit juices (especially those with ‘100% natural’ and ‘no sugar added’ label) may differ in quality with respect to sugar and mineral contents (including heavy metal contents which is deleterious to quality) from extracted juice of fresh fruit, as well as to address in part the ongoing public health concerns of excessive sugar consumption, micronutrient malnutrition and heavy metal contamination. The fruit juices tested included apple, orange, pineapple and red grape juices. All industrially processed fruit juices and fresh fruits used were purchased in Enugu state, Nigeria. The fresh fruits were juiced and all samples including industrially processed and the freshly prepared fruit juices were tested for total soluble solid (TSS) content, fructose, glucose, sucrose, Na, K, Mg, Ca, P, Fe and heavy metals contents such as Cu, Zn, As and Pb. Findings from the analysis of the TSS content of fruit juice samples demonstrated no significant (p > 0.05) difference between the industrially processed and freshly prepared fruit juices; however, difference in sugar and mineral levels between industrially processed and freshly extracted fruit juices was significant (p < 0.05). Industrially processed fruit juices contained higher glucose, sucrose, Na, Ca, P, Cu and Zn contents, and lower fructose, K and Mg contents when compared to freshly prepared fruit juices. There was no significant (p > 0.05) difference in iron (Fe) and arsenic (As) contents of industrially processed fruit juices when compared with the freshly extracted juices. Lead (Pb) was not detected in any of the samples. This study demonstrated no quality issues of concern in relation to the products because all the parameters considered in the study were within the standard acceptable range for fruit juices and nectar.

TABLE OF CONTENTS

Title page

Certification

Dedication

Acknowledgements

Abstract

Table of contents

List of figures

List of tables

List of abbreviations

CHAPTER ONE: INTRODUCTION

1.1       Research terminologies

1.2       Fruit juice

1.2.1    Fresh juice

1.2.2    Reconstituted Juice

1.2.3    Common fruits and fruit juices

1.2.3.1 Apple juice

1.2.3.2 Orange juice

1.2.3.3 Pineapple Juice

1.2.3.4 Red grape juice

1.3       Fruit juice processing

1.3.1    Fruit juice extraction and clarification

1.3.2    Fruit juice preservation and storage

1.3.3    Quality control

1.4       Fruit juice adulteration

1.5       Fruit juice nutrition

1.5.1    The role of fruit juice in a diet

1.5.2    Nutrients delivered by fruit juices

1.5.2.1 Sugars

1.5.2.2 Minerals

1.5.2.2.1          Sodium (Na)

1.5.2.2.2          Potassium (K)

1.5.2.2.3          Magnesium (Mg)

1.5.2.2.4          Calcium (Ca)

1.5.2.2.5          Phosphorus (P)

1.5.2.2.6 Iron (Fe)

1.5.2.3 Phytochemicals

1.5.2.4 Vitamins

1.5.3    Health benefits of fruit juices

1.5.3.1 Fruit juice and cardiovascular health

1.5.3.2 Fruit juice, cancer and inflammation

1.5.3.3 Fruit juice, brain health, cognition and ageing

1.5.3.4 Fruit juice and skin health

1.6       Health concerns associated with fruit juice consumption

1.6.1    Fruit juice and obesity

1.6.2    Fruit juice and dental health

1.6.3    Heavy metals in fruit juices

1.6.3.1 Zinc (Zn)

1.6.3.2 Copper (Cu)

1.6.3.3 Arsenic (As)

1.6.3.4 Lead (Pb)

1.7       Problem statement and justification of the study

1.8       Aim of the study

1.9       Specific objectives of the research

CHAPTER TWO: MATERIALS AND METHODS

2.1       Materials

2.1.1    Plant materials

2.1.2    Collection of samples

2.1.3    Instruments/Equipment

2.1.4    Chemicals

2.1.5    Experimental design

2.2       Methods

2.2.1    Extraction of juice from fresh fruits

2.2.2    Determination of total soluble solid (TSS) content of fruit juice samples

2.2.3    Determination of sugar contents of fruit juice samples

2.2.3.1 Determination of fructose content

2.2.3.2 Determination of glucose content

2.2.3.3 Determination of sucrose content

2.2.4    Determination of mineral contents of fruit juice samples

2.2.4.1 Wet digestion of fruit juice samples

2.2.4.2 Determination of Na and K content

2.2.4.3 Determination of Mg content

2.2.4.4 Determination of Ca content

2.2.4.5 Determination of P content

2.2.4.6 Determination of Fe content

2.2.5    Determination of heavy metal content (Cu, Zn, As, Pb) of fruit juice samples

2.2.6    Statistical analysis

CHAPTER THREE: RESULTS

3.1       Total soluble solid content of fruit juice samples

3.2       Sugar contents of fruit juice samples

3.2.1    Fructose contents of fruit juice samples

3.2.2    Glucose contents of fruit juice samples

3.2.3    Sucrose contents of fruit juice samples

3.2.4    Comparison of the sugar contents of fruit juice samples

3.3       Mineral contents of fruit juice samples

3.3.1    Sodium (Na) contents of fruit juice samples

3.3.2    Potassium (K) contents of fruit juice samples

3.3.3    Magnesium (Mg) contents of fruit juice samples

3.3.4    Calcium (Ca) contents of fruit juice samples

3.3.5    Phosphorus (P) contents of fruit juice samples

3.3.6    Iron (Fe) contents of fruit juice samples

3.3.7    Comparison of the mineral contents of fruit juice samples

3.4       Heavy metal contents of fruit juice samples

3.4.1    Zinc (Zn) contents of fruit juice samples

3.4.2    Copper (Cu) contents of fruit juice samples

3.4.3    Arsenic (As) contents of fruit juice samples

3.4.4    Comparison of the heavy metal contents of fruit juice samples

CHAPTER FOUR: DISCUSSION

4.1       Conclusion

            References

            Appendix

                                LIST OF ABBREVIATIONS

%                           Percentage

As                          Arsenic

ATP                      Adenosine triphosphate

BMI                     Body mass index

Ca                          Calcium

CETP                   Cholesterol ester transfer protein

Cu                         Copper

DNA                    Deoxyribonucleic acid

ECF                      Extracellular fluid

Fe                          Iron

g                             Grammes

GMP                    Good manufacturing practice

HACCP             Hazard analysis and critical control point

HDL                    High density lipoprotein

HFCS                  High fructose corn syrup

Hr                          Hours

K                            Potassium

LDL                     Low density lipoprotein

LDLR                 Low density lipoprotein receptor

mEq/L                 Milliequivalent of solute per litre of solvent

mg                         Milligramme

Mg                        Magnesium

min                        Minutes

ml                          Millilitre

Na                         Sodium

oBrix                    Degree brix

oC                          Degree celsius

P                             Phosphorus

Pb                          Lead

RDA                    Required daily allowance

RNA                    Ribonucleic acid

RNI                      Reference nutrient intake

SON                     Standard Organization of Nigeria

std                         Standard deviation

TSS                       Total soluble solids

UL                        Upper intake level

WHO                   World Health Organization

Zn                          Zinc

CHAPTER ONE

INTRODUCTION

Fruit juices are becoming important part of modern diet in many communities. Their consumption is popular in Nigeria because of their health and invigorating benefits (Alaka et al., 2003; Ndife et al., 2013). They act as nutritious beverages and play significant roles in healthy diets because they offer good taste and varieties of nutrients found naturally in fruits (O’Neil and Nicklas, 2008; Hossain et al., 2012). In Nigeria, different kinds of seasonal fruits are available including apple, orange, pineapple, and grape which provide an abundance of vitamins, minerals, antioxidants and fibers, all of which are essential for human health (Jasmine, 2012). Fruit juice intake is a convenient way by which people receive the benefits of various fruits when whole fruit is not readily available or desired (Nitu et al., 2010). Properly extracted juices are very similar to the fruit; they contain most substances which are found in the original ripe and sound fruit from which the juice is made. Fruit juices are always 100% fruit products and should not be confused with soft drinks or other refreshing drinks (Landon, 2007). They are available either in their freshly prepared form or industrially processed form. In either case, it is expected to be free from contaminants and contain most substances which are found in the original ripe and sound fruit from which the juice is extracted, without added sugar or preservative (Hassan et al., 2014). It should be void of environmental pollutants such as toxic metals which impacts negatively on quality and are deleterious to health. Fruit juices contain water and varying concentrations of carbohydrates such as sucrose, fructose, glucose and sorbitol (Oranusi et al., 2012). They are also rich in phytochemicals, minerals and vitamins which are responsible for the several health benefits associated with their consumption, including reduction in the risk of a variety of chronic diseases such as cardiovascular disease and cancer (Cashwell, 2009). However, the beneficial health effects of fruit juices depends on the amount consumed in a daily diet, type of fruit and the content of biologically active compounds. In recent times, the quality of fruit juices is diminished with increasing concentration of toxic compounds including added sugar, heavy metals and other contaminants. Excessive sugar consumption from fruit juice has been associated with the development of obesity, type II diabetes and dental caries (Cashwell, 2009). The minerals contained in fruit juices including sodium, potassium, magnesium, phosphorus, calcium and iron are essential for good health if present in adequate concentrations (Ofori et al., 2013) and harmful when in excess or deficient, hence the need for their proper representation.

