18D-2 |
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L. ZHANG1, F. Ren, S. Chen, W. Qin, S. Chen1, and L. Wang5. (1) College of Food Science & Nutritional Engineering, China Agricultural University, East Campus, Box 303, No. 17 Qinghua Donglu, Haidian District, Beijing, 100083, China, (2) Grain Processing Corp., 1600 Oregon Street, Muscatine, IA 52761 Quarg cheese is one of the most important fresh acid curd cheese varieties. Starter cultures used in the traditional production of Quarg include Streptococcus. lactis. subsp. Lactis, Streptococcus. lactis. subsp. Cremoris, and Streptococcus. lactis. subsp. Diacetylactis. So far, there were few reported studies focusing on the growth characteristics of the three mesophilic starter cultures. The objectives of this study were to determine the growth kinetics and the storage stability of these three mesophilic lactic bacteria. The population size and acidity of the three starter cultures in RSM (reconstituted skim milk) medium were measured every two hours to provide the growth kinetics and the acidification kinetics of them. To determine the storage stability of the three lactic bacteria, we measured the acid-producing capability and the population of zoetic lactic bacteria after the starter cultures had been stored for 3, 5, 8, 11 and 14 days respectively at 4 degree(Celsius) In the RSM medium, all of the three strains had an adaptation phase of 2 hours. The generation times of Streptococcus. lactis. subsp. Lactis, Streptococcus. lactis. subsp. Cremoris, and Streptococcus. lactis. subsp. diacetylactis were 0.923h, 1.146h, and 1.090h respectively. The maximum acid producing rates (delta pH/h) were was 0.213, 0.243, 0.073 respectively. The population size and acid-producing capability of Streptococcus. lactis. subsp. Lactis and Streptococcus. lactis. subsp. Cremoris were relatively constant in the first 8 days at 4 degree (Celsius). The population size of Streptococcus. lactis. subsp. diacetylactis was constant in 14 days at 4 degree (Celsius). Better understanding of growth kinetics and the storage stability of the three mesophilic lactic bacteria provides basis for improving the process of making Quarg cheeses.
Session 18D, Food Microbiology: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |