BRIEF REVIEW ON IMPROVEMENT TECHNIQUES OF LOCALLY FERMENTED FOODS

ABSTRACT

Fermented foodstuffs and condiments are very popular in Nigeria. In many cases, fermentation is responsible for the development of taste or aroma, improved digestibility, improvement of nutritional composition, stabilization of the original raw materials and detoxification of anti-nutrient factors in these products. Traditional fermented condiments (dawadawa, iru, ogiri) based on vegetable proteins, and consumed by different ethnic groups in Nigeria have been the pride of culinary traditions for centuries. It is evident that these products have played a major role in the food habits of communities in the rural regions serving not only as a nutritious non-meat proteins substitute but also as condiments and flavouring agents in soups. These condiments are being increasingly marketed throughout the country and beyond in informal ways. Differences in the chemical composition of fermented condiments are evident mainly because different ingredients have been used in their preparation. Traditional methods of manufacture should take advantage of biotechnological progress to assure reasonable quality and at the same time assure safety of these products. The requirements for a sustainable biotechnological development of Nigerian condiments are discussed in the scope of the microbiology and biochemical changes of the raw materials. Schemes to standardize the manufacturing stages are proposed. Emphasis is placed on the relevance of the role of starter cultures in the traditional methods of manufacture to ascertain appropriate nutritional quality and physical properties of the final product. Fermented vegetable proteins have potential food uses as protein supplements and as functional ingredients in fabricated foods. Relevant research and development activities are suggested. Moreover, it is essential to increase the knowledge and understanding of the methods of preparation, in order to improve the efficiency of fermentation, especially the traditional processes as the yields of traditional fermentation processes are often low and sometimes the products are unsafe. This Work discusses potential areas for improvement of indigenous fermented fruit and vegetable products.

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CHAPTER ONE

1.0 INTRODUCTION

Traditional diets in West Africa often lack variety and consist of large quantities of the staple food

(cassava, yam, maize) with supplements of plantain, cocoyam, rice, and beans depending on

availability and season (Achi, 1999). Soups eaten with the staples are an essential component of the

diet and may contain a variety of seeds, nuts, pulses, and leaves (Campbell-Platt, 1980).

The staple foods provide the calories but are poor in other nutrients. Soups are the main sources of

proteins and minerals and one of the ways to improve the diet have been to improve the nutrient

content of soups.

Seeds of legumes may account for up to 80% of dietary protein and may be the only source of protein

for some groups. Their cooked forms are eaten as meals and are commonly used in fermented form as

condiments to enhance the flavors of foods (Odunfa, 1985c; Aidoo, 1986; Achi, 1991; Oniofiok, 1996).

With high contents of protein, legume condiments can serve as a tasty complement to sauces and soups

and can substitute for fish or meat.

The food flavouring condiments are prepared by traditional methods of uncontrolled solid substrate

fermentation resulting in extensive hydrolysis of the protein and carbohydrate components (Fetuga et

al., 1973; Eka, 1980). Apart from increasing the shelf life, and a reduction in the anti-nutritional factors

(Odunfa, 1985b; Reddy and Pierson, 1999; Barimalaa et al., 1989; Achiand Okereka, 1999),

fermentation markedly improves the digestibility, nutritive value, and flavors of the raw seeds.

Although fermented food condiments have constituted a significant proportion of the diet of many

people, Nigerians have exhibited an ambivalent attitude in terms of consumer tastes and preferences for

such foods (Achi, 2005). The introduction of foreign high technology products especially processed

ones because of globalization and liberalization of the economy radically changed the Nigerian food

culture into a mixed grill of both foreign and local dishes (Ojo, 1991).

Many developing countries are still preparing traditional fermented products for human consumption

(Campbell Platt, 1987). Fermented products remain of interest since they do not require refrigeration

during distribution and storage. The traditional condiments have not attained commercial status due to

the very short shelf life, objectionable packaging materials, stickiness and the characteristic putrid

odour (Arogba et al., 1995). Fermented condiments often have a stigma attached to them; they are

often considered as food for the poor. The production of fermented vegetable proteins for use as food

condiments is craft-based. Remarkably, in many areas of Nigeria today they are still made in traditional

ways, with success depending upon observance of good manufacturing practices and control of

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environmental conditions during the manufacturing phase. Starter cultures are not normally used and

therefore variations in the quality and stability of the products are often observed.

As with any other fermentation process the\ understanding of the microbial ecology of vegetable

fermentations requires the knowledge of the fermentation substrates, i.e. the seeds of the various plants

as well as the products obtained thereof. Information on the manufacturing and microbiology of

indigenous fermented legumes has been reported (Odunfa, 1981a, 1983a; 1985a, 1985c; Odunfa and

Adewuyi, 1988a,b; Achi, 1992; Sanni, 1993; Sanni and Ogbonna, 1998). The use of these condiments,

it is suggested, could be extended as a food ingredient included into most fabricated foods in order to

further increase their versatility and utility (Giami and Bekebain, 1992; Achi, 1999). Fermented fluted

pumpkin flour has been incorporated into weaning food formulations (Achinewhu, 1987; Banigo and

Akpapunam, 1987).

