Enhanced lactose cheese milk does not guarantee calcium lactate crystals in finished cheddar cheese

Three experimental batches of Cheddar cheese were manufactured in duplicate, with standardization of the initial cheese-milk lactose content to high (5.24%), normal (4.72%, control), and low lactose (3.81%). After 35 d of aging at 4.4 degrees C, the cheeses were subjected to temperature abuse (24 h at 21 degrees C, unopened) and contamination (24 h at 21 degrees C, packages opened and cheeses contaminated with crystal-containing cheese). After aging for 167 d, residual cheese lactose (0.08 to 0.43%) and L(+)-lactate concentrations (1.37 to 1.60%) were high and D(-)-lactate concentrations were low (<0.03%) for all cheeses. No significant differences in lactose concentrations were attributable to temperature abuse or contamination. No significant differences in L(+)- or D(-)-lactate concentrations were attributable to temperature abuse. However, concentrations of L(+)-lactate were significantly lower and D(-)-lactate were significantly higher in contaminated cheeses than in control cheeses, indicating inoculation (at d 35) with heterofermentative nonstarter lactic acid bacteria able to racemize L(+)-lactate to D(-)-lactate. The fact that none of the cheeses exhibited crystals after 167 d demonstrates that high cheese milk or residual lactose concentrations do not guarantee crystal formation. Contamination with nonstarter lactic acid bacteria can significantly contribute to D(-)-lactate accumulation in cheese.