Journal of Scientific & Industrial Research Vol.58, November 1 999, pp 837-843

Industrialization of Fermented Food Processes: How Far in Nigeria?

Ayoade Kuye Department of Chemical Engineering, University of Port Harcourt, PMB 5323, Port Harcourt,

Rivers State, Nigeria

and

Lateef Oladimeji Sanni* Department of Food Science and Technology, University of Agriculture, Abeokuta, Ogun State, Nigeria

Studies on selected fermented foods, indigenous to Nigeria, viz. ogi, gari, fufu, lafun, iru, ogiri, ugba and okpeye, are reviewed. A brief description about their production process is presented. The evaluation about their commercialisation is given. It is ob­served that only iru, ogi and gari have been commercialised to some extent, the other products are still made as a traditional family art. Efforts made so far towards identifying the microorganisms implicated and the biochemical changes that occur, are described. It is pointed out that areas such as development of appropriate starter cultures, effect of process variables and scale-up strategies need further investigations.

1. Introduction Fennentation is indigenous to the Nigerian culture and

is being used for centuries to produce various foods in this country. There are over 20 fennented foods and bev­erages in the country; some are served as main meals, while others are used as condiments. The alt and pro­duction style for these products originated from differ­ent traditional family settings. With increase in the level of scientific awareness, efforts are being made to ex­plain the underlying principles involved and in some cases, to also improve upon the production technique.

During the fennentation of foods, several chemical compounds are fonned. These include steam volatile acids (fonnic, acetic and propionic); non-volatile acids (lactic and succinic) ; volatile neutral compounds (etha­nol, acetone and isopropanol); non-volatile neutral com­pounds (g lycerol and 2 , 3 -bu tanedio l ) ; butyr ic , butanediol, acetoin and some gases l •4 • In natural fer­mentation, the relative amounts of various products fanned change, depending upon the prevailing environ­mental conditions l ike pH, water potential (aw) and tem­perature.

Fennentation offers a number of advantages includ­ing food preservation, improved food safety, enhanced flavor and acceptabi l i ty, increased variety in the diet, improved nutritional value, improved functional prop­erties and reduction in anti-nutritional compoundss. 1 2 •

* Author for correspondence

For instance, it has been shown that certain strains of Lactobacillus planta rum and Leuconostoc mesenteroides, isolated from cassava have the abi lities to produce the I inamarase enzymes 13- 17 . These linamarase enzymes break down the toxic cyanogenic glucosides contained in cassava.

Although a number of workers have done research on the various fennented foods in Nigeria, the industrial production of these foods has not been encouraging. Thus, the purpose of this paper is to review the available l i terature with emphasis on those factors that are neces­sary for industrial application. Furthermore, we shall restrict the presentation to some of the products that are widely consumed in Nigeria. These are, 'Ogi ' , made from cereals such as maize or sorghum, 'Gari' , ' fufu' and ' lafun' , which are products from cassava as well as 1m or Dawadawa, Ogiri-igbo, Ogiri , Ugba and Okpeye which are products from legumes. A description of the production process for these foods i s given in Section 2. In Section 3, we have presented the microorganisms that have been impl icated during the fermentation, while Section 4 discusses process parameters that could influ­ence the fennentation process.

2. Processing of Fermented Foods

The common fermented foods that are indigenous to Nigeria are mainly from legumes, cereals and root fi­bres. While 1m, Ogi and Gari have been commercial-

838 J SCI IND RES VOL.58 NOVEMBER 1 999

Table I -Selected fermented foods in Nigeria

Fermented product Raw material Microorganisms implicated Stage of development

Ogi Maize Lactobacillus plantarum

L. jermelltlllll S. cerevisiae Candida krusei Corynebacterium spp Acetobacter spp

1 ,2,3,5

Gari Cassava Leuconostoc mesenteroide

L. plantarum 1 ,2 ,3,4,5

Fufu Cassava

Lafun Cassava

lru Seeds of Parkia

Ogiri Seeds of castor oil

Bacillus subtilis Candida krusei

L. plantarulll

L. brevis

B. sllbtilis C. krusei

L. plantarum B. subtilis C. krusei

Bacillus spp Staphylococcus sp

B. sllbstilis A lcaligenes sp Streptococcus sp. Staphylococcus sp.

1 ,2,4

1 ,2,4

1 ,2,3,4,5

Ugba Seeds of oil-bean Lueconostoc mesenteroides Bacillus sp

Okpeye Seeds of Prosposis africana

Staphylococcus sp. Micrococcus sp.

