Optimization of the griddling process of kpejigaou (a traditional low fat nutritious cowpea food) using response surface methodology.

Kpejigaou is a griddled cowpea paste product eaten mainly in West Africa. As its processing does not involve the use of fat, it has the potential of meeting consumers' demand for healthy, low fat nutritious foods. Product texture is considered an important quality index by kpejigaou consumers. The objective of this study was to determine the optimum processing conditions of kpejigaou with respect to its textural properties. The study followed a 2 × 3 design with two processing variables each at three levels as follows: griddling temperature (130, 200, 270 °C) and time (5, 7.5 and 10 min). Texture Profile Analysis (TPA) was done on freshly processed samples. The data were fitted into multiple regression models from which the optimum griddling conditions for kpejigaou were determined. Kpejigaou processed at the optimum conditions was evaluated by untrained consumers for acceptability. Traditionally processed kpejigaou served as the control. The TPA results showed that hardness, chewiness and modulus of deformability were significantly affected by griddling conditions. Adjusted R(2) for the models for hardness, chewiness and modulus of deformability were 96%, 97% and 78%, respectively. Using response surface methodology, the optimum griddling conditions for kpejigaou (for acceptable textural properties) were determined to be 170 °C for 5-6 min. The texture of optimized kpejigaou was very much liked for its higher degree of sponginess as compared to the control. It also had acceptable sensory attributes of color, taste and flavor. These findings provide the basis for the development of a process for mass production and quality assurance of kpejigaou.

Lactic acid tolerance determined by measurement of intracellular pH of single cells of Candida krusei and Saccharomyces cerevisiae isolated from fermented maize dough.

Strains of Candida krusei and Saccharomyces cerevisiae were grown together at 30 degrees C in MYGP broth, pH 2.5, in the presence of 106.4 mM undissociated lactic acid. The two C. krusei strains investigated grew within 48 h from initial counts of 2 x 10(4) to approximately 10(7) cells/ml whereas the two S. cerevisiae strains investigated survived but did not grow in the presence of 106.4 mM undissociated lactic acid at pH 2.5. To explain the differences in lactic acid tolerance of the two yeast species, we used fluorescence-ratio-imaging microscopy and a perfusion system to determine the short-term intracellular pH (pH(i)) changes in single cells of C. krusei and S. cerevisiae. The changes were investigated both in the presence of low (20.7 mM) and high (106.4 mM) concentrations of undissociated lactic acid. For both the investigated species 20.7 mM undissociated lactic acid did not seem to influence the initial pH(i) which for C. krusei was found to be approximately 8.0 and for S. cerevisiae 6.9-7.5. For both C. krusei strains, perfusion with 106.4 mM undissociated lactic acid induced only weak short-term pH(i) responses with a decrease in pH(i) of less than one pH unit. Contrary, for both strains of S. cerevisiae perfusion with 106.4 mM undissociated lactic acid resulted in a significant decrease in pH(i) from initially 6.9-7.5 to 6.2-6.4 after 1 min and further to a pH(i) of < or = 5.5 after 3 min after which it remained constant. The results obtained show that C. krusei is more resistant to short-term pH(i) changes caused by lactic acid than S. cerevisiae, and this, in turn, may be part of the explanation why C. krusei is more tolerant to lactic acid than S. cerevisiae.

Volatile compounds produced by Lactobacillus fermentum, Saccharomyces cerevisiae and Candida krusei in single starter culture fermentations of Ghanaian maize dough.

AIMS: To identify and compare the volatile compounds associated with maize dough samples prepared by spontaneous fermentation and by the use of added starter cultures in Ghana. METHODS AND RESULTS: The starter cultures examined were Lactobacillus fermentum, Saccharomyces cerevisiae and Candida krusei. For identification of aroma volatiles, extracts by the Likens-Nickerson simultaneous distillation and extraction technique were analysed by gas chromatography-mass spectrometry (GC-MS) and using a trained panel of four judges by GC-Olfactometry (GC-sniffing). Compounds identified by GC-MS in maize dough samples after 72 h of fermentation included 20 alcohols, 22 carbonyls, 11 esters, seven acids, a furan and three phenolic compounds. Of the total 64 volatile compounds, 51 were detected by GC-sniffing as contributing to the aroma of the different fermented dough samples. Spontaneously fermented maize dough was characterized by higher levels of carbonyl compounds while fermentations with added L. fermentum recorded the highest concentration of acetic acid. S. cerevisiae produced higher amounts of fusel alcohols and increasing levels of esters with fermentation time and C. krusei showed similarity to L. fermentum with lower levels of most volatiles identified. CONCLUSION: The present study has given a detailed picture of the aroma compounds in fermented maize and demonstrated that the predominant micro-organisms in fermented maize dough can be used as starter cultures to modify the aroma of fermented maize dough. SIGNIFICANCE AND IMPACT OF THE STUDY: The study has documented the advantage of using starter cultures in African traditional food processing and provided a scientific background for introducing better controlled fermentations.

Microbiological evaluation of ghanaian maize dough co-fermented with cowpea.

