Effect of high pressure treatment on viability of Lactobacillus delbrueckii ssp. bulgaricus, Streptococcus thermophilus and L. acidophilus and the pH of fermented milk

The effect of high pressure (HP) treatment at 480 mPa on viable populations of Lactobacillus delbrueckii ssp. bulgaricus, Streptococcus thermophilus, and L. acidophilus was studied in reconstituted skim milk. Reductions in viable population were directly related to the HP processing time. L. delbrueckii ssp. bulgaricus, showed the greatest sensitivity to HP treatment, whereas S. thermophilus showed the greatest resistance to HP treatment. All organisms showed a significant recovery in their viability after one week of refrigerated storage. High pressure treatment caused the pH level of fermented milk to increase by 0.49 to 1.01 units. The greatest increase in pH after HP treatment occurred in milk fermented by L. delbrueckii ssp. bulgaricus.link_to_subscribed_fulltex