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M: Food Microbiology & Safety
Thermal Inactivation of Escherichia coli O157:H7 in Strawberry Puree and Its Effect on Anthocyanins and Color
Article first published online: 11 DEC 2013
Journal of Food Science © 2013 Institute of Food Technologists® No claim to original US government works
Journal of Food Science
Volume 79, Issue 1, pages M74–M80, January 2014
How to Cite
Hsu, H.-Y., Huang, L. and Wu, J. S.-B. (2014), Thermal Inactivation of Escherichia coli O157:H7 in Strawberry Puree and Its Effect on Anthocyanins and Color. Journal of Food Science, 79: M74–M80. doi: 10.1111/1750-3841.12327
- Issue published online: 24 JAN 2014
- Article first published online: 11 DEC 2013
- Manuscript Accepted: 7 NOV 2013
- Manuscript Received: 1 JUL 2013
- USDA/NIFA. Grant Number: 2011–68003–20096
- National Science Council of Taiwan
- Escherichia coli O157:H7;
- thermal processing
Raw whole strawberries, if contaminated with pathogens, such as Escherichia coli O157:H7, must be pasteurized prior to consumption. Therefore, the objective of this research was to investigate the thermal inactivation kinetics of E. coli O157:H7 in strawberry puree (SP), and evaluate the changes in anthocyanins and color, and the survival of yeasts and molds (YM) after thermal processing. Inoculated with a 5-strain cocktail, fresh SP, with or without added sugar (20 and 40 °Brix), was heated at 50, 52, 54, 57.5, 60, and 62.5 °C to determine the thermal resistance of E. coli O157:H7. In raw SP, the average D-values of E. coli O157:H7 were 909.1, 454.6, 212.8, 46.1, and 20.2 s at 50, 52, 54, 57.5, and 60 °C, respectively, with a z-value of 5.9 °C. While linearly decreasing with temperature, the log D-values of E. coli O157:H7 increased slightly with sugar concentration. The log degradation rates of anthocyanins increased linearly with temperature, but decreased slightly with sugar concentrations. These results suggest that sugar may provide some protection to both E. coli O157: H7 and anthocyanins in SP. The browning index was not affected by heating at 50 and 52 ºC at low sugar concentrations, but increased by an average of 1.28%, 2.21%, and 10.1% per min when SP was exposed to heating at 54, 57.5, and 60 °C, respectively. YM was also inactivated by heating. This study demonstrated that properly designed thermal processes can effectively inactivate E. coli O157:H7 and YM in contaminated SP, while minimizing the changes in anthocyanins and color.
This study investigated the thermal inactivation kinetics of E. coli O157:H7 in strawberry puree and its effect of degradation of anthocyanins and changes in color. The results of this work may be used to develop and optimize thermal processes that minimize the degradation of anthocyanins during pasteurization of strawberry puree.