Flavour enhancement of direct acidified Kareish cheese using attenuated lactic acid bacteria

Eight batches of Kareish cheese were made by direct acidification to study the effect of adding heat-or freeze-shocked Lactobacillus delbrueckii sp. bulgaricus or Streptococcus salivarius sp. thermophilus alone or along with freeze-shocked Lactococcus diacetylactis on the cheese quality. This cheese was compared with the best cheese obtained in the first part of study, which was made by adding sodium citrate and freeze-shocked Lactococcus diacetylactis. Addition of attenuated Lactobacillus delbrueckii sp. bulgaricus alone or combined with Lactococcus diacetylactis caused a significant (p less than or equal to 0.05) increase in soluble nitrogen (SN), soluble tyrosine (STY) and soluble tryptophan (STR), while it caused significant (p less than or equal to 0.05) decrease in total volatile fatty acids (TVFA) and cheese scores. Cheese made with combination of Lactobacillus bulgaricus and Lactococcus diacetylactis had lower SN, STY and STR, while it had higher TVFA and cheese scores than the corresponding cheese made with Lactobacillus bulgaricus alone. Addition of freeze-shocked Streptococcus salivarius sp. thermophilus alone increased SN, STY and STR, while decreasing TVFA and cheese scores of the resultant cheese. Adding of Lactococcus diactylactis along with Streptococcus salivarius sp. thermophilus caused a significant increase in SN, STY, STR, TVFA and cheese scores compared with cheese made with Streptococcus salivarius sp. thermophilus alone. Cheese made with either freeze-or heat-shocked Streptococcus salivarius sp. thermophilus and freeze-shocked Lactococcus diactylactis were the most acceptable cheese. Pickling period could be shortened by 33% without determinant effect on cheese quality or acceptability. (C) 1997 Canadian Institute of Food Science and Technology. Published by Elsevier Science Ltd.