Production and Proximate Composition of Yoghurts from Tiger nuts and Soybean using Lactic Acid Bacteria Starter Cultures
Abstract
Traditionally, yoghurt is fermented whole milk. It is believed to possess nutritional and therapeutic properties. Appropriate aliquot of commercially prepared yoghurts was sourced and used to isolate LAB bacteria using standard procedures. The morphological characteristics of the isolates were studied and recorded. They were later stored in MRS agar slants at 4oC in the refrigerator for further use. Biochemical and sugar fermentation tests were carried on the isolates and the isolates were identified as Lactobacillus acidophilus, Lactobacillus bulgaricus and Streptococcus thermophilus. They were then inoculated into extracted, sterile tiger nut and soy milks for the production of yoghurts. For pH, it was observed that the highest pH at zero hour was 6 from MILK COM while the lowest after 8 hours of fermentation was 3.6 from both TGN LAB and TGN COM respectively. For temperature, 29.0oC was the lowest temperature at the beginning of the fermentation from MILK LAB while the highest temperature at the end of the fermentation was 31.5oC from TGN LAB, TGN COM, SOY LAB, SOY COM and MILK LAB respectively. The protein content of SOY LAB yoghurt (3.69) was the highest while those of MILK LAB and MILK COM (statistically the same) were the lowest. TGN LAB yoghurt had the lowest (3.09) fat content while MILK LAB (Control 1) had the highest (3.87) value. The fiber content of the four samples produced from soy and tiger nut milks were of the same value statistically while MILK LAB and MILK COM have zero fibre. The lowest carbohydrate content (3.41) was found in yoghurt made from SOY LAB while the highest value (4.90) was in TGN LAB yoghurt. Yoghurt made from TGN LAB has the highest acceptability (7.37). Yoghurts made from soy and tiger nut milks have higher carbohydrate and protein contents than those made from animal milk. They also possess better nutritional values such as lower fat and higher fibre contents than the dairy yoghurts. Yoghurt made from tiger nut milk had best acceptance to the panelists than the dairy yoghurts.
Keywords: Fermentation, LAB, starter culture, Soy milk, Tiger Nut Milk, yoghurt