Apart from dawadawa prepared from the African locust bean, by far the bulk of the indigenous

fermented condiments of Nigeria are to be found in the southern states of Nigeria. The north is very

poor in food fermentations, which are practically confined to the staple sorghum porridges and to

soured milks (Dirar, 1993). However, inter state trade and relocation has widened the scope of the

spread of food condiments throughout the country and beyond (Iwuoha and Eke, 1996).

Excellent reviews of traditional fermented foods have been published by Odunfa (1985c), and Iwuoha

and Eke (1996). Against the background of the significance and benefits of traditional fermented

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condiments, the object of this review was to evaluate the current state of knowledge of fermented food

condiments dealing with aspects of manufacture, biochemical changes, and nutritional properties. Use

of other raw materials other than the traditional legumes for condiment-making will be included.

Traditional diets in West Africa often lack variety and consist of large quantities of the staple food

(cassava, yam, maize) with supplements of plantain, cocoyam, rice,and beans depending on availability

and season (Achi, 1999). Soups eaten with the staples are an essential component of the diet and may

contain a variety of

seeds, nuts, pulses, and leaves (Campbell-Platt, 1980).

The staple foods provide the calories but are poor in other nutrients. Soups are the main sources

of proteins and minerals and one of the ways to improve the diet have been to improve the nutrient

content of soups. Seeds of legumes may account for up to 80% of dietary protein and may be the only

source of protein for some groups. Their cooked forms are eaten as meals and are commonly used in

fermented form as condiments to enhance the flavors of foods (Odunfa, 1985c; Aidoo, 1986; Achi,

1991; Oniofiok, 1996). With high contents of protein, legume condiments can serve as a tasty

complement to sauces and soups and can substitute for fish or meat. The food flavouring condiments

are prepared by traditional methods of uncontrolled solid substrate fermentation resulting in extensive

hydrolysis of the protein and carbohydrate components (Fetuga et al., 1973; Eka, 1980). Apart from

increasing the shelf life, and a reduction in the anti-nutritional factors (Odunfa, 1985b; Reddy and

Pierson, 1999; Barimalaa et al., 1989; Achi and Okereka, 1999), fermentation markedly improves the

digestibility, nutritive value, and flavors of the raw seeds.

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CHAPTER TWO

2.0 A BRIEF REVIEW OF POSSIBLE IMPROVEMENT TECHNOLOGY IN TRADITIONAL FERMENTATION PROCESS

Fermentation is one of the oldest forms of food preservation technology in the world. Indigenous fermented foods such as bread, cheese and wine, have been prepared and consumed for thousands of years and are strongly linked to culture and tradition, especially in rural households and village communities. Fermented foods are popular throughout the world and in some regions make a significant contribution to the diet of millions of individuals. For instance Soy sauce is consumed throughout the world and is a fundamental ingredient in diets from Indonesia to Japan. Over one billion litres of soy sauce are produced each year in Japan alone. In Africa fermented cassava products (like gari and fufu) are a major component of the diet of more than 800 million people and in some areas these products constitute over 50% of the diet. Fermentation is a relatively efficient, low energy preservation process, which increases the shelf life and decreases the need for refrigeration or other forms of food preservation technology. It is therefore a highly appropriate technique for use in developing countries and remote areas where access to sophisticated equipment is limited. There is tremendous scope and potential for the use of micro-organisms towards meeting the growing world demand for food, through efficient utilisation of available natural food and feed stocks and the transformation of waste materials.

There is a danger that the introduction of 'western foods' with their glamorous image will displace these traditional fermented foods. Although fermentation of foods has been in use for thousands of years for the preservation and improvement of a range of foods, the microbial and enzymatic processes responsible for the transformations were, and still are, largely unknown. Because of the tremendously important role indigenous fermented fruits and vegetables play in food preservation and their potential to contribute to the growing food needs of the world, it is essential that the knowledge of their production is not lost. Moreover, it is essential to increase the knowledge and understanding of the methods of preparation, in order to improve the efficiency of fermentation, especially the traditional processes as the yields of traditional fermentation processes are often low and sometimes the products are unsafe. This Work discusses potential areas for improvement of indigenous fermented fruit and vegetable products. It can be divided into four main areas:

Improve the understanding of the fermented products

Refine the processes

Disseminate the improvements

Create a supportive policy environment.

2.1 Improving the understanding of fermented products

For fermented products such as cheese, bread, beer and wine, which are produced on a commercial scale, a good understanding of the microbial processes has been developed. However with many of the fermented products in Africa, Asia and Latin America, knowledge of the processes involved is poor. It is likely that the basic principles apply across the board, but production conditions vary enormously from region to region, giving rise to numerous variations of the basic fermented product. It is not the intention or the desire to standardise the process and thereby lose this huge diversity, rather it is to harness the tremendous potential these methods have to contribute to increasing not only the quantity, but quality of food available to the worlds population.

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There are two main reasons for gaining a better understanding of indigenous fermented products:

Documenting the traditional knowledge to ensure that the huge diversity is not lost

Developing a scientific understanding of the microbial processes, with a view to improving the efficiency of the process

2.1.1 Documenting the traditional knowledge

Fermentation is one of the oldest food processing technologies in the world. The knowledge of how to make these products has often been passed down from parent to child (usually mother to daughter) and belongs to that undervalued body of "indigenous knowledge". Most of this knowledge has not been documented and is in danger of being lost as technologies evolve and families move away from traditional food preservation practices.

