Effect of Processing Techniques on The Contents of Flatulence Factors and Emulsion Properties of Cowpea (Vigna unguiculata)

The effect of some processing techniques (germination boiling and dehulling) on the soluble sugar contents and the emulsion property of processed flour were studied. Results show that germination significantly reduced the raffinose level from the third to the fifth day sprouting period (P<0.05). Boiling and dehulling also reduced the content of this flatus oligosaccharide (raffinose) but not to a significant proportion (P>0.05). The contents of other soluble sugars-galactose, glucose and sucrose were increased by germination (P<0.05) and boiling (P>0.05) but reduced by dehulling (P>0.05). Germination, dehulling and boiling lowered the emulsion stability property of cowpea flour. Even though, it is not conventional to either malt or dehull cowpea seeds before cooking, individuals should be advised to do so, in order to minimize the flatus potential and the accompanied discomfort associated with beans consumption. However, such processing techniques would not be appropriate for foods that need good emulsion. @JASEM. Cowpea, Vigna unguiculata belongs to the group of crops known as legumes which are edible seeds. Cowpea or beans as it is popularly known is indigenous to West Africa (Onigbinde and Onobun, 1993) and it is a major source of human and animal food. The vegetative part of the cowpea plant can be buried into the soil to improve its fertility, and also, cowpea is a well known leguminous cover crop. In Nigeria it is usually interplanted with cereals as a mixed crop (Oyenuga, 1968). However, legumes are especially well known to produce flatulence in humans (Onigbinde and Akinyele, 1983) due to the oligosaccharide content which form a major reserve of soluble carbohydrates during seed dormancy. In man, the enzymes α-galactosidase is not present in the digestive system, and as such man is unable to digest oligosaccharides. However, microflora in the lower intestine previously identified as gram-positive, spore forming anaerobic bacteria of Clostridia group are able to synthesize enzymes that ferment these undigestible oligosaccharides to produce CO2, H2, CH4, H2S and NH3 (Singh et al., 1993) The mixture of these gases produces flatulence, a discomfort that is specifically associated with consumption of low molecular weight oligosaccharides mostly present in legumes (Phillips, 1993). Raffinose, stachyose and verbascose have been identified as flatulence – inducers and when digested cause accumulation of gas, discomfort, diarrhea, pain and cramps (Deshpande and Deshpande, 1991; Liew and Buckle, 1990; Phillips, 1993); a factor which has tended to render legumes less acceptable. Nutritionists are therefore posed with the challenges of innovating processing techniques that could be used to either significantly reduce or completely eliminate the flatulence factors in foods without necessarily reducing its nutritive quality. This study thus, attempts to establish the influence of germination, boiling and dehulling on the soluble sugar (galactose, glucose, sucrose and rafinose) composition of a local cultivar of Vigna unguiculata. The potential food uses of the processed mill would also be analyzed using the emulsion stability index as this is what largely determines its acceptability and application as an ingredient in food systems. MATERIALS AND METHODS Seed Purchase: The seeds of a local black eyed variety of cowpea, Vigna unguiculata were purchased from a peasant farmer in Ekpoma, Edo State, Nigeria. Seed Selection and Treatment: Mature and viable seeds with uniform size were selected by hand picking. Selected seeds were soaked in a 2% sodium hypochlorite solution for 30min and washed thoroughly with distilled water several times in order to prevent microbial contamination during handling and processing. Seed Processing Techniques Germination: The selected and treated seeds (about 35) were placed on a moist tissue paper in a petridish for germination over a period of 1, 2, 3, 4, and 5 days in a dark cupboard. After each day of germination, the cowpea seeds in a particular petridish were harvested and placed in a dryer (Gallen Kamp Size 2) for 18-24h at a temperature regulated between 55 and 60C, until a constant weight of the seeds was obtained. Boiling: Some of the hand-picked, treated seeds were boiled at 100C for 2hrs. This treatment softened the seeds, which were then dried (as above) until a constant weight was obtained. Dehulling: Some of the selected and treated seeds were dehulled by carefully removing the outer coat or testa of the seeds. The dehulled seeds were then JASEM ISSN 1119-8362 All rights reserved J. Appl. Sci. Environ. Mgt. 2005 Vol. 9 (2) 65 72 Available Online at http:// www.bioline.org.br/ja Effect of Processing Techniques on The