Abstract
Fermentation improves quality of food, and is exploited in processing soymilk powder. Unfortunately, there is no unified fermentation procedure for producing powdered soymilk in Nigeria. A fermentation condition to produce high nutritional and most acceptable powdered soymilk is ideal for Nigerians. This study evaluated the effect fermentation media and time on physicochemical and sensory properties of powdered soymilk. Seven batches (600 g each) of soybean seeds were fermented, the first three in neutral water, sample A for 4 h, B for 16 h in the same water, and C for 16 h but changing the water every 4 h. The next two were fermented in alkaline solution for 16 h, D in the same water, and E with changing the water every 4 h. The last two were fermented for 16 h in acidic solution, Fin the same solution and G with changing the water every 4 h. The beans were processed into cooked soy flour and analyzed for physicochemical and sensory properties. Fermentation enhanced better quality than soaking; fermentation time and medium pH significantly (p < 0.05) induced variations in quality of the powder. Soaking produced soy powder with highest carbohydrate (44.47 %) and fibre (1.355%) but significantly (p < 0.05) low in protein, minerals and crude fat. Continuous 16-h fermentation in the same medium produced soy powders with lowestphytochemical contents. Soaked (4 h) soybean in neutral water (A) produced powder with 39.50% protein, 44.47% carbohydrates, 1.35% fibre, 5.58% fat and 2.75% ash while continuous fermentation for 16 h in the same water produced powder (B) with 42.47% protein, 41.71% carbohydrate, 1.22% fibre, 5.81% fat and 2.42% ash. Continuous 16-h fermentation was better than changing the medium; and neutral medium was better than acidic and alkaline medium. All the soy powder high sensory scores (≥ 5) and were acceptable to the panelists. Thus, 16-h continuous fermentation in neutral medium was more cost effective and produced soybean powder of better quality than fermenting in alkaline and acidic media.
 Key words: fermentation time, quality, soaking media, soybean powders
Highlights
The current global economic recession and poor income make it impossible for many families to afford animal protein
Effect of Fermentation Time and Soaking Mediums on Proximate Composition of Soybean Powders Table 1 shows the proximate composition of soy powders produced from soybeans fermented in different media at different time intervals
Soybean powders sample fermented in alkaline pH had significantly (p < 0.05) higher moisture content (Sample F with moisture content of 7.72%) than every other sample
Summary
The current global economic recession and poor income make it impossible for many families to afford animal protein. The seed flour is a good source of protein, for families with low income who cannot afford animal protein. Soybean flour is rich in minerals, especially calcium, potassium, magnesium, iron, zinc and copper (FAO, 2009) It is an excellence source of vitamins including thiamine, riboflavin and niacin (Singh et al, 2000). Soy flour is a good source of protein, essential fatty acids, dietary fiber and many important bioactive compounds such as is flavones. Raw soybeans need to be properly processed to reduce many of these anti-nutritional factors, improve taste and texture of soy flour, making it more acceptable to consumers before consumption. There is currently no standardized soaking time, pH and fermentation period to achieve high quality soy flour. It is the thrust of this study to investigate the effect of soaking time, pH, changing of water during soaking and fermentation on quality characteristics of soy flour
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