16

1.1              Research Terminologies

Beverages

Beverages are liquids specifically prepared for human consumption, usually excluding water. This may include tea, coffee, liquor, beer, milk, juice or soft drinks. Despite the fact that most beverages including juice, soft drinks and carbonated drinks have some form of water in them, water itself is often not classified as a beverage. Beverages can be categorised as alcoholic and non alcoholic based on the percentage ethanol present. Non alcoholic beverages can further be classified into sweetened beverages and fruit/vegetable juices. A sweetened beverage is any beverage to which a caloric sweetener has been added, including carbonated or non-carbonated soft drinks, fruit punch, fruit drinks, lemonade, sweetened powder drinks, or any other artificially sweetened beverages. Fruit juices on the other hand are not sweetened drinks and should not be categorized as such. They are composed exclusively of an aqueous liquid or liquids extracted from one or more fruits with no added caloric sweeteners (Landon, 2007).

Fruit juice

A fruit juice is defined as the clear or uniformly cloudy unfermented liquid recovered from sound fruits by pressing and other mechanical means (Nnam and Njoku, 2005). It is a drink consisting of 100% pure fruit juice, which typically contains no preservatives or other added ingredients. It is a fruit product, which could be easily consumed by infants, children and adults to meet their nutrient needs particularly that of micronutrients (Nzeagwu and Onimawo, 2010).

Freshly squeezed Juice

Freshly squeezed juices are produced by squeezing the juice from the fruit of choice, which is then immediately consumed or packaged and transported to the retailer as the case may be, usually within 24 hours. These juices often do not undergo any form of pasteurization and therefore typically have a very short shelf life usually 2-3 days (Cashwell, 2009).

Concentrate

This is obtained by the removal of water from fruit juice for the purpose of achieving reduction in weight and volume for easier transportation. At the time of usage, water is added back to the concentrate to reconstitute 100% fruit juice. Juices made from concentrates are available and similar in nutrient to the freshly squeezed juice. During production, fruit juices from concentrate are typically heat-treated, to ensure that any unwanted spoilage pathogens, including bacteria or moulds, are destroyed (Cashwell, 2009).

Fruit drinks (Juice drinks)

Fruit drinks are products which contain anything less than 100% pure fruit juice (Landon, 2007; Cashwell, 2009). The level of fruit juice contained in these drinks can be found in the ingredients panel, usually on the back of the pack. There are a vast range of products with differing percentages of fruit juice. These drinks may include those that are purchased in a ready-to-drink format, or those that require dilution prior to consumption which may include products made with sugar, as well as low sugar options made with sweeteners.

Nectars

Fruit juice nectars are defined as the fermentable but unfermented product obtained by the addition of water and sugar to fruit juice or concentrated fruit juice. It consists of less than 100%, but more than 20% fruit juice (Cashwell, 2009). The term nectar is one that is used for a diluted juice to denote a beverage that contains fruit juice and water, and which may contain sweeteners.

Smoothies

Fruit smoothies are typically combinations of homogenized/crushed fruit and juice (Landon, 2007). Most single servings of commercially available fruit smoothies (typically 250 ml) contain at least one 80 g portion of whole fruit, as well as one portion of fruit juice (150 ml).

‘Intrinsic’ and ‘Added’ Sugars

Naturally occurring (intrinsic) sugars refers to sugars that are an integral part of whole fruit, vegetable, and milk products (Johnson et al., 2009) while added sugars are defined as sugars (mainly monosaccharides and disaccharides) and syrups added to foods and beverages by manufacturer, cook or consumer during processing or preparation, including sugars and syrups added at the table. They are also referred to as free sugars (Johnson et al., 2009).

Total Soluble Solids (TSS)

They are defined as the sum of the solids which are dissolved within a substance and it is usually expressed in degree Brix (Maireva et al., 2013). Degree brix is the mass of soluble solids (mainly sugars) contained in 100 g of solution. Sugar and fruit acids are the main contributors to the total soluble solid contents of fruit juices; however, pectins, glycosidic materials and the salts of metals when present also register a small but insignificant influence on the TSS content.

1.2              Fruit Juice

Fruit juice is an unfermented but fermentable liquid or juice intended for direct consumption, obtained from the edible portion of sound, appropriately mature and fresh fruit by mechanical extraction process and preserved exclusively by chemical and physical means (Oranusi et al., 2012). Fruit juice is a fruit product, which could be easily consumed by infants, children and adults to meet their nutrient needs, particularly that of micronutrients (Nnam and Njoku, 2005; Nzeagwu and Onimawo, 2010). It can be freshly squeezed or made from concentrate.

1.2.1        Fresh Juice

Freshly squeezed juices are produced by ‘squeezing’ the juice from the fruit of choice, which is then packaged and transported to the retailer usually within 24 hrs. These juices often do not undergo any form of pasteurization and therefore typically have a very short shelf life usually 2-3 days. However, they may undergo high-pressure treatment and/or modified-atmosphere packaging to increase their shelf life. The term “F resh Juice” in most cases applies to those juices prepared in front of the consumer. If the juice is pasteurized, or contains juice concentrates or “stored” juices, then it is not fresh juice (Cashwe ll, 2009).

1.2.2        Reconstituted Juices

A reconstituted fruit juice is the product obtained by replacing the water extracted from the juice during concentration, and by restoring the flavours. They are commonly referred to as juice ‘from concentrate’. They are common to commercial j uices where there is need to increase shelf life as well as the ease of transportaion. The juice is extracted from the fruit the same way as done for fresh juices after which the extracted fruit juice is concentrated by evaporating the water naturally present in it. This concentrate is properly preserved often by freezing before being transported to its destination, where water is added back to reconstitute the juice to 100% fruit juice or alternatively, the concentrate can be used as an ingredient in a cordial drink. After reconstitution, fruit juices from concentrate are typically pasteurized, to ensure that any unwanted spoilage pathogens, including bacteria or moulds, are destroyed. The shelf life of the product is determined by the temperature of pasteurization. Long-life products are those products pasteurized at a temperature of approximately 90°C for a short time usually10-20 seconds. They have a shelf life of approximately 6-9 months. Short-life products are pasteurized at a lower temperature (70-75°C) for 10-20 seconds and product s typically have a shelf life of 2-6 weeks (Cashwell, 2009).

1.2.3        Common Fruits and Fruit Juices

Fruits have been a part of human diet over the years. They are also considered as food supplements and are recommended internationally as essential to healthy nutrition, because they contain high quantity and quality of water, sugars, vitamins and minerals (Ndife et al., 2013). Fruit consumption has been reported to contribute to the prevention of degenerative processes, particularly lowering the incidence and mortality rate of cancer and cardio-cerebrovascular diseases (Krejpcio et al., 2005). They contain phytochemicals which act against oxidative reactions in the human body (Vanamala et al., 2006; Okwu and Emenike, 2006). Fruits and vegetables are very perishable in nature; therefore high post harvest losses resulting from lack of cold storage facilities on the farms, improper handling and inadequate processing facilities occur immediately after harvest, during distribution and marketing (Alaka et al., 2003; Landon, 2007; Adubofuor et al., 2010; Ndife et al., 2013), hence the need to process them into fruit juices.

1.2.3.1 Apple Juice

Apple (Malus domestica) features oval or pear shaped (Figure 1). Its outer peel comes in different hues and colours depending upon the cultivar type. Internally, its crispy, juicy pulp is off-white to cream in colour, and has a mix of mild sweet and tart flavour.

Figure 1: Fresh apple (Malus domestica)

Apples (Malus domestica) are one of the healthiest foods a person can eat. Studies suggest that its components are essential for optimal growth, development, and overall wellness. They are high in fiber, low in calories, have only a trace of sodium, and no fat or cholesterol. Apples have been shown to have potent antioxidant activity that can greatly inhibit the growth of liver cancer and colon cancer cells (Eberhardt et al., 2000). They are high in polyphenols and notable for their impressive list of phytonutrients and antioxidants including flavonoids. Some of the important flavonoids in apples are quercetin, epicatechin, and procyanidin B2 which help protect the body from deleterious effects of free radicals (Boyer and Liu, 2004). Apple contains good quantities of vitamin C which is a powerful natural antioxidant. Consumption of foods rich in vitamin C helps the body develop resistance against infectious agents and scavenge harmful, pro-inflammatory free radicals from the body. Apple is a good source of B-complex vitamins such as riboflavin, thiamin, and pyridoxine (vitamin B6). Together, these vitamins help as co-factors for enzymes in metabolism as well as in various synthetic functions inside the human body (Eberhardt et al., 2000). Apples also contain small amount of minerals like potassium, phosphorus, and calcium. Potassium is an important component of cell and body fluids that helps control heart rate and blood pressure through countering sodium actions (Soetan et al., 2010).

1.2.3.2 Orange Juice

Orange (specifically, the sweet orange) is the fruit of the citrus species, Citrus sinensis in the family Rutaceae (Figure 2). Oranges, whose flavor may vary from sweet to sour, are commonly peeled and eaten fresh or squeezed for juice.