The collection and preservation of indigenous knowledge is of interest to governments, historians, anthropologists and scientists, to name but a few. Several individuals and organisations are actively involved in research in this area:

Several research institutes and scientists in Africa, Asia and Latin America are recording information on traditional fermented foods. Dr Karki in Nepal and Hamid Dirar have been extensively quoted in this book and their work on fermented products in Nepal and Sudan is of great importance.

Intermediate Technology has been collecting information about traditional food products from Africa, Asia and Latin America. The first volume of products was published in 1997 (Fellows, 1997). This included the following fermented food products: kenkey, ogi, injera, fermented sweet bread, sorghum beer, palm wine, banana beer, pineapple peel vinegar, lime pickle, tamarind pickle, mango pickle, gari, vegetable pickle, coconut toddy, yoghurt, ayib and dawdawa. Volume 2 will be published in 1999 and regional publications on the traditional food products of Bangladesh, Southern Africa and the Andes are planned.

The European Union has just completed an audit of the traditional food products of Europe. The results have been published in a series of publications (Cowan, 1998).

The Special Programme on Biotechnology and Development Cooperation for the Netherlands Government was established in 1992 to improve the access of developing countries to biotechnological expertise and innovation with a focus on using biotechnology for the benefit of small-scale farmers and producers. Part of the programme involved a competition to identify farmers' existing biotechnology practises. This programme resulted in the collection of valuable information about traditional fermented food products (Bunders et al, 1996).

Finally, the Food and Agriculture Organisation of the United Nations sees the value in collecting and preserving this source of knowledge. This book is an example of their work.

2.1.2 Developing a scientific understanding of the microbial processes

Most traditional fermented products are made by natural fermentations carried out in a non-sterile environment. The specific environmental conditions cause a gradual selection of micro-organisms responsible for the desired final product. This is appropriate for small-scale production for home consumption. However the method is difficult to control and there are risks of accompanying micro-flora causing spoilage and unsafe products.

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If the processes are to be refined, with a view to production on a larger scale, it is essential to have a scientific understanding of the fermentation processes. This can be developed by:

The isolation and characterisation of the essential micro-organisms involved;

The determination of the role of external factors in fermentations and the effects of these on the metabolism of micro-organisms

The investigation of the effects of pre-treatments of raw materials on the fermentation process

The identification of the options for further processing and how these affect the taste and texture of the product.

This research is capital intensive and usually requires scarce foreign exchange. It requires the use of sophisticated equipment and reagents backed with a consistent energy and water supply which are not always available in developing countries. To meet the current and future challenges in developing countries, it is important that these countries develop the capabilities to benefit from improvements in fermentation methodologies.

Biotechnologies need to be developed which are affordable by the poor, since it is they who are likely to benefit most by improvements to the traditional processes.

2.2 Refining the process

The art of traditional processes needs to be refined to incorporate objective methods of process control and to standardise quality of the final product without losing their desirable attributes such as improved keeping quality, taste and nutritional qualities.

Science based fermentation research has often focused mainly on improving the metabolic properties of the micro-organisms used as a starter culture, using the techniques of selection, mutation and genetic modification. To achieve this a full understanding of the fermentation process is needed. The properties of the starter culture must be known and culture conditions must be controllable. This means that science based fermentation research currently has little to offer traditional food processing (Broerse and Visser, 1996).

2.2.1 Process control

Once the details of the fermentation process and the microbes involved are known and understood, it is possible to begin to refine and improve the process. The commercially produced products, such as bread, wine, soy sauce and pickles are all examples of processes which have been studied and optimised. Recently traditional fermented products in Africa have been industrialised. In Nigeria, Dadwa (a fermented legume product) is now made by Cadburys and in Zimbabwe, traditional fermented milk is made industrially and sold as "Lacto" (Okafor, 1992).

The areas where the efficiency and yield of food fermentation processes can be increased are:

The selection or development of more productive microbial strains

The control and manipulation of culture conditions

The improvement of product purification and concentration.

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Techniques to control the fermentation processes could include the development of pure starter cultures. Developing these by laboratory selection or genetic engineering is not viable. A more feasible approach would be to exploit the ecological principle of inoculum enrichment by natural selection. Another approach to stabilise fermentation under nonsterile conditions is the use of multi-strain dehydrated starters which can be stored at ambient temperature. These are already used for the manufacture of tempeh (Nout, 1992).

2.2.2 Quality control

The aim of quality control is to ensure that every batch of food produced has a satisfactory and uniform quality. This does not necessarily mean that it is the highest quality possible but that it reaches the standard the customers are willing to pay for (Fellows, 1996) .

Inadequate quality control can have an adverse effect on local demand for the product. This is particularly a problem for small-scale traditional production. In modern industrial applications, the fermentation equipment and processes are controlled using expensive technology, resulting in a consistent product of a known quality. Traditional practises take place in a less predictable environment. This can result in mistakes including sour beer and mouldy pickles.

It is often felt that traditional products made at the small scale are unhygienic and unsafe. This is sometimes true. However the case is often overstated. Many fermented foods are inherently safe due to low moisture contents or high acidity. Lime pickle from India and Gundruk from Nepal are good examples. Several of the steps in traditional processing are designed to reduce contamination. These include boiling, adding salt and sun drying.

