SummaryAutolysis of and proteolysis by variousLactococcus lactissubsp.cremorisstrains were monitored in cheese ‘juice’ extracted by hydraulic pressure up to 63 d ripening. Viability was lowest for strain AM2 (non-bitter), intermediate for strain HP (bitter) and highest for the defined mixed strains G11/C25 (non-bitter). Autolysis monitored by the levels of the intracellular marker enzymes lactate dehydrogenase (EC 1.1.1.27), glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and post-proline dipeptidyl aminopeptidase proceeded in the order AM2 > G11/C25 > HP. Differences in autolysis between strains did not appear to be due to differences in stabilities of the marker enzymes, populations of non-starter lactic acid bacteria or levels of the marker enzymes in the strains. Proteolysis, as measured by gel permeation FPLC and free amino acid analysis of the cheese juice was highest for AM2, intermediate for G11/C25 and lowest for HP. The results of this study provided some evidence that differentLactococcusstrains used for cheesemaking had different autolytic patterns during ripening, the effects of which on ripening and flavour development have not yet been clearly demonstrated.

Summary -The effects of exogenous enzyme preparations, ie FlavourAge-FR or DCA 50, on proteolysis flavour texturai development in high (38%) or low (35%) moisture Cheddar cheeses ripened at 4 or 10°C for 180 days were investigated. Proteolysis, as measured by nitrogen soluble in water (WSN), 75% ethanol (ALC-N) or 5% PTA (PTA-N), was highest in cheeses with added FlavourAge-FR, intermediate in DCA 50-treated cheeses and lowest in control cheeses at both 4 or 10°C. The WSN was chromatographed by fast protein liquid chromatography (FPLC) and free amino acid analysis. The concentrations of low molecular weight « 10000) peptides and free amino acids were highest in FlavourAge-FR-treated cheeses while DCA 50-treated cheeses had intermediate levels compared to control cheeses at 4 or 10 oC. Polyacrylamide gel electrophoresis of the cheeses during ripening showed that FlavourAge-FR caused significant proteolysis of both a 5 1-and p-caseins, while DCA 50 caused no significant degradation of p-casein. Cheese texture, as measured by yield value, was affected most by FlavourAge-FR treatrnent. Taste panel analysis of the cheeses indicated IitIJe acceleration of f1avour development by any of the treatments, and in some cases enzyme treatrnent led to off-flavours and texturai defects.

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During the past few years, synthetic DNA, used as a primer in DNA polymerization, in site-directed mutagenesis or as a probe in gene selection, has assumed a central role in recombinant DNA technology (1). This was made possible by the development of methods for efficient solid phase chemical synthesis. Deoxyribonucleotides are ideally suited to solid-phase synthesis since their relative chemical uniformity allows for application of oligodeoxyribonucleotide (oligonucleotide) purification techniques, which are largely dependent on chain length. Hence, the potential disadvantage of omitting purification after each coupling step is minimized. This contrasts with peptide synthesis in which purification of the final product is more difficult, thereby placing greater demands on coupling efficiency. In practice, coupling efficiencies of at least 95% are now attainable in oligonucleotide synthesis because of the availability of highly reactive mononucleotides and specially developed coupling catalysts. In optimized systems, this allows for synthesis of oligomers greater than 50 bases in length.