CHAPTER ONE
1.0 Introduction
The deliberate fermentation of foods by man predates written history and is possibly the oldest method of preserving perishable foods. Evidence suggests that fermented foods were consumed 7,000 years ago in Babylon (Battcock and Aza-Ali, 1998). Scientist speculates that our ancestors possibly discovered fermentation by accident and continued to use the process out of preference or necessity. Preserving by fermentation not only made foods available for future use, but more digestible and flavorful. The nutritional value produced by fermenting is another benefit of fermenting.
Fermented foods are generally produced using plant or animal ingredients in combination with fungi or bacteria which are either sourced from the environment, or carefully kept in cultures maintained by humans. Just as living organisms cover the surface of the earth, fermentation microbes cover the surface of the organisms. Wild yeasts are found living on grapes, and bacteria line the human digestive tract (Chamberlain et al. 1997).
Fermented foods, whether from plant or animal origin, are an intricate part of the diet of people in all parts of the world. Fermented food plays a very important role in the socio- economics of developing countries. Each nation has its own types of fermented food, representing the staple diet and the raw ingredients available in that particular place. It makes major contributions to the protein requirements of the rural population. The preparation of many indigenous or “traditional” fermented foods and beverages remains a household art today (Chamberlain et al. 1997).
1.1 Purpose and benefits of food fermentation
The primary benefit of fermentation is the conversion of sugars and other carbohydrates to usable end products. According to Steinkraus (1995), the traditional fermentation of foods serves several functions, which includes: enhancement of diet through development of flavor, aroma, and texture in food substrates, preservation and shelf-life extension through lactic acid, alcohol, acetic acid and alkaline fermentation, enhancement of food quality with protein, essential amino acids, essential fatty acids and vitamins, improving digestibility and nutrient availability, detoxification of anti-nutrient through food fermentation processes, and a decrease in cooking time and fuel requirement.
1.2 Nutritional benefits
Fermentation can produce important nutrients or eliminate anti- nutrients. Food can be preserved by fermentation, since fermentation uses up food energy and creates conditions unsuitable for spoilage microorganisms. For instance, in pickling, the acid produced by the dominant organism inhibits the growth of all other microorganisms. Fermenting makes foods more edible by changing chemical compounds, or predigesting, the foods for us. There are extreme examples of poisonous plants like cassava that are converted to edible products by fermenting. Some coffee beans are hulled by a wet fermenting process, as opposed to a dry process (Battcock and Aza-Ali, 1998).
Reduction in anti-nutritional and toxic components in plant foods by fermentation was observed in a research which showed " Cereals, legumes, and tubers that are used for the production of fermented foods may contain significant amounts of antinutritional or toxic components such as phytates, tannins, cyanogenic glycosides, oxalates, saponins, lectins, and inhibitors of enzymes such as alpha-amylase, trypsin, and chymotrypsin.
These substances reduce the nutritional value of foods by interfering with the mineral bioavailability and digestibility of proteins and carbohydrates. In natural or pure mixed-culture fermentations of plant foods by yeasts, molds, and bacteria, antinutritional components (e.g. phytate in whole wheat breads) can be reduced by up to 50%; toxic components, such as lectins in Tempe and other fermented foods made from beans, can be reduced up to 95% (Larsson and Sandberg, 1991).
Fermentation increases nutritional values of foods, and allows us to live healthier lives. Here are a few examples:
1. The sprouting of grains, seeds, and nuts, multiplies the amino acid, vitamin, and mineral content and antioxidant qualities of the starting product (Wigmore, 1986).
2. Fermented beans are easier for the bodies to digest, like the proteins found in soy beans that are nearly indigestible until fermented (Katz, 2003).
3. Fermented dairy products, like, cheese, yogurt, and kifir, can be consumed by those not able to digest the raw milk, and aid the digestion and well-being for those with lactose intolerance and autism.
4. Porridge made from grains allowed to ferment increases the nutritional values so much that it reduces the risk of disease in children (Battcock and Aza-Ali, 1998).
5. Probotic supplements (beneficial bacterial cultures for microbial balance in the body) are capable of fighting cancer and other diseases.
6. Vinegar is used to leach out certain flavors and compounds from plant materials to make healthy and tasty additions to the meals.
1.3 Health benefits
Fermented food, enjoyed across the globe, conveys health benefits through lactic acid fermentation. The fermentation process can transform the flavor of food from the plain and mundane to a mouth-puckering sourness enlivened by colonies of beneficial bacteria and enhanced micronutrients.
1. Studies have revealed that Lactobacillus rhamnosus and Lactobacillus reuteri which are common organisms in Nigerian fermented foods like ogi and kunun- zaki could colonize the vagina, kill viruses, and reduce the risk of infections, including bacterial vaginosis (Reid et al., 2001a; Cadieux et al., 2002). The potential therapeutic effects of Lactic Acid Bacteria (LAB) and ogi, including their immunostimulatory effect, are due primarily to changes in the gastrointestinal (GI) microflora to suppress the growth of pathogens. Increase in population of Lactic acid bacteria in the intestinal or vagina reduces the cause of bacterial vaginosis, which is a major risk factor for the contraction of HIV (Reid, 2002a). It also reduces the occurrence of gonorrhoea, chlamydia, and other sexually transmitted diseases (Reid et al., 2001b) and diarrhoea (Adebolu et al., 2007).
