MICROBIOLOGICAL EXAMINATION ON PROCESSED GARRI SOLD IN OPEN MARKET IN UMUAHIA

 

3          Cultural characteristics of Bacterial isolates from garri samples.                     22

4             Morphology, Biochemical characteristics and Identification of Bacterial isolates from garri.         23

5             Microscopic characteristics and identification of Fungi isolates Obtained from garri samples.     24

6             Distribution and percentage occurrence of Organisms in the garri  samples.        25

7            Source specific distribution of isolates from the garri sample.                      26

 

 

Garri, a roasted granular hygroscopic starchy food product, produced from cassava (Manihot esculentacrantz) is the most popular form in which cassava is consumed in the West Africa sub-region. It is consumed by several millions of people regardless of ethnicity and socio-economic class, making it the commonest meal amongst the rich and the poor. Garri available in the market can be consumed directly without further processing in the dry form with peanut, coconut, smoked fish, soaked in water (sometimes with milk and beverage) or processed minimally using boiled water to form stiff paste popularly called “eba” and eaten with various types of African soups.

Cassava for garri production is harvested manually in the farm with the aid of a cutlass, hoe and flat iron sheet (digger), which occasionally inflicts various degrees of injuries on the root tubers. After harvesting, the root tubers are hauled to the market where they are heaped in 20s, 40s, 50s or 100s for sales under humid and warm tropical conditions. These practice predisposes the root tubers to contamination and infestation by various groups of microorganisms (especially moulds) mites and insects which potentiates bio-deterioration.

Following processing, garri is spread on the bare floor or on a mat to allow it to cool before final sieving and packaging for marketing. In the open market, garri is displayed in open basins, bowls, bags and mats. These practices potentiate contamination by various groups of microorganisms and may predispose public health hazards. 

The general objective of the work is to carry out the microbial examination on processed garri sold in open market in Umuahia.

Aim two – Specific objective

The specific objective include:

Garri is a finished product obtained by artisanal or industrial processing of cassava tuber. The process consists of peeling, washing and grating of the tubers, followed by fermentation, pressing, fragmentation, granulation, drying and suitable heat consumed in the West African sub-region.

Cassava (Manihot esculenta crantz) sometimes also called manioc, is the third largest source of carbohydrate for human consumption in the world, with an estimated annual world production of 208million tones (F.A. O. 2010). Cassava root is long and tapered with a firm homogenous flesh encased in a detachable ring, about 1mn thick and rough and brown of the outside. Cassava is the highest producers of carbohydrates per hectare among staple food crops. According to the food and agriculture organization of the United Nations (F.O.A) it is the fourth most important food crop in developing countries after rice, corn (maize) and wheat. Cassava is the only staple food cultivated widely throughout the world that is poisonous to consume prior to processing. It has played vital roles in the diets of many African countries as a major source of low cost carbohydrates (O’Hair, 1990).

Cassava contains significant amount of iron, phosphorus, calcium and is relatively rich in vitamin  C. Two parts of the cassava plant are used for human consumption, the starchy roots and the leaves. Though the root is the main crop in most cassava-growing countries in Africa, the leaves are also consumed as green vegetable which provides protein and vitamins A and B. In 1993, 58% of the world production was used for food, 25 to 28% for animal feed, 2 to 3% in industry and 14% was waste (Balogun, 2002).

The fermentation of cassava to produce garri is an important step to achieve value addition and preserves this starchy food in a wide diversity of textures, flavors and aromas that enrich the human diet (Steinkraus, 2005) and helps to ensure distribution and storage of the product without the need for refrigeration.

Current processing of garri is often crude and strenuous and varies from one area to another giving rise to a non-uniform product with respect to safety, quality and shelf-life. In some locality the processing of garri involves harvesting, peeling and washing, grating and packing of the fresh cassava roots into closely knit bags, the mash is placed in bags and squeezed (either by tying it up with sticks and continuously tightening the ropes or by a variety of screw and hydraulic presses) for a minimum of 48hrs to allow detoxification by fermentation at ambient temperature (Huch et al., 2008 and Steinkraus, 2005). Fermentation pulp is then dried to about 10% moisture content by frying (sometimes with palm oil) at high temperatures which probably results in the partial conversion of starch to dextrin (Ikediobi and Onyike 2002) and used mainly as adhesives and thickening agents (Osho and Dashiell, 2002) destruction of enzymes and microorganisms and the expulsion of cyanide gas from the product (Asegbeloyin and Onyimonyi, 2007; Harbor and Ogundu 2009).

