Citrate is present in only low levels (0.15-0.2%) in milk and O-type starters do not include the citrate utilizing Lc. lactis subsp. lactis biovar diacetylactis. Diacetyl, an end product of citrate catabolism, however, is an important flavor component in Cheddar cheese (17).
Other end products of citrate metabolism—acetoin and 2,3-butanediol—are flavorless, although the carbon dioxide released may affect the texture of the cheese. In Cheddar cheese it is probable that the citrate is metabolized by the adventitious lactobacilli (100,101) although its value as an energy source for growth is equivocal (82,100).
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