Water activity cheese ripening

It is the principal factor affecting the water activity of young cheeses and has a major effect on the growth and survival of bacteria and the activity of enzymes in cheese, and hence affects and controls the biochemistry of cheese ripening. 

Psychrotrophs, which can dominant the microflora of refrigerated milk, are a potentially important source of potent lipases in cheese. Cousins et al. (1977) considered that active lipase would be present in cheese if psychrotroph numbers exceed 10 CFU ml K Many psychrotroph lipases are heat stable and thus may cause rancidity in cheese over the course of a long ripening period. The subject of psychrotroph enzymes in cheese was discussed by Mottar (1989). Unlike psychrotroph proteinases, which are largely water-soluble and are lost in the whey, psychrotroph lipases adsorb onto the fat globules and are therefore concentrated in the cheese. 

Some of the ACE-inhibitory peptide fractions from cheese have shown in vivo activities in SHR. A water-soluble peptide preparation isolated from Gouda ripened for 8 months was found to have the most potent anti-hypertensive activity (maximum decrease in SBP=24.7 ( 0.3) mmHg (E<0.01) after 6h) when administered to SHR by gastric intubation at doses between 6.1 and 7.5mg/kg body weight. Three peptide fractions were isolated from water-soluble extract by hydrophobic chromatography using different concentrations of acetonitrile (Saito et al., 2000). 

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