Quality control procedures are essential for the production of safe products and contribute to the success of small food processing businesses. Appropriate quality control procedures need to be developed and implemented. These procedures need to be developed with the processors who must understand and apply them. The quality of food is highly subjective. What is acceptable to one customer is not acceptable to another. It is important to carry out participative research to identify ways to improve the quality control procedures for fermented food products.

The sort of areas that should be investigated include:

Selecting good quality raw materials

Processing under correct conditions

Ensuring high standards of personal hygiene by the food processors

Ensuring the processing area is sufficiently clean

Using correct packaging

2.3 Disseminating improvements

Documentation of the traditional methods of food fermentation and research to identify improved methods of production are meaningless if the results are not disseminated to those who are likely to put them into practice.

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There is a danger of mystifying the fermentation process by enrobing it in scientific theory. What was once a simple process carried out by any family member, in the confines of the household, using locally available equipment and materials, could become a process to be feared. It is important to be realistic and to ensure that the improvements recommended are ones which can easily be put into practice. The aim is not to deter the production of fermented foods at the small scale, but to encourage their production and consumption on a larger scale.

Fermented foods often have a stigma attached to them – they are considered as poor mans food. As soon as a family can afford to buy processed foods, they move away from carrying out home fermentation. This is a pity, because as we have seen earlier, fermented food products have many nutritional advantages which surpass western-style fast foods and processed foods. Where cultural values attached to the fermented food are strong, it is unlikely that there will be an image problem. For example, kimchi is considered part of the national heritage in Korea. It is a vital ingredient of all meals and as such is a highly valued food. This is reflected in the amount of research carried out on the product and the detailed understanding of the process, which already exists.

It is not difficult to gain access to village people, both to collect the traditional information and to disseminate improved practices. Numerous organisations are involved in field projects. They can be used to organise training sessions and group meetings for the dissemination of new methods, for example, for the use of pure starter cultures.

One of the problems likely to be encountered is gaining access to starter cultures and other improved methods. Agricultural extension services should take a responsibility for the promotion and the supply of starter cultures at a price which is affordable.

2.4 Creating a supportive environment for production of fermented food products

Developing countries need to build their resources of trained, knowledgeable individuals, who are able to apply the basic microbiological principles to the production of fermented foods. Extra support should be made available to train professionals in this discipline.

Fermented foods should be recognised as part of each countries heritage and culture and efforts made to preserve the methods of production. A recognised body (government or non-government) should take the responsibility for the collection of details and the promotion of fermented food products. Consumers need to be made aware of the numerous benefits of fermented foods and their prejudices against fermented foods, especially those traditionally produced at the home scale, dispelled.

Many traditional fermented foods are produced from minor or wild fruits and vegetables, many of which are being lost through deforestation and loss of biodiversity.

For the purpose of this literally research review, traditional fermentation of vegetable protein condiments are considered.

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CHAPTER THREE

3.0 Traditional Fermented Protein Condiments in Nigeria

Traditional fermented condiments (dawadawa, iru, ogiri) based on vegetable proteins, and consumed

by different ethnic groups in Nigeria have been the pride of culinary traditions for centuries. It is

evident that these products have played a major role in the food habits of communities in the rural

regions serving not only as a nutritious non-meat proteins substitute but also as condiments and

flavouring agents in soups. These condiments are being increasingly marketed throughout the country

and beyond in informal ways. Differences in the chemical composition of fermented condiments are

evident mainly because different ingredients have been used in their preparation. Traditional methods

of manufacture should take advantage of biotechnological progress to assure reasonable quality and at

the same time assure safety of these products. The requirements for a sustainable biotechnological

development of Nigerian condiments are discussed in the scope of the microbiology and biochemical

changes of the raw materials. Schemes to standardize the manufacturing stages are proposed.

Emphasis is placed on the relevance of the role of starter cultures in the traditional methods of

manufacture to ascertain appropriate nutritional quality and physical properties of the final product.

Fermented vegetable proteins have potential food uses as protein supplements and as functional

ingredients in fabricated foods. Relevant research and development activities are suggested.

Key words: Traditional condiment fermentation, dawadawa, iru, ogiri, manufacturing process, starter

cultures.

3.1 Names and Substrates of Fermented Condiments

Throughout Nigeria, many names are applied to the multitude of fermented food condiments. Table 1 shows the variety of names by which the products are known in different parts of the country. The exact origin of such names could be attributed to (a) the region or area of manufacture (b) the type of legume or oil seed used and (c) the spelling according to region or area. The Yorubas of the southwestern Nigeria locally call fermented condiments ‘iru’ while the Hausas who inhabit most of the northern part of Nigeria call it dawadawa. Ogiri’ is the name used by the Ibos of the southeastern Nigeria. Owoh on the other hand, is the popular name among the Urhobos and Itsekiris in the Niger Delta region for foodcondiments. Similarly, okpiye is popular among the Igala and Idoma people of the Middle Belt region.

The conventional substrates for condiment production are diverse and each can be produced from more than one raw material. Almost any edible plant material can be subjected to fermentation. Judging by the available literature, over nine different fermented products are condiments. A list of these substrates is given in Table 1. For instance, dawadawa or iru is traditionally prepared from African locust bean (Parkia biglobosa) (Campbell- Platt, 1980; Odunfa, 1981a; Antai and Ibrahim, 1986), soybean (Glycine max) (Popoola and Akueshi, 1984; Ogbadu and Okagbue, 1988) and bambara groundnut (Vigna subterranea)(Barimalaa et al., 1994).

