Effect of heat treatment on the activity of hydrolyzed whey peptides on culture agglutination

Papain-hydrolyzed sweet whey was ultrafiltered (10,000 MW cut-off hollow fiber polysulfone membrane) in a batch mode system. Permeate containing low MW peptides was either frozen (--40°C), freeze-dried, or spray-dried. Frozen, freeze-dried and spray-dried peptides were used to prepare lactic culture media. A control medium was prepared from InsureRTM media (contains unhydrolyzed whey (58%), buffer salt (40%) and yeast extract (2%) in equivalent amounts). Commercial Lactococcus lactis ssp. lactis B62 culture was grown in each medium to prepare bulk starters. Milk was inoculated with bulk starter (10 ml). Severity of culture agglutination was determined by measuring pH differentials (top pH-pH bottom).; Culture grown in media containing frozen, freeze-dried and spray-dried hydrolyzed whey peptides and inoculated into skim milk were less agglutinated than culture grown in unhydrolyzed whey medium. No significant differences in culture agglutination were observed among the media containing the 3 types of processed peptides.; Media containing hydrolyzed freeze-dried whey peptides were heat treated at 50, 60, 70, 80, and 90°C for 30, 45, and 60 min prior to inoculation with B62 culture. Significant differences between the different heat treatments and between the different times of heat exposure were observed. Bulk starter media made with hydrolyzed whey peptides heat treated at 70°C for 60 min was the best medium for reducing culture agglutination. Possible peptide re-conformation into a more active form of the peptide was suspected upon cooling.; The main mechanism of how whey peptides reduce culture agglutination was by binding to the bacterial cells. This interaction prevent agglutinins from binding to the bacterial cells thus causing severe culture agglutination. Peptides appeared to bind tighter to the antigenic sites of bacterial cells when the bulk starter media was heated to 70°C for 60 min. Hydrolyzed whey peptides were shown to be active after exposure to temperature as high as 90°C for 30 min. This data indicated the whey peptides had a greater thermal stability than initially reported. Today's processing temperatures used to treat culture media should not effect the ability of hydrolyzed whey peptides to reduce culture agglutination.