L. plantarulIl L. bulgaricus

MiclVcoccus sp. B. subtilis.

Key: I = OrgalJisms isolated and idclltified 2 = Roles of organisms determined 3 = Stane. cultures development attempted 4 = Process optimization 5 = Semi-industrialization of process

ized to some extent, the other products are still made as a traditional fami ly art. The basic raw materials required for these' foods are l isted i n Table 1 and the production process is described below. It should be noted that some of these products are consumed in other African coun­tries, also.

Ogi: Ogi is a fermented product of either maize or sorghum or mil let grains. It is obtained by washing the grains fol lowed by steeping or fermentation for 72 h. During steeping, the grains are also fermented. The fer­mented grains are wet milled, sieved (using muslin cloth) and decanted to get ogi slurry. Optionally, the sieved slurry may be al lowed to further ferment for 24-72 h I I .

The slurry is boi led in water to obtain the ogi porridge . . Soy-beans are sometimes added to ogi to yield soy­

ogi (30% soy-beans and 70% corn), It is being produced on a pilot plant scale in Nigeria as a weaning food. The

product is fortified with vitamins and minerals, pasteur­ized, spray-dried and packaged.

Another approach suggested for the production of ogi involves dry-milling of the maize to produce maize flour. It is then mixed with water, inoculated and fermented with a mixed culture of L. plantarum, Streptococcus lactis, and Saccharomyces lactislx. Adeyemi l9 also de­scribed a method for manufacturing of ogi from sorghum.

Gad It i s also a fermented cassava product. To pre­pare i t, fresh roots are peeled, grated into mash, and then put in sacks. The sacks are pressed, using heavy objects, to extract excess l iquid from the pulp during fermenta­tion. After 3-4 days, the dewatered and fermented mash is sieved and garified in a pan. Palm oi l is often added during garify ing to prevent burning. Addition of oil also changes the color of the product from white to yellow. Many authors21 -24 have worked on various ways for

KUYE & SANNI : FERMENTED FOOD PROCESSES 839

mechanizing the processing steps, especially grating, milling and water expressing. Gari is preferred by urban consumers because it is a precooked convenient food. It is commonly consumed either by soaking in cold water with sugar, coconut, peanut, fish, boiled cowpea as complement or as a paste made with hot water and eaten with vegetable sauce.

Gari is probably the only food for which Africa has developed a patented planes. The Federal Institute of Industrial Research, Oshodi, Nigeria, has designed plants with capacities up to 1 0 tons/day.

Fufu: Fufu is made by steeping whole or cut-peeled cassava or unpeeled cassava water to ferment for 3-5 days. During steeping, the fermentation decreases the pH, softens the roots and faci litates reduction of poten­tially toxic cyanogenic compounds of the roots26• When sufficiently soft, the roots are taken out, broken manu­ally, and the fibres removed by sieving. The sieving is done manually by adding water to the retted mass on a nylon or cloth screen. The sieved mass is allowed to sedi­ment in a large container for about 24 hours. After sedi­mentation, the water is decanted while the fine, clean filtrate (mainly starch) is dewatered overnight in raffia or cotton bags, using heavy stones as presses. The fufu is collected and sold to the consumers in its wet form in small units packaged in plastic or polypropylene bags. Fufu is consumed as a paste made with boiled water27•2R• Cooked fufu is usually eaten warm with fish, meat, and vegetable sauce.

Lafun: Lafun is similar to fufu in Nigeria. The prin­cipal difference is that lafun is dried providing enhanced storage characteristics, while fufu has reduced fibre con­tenet . Lafun is produced by cutting fresh cassava root into chunks and steeping for 3-4 days or uritil the roots become soft. The fermented roots are peeled, broken into small pieces and sun-dried. Alternatively, chips are made directly from fresh roots, cut into chunks and sun-dried. The dried pieces are milled into flour, which is made into a dough in boil ing water before consumption.

The sun-drying of raw cassava takes 4 days to 3 weeks, depending upon the weather and size of the pieces. Al­though this approach is very simple and practised in ar­eas where water for fermentation is scarce, the product has been found to contain considerable amounts of cya­nides27•

Iru: This is a fermented product of African locust bean. It is known by three different names in Nigeria -lru in the South West, Dawadawa in the North and Ogiri� igala in the South East. It is widely acceptable for its

flavoring characteristics as a condiment. In addition, it also serves as a low cost animal protein substitute. The processing method of iru has been documented by many workers29.3 ' .

