Cheddar cheese lactate

Lactate in cheese may be oxidized to acetate. Pediococci produce 1 mol of acetate and 1 mol of CO2 and consume 1 mol of O2 per mole of lactate utilized (Thomas et al, 1985). The concentration of lactate in cheese far exceeds that required for optimal oxidation, and lactate is not oxidized until all sugars have been exhausted. The oxidation of lactate to acetate in cheese depends on the NSLAB population and on the availability of O2, which is determined by the size of the block and the oxygen permeability of the packaging material (Thomas, 1987). Acetate, which may also be produced by starter bacteria from lactose (Thomas et al., 1979) or citrate or from amino acids by starter bacteria and lactobacilli (Nakae and Elliott, 1965), is usually present at fairly high concentrations in Cheddar cheese and is considered to contribute to cheese flavor, although high concentrations may cause off-flavors (see Aston and Dulley, 1982). Thus, the oxidation of lactate to acetate probably contributes to Cheddar cheese flavor. 

Thomas, T. D. (1987). Acetate production from lactate and citrate by non-starter bacteria in Cheddar cheese. N.Z. J. Dairy Sci. TechnoL 22, 25-38. 

Agarwal, S., Sharma, K., Swanson, B.G., et al. (2006) Nonstarter lactic acid bacteria biofilms and caldum lactate crystals in Cheddar cheese. J Dairy Sci 89,1452-1466. 

Typical levels of lactate in Camembert, Swiss, and Cheddar are 1.0,1.4, and 0.5%, respectively (Karahadian and Lindsay, 1987 Turner et al, 1983 Turner and Thomas, 1980). The fate of lactic acid in cheese depends on the variety. Initially, Cheddar contains only l(+) lactic acid but as the cheese matures, the concentration of o-lactate increases. The latter could be formed from residual lactose by lactobacilli (Turner and Thomas, 1980 Thomas and Pearce, 1981 Tinson et al, 1982) or by racemization of l-lactate by NSLAB. Except in cases where the post-milling activity of the starter is suppressed (e.g., by S/M > 6%), racemization is likely to be the principal mechanism (Thomas and Crow, 1983). Racemization of L-lactate, which appears to occur in several cheese varieties (Thomas and Crow, 1983), is probably not significant from the flavor viewpoint. However, calcium D-lactate may crystallize on the surface of cheese, causing undesirable white specks (Pearce et al, 1973 Severn et al, 1986 Dybing et al, 1988). 

Of the three primary events in cheese ripening, i.e., glycolysis, lipolysis, and proteolysis, proteolysis is usually the rate-limiting one. Glycolysis is normally very rapid and is complete in most varieties within 24 hr therefore, acceleration of glycolysis is not of interest. The modification and catabolism of lactate is either of little or no consequence (e.g., Cheddar or Dutch varieties) or is quite rapid—2-3 weeks (e.g., Swiss types, Camembert)—and consequently its acceleration is not important. Lipolysis is limited in most cheese varieties, exceptions being some Italian varieties, e.g., Romano and... 

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