Fermented maize dough meals form a large proportion of people's diet in Ghana. To enhance the nutritive value of these carbohydrate-rich foods, protein complementation was introduced. In this study, microbial ecology of fermenting maize dough fortified with 20% cowpea was investigated. A total of 106 microbial strains were isolated from different batches of the fermenting dough at periodic intervals. Ten genera of microorganisms namely Lactobacillus, Leuconostoc, Saccharomyces, Debaryomyces, Candida, Bacillus, Micrococcus, Klebsiella, Escherichia and Aspergillus were identified, with lactic acid bacteria species being predominant. A lactic count of log 9.9 cfu/g was obtained at the end of 72 h fermentation relative to log 6.6 cfu/g recorded for aerobic mesophiles. At the 12 h fermentation period, the population of yeasts was less than log 1.0 cfu/g, but gradually rose to log 5.36 cfu/g by 48 h followed a slight decline at the end of 72 h fermentation period (log 4.08 cfu/g). Enteric microorganisms that were isolated from the raw cowpea were less than log 1.0 cfu/g at 12 h of fermentation, while the Aspergillus species were isolated from the raw maize and the dough subjected to drying treatment. The growth of inoculated enteropathogenic E. coli and S. typhimurium was inhibited in the cooked, fermented maize-cowpea dough, and at 72 h, they were not within detectable limit. The study concluded that addition of cowpea at 20% level did not affect the natural fermentation characteristics of the maize dough.

Acceptability of extrusion cooked cereal/legume weaning food supplements to Ghanaian mothers.

Six cereal/legume mixtures were developed with the aid of computer-assisted optimization software from cereal and legume staples indigenous to the West African sub-region. The mixtures had 45-50% maize, 35-40% decorticated cowpeas and either blanched peanuts or decorticated soybeans as a source of lipid and complementary amino acids. Three processing schemes involving roasting, amylase digestion and extrusion cooking were employed. The proportion of ingredients in each cereal/legume blend was based on meeting the nutrient requirement of the 0.5-0.9-year-old infant and cost considerations. Nutrient composition of the blends (proximate, amino acid, mineral and vitamin composition) indicated that these formulations were adequate nutritionally as weaning supplements (Mensa-Wilmot et al, 2000a,2000b). These formulations were evaluated by mothers of weanling children based on their preferences with respect to color, flavor, texture and willingness to purchase the product assessed. A total of 133 one-on-one interviews and 23 group discussions were conducted (involving 6-12 respondents) with selected Ghanaian women. The mothers found the convenience of a weaning food made from local staples that could be processed on village/market scale very attractive.

Aerobic spore-forming bacteria and chemical composition of some Nigerian fermented soup condiments.

A total of 97 strains of spore-forming Bacillus were isolated from 45 samples of three Nigerian fermented condiments, obtained from retail markets located in Southwestern Nigeria. The isolates were identified as B. subtilis (33%), B. pumilus (19%), B. licheniformis (22%), B. brevis (9%), B. megaterium (12%) and B. polymyxa (5%). The microbial load of the condiments showed that the average count of spore-formers was between 107 to 109 cfu/g. The moisture contents of iru, ugba and ogiri were 57.18%, 46.32% and 42.34%, respectively, while the protein contents were 18.26%, 17.17% and 17.96%. The percentage fat was 29.88%, 40.25% and 44.14% for iru, ugba and ogiri. The ash content ranged from 5.8 to 6.1%; a 0.1% titratable acidity and pH values above 7.0 were obtained for the three condiments.

The contribution of moulds and yeasts to the fermentation of 'agbelima' cassava dough.

Agbelima, a fermented cassava meal widely consumed in Ghana, Togo and Benin, is produced by fermenting grated cassava with one of several types of traditional cassava dough inoculum. During fermentation a smooth textured sour dough is produced, the toxicity of cassava is reduced and there is a build up of volatile aroma compounds. Four types of inocula were included in the present investigation. In one type moulds were found to form a dominant part of the microbiota, the species present being Penicillium sclerotiorum, P. citrinum, P. nodulum, Geotrichum candidum and a basidiomycete. All these moulds were found to possess cellulase activity which was responsible for the hydrolysis of cassava tuber cellulose during fermentation leading to a breakdown of the coarse texture of cassava dough. The yeasts Candida krusei, C. tropicalis and Zygosaccharomyces spp. were present in high numbers in the four types of inocula including the moudly inoculum. The yeasts C. tropicalis and some strains of Zygosaccharomyces, all of which possessed cellulase activity, were also found to contribute to the modification of cassava texture during fermentation. All yeasts and moulds exhibited linamarase activity and were therefore capable of breaking down the cyanogenic glucosides present in cassava.

Jack bean (Canavalia ensiformis): nutrition related aspects and needed nutrition research.

The nutritional characteristics and food potentials of jack bean (Canavalia ensiformis) have been reviewed. The bean is a good sources of protein, 23% to 34%, and carbohydrate 55%. It is also a good source of Ca, Zn, P, Mg, Cu and Ni. Jack bean protein is adequate in most essential amino acids with the exception of methionine and cystine which may be nutritionally limiting. Antinutritional and toxic factors including trypsin inhibitors, hemagglutinins, cyanogen glucosides, oligosaccharides and others are present in jack bean. Properly processed jack bean could be used to prepare some of the popular dishes made from cowpea, peanut, pigeon pea and soybean. Industrial products such as protein concentrates and isolates, starch, flakes, grits and flours can be produced from the bean. Further research is needed to identify varieties with high protein and nutritional quality. Development of new highly nutritious food products based on whole or processed jack bean should increase production and expand use.