Effect of fermentation media and time on physicochemical and sensory properties of soybean powders

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