15C-10 |
Effect of extended refrigerated storage on microbial populations of soft goat milk cheeses |
Y. W. PARK1, A. Kalantari1, M. R. Lim1, K. L. Arora2, and J. F. Frank3. (1) Agricultural Research Station, Fort Valley State University, 1005 State University Drive, Fort Valley, GA 31030-4313, (2) Department of Veterinary Science, Fort Valley State University, 1005 State University Drive, Fort Valley, GA 31030, (3) Department of Food Science and Technology, University of Georgia, Athens, GA 30602-7610 Although significant quantities of goat milk cheeses have been domestically produced and imported to the U.S., few research data are available on microbiological and food qualities of commercial goat milk cheeses. This study determined total aerobic, E. coli and coliform, yeast and mold, and staphylococcus aureus populations in commercially manufactured soft goat milk cheeses stored for different lengths under refrigeration. Three different lots of plain soft goat milk cheeses manufactured by a Grade A farmstead goat dairy in a southern state were stored for 0, 7, 14, and 21 days at 4oC, and examined for microbiological counts, pH and acid degree value (ADV). 3M Petrifilm plates were used to enumerate microbial populations as recommended by the manufacturer. E. coli/coliform counts utilized Violet Red Bile nutrients, a gelling agent and indicator of glucuronidase activity, and S. aureus counts involved 3 plates of baired-Parker agar and tube coagulase test with a thermostable nuclease (TNase) reactive disk. pH and ADVs were also obtained to evaluate lipolysis and shelf-life of the cheeses relative to the microbiological counts. Total aerobic counts of all soft goat cheeses regardless of the storage periods were 108/g or greater. Coliform counts ranged from 102 to 104/g with large variations, while no noticeable levels of E. coli was found. Yeast and S. aureus counts were 102 to 105/g, whereas mold counts were less than 102/g. The pH ranged from 4.22 – 4.50. ADV values significantly (P<0.01) increased with storage time (from 0.45 to 1.5 or above), indicating a high degree of lipolysis during the 21 day storage. The results indicate that commercial goat milk cheeses may contain high and variable microbial counts depending upon different lots, locations, time and manufacturers. Soft goat cheeses will substantially change in flavor during 21 days of refrigeration storage. Research will continue on consumer acceptance of this flavor change.
Session 15C, Dairy Foods
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