Hydrolysis of caseins and formation of hydrophilic and hydrophobic peptides by wild Lactococcus lactis strains isolated from raw ewes' milk cheese (original) (raw)
2001, Journal of Applied Microbiology
To investigate the hydrolysis of a S1-, a S0-, b B-, b A1-and b A2-caseins by 32 wild lactococci of different randomly ampli®ed polymorphic DNA (RAPD) patterns, isolated from raw ewes' milk cheese, and the production of hydrophilic and hydrophobic peptides from whole casein by those strains. Methods and Results: Most strains hydrolysed all caseins, and degraded b-caseins to a larger extent than a S-caseins, when the proteolytic activity of whole cells was determined by capillary electrophoresis. Higher levels of hydrophilic than of hydrophobic peptides were produced from whole casein by all strains, according to reverse-phase high performance liquid chromatography analyses. Conclusions: Cell envelope proteinases of most lactococci isolated from raw ewes' milk cheese were CEP II , CEP II/III or CEP III (classi®cation of Exterkate et al. 1993). A negative correlation was found between degraded a Sand b-caseins and a highly positive correlation between hydrophilic and hydrophobic peptides. Signi®cance and Impact of the Study: Fast acid-producing lactococci from raw ewes' milk cheese have considerable and diverse caseinolytic activities. Their peptide production patterns do not reveal serious risks of bitter-¯avour defect in cheeses if used as components of dairy starters.
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