Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 31, 2007
Publication Date: October 24, 2007
Citation: Kou, L., Luo, Y., Liu, X. 2007. Effects of mild heat treatment on microbial growth and product quality of packaged fresh-cut table grapes. Journal of Food Science. 72(8):S567-573.
Interpretive Summary: Packaged fresh-cut table grapes have emerged as a popular snack food sold or served in supermarkets and school lunch programs. However, tissue injury sustained during stem removal, and the openings created after stem removal make grapes susceptible to microbial growth, product decay and quality deterioration. In this research, we explored the possibility of using a mild heat treatment as an alternative to chemical treatment to control microbial growth and reduce decay, and a new method of preparing fresh-cut grapes with minimal tissue damage. We demonstrated that a combination of hot water treatment (45 °C, 8 min) and minimizing tissue injury significantly reduced microbial growth and decay development with no negative effects on grape color and texture. This hot water treatment showed a strong potential to extend the storage life of fresh-cut grapes from 14 days to 28 days with acceptable quality. This information is important to the fresh-cut grape processors and the grape industry to control decay and maintain the quality of grapes.
Table grapes with or without cap stems were sanitized in 100 µL L-1 chlorine solution for 1 min, followed by a mild heat treatment in a water bath (45 °C, 8 min) or an incubator (55 °C, 5min). After cooling, the berries were packaged in rigid trays sealed with a gas permeable film and stored at 5 °C for 14 days. Package atmospheres, product quality and decay rate, as well as microbial populations were evaluated at days 0, 7 and 14. Results indicate that hot water treatment retained significantly slower changes in O2, CO2 and C2H4 partial pressures in the package headspace than for the control and hot air treatment. Hot water treatment also maintained a significantly lower decay rate and microbial populations than for the control and hot air treatment at the end of storage. Color and texture were not significantly affected by either hot water or hot air treatment. Grapes that retained the cap stems maintained higher O2 and lower CO2 and C2H4 partial pressures in package headspace and lower decay rates and microbial populations than those without stems.