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Ogiri is traditionally prepared by fermenting melon seeds (Citrullus vulgaris) (Odunfa, 1981b; Ogundana, 1980), fluted pumpkin (Telferia occidentale) (Odibo and Umeh, 1989) or castor oil seed (Ricinus communis) (Anosike and Egwuatu, 1981; Odunfa 1985b; Barber et al., 1988).Owoh is processed from fermented seeds of the cotton plant (Gossypium hirsutum) (Sanni and Ogbonna, 1991; Sanni and Ogbonna, 1992) and African yam bean (Sphenostylis stenocarpa) (Sanni et al., 2001), while Okpiye is prepared from the seeds of Prosopis africana (Achi, 1992: Odibo et al., 1992; Sanni, 1993). Quite often seeds that are used for fermentation are inedible in their raw unfermented or cooked state.

3.2 Basics of Manufacturing Processes

The methods employed in the manufacture of fermented condiments differ from one region to another because these processes are based on traditional systems, some of which are summarized in Table 2. A basic scheme of vegetable fermentation for production of condiments is depicted in Figure 1. According to local custom, climate conditions and the type of substrates used, specific process variations occur. In general, fermentation takes place under conditions which the producers have found to be favorable for the appropriate growth and activity of the microorganisms.

Traditionally, raw beans are cooked for upward of 12 hours in excess water until they are very soft to allow for hand de-hulling. The length of time of cooking depends on the strength of the testa and on the de-hulling efficiency of the seeds. Parkia biglobosa can be cooked for 8-12 h (Oyewole and Odunfa, 1990), though Prosopis africana can be cooked for 5-6 h (Achi, 1992). Boiling in 0.1 M Na2CO3 reduces the cooking time to 4 h and increases the de-hulling efficiency to 89% (Achi and Okereka, 1999). While Telferia seeds require minor cooking for 30 to 60 min, Citrullus vulgaris and castor seeds are deshelled before cooking.

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At present, most de-hulling processes rely on the tedious method of hand separation. Abrasive de-hulling of dry beans of Parkia or Prosopis is not possible because of the strong adherence of hulls to the seed. Nevertheless, roasting prior to boiling in water has been identified as a technique for effecting reduction in cooking time (Ijabo et al., 2000). Boiling in excess water serves not only the purpose of partial cooking, but facilitates microbial penetration and human digestion. The bitter and beany taste of soybean disappears in less than 15 min at 95°C (Nout et al., 1985).After cooking and de-hulling processes have been completed, the cotyledons are prepared for fermentation. For some seeds, such as the African oil bean (Pentaclethra macrophylla), the cotyledon may be boiled again for 1-2 h. A softening agent ‘kaun’ (potassium carbonate) may be added to aid softening of the cotyledons (Odunfa, 1985c; Ikenebomeh et al., 1986). Ugba is produced from the sliced seeds of Pentaclethra macrophylla. These slices are mixed well with salt and wrapped in banana leaves. A three-day fermentation provides the delicacy, while 5 days of fermentation produces the soup condiment (Odunfa and Oyeyiola, 1985). Other substrates are pounded into a batter before wrapping in banana leaves or other suitable leaves. Incubation takes 72-96 h at 28-42°C. The process involves moist solid substrate fermentation by spontaneous natural inoculation. This is unlike most other

Nigerian fermented foods, which take place in a liquid environment. The imperative incubation condition could be described as that of oxygen starvation, allowing microbial growth. In practice this is achieved by wrapping with suitable leaves so that the package can be opened for aeration and cooling if necessary.

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Insufficient packaging density with consequent pockets of air, non slicing of African oil bean, including packaging in polyethylene bags and other factors may result in fermentation failure as reported by Ogbonna et al. (2001).

The consistency of the fermenting vegetable mash as fermentation progressed could be described as a thick cheesy pudding. After fermentation for 72-96 h, the mash become soft and dark and has a characteristic strong ammoniacal odour resembling Japanese natto (Odunfa, 1985c, 1986; Achi, 1992; Barimalaa et al., 1994).

Fermented condiments do not keep well if the fermentation is allowed to continue long uninhibited. If fermentation is prolonged, the environment will be changed to become suitable for yeast growth (Campbell- Platt, 1987). Furthermore, over-fermentation is capable of generating unacceptable levels of volatile fatty acids.

3.3 MICROBIAL ECOLOGYThe dynamics of fermentation in any food matrix is a complex microbiological process involving interactions between quite different microorganisms (Daeschel, 1987). The contribution of the accompanying flora of fermenting substrates is determined by the substrate composition and hygiene during production. During fermentation, the microorganisms use the nutritional components of the seeds, converting them into products that contribute to the chemical composition and taste of the condiment. Quite a number of Bacillus species have been isolated from various fermented food condiments (Table 3). Although yeasts and other bacteria are also seen, only part of them can be considered to play a substantial role in fermentation processes. For example, non-fermenting species may just be ubiquitous contaminants although they may affect the flavour of the final product when occurring in high numbers. Other bacteria present include Staphylococcus spp. Proteolytic and salt-tolerant microorganisms have been detected in appreciable numbers (from 104 to 10 6 cfu/g) in samples of fermenting Parkia seeds after 36 h (Odunfa, 1981a).

