Bitterness in Cheddar is associated with the accumulation of hydrophobic peptides, which are formed by action of the coagulant and starter proteinases (15). Bitter peptides can be derived from both as- and h-caseins. Chymosin is important in the production of bitter peptides, because residual coagulant in Cheddar releases extremely hydrophobic peptides from h-casein. Cutting the coagulum at low pH in Cheddar manufacture results in excessive retention of chymosin and the development of bitterness (15). A low salt content in the final cheese will enhance chymosin activity and result in the accumulation of bitter peptides. The overall level of bitterness in Cheddar will depend on the relative rates at which bitter peptides are formed and degraded to nonbitter peptides (15). Certain Lactococcus lactis strains are associated with development of bitterness in Cheddar cheese. The total proteolytic activity of the starter strains can have a significant effect on development of bitterness. Strains for Cheddar production in New Zealand are carefully selected for specificity of lactococcal CEP, and mixed strain starters normally include one proteinase-negative strain in order to limit total proteolytic activity and control bitterness (20).
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