Cheese milk composition and calcium lactate crystals in Cheddar cheese
K. SHARMA and S. Clark. Dept. of Food Science & Human Nutrition, Washington State Univ., 106 FSHN Bldg., PO Box 646376, Pullman, WA 99164-6376
White crystals in cheese, often identified as calcium lactate, are a problem for many Cheddar cheese manufacturers. The objective of this research is to understand how cheese-milk composition (lactose:protein ratio), lactic acid bacteria and aging temperature contribute to Calcium lactate crystals (CLC). Non-starter lactic acid bacteria (NSLAB) were isolated from a commercial cheese plant and finished cheeses. Isolates with highest rate of D/L-lactate racemization (Pediococcus acidilactici and Lactobacillus curvatus) were selected as adjunct cultures for use in cheese-making trials. The lactose:protein ratio was maintained at 1.23 for ultrafiltrated (UF) milk and 1.47 for standard milk with lactose concentration of 4.8% wt/vol for duplicates of both batches. Finished cheeses were aged at 7.2oC and 10oC. The cheeses were analyzed for lactose, L(+)-lactate, D(–)-lactate, and CLC for 6 months. Lactose concentration declined to 0.02-0.07% within one week of storage in all cheeses. Lactose was replaced by L(+)-lactic acid in all cheeses, but as aging progressed L(+)-lactic acid was replaced by D(-)-lactic acid in cheeses containing NSLAB. Cheeses stored at 10oC had higher levels of D(-)-lactic acid than cheeses stored at 7.2oC, due to faster NSLAB metabolism at higher temperature. D(-)-lactic acid increased to 40% of total lactic acid in cheeses with adjunct L. curvatus at the end of 8 weeks but was less than 15% in cheeses made with added P. acidilactici at the end of 6 months, indicating fast racemization by L. curvatus and slow racemization by P. acidilactici. Cheeses containing L. curvatus and stored at 10oC had crystals after 2 months. Contamination of cheese milk with certain NSLAB, regardless of lactose:protein ratio may lead to CLC, particularly at elevated storage temperature.
Session 41, Dairy Foods: Dairy microbiology