Use of Bifidobacterium bifidum in the manufacture of bifidus milk and its antibacterial activity

Abstract

A method to prepare bifidus milk on a commercial basis was standardised by addition of 10% inoculum of Bifidobacterium bifidum NDRI to 9% reconstituted skim milk (0.5% fat, 8.7% non-fat solids) heated at 95-degrees-C for 30 min and incubated at 37-degrees-C for 18 h. The product was able to meet all the criteria regarding technological and dietetic properties required in a quality product. The effect of various factors influencing the antibacterial activity of bifidus milk against 4 test organisms viz Escherichia coli, Shigella dysenteriae, Staphylococcus aureus and Bacillus cereus was determined. There was a significant variation (P < 0.05) in the antibacterial activity of bifidus milk made from various types of milk (reconstituted skim milk, cow milk, buffalo milk, reconstituted infant food) and with various types of heat treatment. Reconstituted skim milk was recommended for preparation of bifidus milk. Heating of milk to sterilization temperature or at 95-degrees-C for 30 min had a maximum effect on antibacterial activity. There was no significant variation (P > 0.05) in the antibacterial activity at different levels of inoculum (5.1 0 and 15%) or due to varying concentrations of sugar. Incubation at 37-degrees-C showed highest inhibitory activity. Bifidus milk had a minimum storage life of 3 weeks under refrigeration, retaining a sufficiently good taste and the requisite amount of microbial population (10(8) cfu/g) to be potentially beneficial.