Figure 2: Sweet orange (Citrus sinensis)

Delicious and juicy orange contains an impressive list of essential nutrients, vitamins, minerals for normal growth and development and overall well-being. Nutrients in oranges are plenty and diverse (Franke et al., 2005). The fruit is low in calories, contains no saturated fats or cholesterol, but is rich in dietary fiber, pectin. They are an excellent source of vitamin C, which is a powerful natural antioxidant. Oranges contain a variety of phytochemicals. They contain very good levels of vitamin A, and other flavonoid antioxidants such as alpha and beta-carotenes, beta-cryptoxanthin, zea-xanthin and lutein which are known to have antioxidant properties. Vitamin A is required for maintaining healthy mucus membranes and skin and is essential for vision. Consumption of natural fruits rich in flavonoids protects the body from lung and oral cavity cancers (Ndife and Abbo, 2009). Flavonoids especially flavonones in oranges have been shown to possess several physiological properties which can help inhibit cell proliferation and promote cell differentiation (Vanamala et al., 2006). Orange is a very good source of B-complex vitamins such as thiamin, pyridoxine, and folates. These vitamins are essential in the sense that the body requires them from external sources to replenish. Orange also contains a very good amount of minerals like potassium and calcium.

Orange juice is obtained by squeezing the fruit on a special tool usually a juicer or squeezer and collecting the juice. This can be made at home or, on a much larger scale, industrially. Orange juice just as orange is also rich in vitamin C, folic acid and potassium. It is an excellent source of bioavailable antioxidant phytochemicals (Franke et al., 2005) and significantly improves blood lipid profiles in people affected with hypercholesterolemia (Kurowska et al., 2000).

1.2.3.3 Pineapple Juice

Pineapple (Ananas comosus) is the ovoid fruit of the tropical, perennial, drought-tolerant pineapple plant. It is a type of fruit that develops from many small fruitlets fused together around central core. Its pulp is juicy and fleshy with the stem serving as a supporting fibrous core. The outer skin features rough, tough, and scaly rind (Figure 3). The colour in the ripe fruits may be yellow, orange-yellow or reddish. Internally, its juicy flesh may range from creamy white to yellow and has a mix of sweet and tart taste with rich flavour. It is one of the most important commercial fruit crops in the world. It is known as the queen of fruits due to its excellent flavour and taste (Baruwa, 2013). Pineapple is the third most important tropical fruit in the world after Banana and Citrus. It is highly perishable and seasonal.

Figure 3: Fresh pineapple (Ananas comosus)

Pineapples are served fresh, cooked, juiced and can be preserved. Fresh pineapple is low in calories. Nonetheless, it is a storehouse for several unique health-promoting compounds, minerals and vitamins that are essential for optimum health. Mature and fresh pineapple contains water, 14% of carbohydrate, a protein digesting enzyme (bromelain), and good amount of citric acid, malic acid and B-complex group of vitamins (Hossain et al., 2015). It contains little or no protein, no saturated fats or cholesterol. The carbohydrates in pineapples are mostly simple sugars, such as sucrose, fructose and glucose. They also contain some fiber. The glycemic index value of pineapples can range from 45-66, which is in the medium range (Landon, 2007). Fresh pineapple is an excellent source of vitamin C. It contains low levels of vitamin A and beta-carotene which are known to possess antioxidant properties. Pineapple is also rich in minerals like copper, manganese and potassium. Vitamin A is essential for vision and also required for maintaining healthy mucusa and skin. Bromelain found in pineapple is a proteolytic enzyme that digests food by breaking down protein. Bromelain also has anti-inflammatory, anti-clotting and anti-cancer properties (Debnath et al., 2012). Studies have shown that consumption of pineapple regularly helps fight against arthritis, indigestion and worm infestation (Debnath et al., 2012; Hossain et al., 2015).

Pineapple was originally consumed only as a fresh fruit. With the development of the processing industry, the fruit is now prepared and consumed in various forms such as pineapple chunks, slices, juices, syrups, jams, crushed pineapple, diced pineapple etc. The wastes from processing the fruit are further processed into sugar, wines, vinegar and animal feed (Baruwa, 2013). Pineapple juice's composition varies depending on geography, season, process and time of harvest. Like many fruit juices, pineapple juice contains vitamin C, or ascorbic acid. It also contains vitamins B6 (pyridoxine) and manganese which benefits the body (Hossain et al., 2015). Manganese helps fight the ageing process by protecting the cells from free radicals that cause cellular damage associated with ageing and disease. It also helps the skin produce new collagen to allow for healing after injury (Hossain et al., 2015).

1.2.3.4 Red Grape Juice

Grape (Vitis vinifera) is another tropical fruit rich in high-profile nutrients. They are the storehouse of numerous health-promoting phytonutrients such as polyphenolic antioxidants, vitamins, and minerals (Xia et al., 2010). They are included in most modern diet in form of fresh table fruits, dry fruits, juice, or simply in salads. Botanically, they are small, round berries growing in clusters on a perennial and deciduous woody vine in the genus, Vitis (Figure 4).

Figure 4: Fresh red grape (Vitis vinifera)

Grapes are rich in polyphenolic compound, resveratrol (Xia et al., 2010). Resveratrol is one of the powerful antioxidant which has been found to play a protective role against cancers of colon and prostate, coronary heart disease (CHD), degenerative nerve disease, Alzheimer's disease and viral/ fungal infections (Wenzel et al., 2000; Kuwajerwala et al., 2002). Anthocyanins are another class of polyphenolic antioxidants present abundantly in the red grapes (Xia et al., 2010). They have been found to have an anti-allergic, anti-inflammatory, antimicrobial, as well as anticancer activity (Li et al., 2001; Bagchi et al., 2004). Grapes are rich source of micronutrient minerals like copper, iron, potassium and manganese (Li et al., 2001). Copper and manganese are an essential cofactor of antioxidant enzyme, superoxide dismutase. Grapes are also a good source of vitamin C, vitamin A, vitamin K, carotenes and B complex vitamins such as pyridoxine, riboflavin, and thiamin (Xia et al., 2010).

1.3    Fruit Juice Processing

The basis of fruit juice processing for all fruit based beverages involve the following key manufacturing stages:

·         Selection and preparation of raw material

·         Juice extraction and clarification

·         Filtration

·         Pasteurization

·         Filling and bottling.

1.3.1        Fruit Juice Extraction and Clarification

In general terms, fruits are collected, sorted and washed, and then subjected to a type of mechanical compression appropriate to the fruit concerned. Although there are general fruit pressers that can be used for more than one fruit type, fruits such as citrus, pineapple and stone fruits are usually processed in specially designed equipment. Some fruit types that produce usually very cloudy juices (e.g. pome fruits such as apples and pears) may require mechanical treatment (milling) coupled with a biochemical process (involving enzymes) to break down the cellular structure so as to achieve total liquefaction and obtain best yields (Sharma et al., 2014). Although juice is naturally cloudy, but for some consumers who prefer a clear product, enzyme treatment is also applied to clear the juice. Pectic enzymes (pectinases) are used to break down the pectin, responsible for cloudiness and this helps to clear the juice prior filtration (Sharma et al., 2014).

1.3.2        Fruit Juice Preservation (Pasteurization) and Storage

After extraction, if juice is to be sold as ‘not from concentrate’ it is usually screened (filtered) through a muslin cloth or a stainless steel filter and pasteurized immediately at a temperature of 80-95oC for 1-10 min prior to hot filling into sterile bottles. Pasteurization is an operation with two main objectives. First, to control the growth of spoilage micro-organisms (mainly yeasts and moulds) that live on the fruit surface (Cashwell 2009) and secondly, to destroy the pectolytic enzymes that occur naturally in fruit that would otherwise break down the cloudy nature of the juice where a clear juice is not needed. If, however, a clear juice is required (e.g. apple or raspberry), enzymes can be added to accelerate this natural process (Sharma et al., 2014).

On the other hand, juice for concentration after extraction is normally subjected to filtration to remove cellular debris and then fed to a one- or multi-stage evaporation process to remove most of the water and other volatile material. After concentration, the concentrates are normally held in storage usually by freezing until they are reconstituted. The freezing temperature is greatly determined by degree of concentration and is usually below10oC for efficient preservation (Cashwell 2009). An alternative method of storage of concentrates is to hold them under aseptic conditions in drums or other containers. The concentrates are held in sulphited conditions (e.g. 1500-2000 ppm sulphur dioxide) but this is suitable only for juices destined for other uses (fruit drinks) other than reconstitution as pure fruit juice. The shelf life of concentrates destined for use as ingredient for fruit drinks are prolonged by the addition of chemical preservatives such as sulphites of potassium and sodium, potassium sorbate, sodium sorbate, sodium benzoate and citric acid (Franke et al., 2005; Shahnawaz et al., 2013). However, processors need to check with local authorities or standards agencies to find the maximum permitted levels.

After the reconstitution of concentrate to fruit juice by addition of water, the juice is pasteurized, to ensure that any unwanted spoilage pathogens, including bacteria or moulds, are destroyed. The type of heat treatment the juice is subjected to affects the shelf life of the product which makes it a long life or a short life product. Long-life products are those products pasteurized at a temperature of approximately 90°C for a short time usually 10-20 seconds prior packaging into sterilized containers. These products have a shelf life of approximately 6-9 months, but once opened must be stored in a chilled environment and consumed within the stated period of a few days. On the contrary, short-life products are pasteurized at a lower temperature (70-75°C) for 10-20 seconds. They have a shelf life of 2-6 weeks. However, as with longer-life products, once opened, they must be consumed within the period stated on pack (Cashwell, 2009).

