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Influence of different combinations of Lactobacillus helveticus and Propionibacterium shermani on split defect in Swiss cheese. |
S. R. WHITE1, D. J. McMahon, J. R. Broadbent, C. J. Oberg, and G. L. Hong5. (1) Western Dairy Center, Dept. of Nutrition and Food Sciences, Utah State University, Old Main Hill 8700, Logan, UT 84322-8700, (2) Brewster Dairy, 675 Wabash Ave S., Brewster, OH 44613 JUSTIFICATION: One of the least controlled defects in Swiss cheese is development of splits. This defect appears during refrigerated storage after the cheese is removed from the warm room. Swiss cheese with splits is downgraded because it is unsuitable for slicing. OBJECTIVES: An experiment was designed to determine if splits are a result of an imbalance between the lactobacilli (rods) and propionibacteria (props) used to make the cheese. METHODS: A fast and a slow ripening strain of Lactobacillus helveticus and a fast and slower gas-forming strain of Propionibacterium shermani were used in a 2*2 factorial experiment. Eight vats of Swiss cheese, each producing five 200-lb blocks, were manufactured. Cheese was sampled and analyzed for pH, total lactobacilli (MRS agar), lactate D/L ratio, and leucine aminopeptidase activity. After 90 days, the cheese was cut into 8-lb blocks and evaluated for splits. RESULTS: Cheese pH was 5.2 prior to brining and increased to pH 5.4 during 28 days of aging. Lactate D/L ratios prior to brining were in the range 0.05-0.35. There were differences between treatments but no correlation between D/L ratio and percent splits was observed. Nor did there appear to be a correlation between leucine aminopetidase activity and percent splits. There was a slight initial drop in the number of lactobacilli in the cheese but then from 7 to 90 days it remained constant between 1*10^8 and 2*10^8 cfu/g in all cheeses. Cheese made using the slower prop had more splits (74% of blocks downgraded), especially when combined with the fast rod. The best combination was the faster prop combined with the slower rod (only 17% of the blocks downgraded). SIGNIFICANCE: Proper combination of the rod and gas-forming prop are important for making a high quality Swiss cheese.
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