The hard, dried locust beans are boiled in water i n a covered earthen-wall or metallic pot for 1 2-24 h to soften the tough, hard testa cotyledons. The black beans testa are then removed by either rubbing between the hands, rubbing against the walls of a basket, under the foot or by pounding gently in a wooden mortar. A l ittle sand or wood ash is often added as an abrasive to aid the re­moval of the testa. The cotyledons are then washed thor-0ughly and boiled again for 30 to 1 20 m inutes. During

. this second boiling, potassium carbonate and potassium bicarbonate (obtained from a native rock called kaun) may be added to aid softening of the cotyledons. The seeds are drained after boiling and spread in calabash trays in layers of about 10 cm deep.

About two or three trays are stacked together and wrapped in many layers of jute sacks and coarse cotton cloth to provide warm and humid atmosphere. During this period, the seeds ferment, the color changes to dark brown/black and become softer. The odor of the fer­mented beans also changes from initial sweet beany to a strong proteolytic ammoniacal.

Ogiri: Ogiri is obtained from water melon seeds. The seeds with the hulls removed, are boiled until soft. The pulpy melon seeds are wrapped in blanched plantain leaves and cooked again for 2-3 h. After draining off the associated water and oil , the seeds are pre-fermented at ambient temperatures for 3 days. At the end of this period, the seeds are ground in a sterile mortar and some salt is added. The resulting paste is rewrapped in plan­tain leaves and fermented for additional 4 days at am­bient temperature32• Like iru, ogiri is used as a food con­diment. .

Ugba: Ugba is made from oil bean seeds. The seeds are obtained from a perennial legumes tree, Pentaclethra macrophylla Benth, commonly called the oil bean tree, Congo acacia, or Atta bean tree. The oil bean seeds are boiled in water for about 4- 1 2 h. The cotyledons (ker­nels) are separated from the cooked seeds by removing the seed coats and washing. The separated cotyledons are boiled again in water to remove bitter components in the colyledons. The bitter components of the oil bean seeds are water soiuble. The wa,shed cotyledons are cut into thin sl ices which are mixed with salt, put in a clean pot without water, covered and fermented for about 5 days at room temperature33.35 . U gba is consumed as a basic food or used as a flavoring agent.

840 J SCI IND RES VOL.58 NOVEMBER 1 999

Okpeye: The production of okpeye, a condiment pro­duced from the seeds of Prosopsis africana by fermen­tation is s imilar to other Nigerian condiments produced from plant seeds. The seeds are boiled in water to re­move the seed coats. The seeds, which become l ight brown, are spread in a layer roughly 2-cm thick on washed leaves of Alchornea cordifolia in a basket tray and covered with more leaves. Clean pieces of broken clay pots are placed on the top to hold the leaves in posi­tion. The baskets tray is incubated at room temperature for 96 h to give okpeye33•

3. Microorganisms Involved in the Fermentation Process

A large number of references are available in the lit­erature on the microorganisms implicated during the fer­mentation process. According to Oyewole37, these mi­croorganisms belong to four major groups, namely Lac­tobacillus, Lactococcus, Leuconostoc, and Pediococcus. Some of the specific studies on each of the products mentioned in Section 2 are discussed below. A summary is also included in Table 1 .

For ogi production, Akinrele1 found that Corynebac­teria, S. cerevisae, Enterobacter cloacae and L. plantarum were prominent. Adegoke and Babalola3x also showed that K. oxytocia dominated the fermentation of ogi (24-48 h) after which S. cerevisae took over the fer­mentation processes.

Collard and Levj39 in their study on the cassava fer­mentation for Gari production, reported a two-stage pro­cess in which the fermentation was said to be started by Corynebacterium manihot. It breaks down starch and releases organic acids within the first 48 hours of fer­mentation . The acid produced and the lowered pH con­dition that developed in the first stage was said to create favorable conditions for the growth of a fungus called Geotrichum sp. This latter organism then proliferates into the second stage, producing a variety of aldehydes and esters which appeared to be responsible for the charac­teristic odour of gari. The validity of this two-stage con­cept of "gari" production has been questioned in some recent works40.43 • Okafor43 implicated various genera of lactic acid bacteria including Leuconostoc sp, and L. plantarum and some yeasts during Nigeria gari produc­tion. Ngaba and Lee41 implicated L. plantarwn, L. buchneri, Leuconostoc sp. Streptococcus sp, and a yeast identified as Beltranomyces sp. Todate, the microflora found in gari include C. manihot and Geotrichul1l can­dida, Streptococcus, Leuconostoc, Alkaligens, Lactoba­cillus, Bacillus, Klebsiella spp and Saccharomyces

cerevisaeW•45• It should be noted that the term lactic acid bacteria is used to describe a broad group of gram-posi­tive, catalase negative, non-sporing rods and cocci, usu­ally non-motile, that util ize carbohydrates fermentatively and form lactic acid as , he major end product.