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The spore-forming species B. subtilis and B. lichenformis were identified as the main bacteria present. The predominance of Bacillus species has been demonstrated in other fermenting legume proteins (Achi, 1992; Barimalaa et al., 1994; Barber et al., 1998; Omafuvbe et al., 2002). The codominance ofStaphylococcus and Bacillus spp. was typical of the microflora of fermenting beans (Obeta, 1983; Antai and Ibrahim, 1986; Achi, 1992). Staphylococcus species have been associated with fermenting foods of plant origin especially vegetable proteins (Odunfa and Komolafe, 1989; Jideani and Okeke, 1991). Fresh fruits and vegetable often carry high levels of these organisms as part of their normal flora. Members of the Enterobacteriacceae also contributed to the ecology of fermenting plant proteins especially at the early stages (Mulyowidarso et al., 1989; Achi, 1992). These species do not survive until the end of the fermentation, presumably because of the modified environment, which had developed at later stages.

In view of the fact that the major constituents of vegetable seeds are proteins, the organisms responsible for fermenting them must be capable of utilizing these constituents (Antai and Ibrahim, 1986; Ouoba et al., 2003a). Bacillus species isolated from variable sources have been reported to be proteolytic and are able to breakdown oils (Frazier, 1967; Forgarty and Griffin, 1973; Ouoba et al., 2003b). It is evident that production of fermented condiments is initially mediated by a diverse microbial flora, which eventually becomes Gram-positive flora (a reflection of many African fermented foods) (Odunfa, 1985c). The contribution of this accompanying flora of bacteria to the properties of the legume product is only partly understood (Iwuoha and Eke, 1996). Most probably, they play a role in flavour development and influence the chemical composition through substrate modification and synthesis of vitamins (Nout and Rombouts, 1995). However it is necessary to ascertain the contribution of these organisms in vegetable fermentations. Undoubtedly, traditionally fermented condiments have not been incriminated in relation to food poisoning.

3.4 STARTER DEVELOPMENT

The fermentation process for condiment production is still being carried out by the traditional village-art method.There is need to apply modern biotechnological techniques like the use of starter cultures in improving traditional food processing technologies (Achi, 2005). It has been suggested that even though hitherto most fermentation processes used in developing countries do not use innocula or extrinsic cultures, these processes could be improved by using starter cultures, and also by backslopping, which entails application of brine from prior fermentation cycles (Holzapfel, 2002; Naiba, 2003).

Starter cultures have been found to reduce fermentation time as well as guarantee product quality. In the traditional method of manufacture, the fermentation of the legume seeds is achieved by indigenous microflora or the addition of fermented material from a previous production through back slopping. Thus, it may be assumed that undefined starter cultures have traditionally beenemployed in the manufacture of these products. (Suberu and Akinyanju, 1996; Omafuvbe et al., 2002; Ouoba et al., 2003 a,b; Dakwa et al., 2005). A pure culture starter is essential for controlledexperimental fermentations, and for this purpose a number of Bacillus species, Staphylococcus andStreptococcus enterococcus have been explored (Suberu and Akinyanju, 1996; Omafuvbe et al., 2003; Ouoba et al., 2003a,b). Controlled fermentation of soybeans was achieved by using pure single cultures of Bacillus subtilis, B. licheniformis or in combinations (Suberu and Akinyanju, 1996; Sarkar et al., 1993). Mixed cultures of B. subtilis and B. licheniformis were highly recommended by the same authors and fermentation was achieved in 72 h. Omafuvbe et al. (2003) on the other hand, tested threeBacillus species namely B. subtilis, B. licheniformis and B. pumilis singly and in combinations for their ability to ferment soybean for the production of daddawa. B. subtilis as single or member of a mixed starter produced soy-daddawa, which was considered most suitable as it gave acceptable pure culture condiment supposedly due to its proteolytic enzyme activity and high level of free amino acid.Most authors now agree that there is a predominant development of Bacillus species during the various legume fermentation processes (Aderibigbe and Odunfa, 1990; Odunfa and Oyewole, 1986; Achi,

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1992; Odibo et al., 1992; Ouoba et al., 2003a). The use of a single strain would seem too restrictive for the production of a foodstuff with a generous range of organoleptic characteristics. The use of a mixture of microorganisms with complementary physiological and metabolic properties seems to be the best approach for obtaining a product with the nutritional and sensory properties desired. Understanding of the phenomena of succession of the different populations involved in these natural processes is therefore required. The significant point in the comprehension of the mechanism of effecting degradation of legume proteins lies in the analysis of the amino acids produced by the isolated bacteria. The study of the starters contributing to the production of amino acids is still meager (Ouoba et al., 2003a) compared to the research works conducted on other aspects fermentation.

3.5 BIOCHEMICAL CHANGES ACCOMPANYING FERMENTATION

Since the major constituents of legumes and oilseeds used in condiment production are proteins, fats and fewer carbohydrates, the organisms responsible for the hydrolysis must be capable of utilizing these constituents.