1.3.3        Quality Control

The quality of each production should be monitored and controlled to ensure that every bottle of juice has the correct keeping and drinking qualities which is important for consumers’ safety and continuous patronage by customers. As soon as the juice is extracted from the fruit it starts to deteriorate, both as a result of chemical activity and bacterial spoilage (Shahnawaz et al., 2013). It is important to move from the juice extraction stage to pasteurization as quickly as possible to minimize any spoilage. More so, all equipment, surfaces and floors should be thoroughly cleaned. The freshness and quality of fruit is central to the quality of the final product. Only fresh, fully ripe fruits should be used; mouldy or insect damaged fruit should be discarded. All unwanted parts (dirt, skins, stones etc) should be removed. Water quality as well as the temperature and time of heating during pasteurization should be properly monitored because they are critical for achieving both the correct shelf life of the drink and retaining a good colour and flavour (Cashwell, 2009).

1.4              Fruit Juice Adulteration

The adulteration of fruit juices is widespread (Oranusi et al., 2012; Maireva et al., 2013; Mayaly, 2013). As with any commodity, juice manufacturers, blenders and users can secure considerable financial benefit from adulterating fruit juice. Adulteration, apart from concerns about food safety also defrauds consumers. Adulteration also encompasses mislabeling such that a fruit juice sold as pure fruit juice is not as it has been labeled (Oranusi et al., 2012). Although adulteration is becoming increasingly sophisticated, it is normally seen as falling into one of three types:

·         Over dilution of juices with water;

·         Use of cheaper solid ingredients (particularly sugars);

·         Blending of cheaper juices with more expensive juices.

The issue of too much water being added to juices has largely been addressed through the application of a minimum solids content (measured in degrees Brix). Many countries now have in place a minimum Brix value for various juices. These minima are backed either by legal statute or industry code of practice. They normally apply to juices prepared by adding water to concentrate and not to those labeled ‘not from concentrate’ products. The second category of adulteration is by far the most common. For example, apple juice will normally contain around 11% by weight of solids. At least 90% of these solids are carbohydrates with sucrose, dextrose and fructose predominating. Considerably cheaper sources of carbohydrates can be found, and the simple addition of a mixture of carbohydrates in roughly the same proportion as those found naturally in apple juice can be used to ‘stretch’ a pple juice by a considerable proportion. In more sophisticated forms of adulteration, the added components can be made to carry a similar signature to the juice. In the third category, a cheaper juice can be used to adulterate a more expensive one; for example, elderberry juice can be used to extend strawberry or raspberry juice. The detection of adulteration and its quantification have spawned some elegant scientific techniques, some borrowed from other fields and some developed specifically for use in fruit juice work.

1.4    Fruit Juice Nutrition

The importance of fruit juice in human nutrition is far beyond its use as a refreshing source of liquid. Juices are fat-free, nutrient dense beverages that are rich in vitamins, minerals and naturally occurring phytonutrients that contribute to good health (Klee, 2010). Many fruits contain a variety of minor ingredients, particularly vitamins and minerals, as well as carbohydrates, which are the predominant solid component of fruit juices. Although fruit contains small amounts of protein and fat, these are not important ingredients of juices. Apart from the more obvious benefits of fruit juice, such as being a source of potassium, it contains other substances that have useful pharmacological activity. For example, limonin and other related limonoid substances present in citrus fruit are believed to have a role in inhibiting certain forms of cancer (Wu et al., 2009). Sorbitol, which occurs in many fruit juices, has a laxative effect. Several components with antioxidant activity are found in fruit juices. These include ascorbic acid, tocopherols (vitamin E), beta-carotene and flavonoids. Beta-carotene has antioxidant activity that can quench the singlet oxygen that can induce precancerous cellular changes (Kyle et al., 2009). Changes occur during storage, particularly to the minor components of juices mainly vitamins under adverse conditions (e.g. light, increasing temperature, time).

1.5.1        The Role of Fruit Juice in a Diet

Fruit juices have an important role to play as part of a healthy diet. One glass of fruit juice is an important source of fluids and can provide vitamin C, folate, potassium and antioxidants (Landon, 2007). Some fruit juices available in the market are also fortified with calcium, folate, fibre and vitamin A, so that their nutritional contribution to the diet is further enhanced. Nutrients frequently consumed in sub-optimal concentrations by humans including calcium, iron, vitamin A, thiamin (vitamin B1), riboflavin (vitamin B2) and ascorbic acid (vitamin C) occur in higher concentrations in fruit juices than in other foods. Fruit juices generally have a low glycemic index (GI) (Brand-Miller, 2003). The glycaemic index is a ranking of carbohydrate foods based upon their effect on blood sugar levels. Because carbohydrates in low glycaemic index foods break down more slowly than in high glycaemic index foods, there is a more gradual rise in blood sugar levels. Low glycaemic index foods help people manage diabetes and lessen the risk of coronary heart disease. In general, it is recommended that a low GI product be eaten with every meal (Landon, 2007); however excessive consumption is discouraged. The GI of some popular fruit juices such as orange, apple, pineapple and grapefruit are 52, 40, 46 and 48 respectively (Brand-Miller, 2003).

1.5.2        Nutrients Delivered by Fruit Juices

Fruits and vegetables form a versatile and complex group of foods containing carbohydrates, acids, minerals, polyphenols (tannins) including the colourful anthocyanins, water-soluble vitamins, amino acids, aroma compounds, carotenoids, fibers and other bioactive substances (Cashwell, 2009). During processing, they are essentially transferred into the pressed juice. Many trace elements of fruits are also found in the corresponding fruit juices. Fruit juices are important in the delivery of fluid and nutrients and in addition can count towards a serve of fruit daily. Water is the predominant component of fruit juice. It contains carbohydrates including glucose, fructose, sucrose and sorbitol as its main macronutrients (Cashwell, 2009; Oranusi et al., 2012). Fruit juices also contain a variety of beneficial micronutrients, including significant quantities of minerals, like potassium, calcium and magnesium. They are rich in phytochemicals and vitamins (O’Neil and Nicklas, 2008). They contain small amount of protein, no fat, cholesterol and fiber (Pao et al., 2000; Landon, 2007).

1.5.2.1 Sugars

Sugars are a ubiquitous component of food supply and are consumed as a naturally occurring component of many foods and as additions to foods during processing, preparation, or at the table (Murphy and Johnson, 2003). Sugars are part of the make-up of fruit juice. They are the main macronutrient in fruit juices. Depending on the fruit juices, they contain varying concentrations of carbohydrates such as sucrose, fructose, glucose and sorbitol (Oranusi et al., 2012). Sugars occur naturally in a wide variety of fruits. When metabolized, sugars have approximately 4 calories per gram, the same as both protein and other carbohydrates. Some common sugars found in fruits are:

·         Glucose: This is a monosaccharide found naturally in food. Glucose is the primary source of energy for the body and is the only fuel used by brain cells (Jasmine, 2012). Starch digestion in the body yields glucose; even non-digestible carbohydrates (e.g. cellulose) are composed primarily of glucose.

·         Fructose: Fructose is a monosaccharide naturally found in fruits and honey (Johnson et al., 2009). It is the most abundant sugar found in fruits. It is also found in root vegetables. When it occurs naturally, it is always found along with other sugars such as glucose. Fructose makes up half of the sugar of sucrose (table sugar) and about half of the most common form of high-fructose corn syrup (HFCS). High-fructose corn syrup is produced from corn syrup (nearly all glucose), which undergoes enzymatic processing to increase the fructose content and is then mixed with glucose. It is composed of either 42% or 55% fructose and is similar in composition to sucrose (Coulston and Johnson, 2002). It is the sweetener commonly used by the beverage industry. Pure fructose is also a caloric sweetener added to foods and beverages in crystalline or liquid form. It is made from corn syrup in a process similar to making HFCS. Many consumers mistakenly believe that high-fructose corn syrup is pure fructose.

·         Sucrose: Sucrose is a disaccharide that is composed of one glucose unit and one fructose unit joined together by a chemical bond (glycosidic bond) that is readily broken in the small intestine. It is often called table sugar (Jasmine, 2012). It is found naturally in fruits and vegetables, but in the highest quantities in sugar beets and sugar cane (Johnson et al., 2009). When sucrose is digested or placed in an acidic environment (such as in many ready-to-drink beverages), it ‘inverts’ and yields 50% glucose and 50% fructose.

Once ingested, carbohydrates (polysaccharides and disaccharides) are broken down into their component monosaccharides. In the digestion of sucrose, both glucose and fructose are released into the bloodstream. Glucose, but not fructose, utilization is insulin-dependent (Jasmine, 2012). Under normal circumstances, glucose is the only fuel utilized by the brain and the primary fuel used by working muscles. To protect the brain from a potential fuel shortage, the body maintains a relatively constant glucose level in the blood. Blood glucose levels are maintained by the regulatory hormones, insulin and glucagon (Johnson et al., 2009). Human metabolism does not distinguish between sugars that are added to foods and sugars that occur naturally in foods, as they are chemically identical. Fructose is predominantly metabolized in the liver, and unlike glucose it does not require insulin in order to be utilized by the body. The rate of fructose metabolism is more rapid than that of glucose, as metabolites by-pass the rate-limiting step in glycolysis. Glucose and fructose are metabolized via separate pathways, but converge at a common point for energy production.