As for fufu production, B. subtillis, Klebsiella spp, Candida tropicalis, Canadida krusei and numerous spe­cies of lactic sacid bacteria, especially L. plantarum and L. mesenteroides are involved46-4x • L. mesenteroides which initiates many fermentation processes, was found to initiate the fermentation of cassava in submerged sys­tem while L. plantarum dominated the entire last phase of fermentation4x• Some strains of Bacillus spp along with Klebsiella spp contribute significantly to the retting of cassava roots. B. substilis has h igh retting abi lity and produces amylases and pectin methyl esterase enzymes which are responsible for reducing sugar production and cassava tissues softening, respectively26.

Only a few reports are available on the microbiology of Lafun production. The microorganisms isolated are B. substilis, Escherichia coli, Micrococcus luteus, Pseudomonas sp, Serratia sp, Streptococcus faecalis, Aspergillus niger, Penicillum sp, and Geotrichum can­dida49• Among these, B. substilis, Serratia sp, and S. faecalis are reported to decrease as the fermentation progressed while G. candida was found to be the most commonly isolated fungus after 72 hours of fermenta­tion49•

The predominant microorganisms involved in the fer­mentation process of Iru are: Bacillus sp, B. substilis, B. licheniformis, B. firmus, Staphylococcus, Micrococcus and Escherichia50• Odunfa and Adewuyi5 1 found that of all the microorganisms isolated, B. substilis strains fer­mented the locust bean strongly to produce acceptable iru. The ability of the Bacillus strains to bring about this fermentation was probably due to the proteolytic ability of the organisms. Moreover, B. substilis grows on am­monia or n itrogen source and does not require growth factors. The . B. substilis sp. also have the abi lity to pro-

. duce antibiotic which can inhibit the growth of other microorganisms such as S. lactis, S. uvarum and S. faecium29•

The microorganisms isolated at different stages offer­mentation of ugba are mainly proteolytic B. substilis and coagulate-negative Staphylococcus Sp52. B. substilis is reported to be more predominant and its population in­creases throughout the fermentation while that of Sta­phylococcus decreases. Obteta and Ugwuanye35 con­firmed the presence of B. substilis and various other bac­teria including Micrococcus luteus, M. roseus, B.

..

KUYE & SANNI : FERMENTED FOOD PROCESSES 841

circulans and B. macerans in the ugba fermentation. Bacillus sp was reported to be responsible for the char­acteristic aroma ofugba35 . The microorganisms involved in ugba are natural contaminants from the air, handling and utensils used in slicing the cooked cotyledon::.. Sta­phylococcus sp is associated with handling since it com­monly occurs on the skin. The salt added before the fer­mentation selects the Staphylococcus and Micrococcus Sp53 . This probably confirms the observation that Sta­phylococcus spp were present only during 24 h of fer­mentation54.

The microorganisms isolated from fermenting melon seeds to produce Ogiri include Bacillus sp, Alcaligenes sp, Streptococcus sp and Staphylococcus sp. While Ba­cillus sp and Alcaligenes sp have been documented with fermenting of seeds32.55, the presence of Staphylococcus sp. could hardly be associated with the fermentation and hence the need for improved processing techniques. Barber and Achinewhu56 suggested that a combination of Bacillus sp and Alcaligenes sp. was necessary for melon seed fermentation, since neither organism gave the typical characteristics of ogiri when used. Further research is sti l l needed to determine the specific roles of these organisms in melon seed fermentation and to fully identify the species of these organisms, best suited for the fermentation.

Strains of B. substilis appear to be the most important organisms in Okpeye production. Other organisms in­clude B. Licheniformis, Lactobacillus sp, L. bulgaricus and L. plantarum35•57• The absence of fungi in the prod­uct excludes the danger of mycotoxins35.

lideani and Okeke54 presented a comparative study of microorganisms involved during the fermentation of seeds of African locust bean, melon, castor oil bean and soybean. Their results indicate that three genera of bac­teria (Bacillus, Staphylococcus and Pseudomonas) were isolated. Furthermore, it was shown that Bacillus spe­cies were present throughout the 72 hour period of fer­mentation. Staphylococcus was not isolated from the melon fermentation. Also, more species of bapteria, es­pecially Bacillus, were involved in soybean and castor bean fermentation than in the other two bean-types.