2. All lactic acid producing bacteria (e.g. Lactobacillus acidophilus, Lactobacillus bulgaricus, Lactobacillus plantarum, Lactobacillus caret, Lactobacillus pentoaceticus, Lactobacillus brevis and Lactobacillus themophilus) produces high acidity during fermentation. The lactic acid they produce is effective in inhibiting the growth of other bacteria that may decompose or spoil the food. Despite their complexity, the whole basis of lactic acid fermentation centers on the ability of lactic acid bacteria to produce acid, which then inhibits the growth of other non-desirable organisms. Other compounds are important as they improve particular testes and aromas to the final products. The Lactobacillus mesenteroides initiates growth in vegetables more rapidly over a range of temperatures and salt concentrations than any other lactic acid bacteria. It produces carbon dioxide and acids which rapidly lower the pH and inhibit the development of undesirable microorganism.
3. Over 200 species of bacteria live in gut of humans. These microbes help break down food in the intestines, aid in the digestion process, help fight off disease, and boost the immune system. A good balance of intestinal flora is very important to the overall health. If we eat nothing but overly processed and hard to digest foods, then the fermentation process occurs within the GIT resulting into gas, bloating, diarrhea, and constipation might possibly lead to other diseases like cancer. However, providing the body with predigested foods such as fermented foods will help the existing microbes within to do the job they need to do.
4. Fermentation is not only a way to preserve certain foods, in some cases it actually adds to the nutrient value of it. Fermented vegetables contain more vitamin C and fermented milk products have ample amounts of B vitamins. The bioavailability of these vitamins also increases with fermentation. Probiotics, or "good bacteria" are also formed through the process of fermentation. Fermented soy products contain more vitamin B12 (Chung et al, 2010)
5. The desirable bacteria cause less deterioration of the food by inhibiting the growth of the spoiling types of bacteria. Some fermenting processes lower the pH of foods preventing harmful microorganisms to live with too acidic an environment. Controlled fermentation processes encourage the growth of good bacteria which starves, or fights off, the bad microbes.
6. The fermentation process can be stopped by other means of preserving, such as, canning (heating), drying, or freezing. Heat (pasteurization, 63°C), and low temperatures (freezing, 0°C or below) stops the fermenting process by slowing, or killing, the preferred microorganisms, and other bacteria. A few undesirable bacteria are not killed by either means, and continue to grow. When the beneficial bacteria are gone, the unfavorable bacteria take over, growing exponentially! This causes rotting, disease, illness, and inedible foods. When the good guys are present and happy, the food remains edible.
7. Phytates (phytic acid) are the storage form of phosphorus [a mineral] bound to inositol [a B vitamin] in foods high in fiber (all plant foods), and particularly the fiber of raw whole grains, legumes, seeds, and nuts. Although these foods have high phosphorus content, the phosphates in phytates are not released by human digestion. Phytates, particularly in such raw foods as bran, are a concern because they can bind a portion of the iron, zinc, and calcium in foods, making the minerals unavailable for absorption. When bread is leavened (fermented) by yeast, enzymes degrade phytic acid, and phytates pose no problem. Enzymes, called phytases, destroy phytates during fermentation processes such as: the yeast-raising of dough, Even a small amount of phytates in food can reduce iron absorption by half (by 50%), but the effect is less marked if a meal is supplemented with ascorbic acid (Vitamin C) which also helps the absorption of zinc and calcium.
8. Fermented food, enjoyed across the globe, conveys health benefits through lactic acid fermentation. The fermentation process can transform the flavor of food from the plain and mundane to a mouth-puckering sourness enlivened by colonies of beneficial bacteria and enhanced micronutrients. While fermented food like yogurt, sauerkraut and kefir are well-known many other lesser-known foods also benefit from the lactic acid fermentation process. Indeed, virtually every food with a complex or simple sugar content can be successfully fermented.
9. Born of both necessity and practicality, lactic acid fermentation proved to be not only an efficient method of preserving food for our ancestors, but also a critical one. Indeed, fermented food like sauerkraut, cheese, wine, kvass, soured grain porridge and breads often sustained tribes and villages during harsh winters when fresh food simply wasn’t available let alone plentiful.
10. In many societies including our own where yogurt has been heralded as a health food since the 19th century, fermented food has gained a reputation for its beneficial effects on immunity, intestinal health and general well-being. Modern researchers are just beginning to understand what the sages of old were tuned in to: fermented food conveys clear and calculable health benefits to the human diet. Lactic acid fermentation in and of itself enhances the micronutrient profile of several foods.
1.4 Detoxification
Detoxification of anti-nutrients through food fermentation processes. The renewal of anti- nutrient from the Nigerian fermented food is an important step in ensuring that the fermented food is safe to eat. Many fermentation foods contain naturally accruing toxins and anti-nutritional compounds. These can be removed or detoxified by the action of micro- organism during fermentation for instance, the fermentation process that produces the Sudanese product, kawal, removes the toxins from the leaves of Cassia obtusitfolia and fermentation is an important step in insuring that the fermentation foods are safe to eat.