As expected, a healthy, well-balanced diet contains naturally occurring sugars, because monosaccharides such as fructose and disaccharides such as sucrose and lactose are integral components of fruit, vegetables, dairy products, and many grains. In addition, sugars add desirable sensory effects to many foods, and a sweet taste promotes enjoyment of meals and snacks. The addition of sugar to otherwise nutrient-rich foods, such as sugar-sweetened dairy products (like flavoured milk and yogurt) and sugar-sweetened cereals improves the quality of children’s and adolescents’ diets (Johnson et al., 2002; Frary et al., 2004); however, deleterious health effects including weight gain and dental caries may occur when sugars are consumed in large amounts. There is increasing concern that intake of added sugars particularly in the form of sugar sweetened beverages increases overall energy intake and may reduce the intake of foods containing more nutritionally adequate calories, leading to an unhealthy diet and increased risk of obesity (Malik et al., 2006; Malik et al., 2010; Malik et al., 2013). Another concern is the association between intake of free sugars and dental caries, which has received increasing interest in recent years (Moynihan and Petersen, 2004).

1.5.2.2 Minerals

Juices contain a variety of beneficial micronutrients, including significant quantities of minerals, like potassium, calcium and magnesium. Many trace elements of fruits are found in the corresponding fruit juices.

1.5.2.2.1 Sodium

Sodium is a mineral that is essential for good health. Sodium ions are the major cation in the extracellular fluid (ECF) and as such are the major contributor to the ECF osmotic pressure, and thus ECF compartment volume (Agrawal et al., 2008). In humans, sodium is an essential nutrient that regulates blood volume, blood pressure, osmotic equilibrium and pH (Geleijnse et al., 2004; Soetan et al., 2010). The body also needs sodium for the muscles and nerves to work properly. Most dietary sodium is found in the form of sodium chloride, the compound commonly known as table salt which is 40 percent sodium and 60 percent chloride. All foods and beverages contain some amount of sodium, both natural and added. Natural sodium is found in table salt (sodium chloride), fresh meats, poultry, fish, vegetables, fruits, potatoes, and rice. Added sodium is found in large amounts in many processed foods. Some of these added forms are monosodium glutamate, sodium nitrite, sodium saccharin, baking soda (sodium bicarbonate), and sodium benzoate. A small amount of sodium is needed to keep the body working properly. The minimum physiological requirement for sodium is 500 milligrams per day. The upper intake level (UL) for sodium is 2.3 grams per day, the threshold which could lead to hypertension when exceeded (Agrawal et al., 2008). Research shows a strong dose-dependent relationship between high sodium consumption and raised levels of blood pressure (Geleijnse et al., 2004). Hypernatremia and hyponatremia are the medical terms used in describing unusually high and low levels of serum sodium respectively (Agrawal et al., 2008).

1.5.2.2.2 Potassium

Potassium is a nutrient that is essential for health at the most basic level. It is the major intracellular cation. It is an electrolyte, working to regulate the balance of body fluids (Soetan et al., 2010). It helps to keep the heart and other muscles functioning normally, along with sodium and other compounds. The movement of potassium out of cells, and sodium in, changes electrical potentials in nerves and muscles to allow them function effectively (Landon, 2007; Soetan et al., 2010). Potassium comes into the body through food and the kidneys remove excess of it to keep a proper balance of mineral in the body. Potassium rich foods include fruits, vegetables, and food products made from them (juices, pastes, etc.). Many fruits and fruit juices including grape juice, orange juice, pineapple juice and apple juice are important sources of potassium. The recommended daily intake of potassium in the diet is 2000‐4000 mg daily (John, 2002). A diet rich in potassium, or greater than 4000 mg daily may be helpful as part of the dietary treatment for high blood pressure, hypertension and potassium deficiency (He and MacGregor, 2008). Fruit and vegetable consumption has been demonstrated to help reduce blood pressure, particularly in hypertensive individuals (John, 2002). Excess potassium is removed from the body by the kidneys. Therefore, people with kidney disease may need to restrict their dietary potassium generally to less than 2000 mg daily. Hyperkalemia is a disorder that occurs when serum potassium concentration is greater than 5.5 mEq/L. It is generally associated with impairment in urinary excretion of potassium, although shifts in intracellular and extracellular potassium may contribute to elevated levels. Increased intake is an unlikely cause if both renal and adrenal functions are normal (Adesola, 2014). On the other hand, hypokalemia is a disorder that occurs when the serum potassium in the blood drops to < 3.5 mEq/L (Hemant, 2012) and it is more common than hyperkalemia. Hypokalemia occurs as a consequence of potassium depletion because of increased excretion, redistribution, or inadequate potassium intake. Unless severe, hypokalemia typically has no clinical signs. Cardiac and neuromuscular cells are the most susceptible targets; serious and potentially fatal effects are usually related to disturbances in cardiac electrical activity.

1.5.2.2.3 Magnesium

Magnesium is an essential mineral. It is one of the seven macro minerals, including calcium, potassium, sodium, chlorine, phosphorous, and sulfur. It is an abundant mineral in the body with about 60 to 65 percent housed in the bones and teeth with the remaining 35 to 40 percent housed in the rest of the body, including muscle, tissue cells, and body fluids. Because of the important interaction between phosphate and magnesium ions, magnesium ions are essential to the basic nucleic acid chemistry of life, and thus are essential to all cells of all known living organisms (Soetan et al., 2010). Magnesium is a cofactor in more than 300 enzyme systems that regulate diverse biochemical reactions in the body including protein synthesis, muscle and nerve functions, blood glucose control and blood pressure regulation (Faryadi, 2012). It is required for energy production, oxidative phosphorylation and glycolysis. It contributes to the structural development of bones, and is required for the synthesis of RNA, DNA, and the antioxidant glutathione (Romani, 2013). Magnesium plays a role in the active transport of calcium and potassium ions across the cell membranes, a process that is important to nerve impulse conduction, muscle contraction and normal heart rhythm (Guerrera et al., 2009). It also helps to boost the immune system (Laurie, 2010). Magnesium is naturally present in many foods and beverages including fruit juice, and on the other hand added to other food products (Rude, 2012). The recommended daily allowance (RDA) of magnesium ranges from 130-240 mg in children within 4 to 13 years of age and from 310-420 mg in men and women above the 14 years of age (Guerrera et al., 2009). According to research, 75 percent of the U.S. population obtains less than the RDA. This nutritional shortfall of the recommended daily allowance (RDA) of magnesium can have serious health repercussions. Some of the symptoms commonly associated with low magnesium include confusion, irritability, fatigue, muscle cramps, heart arrhythmias, high blood pressure and migraine headaches (Guerrera et al., 2009).

1.5.2.2.4 Calcium

Calcium is the most abundant mineral in the body. It makes up 1.9% of the body by weight. The majority (~99%) of calcium present in the body is found in bone, with a smaller amount found in teeth (Soetan et al., 2010). The remainder (<1%) is found in soft tissues and body fluids. The average adult skeleton contains 1200 g of calcium, present in the form of hydroxyapatite, an inorganic crystalline structure made up of calcium and phosphorus [Ca10 (PO4)6(OH)2], which provides rigidity (Theobald, 2005). As well as having a skeletal function, calcium plays a regulatory role in a number of specialized functions in the body. Calcium plays a role in muscle (including cardiac muscle) contraction, neurotransmitter secretion, digestion and blood coagulation (clotting). Calcium also plays a structural role outside of the skeleton, for example in organelles and membranes. Disturbances in the structural and regulatory roles of calcium can have implications for health and disease. A wide number of foods contain calcium. The major source of calcium in British diets is milk and milk products, followed by cereals and cereal products. Additional sources of calcium include plant foods (e.g. soya beans), some animal products (e.g. eggs) and water (Galan et al., 2002). The UK reference nutrient intake (RNI) for calcium for adults over 19 years of age is 700 mg/day; requirements are higher during childhood, adolescence and during lactation (Theobald, 2005). Chronic calcium deficiency due to inadequate intake or poor intestinal absorption is one of the causes of reduced bone mass and osteoporosis (Cashman, 2002; Bainbridge et al., 2004). Low levels of free ionized calcium in the blood (hypocalcaemia) can also result in tetany, which is manifested by intermittent muscle contractions, muscle pain, spasms and numbness in the hands and feet (Soetan et al., 2010). There is also evidence that implicates low plasma calcium with chronic diseases such as hypertension and colon cancer (Hatton et al., 2003; Lamprecht and Lipkin, 2003). Early ecological studies suggested that consumption of hard (calcium-containing) water was associated with a reduced risk of cardiovascular disease (Nerbrand et al., 2003). Abnormally high calcium concentrations may occur but usually secondary to diseases such as bone cancer, hyperthyroidism and hyperparathyroidism. The common adverse effects of excessive calcium intakes (>1500 mg calcium/day) are stomach pain, diarrhea, kidney stones (nephrolithiasis), milk-alkali syndrome and interaction of calcium with absorption of other essential minerals such as iron, zinc, magnesium and phosphorus (Theobald, 2005; Soetan et al., 2010).