4. Process Factors in Fermentation Different conditions which affect the fermentation of

the different foods have been studied by many authors. The parameters studied include temperature, relative humidity, fermentation period, aeration and mixing. A majority of such studies are for cassava fermentation. For gari production, Akinrele44 showed that the cassava fermentation was best at 35"e. Also, the flavor of ac-

ceptable gari should be made from fermented cassava at pH 3 .95 . Inoculation of cassava pulp with fermented cassava juice reduces the fermentation period to 1 5 h, compared to the traditional duration of 3-4 days. It was found that aeration during fermentation was inhibitory.

For fufu production, the effect of processing methods h as been studied by a number of authors26.47.5M.59. Akingbala et aL.5M showed that grating the cassava roots before steeping improved the aroma and periodical change of water during steeping improved the taste, color and texture of fufu over that produced by the traditional method. Oyewole and Odunfa26 as well as B lanshard et al.59 reported that the retting of cassava occurred after " 60 hours of steeping at temperatures 30-35°e. Ampe et al. /iO optimized the retting process in terms of period and the quality of the end-product. It was also shown that small pieces of cassava allowed retting to be completed more quickly than when whole roots were used26.47.

For the fermentation of legumes, Odunfa61 showed that the cooking period for da'Yadawa production could be reduced by first soaking the beans in water for 1 2 hours before cooking in a pressure cooker for 30 min. However, i t took more time to remove seed coats from the beans cooked in this manner. In contrast, Osinow062 cooked beans in a pressure cooker for 90 min without presoaking and found that the seed coats were easily re­moved from the cooked beans. The effects of period, temperature and relative humidity on locust bean fer­mentation have been reported by Odunfa and Adewuypl . The optimal duration was 48 h and the corresponding temperature was 35-40"e. The optimum relative humid­ity was 5 1 % at 35"C and 7 1 % at 40"e.

For the foods considered in this paper, it is generally agreed that the fermentation process is exothermic. How­ever, we are not aware of any effort to quantify the amount of heat involved.

Some authors have worked on the post-fermentation handling of the foods with a view to improving their shelf­life. The usual approach is to dry the products. B lanshard et al.59 reported that the storage of wet fufu in plastic bottles at room temperature over eight weeks affected its acidity and microbial qualities. Okpokiri et al.63 found that good quality dried fufu could be obtained by drying wet fufu in an oven at 55"C for the first 8 hours and thereafter in­creasing the temperature to 80"e. Drying of fufu at 60"C also reduced the strong odor but the product was not ac­ceptable5H• The effect of different drying methods on the composition and properties of lafun fermented flour, was reported by Sanni et al.64• Recently, Sanni et al.65•66 pre­sented the moisture sorption isotherms for fufu.

842 J SCI IND RES VOL.58 NOVEMBER 1 999

The provision of pure starter cultures has been at­tempted by some workersSI .67.6R. There are three main ap­proaches, namely natural inoculation, transfer of an old batch of fermented products to a new batch (back-slop­ping) and indigenously derived culture. The success so far has been l imited probably because most of the indig­enous fermentation processes are "wi ld", that is, the ef­fective microorganisms are not controlled. 5. Conclusion

The work done in Nigeria so far on fermented foods is reviewed in this paper. As can be seen, quite a lot has been done in the area of understanding the production process especially that of identifying the microorgan­isms implicated and the biochemical changes that occur. Also, for gari and dawadawa, attempts have been made towards developing appropriate starter cultures.

Future Studies To ful ly commercialize different procedures, more

research is stil l needed. For instance, the effect of vari­ous process variables (raw materials, temperature, mois­ture, fermentation duration, etc.) on the quality of the foods need be investigated to optimize the fermentation process. There is need to develop starter cultures with appropriate carriers so that they can easily be handled and used by local processors without the problem of contamination.

Also, no work seems to have been done on the scale­up strategies for any of the processes described above. Such information is necessary if the resulting fermenta­tion plants are not labor and energy intensive.

Acknowledgement The travel grant given to one of the authors (L 0 Sanni)

by International Foundation for Science is gratefully acknoowledged.

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