Removing cyanide by fermentation: Cassava contains naturally occurring chemicals, cyanogenic glycoside. When eaten raw or improperly processed, this substances releases cyanide into the body, which can be fatal, correct processing removers this chemicals. The cassava is first peeled (as about 60-70% of the poison is in the peel) and then soaked in stagnant water or fermented in sacks for about three days. It is sometimes grated or rasped as this helps to speed up the fermentation process. At the beginning of the fermentation, Geotricum candidia acts on the cassava. This helps to make the product acidic, which finally kills off the microorganisms as they cannot exist in such a medium. A second strain of microorganisms (Corynebacterium lactis) which can tolerate the acidic environment then take over and by the third day 90-95% of the dangerous chemicals would have been hydrolyzed. The cassava also develops its characteristic flavour. The product is then sieved and the fine starch particles are fried in an iron pan over aflame or with some oil. During this process most, if not all the remaining toxins are given off. The liquor from a previous fermentation is used as a starter, thereby reducing the period of fermentation to about 6-8hours.
1.5 Some Nigeria fermented foods
1.5.1 Fermented tubers
Nigeria is one of the leading producers of cassava in the world with an annual production of 35-40 million metric tons. Over 40 varieties of cassava are grown in Nigeria and cassava is the most important dietary staple in the country accounting for over 209 of all food crops consumed in Nigeria. Cassava tubers are rich in starch [20-30%] and with possible exception of sugar cane; cassava is considered the highest producer of carbohydrates among crop plants. Despite its vast potentials, the presence of the two gynogenic glycosides, lineman calculating for 93% of total content and lotaustralin or methyl linamarin, hydrolysis by the enzymes linamarase to release toxic HCN, is the most important problem limiting cassava utilization. Generally cassava contains 10-500 mg HCN/KG of root depending on the variety, although much higher levels, exceeding 1000 mg HCN/kg, may be present in unusual cases. Cassava varieties are frequently described as sweet or bitter. Sweet cassava varieties are low in cyanogen with most of the cyanogen present in the peels. Bitter cassava varieties are high in cyanogen that tend to be evenly distributed throughout the roots. Environmental (soil, moisture, temperature) and other factors also influence the cyanide content of cassava. Low rainfall or drought increase cyanide level in cassava tools due to water stress on plant. Apart from acute toxicity that may result in death, consumption of sub-lethal dose of cyanide from cassava production over a long period of time results in chronic cyanide toxicity. That increases the prevalence of goiter and cretinism in iodine deficient area. Symptoms of cyanide poisoning from consumption of cassava with high level of cyanogen include vomiting, stomach pains, dizziness, headache, weakness and charkha. Chronic cyanide toxicity is also associated with several pathological conditions including konzo, an irresistible paralysis of the legs reported in eastern, central and southern Africa. And tropical ataxic neuropathy, reported in west Africa, characterized by lesion of the skin, mucous membranes, optics and auditory nerves, spinal cord and peripheral nerves and other symptoms. Without the benefits of modem science, a process for detoxifying cassava roots by canvassing potentially toxic roots into garri and fufu was developed, presumably empirically in West Africa.
1.5.2 Fermented cereals
Cereals which include maize (Zea mays), Sorghum (Sorghum bicolor), millet (Peninselum americarum) and acha etc. are used in the production of gruels which is used as complementary food for babies and serves as breakfast for adults.
Maize, millet, rice and sorghum cereals provide mainly carbohydrates and low quality protein. The generation and fermentation of cereals enhance the availability of elemental iron, the deficiency of which is responsible for the high incidence of anemia in tropical countries. It is estimated that about 50% of perishable food commodities including fruits, vegetables, roots and tubers and about 30% of food commodities including maize, sorghum millet, rice and cowpeas are lost after harvest in Nigeria. Nigerian in fact experience a slower growth rate and weight gain during the weaning period than during breastfeeding, due primarily to the poor nutritional qualities of traditional Nigerian complementary food such as “Ogi” which are mainly produced from cereal fermentation. Apart from their poor nutritional qualities, traditional Nigerian cereal based gruels used as complementary foods have high paste viscosity and require considerable dilution before feeding; a factor that further reduces energy and nutrient density.
Although nutritious and safe complementary foods produced by food multinationals are available in Nigeria, they are far, too expensive for most families. The economic situation in these country necessitate the adoption of simple, inexpressive processing techniques that result in quality improvement and that can be carried out at household and community levels for the production of nutritious, safe and affordable complementary foods which is the leading cause of protein-energy malnutrition in infants and preschool children in Nigeria.
1.5.3 Fruits and vegetables
a. Ogiri
This is a condiments gotten from the fermentation of castor oil seeds. The raw castor oil seed are boiled for two hours until the seed changes colour to brown. The seeds are dehaulled, rinsed in clean water. The boiled seeds are boiled again for one more hour. It is then cooled and wrapped with enough banana leaves, which is then packed in a clean container with cover to ferment at room temperature.
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