Hydrolysis of caseins and formation of hydrophilic and hydrophobic peptides by wild Lactococcus lactis strains isolated from raw ewes' milk cheese
Aims To investigate the hydrolysis of αS1-, αS0-, βB-, βA1- and βA2-caseins by 32 wild lactococci of different randomly amplified 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 β-caseins to a larger extent than αS-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 CEPII, CEPII/III or CEPIII (classification of Exterkate et al. 1993). A negative correlation was found between degraded αS- and β-caseins and a highly positive correlation between hydrophilic and hydrophobic peptides. Significance 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-flavour defect in cheeses if used as components of dairy starters.
| Main Authors: | , , , , |
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| Format: | artículo biblioteca |
| Language: | English |
| Published: |
Wiley
2001
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| Online Access: | http://hdl.handle.net/20.500.12792/2978 http://hdl.handle.net/10261/289867 |
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| Summary: | Aims To investigate the hydrolysis of αS1-, αS0-, βB-, βA1- and βA2-caseins by 32 wild lactococci of different randomly amplified 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 β-caseins to a larger extent than αS-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 CEPII, CEPII/III or CEPIII (classification of Exterkate et al. 1993). A negative correlation was found between degraded αS- and β-caseins and a highly positive correlation between hydrophilic and hydrophobic peptides. Significance 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-flavour defect in cheeses if used as components of dairy starters. |
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