1.5.2.2.5 Phosphorus

Phosphorus is a major structural component of bone in the form of calcium phosphate or hydroxyapatite (Theobald, 2005). Phosphorus is essential for life. It keeps the bones healthy and also helps keep the blood vessels and muscles working properly. Phosphates are a component of DNA, RNA, ATP, and also the phospholipids, which form all cell membranes (Soetan et al., 2010). Phosphorus works with calcium to build bone; the body works best when these minerals are in balance. The regulation of blood calcium and phosphorus levels is interrelated through the actions of parathyroid hormone and vitamin D in the kidney. High dietary intake of phosphorus reduces blood calcium that may be detrimental to bone mineral content (Karp et al., 2007). Low blood calcium resulting from inadequate dietary calcium intake results in decreased urinary excretion of calcium and increased urinary excretion of phosphorus which helps bring blood calcium level up to normal (Theobald, 2005). Phosphorus is found naturally in foods rich in protein, such as meat, poultry, fish, nuts, beans, and dairy products and low in fresh fruits and vegetables (Sherman and Mehta, 2009; Kalantar-Zadeh et al., 2010). Phosphorus is also added to many processed foods. Some foods are very high in phosphorus and intake of such foods should be limited. Concerns for phosphorus intake have arisen due to presence of phosphoric acid in soft drinks and phosphate additives in a number of commercially prepared foods (Uribarri, 2007). Phosphorus intake from food and drinks should be less than 900 mg per day. Some common symptoms of high phosphorus include bone and joint pain, weakness, itching, bone weakness and red eyes. Phosphate intakes in excess of the nutrient needs of the healthy population may significantly disrupt hormonal regulation of phosphorus, calcium, and vitamin D, contributing to disordered mineral metabolism, vascular calcification, impaired kidney function, and bone loss (Hruska, 2007; Soetan et al., 2010). The most serious adverse effect of abnormally elevated blood levels of phosphate (hyperphosphatemia) is the calcification of non skeletal tissues most commonly the kidneys (Uribarri, 2007). Such calcium phosphate deposition can lead to organ damage. Hyperphosphatemia from dietary cause is a problem mainly in people with kidney failure, since the kidneys are normally efficient at eliminating excess phosphate from the circulation. However, large epidemiological studies suggest that mild elevations of serum phosphorus within the normal range are associated with cardiovascular disease risk in healthy populations without evidence of kidney disease (Uribarri, 2007; Uribarri and Calvo, 2013).

1.5.2.2.6 Iron

Iron is an essential trace element in living organisms. It is an important dietary mineral that functions as haemoglobin in the transport of oxygen to all parts of the body. In cellular respiration, it functions as essential component of enzymes involved in biological oxidation (Soetan et al., 2010). It is involved in synthesis and packaging of neurotransmitters, their uptake and degradation into other iron-containing proteins which may directly or indirectly alter brain function (Beard, 2001). Iron occurs as a natural constituent in plants and animals. Animal sources of iron (called haem iron) include meat, fish and poultry. The body easily absorbs this type of iron. Plant sources (called non-haem iron) include dried beans, peas and lentils and some fruits and vegetables. Rice and many fruits and vegetables have low iron contents (1-10 mg/kg). Most iron is absorbed in the duodenum and upper jejunum. Absorption depends on the individual's iron status and is regulated so that excessive amounts of iron are not stored in the body. The largest fraction of iron in the body is present as haemoglobin, myoglobin, and haem-containing enzymes (Soetan et al., 2010). The other fractions are stored in the body as ferritin and haemosiderin, mainly in the spleen, liver, bone marrow and striate muscle. Estimates of the minimum daily requirement for iron depend on age, sex, physiological status, and iron bioavailability and range from about 10 to 50 mg/day (WHO, 2003). Reported daily intakes of iron in food which is the major source of exposure ranges from 10 to 14 mg. Concentrations of iron in drinking-water are normally less than 0.3 mg/litre but may be higher in places where various iron salts are used as coagulating agents in water-treatment plants and where cast iron, steel, and galvanized iron pipes are used for water distribution (WHO, 2003). Low iron levels may lead to low levels of haemoglobin in the blood, hence anaemia leading to tiredness and an increased risk of infection. Iron deficiency is also associated with alterations in many metabolic processes that may impact brain functioning, among whom are neurotransmitter metabolism, protein synthesis, organogenesis etc (Soetan et al., 2010). The effects of toxic doses of iron include depression, rapid and shallow respiration, coma, convulsions, respiratory failure, cardiac arrest and risk of colorectal cancer (Senesse et al., 2004). Fe accumulation has also been related to some neurologic disorders such as Alzheimer disease, Parkinson disease, type-1 neuro-degeneration with brain iron accumulation and other disorders (Sadrzadeh and Saffari, 2004).

1.5.2.3 Phytochemicals

The intake of polyphenols in the diet is about 1 g/day (Scalbert and Williamson 2000), the major sources being fruit juices, red wine, coffee and tea. Juices are particularly high in flavonoids, a subclass of polyphenols (Landon, 2007). Orange has over 170 different phytochemicals, including more than 60 flavonoids, many of which have been shown not only to have antioxidant effects but also anti-inflammatory and anti-tumour activity. Apples and cloudy apple juice contain quercetin, chlorogenic and other phenolic acids as well as phloridzin and phloretin xyloglucoside. Pomegranate juice is rich in ellagitannins, like punicalagin. Citrus contains flavanones (hesperidin, naringin). Carotenoids such as beta-carotene, alpha-carotene, beta-cryptoxanthin, lutein zeaxanthin, lycopene and limonoids are found in grapefruits (Landon, 2007). These substances are antioxidative and anti-inflammatory. Grape juice is well known for the presence of resveratrol, flavonoids and anthocyanins and tomato juice is a major source of lycopene (Lee et al., 2009). These substances contribute to optimal health and protect against some of the common chronic diseases such as cancer and cardiovascular disease, degenerative eye and cognitive conditions and general damage caused by ageing (Benavente-Garcia and Castillo, 2008).

1.5.2.4 Vitamins

Fruit juice makes a significant contribution to the vitamin intakes of both men and women of all ages, but most notably older teenagers (15-18 years of age). Fruits, vegetables and fruit juices are the main dietary sources of vitamin C (Cashwell, 2009). Vitamin C is a water soluble vitamin and has an important role in wound healing and collagen formation. In addition, vitamin C increases iron absorption from meals and plays a role in the prevention of chronic disease (Landon, 2007). In addition to vitamin C, fruit juice also contributes to population intakes of other vitamins, including folate, although this contribution is a lot less than the contribution by vitamin C intakes. Folate is an essential vitamin and has an important role in cell production (Cashwell, 2009). Folate also has important implications in heart health as it has been demonstrated to lower homocysteine levels. Folate helps in maintaining a low level of the amino acid homocysteine, a marker of inflammation that has been associated with a higher risk for heart disease, stroke, and heart failure (Landon, 2007). Folate from citrus and pineapple is essential for women of child bearing age where folate deficiency is linked to neural tube defects. It is important for the prevention of premature birth (Baghurst et al., 2003).

1.5.3        Health Benefits of Fruit Juices

It is widely accepted that a diet rich in fruits is a good source of vitamin C, carotenoids, minerals (especially Mg, K) and various kinds of antioxidants and dietary fibre (pectin) that is protective against degenerative and chronic diseases such as cancer and cardiovascular diseases (Krejpcio et al., 2005). Some of these functional compounds remain after processing and are present also in fruit products, including juices. Fruit juices are a good source of the sugars needed by the body, and also provide phytochemicals with a wide range of health benefits. Many of the studies looking at the health benefits of fruit juice consumption focus on its ability to promote a better nutrient intake in consumers versus non consumers, and indicate that people who consume fruit juice tend to have healthier overall dietary habits than those who do not. Fruit juice consumers had significantly higher intakes of total carbohydrate, vitamins C and B6, folate, potassium, magnesium and iron, and significantly lower intakes of total and saturated fat and added sugar (Nicklas et al., 2008; Cashwell, 2009). The micronutrients present in fruit juices are needed for numerous biochemical processes in the body; they are essential for good health if present in adequate concentration (Ofori et al., 2013). These nutrients contained in fruit juices have been shown to have many health benefits. Fruit juices appear to be most active on diseases related to chronic inflammation, cancer, heart and bone diseases as well as problems related to cognition and ageing. The high potassium and low sodium characteristic of most juices help to maintain a healthy blood pressure. Furthermore, the lack or near absence of fat in fruit juices is beneficial for the cardiovascular system (Landon, 2007). The beneficial health effects of fruit juices depends on the amount consumed in a daily diet, type of fruit and the content of biologically active compounds. Fruit juices, consumed in moderation as part of a balanced diet, offer both health and disease risk reduction properties.

