Growth characteristics and bioactivity of probiotics in tofu-based medium during storage

Lactobacillus acidophilus FTCC 0291, Lactobacillus bulgaricus FTCC 0411, Lactobacillus casei FTCC 0442, Lactobacillus fermentum FTD 13 and Bifidobacterium bifidum BB 12 were screened for their alpha-galactosidase activity over 24 h. Lactobacillus bulgaricus FTCC 0411 and L. fermentum FTD 13 showed highest alpha-galactosidase specific activity and were selected to be incorporated into tofufa for a storage study of 9 days at 25 and 4 degrees C. The viability of both probiotics in tofufa exceeded 10(6) CFU/g and was maintained over storage, mainly contributed by their ability to hydrolyse oligosaccharides and to utilise the reducing sugars produced. The presence of probiotics in tofufa showed an increase in the concentrations of organic acids which led to a decrease in pH levels. This exhibited a preservative effect, where total aerobes and total anaerobes were 2 log(10) CFU/g lower than the control. Probiotics in tofufa also liberated peptides with angiotensin-converting enzyme (ACE) inhibitory properties. Consistent viability and high proteolytic activity of probiotics in tofufa during storage suggested that tofufa is a suitable carrier for live probiotics with bioactive potential.