Effect of lactose hydrolysed condensed whey and bifidobacterium bifidum in yogurt

Abstract

An experiment was conducted to assess the possibilities of utilizing whey solids in the form of condensed whey or lactose hydrolysed condensed whey as a substitute for NDM. Their effect was also studied in conjunction with B. bifidum as a dietary adjunct.

A detailed review of literature has been presented on the issues of lactose intolerance, hypercholesteraemia, beneficial effects of lactic acid bacteria in alleviating these conditions and also on acid tolerance and bile tolerance of cultures used in the present study. Methodology for the condensation of cheese whey, estimation of lactose in whey, B-galactosidase specific activity in the products, total cholesterol, HDL-cholesetrol and triglycerides in serum, assessment of acid tolerance and bile tolerance of lactic cultures used here have been detailed.

The experiment comprised of preparation of yogurt and bifidus yogurt using three methods of fortification viz. skim milk powder, condensed whey and lactose hydrolysed condensed whey. The products prepared were then analysed for B-galacosidase specific activity. Hypocholesteraemic and growth promoting effects of these products were assessed in a biological study using rats. Hypocholesteraemic and growth promoting effects of whole milk was also assessed in the biological study. Acid tolerance and bile tolerance of lactic cultures used in this study were also determined, in vitro.

From the above study, following conclusions were made.

1. B-galactosidase specific activity was noticed in substantial amount, in yogurt under different treatments. Bifidus yogurt showed a reduction in B-galactosidase specific activity, however, the activity was found to be enhanced when fortification was done with lactose hydrolysed condensed whey indicating that bifidus yogurt fortified with lactose hydrolysed condensed whey is superior. 2. No significant hypocholesteraemic effect was noticed in rats due to consumption of milk. All the rats fed with yogurt and bifidus yogurt except that given yogurt A1 showed a substantial reduction in serum LDL-cholesterol level and cardiac risk factor. However, bifidus yogurt supplemented with whey proteins showed maximum hypocholesteraemic effect and lowest cardiac risk factor showing the superiority of bifidus yogurt with whey proteins.

3. All rats given yogurt and bifidus yogurt showed a better daily weight gain when compared to the group fed whole milk along with feed and cholesterol.

4. Evaluation of acid tolerance of lactic cultures showed that, among the three cultures tested, B. bifidum exhibited maximum acid tolerance followed by S. salivarius ssp. Thermophilius. L. delbrueckii spp. Bulgaricus was found to be acid sensitive. 5. Bile tolerance study of pure and active cultures revealed that none of the tested cultures were completely inhibited by bile indicating theses cultures were bile tolerant to some extent.