3.5.1 Changes in carbohydratesBacillus species have been reported as producers of certain enzymes such as amylase, galactanase,1618 Afr. J. Biotechnol. galactosidase, glucosidase and fructofuranosidase, which are involved in the degradation of carbohydrates (Aderibigbe and Odunfa, 1990; Sarkar et al., 1997b;Omafuvbe et al., 2000; Kiers et al., 2000). Microbial amylases hydrolyze carbohydrates into sugars, which are then readily digestible by humans. Similarly, galactanases soften the texture of the seeds and liberate sugars for digestion. Most legumes contain large amounts of non-digestible carbohydrates, which may include arabinogalactan, stachyose, sucrose and raffinose (Irvine, 1961; Odunfa, 1983). Soybean may contain in addition, verbascose. These carbohydrates are associated with abdominaldistention and flatulence in humans (Sarkar et al., 1997b; Naczk et al., 1997). Fermentation reduced total flatus factors from 16.5 to 2.0 mg/g in soybeans (Winarno and Reddy, 1986), and from 0.16% to <0.1% in groundnut (Fardiaz and Markakis, 1981). Trypsin inhibitor activity of Bambara groundnut (Barimalaa et al., 1994) was also reduced during fermentation.

3.5.2 Changes in amino acidsIn most fermented high-protein products, the extent of protein hydrolysis is one of the most important factors in the changes in texture and flavour (Whitaker, 1978). Soluble low molecular weight peptides and amino acids that contribute to flavour are produced through the enzymatic breakdown of proteins (Odunfa, 1985c; Njoku and Okemadu 1989; Ogbonna et al., 2001; Ouboa et al., 2003a). Condiment of good quality has a characteristic strong smell of ammonia, a dark colour and is semi hard.

Amino acids produced because of protein metabolism are responsible for the gradual pH increase and leveling off towards 7.5-8.0 (Barimalaa et al., 1989; Achi, 1992; Barber and Achinewhu, 1992; Sarker et al., 1997a) (Table 3). The increase in pH into the alkaline range may be physiologically important for tolerance and adaptation of fermenting microorganisms in the environment. However, pH increases due to the formation of ammonia from amino acids may consequently encourage growth ofspoilage organisms such as lactobacilli and pediococci. The effect of vegetable protein fermentation on total nitrogen is negligible. However, slight increases may be observed in some legume seeds (Winarno and Reddy, 1986; Achinewhu et al., 1992). Free amino acids increase but longer fermentation results in losses of lysine or other essential amino acids (Winarno and Reddy, 1986).

3.5.3 Changes in lipidsThe significant lipolysis of legumes yields predominantly oleic, linoleic and linolenic acids (Achinewhu, 1987b; Ouoba et al., 2003b; Nout and Rombouts, 1990). Free fatty acids, particularly oleic, linoleic and linolenic acids were associated with non-specific antitryptic activity

15

(Winarno and Reddy, 1986). As such, extensive hydrolysis could diminish nutritional quality. Although oils constitute up to 40% of the legumes used in food fermentations, extensive lipolysis does not take place. Odunfa (1985c) reported low levels of lipase activity in Parkia biglobosa during dawadawa production. The same author had earlier reported low levels of lipase in melon seed fermentation (Odunfa, 1983b). Similarly, Njoku and Okemadu (1989) observed minimal participation of lipase in Pentachletera macrophylla during ugba production. Low lipase activity in some fermented foods has been considered desirable because of problems of objectionable taste and development of rancidity (Yong and Wood, 1977; Odunfa, 1983b, 1985b). However, there are reports of beneficial effects of lipase in the developments of characteristic flavours and aroma(Whitaker, 1978, Ouoba et al.2005). These results appear contradictory and require further study. Aninteresting area would involve the effects of change of lipid quantity and quality on the organolepticcharacteristics of fermented condiments. Darweesh et al. (1991) have reported that aldehydes resulting from oxidation of lipids cause off-flavour and odour problems.

However, organic solvent treatment of fermented condiments from locust bean, melon seed and soya bean on the objectionable odour, did not show any appreciation of the odour (Arogba et al., 1995). Not much can be said about the flavouring components of fermented vegetable proteins used as condiments as no research has been carried out on this aspect. However, there is no doubt that amines, peptides and glutamic acid all contribute to this flavour.

3.6 NUTRITIONAL QUALITY OF FERMENTED CONDIMENTSClassical techniques for assessment of bioavailability of nutrients generally involve in vitro tests with animals. Protein utilization measured as Protein Efficiency Ratio (PER) and the digestibility of soya bean and some legumes are hardly improved by fermentation (Obizoba, 1998; Nout and Rombouts, 1990). It was reported that rats do not utilize proteins from fermented soybean any better than from the cooked substrate. Nevertheless, some reports indicate otherwise. Achinewhu (1983)reported that fermentation and heat treatment improved apparent digestibility, feed conversion efficiency and protein efficiency ratio when rats were fed on diets of African oil bean seed rations.Eka (1980) studied the effect of fermentation on the nutrient content of locust beans and reported that protein and fat increased when fermented whereas the quantity of carbohydrates decreased. Increased levels of the amino acids were also reported except for arginine, leucine and phenylalanine. Similar results were reported for other seed legumes (Odunfa, 1985b; Achinewhu, 1988; Sarkar et al., 1998). Soluble products increased during fermentation of melon seeds resulting in high digestibility of the fermented product. Alanine, lysine and glutamic acid were the predominant amino acids, with arginine and proline occurring in small amounts (Odunfa, 1983a; Aidoo, 1986). The improved nutritive values were attributed to the increase in amino acid profiles due tofermentation.

