Dept. of Dairy Science and Technology. Fac. of Agric... Alex. Univ. Egypt
Abstract
The proteolytic and autolytic activities in buffer system of six strains of lactic
acid bacteria isolated from Egyptian dairy products were examined. The selected
strains (Lactococcus lactis sub sp. iecris 04RM. Lactococcus lactis sub sp. iaciis
608M. Lactobaciiius saiiverius 194KC. Lactobaciiius mamnosus 56R. Enterococcus
iaeciurn 151D and Enterococcus faecium 174RM) were blended into freshly made
starter—free Ras cheese (acidified with gluoono- o -lactone. GDL) to town slum'es that
were ripened anaerobically at 30°C for 5 days. Results showed relatively constant
values of moisture and fat contents in slurries. while pH values decline after five days
of ripening. The highest release of free fatty acids was noticed in four slurries (Eni.
faeciurn 174RM. Lb. saiiverious 194KC. Lb. mamnosus 56R and Lo. iectis subsp.
iaciis EDEN). on the contrary. the mixture of strains in slum‘es showed a moderate
release of free fatty acids. Peptidase activities in the proteolytic system of the tested
Ras cheese sium‘es have been demonstrated from the Cadmium- ninhydrine (Cd-
ninhydrine) reaction of water-soluble extract. The highest values of free amino acids
(FAA) were noticed in the individual tested Iactobacillus strains. Whereas. sluny
containing mixed strains showed a moderate release of FAA (Lb. seiivarious 194KC +
Lc. lactis subsp. iactis 64RM). Proteolysis of studied slun-ies was also qualitatively
followed by using Urea- poiyacrylamide gel electrophoresis ten. 'nnlque. Casein
degradation an‘ses quickly in slurries during 5 days of ripening. tin-casein hydrolysed
to small weight peptides. while. the B- casein is apparently not degraded. The
organoleptic evaluations were correlated with the release of free amino acids and
aminopeptidase activity. So. the present investigation emphasizes the importance of
proteolytic system of selected strains in improving the flavour and texture of cheese.
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