1.5.3.1 Fruit Juice and Cardiovascular Health

The most promising potential for the beneficial effects of fruit juice has been shown in the area of cardiovascular health (Duthie et al., 2006; Leifert and Abeywardena, 2008; Dalgard et al., 2009; Grassi et al., 2009; Ross, 2009; Chong et al., 2010). The formation of a blood clot in the circulatory system (thrombosis) can lead to disturbance in the blood supply resulting in embolism and stroke. Several fruit juices seem to be able to limit blood clot formation by preventing platelets from aggregating in the blood vessels (Freedman et al., 2001; Mattiello et al., 2009). Fruit juices have been shown to act at the various levels of the processes leading to atherosclerosis (Aviram et al., 2002). It has been shown that fruit juices can increase the level of high density lipoproteins (HDL), the lipids disposed of in the liver (good lipids) and decrease the formation and oxidation of low density lipoproteins (LDL) that are deposited in the blood vessels (bad lipids) (Gorinstein et al., 2004; Gorinstein et al., 2006). Fruit juice components have been shown to act at every level of the blood lipid process from cholesterol synthesis to the formation of lipoproteins (LDL, HDL) by inhibiting the synthesis of the enzymes required for those processes (Aviram et al., 2002). Apple polyphenols may act by inhibiting cholesterol ester transfer protein (CETP) (Lam et al., 2008). Morin et al. (2008) showed that a reduction of plasma cholesterol by citrus flavonoids is associated with a modulation of the expression of the LDL receptor (LDLR) gene.

Another signaling molecule affected by fruit juices is nitric oxide (NO). The endothelium (inner lining) of blood vessels uses nitric oxide to signal the surrounding smooth muscle to relax, thus resulting in vasodilation and increasing blood flow. The proper level of NO is largely modulated by enzymes such as endothelial nitric oxide synthase and nitric oxide oxidase. Fruit juices play a major role in the maintenance of NO levels. This has been shown to occur with many juices (George et al., 2009) including grape (Ekshyyan et al., 2007), pomegranate (De-Nigris et al., 2005) and citrus juices (Morand et al., 2011). These beneficial changes have been noted at various levels of the cardiovascular system including blood pressure (Reshef et al., 2005; Morand et al., 2011). Potassium contained in fruit juices has also shown blood pressure lowering effects by countering the effects of sodium (Cashwell, 2009).

1.5.3.2 Fruit Juice, Cancer and Inflammation

Several epidemiological studies have shown the beneficial roles of fruit juices in preventing the development of cancer (Cutler et al., 2008; Kyle et al., 2009; Wu et al., 2009). Many juice phytochemicals, polyphenols, carotenoids and limonoids may influence mechanisms relevant for cancer prevention. These include antimutagenic activity, control of angiogenesis, anti-inflammatory mechanisms, modulation of signal transduction pathways. Positive results have been associated with most juices, including apple juice (Gerhaeuser, 2008) grapes and grape juice (Iriti and Faoro, 2009). Anthocyanins from various berry juice (Thomasset et al., 2009), citrus flavonoids (Benavente-Garcia and Castillo, 2008) and limonoids (Poulose et al., 2006) may also have potential anticarcinogenic activities. Cranberry juice has long been associated with a reduction in urinary infections. Anthocyanidin and proanthocyanidin may inhibit the adhesion of uropathogens (e.g. uropathogenic E. coli) to the uroepithelium, thus impairing colonization and subsequent infection (Guay, 2009).

Various minerals have been reported to be directly linked to health as well as cancer development in the body. They have some preventive values especially with colon cancer. The immune system is the natural mechanism which defends against cancer. Minerals like magnesium, calcium and zinc augment this natural mechanism (Sliwinski et al., 2009). Ma et al. (2010) in their research reported that high dietary intake of magnesium may decrease risk of colorectal cancer. Calcium acts as an anti-cancer agent in the colon by inhibiting cell growth and/or disarming potential toxins by binding them to fatty acids. Zinc is an essential mineral involved in cancer development and it can be used in the treatment of various types of cancers and various anticancer therapies (Singh et al., 2012).

1.5.3.3 Fruit Juice, Brain health, cognition and ageing

Prevention of age-related, quantitative loss or qualitative changes in brain neurons, brain atrophy, cognitive impairment, and depression are all crucial anti-ageing measures for the brain. Insufficient intake of nutrients, including glucose, amino acids, vitamins and minerals causes abnormal metabolism in the brain and decreased production of neurotransmitter, leading to deterioration of neuropsychiatric function (Igase et al., 2010). Many reports have shown that fruit juices may play an important role in maintaining cognition, limiting brain ageing and possibly slowing the progress of Alzheimer's disease (Dai et al., 2006). The beneficial effects of grape juice (Joseph et al., 2009; Wang et al., 2008) and citrus (Datla et al., 2001) have been examined. The ability of juice compounds, particularly flavonoids, to cross the barrier protecting the brain (blood brain barrier) is at the origin of their beneficial activity (Youdim, 2003). Spencer (2009) reviewed the neuroprotective properties of dietary flavonoids. Firstly, they promote cerebral vascular blood flow. Secondly, they interact with neuronal signaling cascades leading to an inhibition of cell death and promotion of neuronal differentiation. As a result, they prevent deterioration or even improve cognitive performance (Spencer, 2009). Vitamin C can also reach the brain and it is proposed as a neuromodulator of neurotransmitters, thus vitamin C may have potential therapeutic roles against ischaemic stroke, Alzheimer's disease, Parkinson's disease, and Huntington's disease (Harrison and May, 2009).

1.5.3.4 Fruit Juice and Skin Health

Majority of people are born with healthy and supple skin, however, with ageing, the skin becomes less able to cope with everyday’s wear and tear. Although good skin is partly due to genetic make-up, nutrition has also been shown to contribute a lot to healthy skin. Food and drinks are the best ways to give the skin and body the nutrients they need. Certain vitamins and minerals such as vitamins A, C and E, riboflavin, niacin, pyridoxine, zinc and selenium have important roles to play in skin health. Drinking plenty of fluids including water, tea and juices is very important for healthy skin. The fluids help the body stay hydrated and helps clear the body of toxins. Studies have shown that juices and their phytochemicals can improve skin health (Cosgrove et al., 2007) and have sometimes been referred to as providing “Beauty from within”.

Vitamin C has long been known to maintain skin collagen (Bae et al., 2009). Arai et al. (2009) and Duarte et al. (2009) revealed the beneficial effects of vitamin C on skin, starting at the gene expression level. Flavonoids have been shown to improve skin microcirculation (Neukam et al., 2007) and collagen formation (Stipcevic et al., 2006; Bae et al., 2009). Carotenoids have also been shown to improve skin health (Stahl and Sies, 2007).

1.6              Health Concerns Associated with Fruit Juice Consumption

The excessive consumption of fruit juice has been associated with the development of obesity, type 2 diabetes and dental caries (Cashwell, 2009) which are all attributed to its sugar content.

1.6.1        Fruit Juice and Obesity

Excessive consumption of any calorie source is likely to lead to obesity. Faith et al. (2006) in their research showed that the consumption of very high levels of fruit juice could have negative effects. Concern has been expressed that fruit juice sugar can contribute to weight gain, especially for children. Some studies have highlighted possible detrimental effects associated with fruit juice consumption, such as possible increase in risk of obesity and short stature in children who consume juice. There has also been interest in the potential effect that energy consumed as ‘liquid calories’ has on weight control , with suggestions that energy from liquids is less satiating than energy from solids (Di-Meglo and Mattes, 2000; Benelam, 2009). This interest has stemmed from the observation that an increase in the consumption of sugared beverages parallels the rising obesity levels seen in many countries (Mattes, 2006; Mourao, et al., 2007). Studies on the role of fruit juice and juice drinks on weight control have produced seemingly conflicting results. In some studies, average energy contribution of fruit juice across all age segments was revealed to be consistent with a healthy diet and not associated with weight status or the likelihood of being overweight (Schulz et al., 2005; Landon, 2007; O’Neil and Nicklas, 2008) while Faith et al. (2006) and Tam et al. (2006) in their studies associated fruit juice consumption with an increase in body mass index (BMI). Therefore time and dose-dependent controlled studies are needed to clarify these assertions.

1.6.2        Fruit Juice and Dental Health

Dental caries (tooth decay) are caused by the progressive destruction of the teeth by acid produced by bacteria on the tooth surface. These bacteria produce acid by fermenting sugars found in foods, which decreases the pH at the tooth surface and causes demineralization of the tooth enamel. Over time, these acids are gradually neutralized by saliva, and when the pH of the mouth rises to its original level, remineralization of the tooth occurs using calcium and other minerals present in saliva. When food and drinks containing sugar are consumed frequently throughout the day, there is little time for this remineralization process to occur, and tooth decay results (Cashwell, 2009). The metabolism of fermentable carbohydrates (which includes sugars from fruit, fruit juice and starchy foods) plays a part in the dental caries or erosion process (Moynihan, 2005). Report has postulated that fruit juices can affect dental health, promote caries and dissolve enamel (Landon, 2007). The sugar in fruit juice and juice drinks have a much greater cariogenic potential than whole fruits, which are not associated with the production of dental caries (Moynihan and Petersen, 2004). Of particular concern with regards to the cariogenic potential of fruit juices are situations where young children are given juices in bottles or sip cups, causing the juice to be in contact with the teeth for a prolonged period of time. This practice is thought to be associated with an increase in caries risk (Tinanoff and Palmer, 2000). Evidence indicates that a high frequency of sugar consumption is more damaging in terms of caries development than the total amount of sugar consumed at any one time (Moynihan, 2005). Marshall et al. (2003) and Lim et al. (2008) reported that children with a high consumption of soft drinks are at a higher risk of developing dental caries relative to those consuming milk and 100 percent fruit juice. However, this detrimental effect of juice sugar and acidity can easily be eliminated by regular use of a fluoridated dentifrice and proper hygiene (Landon, 2007).