Food condiments made from vegetable proteins maybe a good source of certain B vitamins, but are deficient in ascorbate and some fat-soluble vitamins, which are lost during fermentation. Achinewhu and Ryley (1986) have shown that fermentation significantly increased the content of thiamine, riboflavin and niacin in the African oil bean. Similar changes were observed during thefermentation of melon seed and fluted pumpkin seed (Achinewhu, 1986a,b). Ogbonna et al. (2001) observed increases in calcium, phosphorus and potassium when African yam bean was fermented for condiment production. This is in contrast to previous results of Achinewhu (1986b), which reported decrease in calcium, copper and phosphorus but increased iron and zinc in fluted pumpkin. It is evident that fermented food condiments is a good source of nutrients and could be used to produce complementary food supplements. Macronutrients in fermented legumes contribute to enhanced food quality.

3.7 FUTURE OF FERMENTED CONDIMENTS IN NIGERIAA substantial literature documents the successful fermentation of vegetable proteins for condimentproduction. Both microbial and biochemical changes involved therein have received much attention.

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A further understanding about the interactions of the microorganisms and plant materials is necessary to improve the quality of fermented condiments. Such understanding will aid in further development and control of the fermentation process.

Selection of starter cultures for large-scale industrial processes may require genetic modification to introduce a number of properties. These may offer nutritional benefit in the form of increased protein production or compatibility to mixed culture fermentations. Fermentedcondiments have a characteristic organoleptic quality, which probably are the most important factors for consumers. There are a few data on the flavour components of fermented condiments and how this can be improved by fermenting microorganisms (Dakwa et al., 2005). Further research is needed in these areas.

Taking into account the increasing demand particularly by urban populations in Nigeria, there are certainly prospects for industrialization of traditional fermented condiments. Commercial availability of ready-to-use fermented products saves much labour and time in the household (Nout and Sarkar, 1999). Better control of fermentation and quality of fermented foods is required in the scaling up process. Mention was made already of the choice of raw materials, fermentation conditions, and starter cultures used (Achi, 2005).

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CHAPTER FOUR

4.0 CONCLUSION AND RECOMMENDATION

4.1 CONCLUSION

The importance of traditional fermentation of soybean for Iru production cannot be

overemphasized. Ogiri or Iru an important Nigerian indigenous fermented food condiment when used

in a soup imparts a desirable flavour and enrichment to the soup. Iru from soybean has also high

protein content having made from soybean, which has about 40% protein content as reported in the

literature. However, Iru as well as other traditional indigenous foods are produce under primitive

condition which results in low yield and poor quality product. Women and some men engaged in the

production activities. The techniques they use are labour intensive, time consuming, have low

productivity and have a wide range of variations as regards to product quality due to lack of

standardization. This is a need for improvement in order to upgrade the product.

4.2 RECOMMENDATION

In order to upgrade Iru production, there should be change from Craft to a Technology based

production system. Several strategies should be adopted, which include:

The use of starter cultures for production

There should be stabilization of spontaneous fermentation and

There should be production of food processing enzymes

In addition, there should be Raw material development

The use of Genetic engineering

Process development

Finished product development

These will go a long way to upgrade Iru production and traditional food fermentation as a

whole. Indigenous fermented foods are produced at the household level in a majority of African

countries. Increasing industrialization and urbanization trends in these countries will however dictate

the need for larger scale production of fermented foods of consistent quality. Additionally, variation of

the quality attributes of these foods to meet the demands of the sophisticated and varied palates of

industrialized communities will eventually be required.

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Upgrading the production of fermented foods from the household to the industrial level will necessitate several critical steps:

1. Isolation and identification of the microorganisms associated with the fermentations

Microorganisms associated with indigenous fermentations need to be isolated, properly identified and preserved preferably in a recognised culture collection for future use.

2. Determination of the role(s) of the microorganism(s)

The biochemical role(s) of microorganisms associated with food fermentations needs to be determined through chemical analysis of products released by the microorganisms under controlled laboratory conditions.

3. Selection and genetic improvement of microorganisms

Microorganisms responsible for effecting important changes in the food during fermentation should be selected and subjected to genetic improvement geared toward maximizing desirable quality attributes in the food and the limiting any undesirable attributes.

4. Improvement in process controls for the manufacture of fermented foods

Improvements in the quality and quantity of fermented foods may be achieved by manipulating environmental factors such as temperature, moisture content, aeration, pH, acidity etc. which influence the activity of microorganisms during the fermentation process.

5. Improvement in the quality of raw materials used in the production of fermented foods

Both the quality and the quantity of fermented foods may be improved by choosing raw materials other than those traditionally used for their production.

6. Laboratory simulation of the fermented foods

Prior to pilot scale production, and (ideally) after all the five stages above have been well studied, fermented products may be produced under laboratory conditions. Laboratory simulation of fermented foods will involve the production of fermented foods by innoculating microbial isolates having desirable properties, into raw materials.

7. Pilot stage production

The pilot stage is the first clear departure from small scale production and should be based on the result of laboratory experiments.

8. Production or industrial plant stage

The production stage is the culmination of all the previous efforts and should lead to the availability of food of predictable and consistent quality on a large scale. 

 

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