Before the advent of machines, the cassava was hand grated. The grated produce is then put into a jute sack and the sack tied. Traditionally, this is left to ferment for three to seven days depending on the type of garri being made. This step is important as the fermentation process helps to reduce and detoxify the high cyanide content of cassava (Ikediobi and Onyike, 2002). The garri-filled sacks are stacked up on each other and a wooden board placed below and above the sacks. The wooden boards are tied together with the sacks full of the grated cassava in between. Tension is created by tightening the rope and thus allowing water to run of the grated cassava being processed. 

Usually, by day three, the grated cassava would have lost some water, thus become dry. With the advent of machines that could compress and squeeze out water from the grated cassava, this step is been by-passed. There is spontaneous fermentation of the cassava pulp during the drying period (Okafor, 2000) and water running out is rich in starch. This fermentation and raw grated cassava is now sieved to remove large particles and fibres and the smaller grain like bits are collected for further processing.

This is now fried in dry wide pot. Some at a time of the grated cassava and then put in a large pot and stirred continuously until it becomes crispy and when it begins to give a sharp pleasant aroma then it is collected gently, with a saucer into a container. This baked product is what is known as garri.

The introduction of machines has made garri processing simple, and pilot plants have been established in Nigeria and Ghana. (Okafor, 2000; Ekundayo, 2000). The traditional method of garri production as outlined above has a number of disadvantages ranging from a short shelf-life, lack of uniformity of product quality and high labour intensity.

Depending on the method of processing, garri could be established into the following types, white and yellow garri, fine garri and extra fine grain garri, coarse garri and extra coarse grain garri, Ghana and Ijebu garri (Steinkraus, 2005).

Garri is rich in starch. It also has very high fibre content, contains proteins and some essential vitamins. The high fibre conten makes it very filling and also makes this good in preventing or at least reduces likelihood of constipation and bowel diseases (Oduro and Akpoti (200).

Microbial deterioration of garri refers to the change in the natural state of the garri which reduces its desirability and quality either for aesthetic or health purposed. (Jay (2006) in general, these changes are, of biological nature brought about by enzymes produced within the tissue itself. In some cases, changes result from oxidation. These factors may at alone or in combination. Microorganisms may synthesize compounds that alter the flavor, colour or odour of the food (Jay, 2006).

Microbial deterioration of garri is a major economic concern because it poses great risk to the end consumer. The contamination of garri mostly begins during post processing and includes loss of microbial stability and spoilage during storage, distribution and marketing. In Nigeria, the practices associated with production, processing and post process handling of garri in local markets such as spreading on the floor, display of product in open buckets, hessian bags, bowls and mats at points of sales and the use of bare hands during handling and sales may exacerbate microbial contamination due to deposition of bioaerosols on exposed products, transfer of microbes from dirty hands and utensils and frequent visits by animals and fomites (Ogiehor  and Ikeneboneh, 2005). Previous reports have revealed high bioload and a vast array of microorganisms in market samples of garri. The main agents that contaminate and spoil garri are moulds, insects and mites (Igbeka, 2004). Various groups of moulds such as Aspergillu, periculium fusarium, cladosporium and mucor have been reported to be associated with garri during storage and distribution (Adeniyi, 2004; Oyeniran 2007; Ekundayo, 2009). The presence of these organisms results in change in the nutritive, organoleptic and microbiological quality which could lead to spoilage and in turn could lead to economic losses, serious food borne illness and may pose a threat to public health. Moreover, the source of these microbial contamination may also be a portal for contamination by more potent pathogenic microbes which may cause an epidemic considering the popularity of the food product (Steinkraus, 2005). Thus, there is need for increasing attention to be paid to microbiological quality control of garri processing establishment throughout the production areas and a regular appraisal of the techniques used is necessary.

According to Mill (2006) the relative humidity (RH) of the air within and around any commodity is the controlling factor of its biological determination. Seventy percent (70%) RH is regarded as a “safe” limit and commodities with moisture contents in equilibrium with relative humidity of 70% are relatively safe from microbial deterioration.

An occasional check is necessary on the moisture content if stored in atmosphere with fluctuating relative humidity. It is also possible for farm produce stored in bags and placed on the floor directly to absorb moisture through the floor (Best 2002). A high moisture level in garri can be influenced by the cassava cultivar. This gives garri a dull appearance and poor keeping quality (Ekundaayo (1999); Oyeniran (2003) and Akano et al., (2005) have reported Asperigillus chevelleri, Asperigillus glacia, Aperigillus flavus, Asperigillus niger, Mucor pusillus and Fusarium moniliforme  in garri stored for three months in jute bags.