1.6.3        Heavy Metals in Fruit Juice

The majority of metals are natural components of the earth’s crust. Metals and other elements including heavy metals can occur in foods as natural or inherent components of plant and animal tissues and fluid, and may also be present in food as contaminants resulting from human activities such as industrial and agricultural processes. One form of food contamination by heavy metals arises from exposure to water polluted by industrial waste (Hossain et al., 2012). As a result of soil, atmosphere, underground and surface water pollution, our foods and beverages are contaminated with heavy metals. Industrial exposure is common in adults while ingestion is the most common route in children. Not all forms of heavy metals are particularly toxic. Some of these heavy metals such as Fe, zinc and copper are essential in trace quantities for maintenance of cellular processes and are not normally found in food at levels that could cause toxicity while others such as Pb, As, Cd etc have no functional effects in the body and can be harmful to health if foodstuffs containing them are consumed regularly in the diet (Soetan et al., 2011).

1.6.3.1 Zinc (Zn)

Zinc constitutes about 33 ppm of adult body weight. It is an essential mineral involved in numerous aspects of cellular metabolism. It is required for the catalytic activity of many enzymes including lactate dehydrogenase, alcohol dehydrogenase, glutamic dehydrogenase, alkaline phosphatase, carbonic anhydrase, carboxypeptidase, superoxide dismutase, retinene reductase, DNA and RNA polymerase (Arinola, 2008; Soetan et al., 2010). It plays a role in immune function, wound healing, protein and DNA syntheses, and cell division (Osredkar and Sustar, 2011). Zinc is required for proper sense of taste and smell and supports normal growth and development during pregnancy, childhood, and adolescence (Singh et al., 2012). It is believed to possess antioxidant properties, which may protect against accelerated ageing and helps speed up the healing process after an injury. Zinc ions are effective antimicrobial agents even at low concentrations. Gastroenteritis is strongly attenuated by ingestion of zinc and this effect could be due to direct antimicrobial action of the zinc ions in the gastrointestinal tract, or to the absorption of the zinc and re-release from immune cells (all granulocytes secrete zinc), or both (Osredkar and Sustar, 2011). Cells in the salivary gland, prostate, immune system and intestine use Zn signaling as one way to communicate with other cells. In the brain, zinc is stored in specific synaptic vesicles by glutamatergic neurons and can modulate brain excitability (Harold, 2003). It plays a key role in synaptic plasticity and so in learning. Zinc can also be a neurotoxin, suggesting zinc homeostasis plays a critical role in normal functioning of the brain and central nervous system. Although zinc is an essential requirement for good health, excess zinc can be harmful (Valko et al., 2005). Zinc deficiency, resulting from poor diet, alcoholism and malabsorption, causes dwarfism, hypogonadism and dermatitis, while toxicity of Zn due to excessive intake may lead to electrolyte imbalance, nausea, anemia and lethargy (Ofori et al., 2013). Excessive absorption of zinc suppresses copper and iron absorption. Acute adverse effects of high zinc intake include nausea, vomiting, loss of appetite, abdominal cramps, diarrhea, and headaches. Intakes of 150-450 mg of zinc per day have been associated with such chronic effects as low copper status, altered iron function, reduced immune function, and reduced levels of high-density lipoproteins. A daily intake of Cu and Zn is required to maintain a steady state because the body has no specialized storage system of these two elements. A wide variety of foods contain zinc. Oysters contain more zinc per serving than any other food, but red meat, especially beef, lamb and liver have some of the highest concentrations of zinc in food. Other good food sources include beans, nuts, other types of seafood (such as crab and lobster), whole grains, cereals, almonds, pumpkin seeds, sunflower seeds (Osredkar and Sustar, 2011).

1.6.3.2 Copper (Cu)

Copper plays an important role in metabolism, largely because it allows many critical enzymes to function properly. Copper is essential for maintaining the strength of the skin, blood vessels, epithelial and connective tissue throughout the body. It also plays a role in the production of haemoglobin, myelin, melanin and keeps thyroid gland functioning normally, as well (Harris, 2001). Copper can act as both an antioxidant and a pro-oxidant. As an antioxidant, Cu scavenges or neutralize free radicals and may reduce or help prevent some of the damage they cause (Araya et al., 2006). When copper acts as a pro-oxidant at times, it promotes free radical damage and may contribute to the development of Alzheimer’s disease (Soetan et al., 2010). Maintaining the proper dietary balance of Cu, along with other minerals such as zinc and manganese, is important. Adult human body contains about 1.5-2.0 ppm of Cu which is essential as a constituent of some metalloenzymes and is required in haemoglobin synthesis and in the catalysis of metabolic oxidation. Symptoms of Cu deficiency in humans include bone demineralization, depressed growth, depigmentation and gastro-intestinal disturbances, among others, while excessive copper intake can cause nausea, vomiting, abdominal pain and cramps, headache, dizziness, weakness, diarrhea (Soetan et al., 2010). Toxicity due to excessive intake has also been reported to cause liver cirrhosis, dermatitis and neurological disorders (Silvestre et al., 2000). Nutritionists have been more concerned about copper toxicity than copper deficiency. This is as a result of increase in the amount of copper found in drinking water due to the switch in some areas from galvanized water pipes to copper water pipes (WHO, 2004). High uptakes of copper may cause liver and kidney damage and even death. (Osredkar and Sustar, 2011).

1.6.3.3 Arsenic

Arsenic is a highly toxic element and its presence in food composites is a matter of concern to the human well-being (Al-Ramalli et al., 2005). It is more acutely toxic than other metallic compounds and continual low level exposure to arsenic is associated with skin, vascular and nervous system disorders. Acute and chronic exposures to arsenic causes a variety of adverse health effects to humans such as dermal changes, respiratory, pulmonary, cardiovascular, gastrointestinal, hematological, hepatic, renal, neurological, developmental, reproductive, immunologic, genotoxic, mutagenic and carcinogenic effects (Mandal and Suzuki, 2002). Arsenic has been classified by the International Agency for Research into Cancer (IARC) as a human carcinogen on the basis of increased incidence of cancers at several sites in people exposed to arsenic at work, in the environment or through their diet (Mayaly, 2013).

1.6.3.4 Lead (Pb)

Lead is a potentially harmful metal that has aroused considerable concern. It has become widely distributed and mobilized in the environment and human exposure to and uptake of this non-essential element has consequently increased. Consumption of foods and drinks containing lead is the major source of public exposure to lead (Shilu et al., 2000). Lead poisoning results from the use of lead in water pipes, earthenware containers and in wine storage (Abdullahi et al., 2013). At high levels of human exposure, there is damage to almost all organs and systems, most importantly the central nervous system, kidneys and blood, culminating in death at excessive levels. At low levels, haeme synthesis and other biochemical processes are affected, psychological and neurobehavioural functions are impaired, and there is a range of other effects. Impairments related to lead toxicity in humans include abnormal size and haemoglobin content of the erythrocytes, hyperstimulation of erythropoiesis and inhibition of haeme synthesis. Short-term exposure to high levels of lead can cause brain damage, paralysis (lead palsy), anaemia and gastrointestinal symptoms. Longer-term exposure can cause damage to the kidneys, reproductive and immune systems in addition to effects on the nervous system (Sharma et al., 2011).

1.7              Problem Statement and Justification

Fruit juice is becoming an important part of the modern diet in many communities including Enugu State, Nigeria. Its consumption is becoming popular in Nigeria because of its health and invigorating benefits. This is because the micronutrients and phytochemicals contained in fruit juices help reduce the risk of a variety of chronic diseases including cardiovascular disease and cancer. However, the beneficial and health effects of fruit juices depends on the amount consumed in a daily diet, type of fruit and the content of biologically active compounds. In recent time, the quality of fruit juices is diminishing with increasing concentration of toxic compounds including added sugar, heavy metals and other contaminants (Oranusi et al., 2012; Maireva et al., 2013; Ofori et al., 2013; Hassan, 2014). The liquid nature as well as versatility of juice which is as a result of the availability of several raw fruit materials and several mixing and blending options has increased the ease with which it can be altered with sugar, contaminants, water or inferior juices and this has continued to attract unethical suppliers. However, valid data are not available on the extent to which the commercial fruit juices and drinks available in Nigeria market are either mislabeled, adulterated or of inferior quality (Dosumu et al., 2009; Oranusi et al., 2012). Excessive sugar consumption from fruit juice has been associated with the development of obesity, type II diabetes and dental caries (Cashwell, 2009). The minerals contained in fruit juices are also beneficial at adequate quantities and harmful when in excess or deficient (Ofori et al., 2013), hence the need for their proper representation. Excessive sugar consumption, micronutrient malnutrition and heavy metal contamination are ongoing public health concerns (Nzeagwu and Onimawo, 2010; Ofori et al., 2013) and in part to address these concerns, it is necessary to scrutinize the industrially processed fruit juices (especially those with ‘100% natural’ and ‘no sugar added’ label) made ava ilable to consumers in Enugu state, Nigeria with an aim to detect adulteration in quality with respect to sugar and mineral levels as well as heavy metal contamination by comparing them with freshly prepared fruit juices. This will help consumers to make evidence-based decisions on the safety, quality and the amount of juice to consume.