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United States Department of Agriculture

Agricultural Research Service

Research Project: EVALUATION AND MAINTENANCE OF FLAVOR, NUTRITIONAL AND OTHER QUALITY ATTRIBUTES OF FRESH AND FRESH-CUT PRODUCE

Location: Food Quality Laboratory

Title: Effect of dynamic temperature storage in retail display case on the quality and microbiota of packaged fresh-cut leafy greens

Authors
item Kou, Liping -
item Luo, Yaguang
item Yan, Shoulei -
item Ingram, David

Submitted to: Annual Meeting of the Institute of Food Technologists
Publication Type: Abstract Only
Publication Acceptance Date: February 12, 2013
Publication Date: N/A

Technical Abstract: Commercial refrigeration equipment is projected to rise 5.2% annually to meet the consumer demand for fresh-cut produce items. The highly variable temperature conditions associated with storage of fresh-cuts in commercial open-refrigerated display cases dramatically affects the shelf-life and quality of produce. High temperature also promotes pathogen growth and the FDA Food Code requires packaged fresh-cut leafy-green vegetables to be maintained = 41 ºF (5 ºC) for safety. However, industry is facing technical challenges in meeting this requirement. In this study, thermograph profiles were determined for a retail display case to investigate how packaged leafy-green vegetables are affected at different shelf positions during industry standard duty schedules. The temperatures of commercially packaged salads were recorded every 10 minute for three days or until their labeled use-by dates. The temperature profiles of product located at different depths within the same shelf were significantly different, where products closest to the aisle were above the 4-5 ºF requirement. Conversely, products located at the rear of the case were near freezing temperatures. In order to reduce this temperature differential, a number of technical options were tested, including the use of insulating plates to reduce the heat exchange between the refrigerated air from the back and the warm ambient air from the aisle. Also optimized was product loading patterns to facilitate convective heat transfer in the front of the case, as well as reducing the flow of refrigerated air to the products in the rear of the case to eliminate product freezing. Studies show that the insulating plates, when installed in the front of each shelf, can significantly decrease the front-to-back temperature differential of each leafy-green bag by at least 4-5 ºF. These results provide important information to increase consumer knowledge and help industry stakeholders enhance existing technology to maintaining food quality and safety.

Last Modified: 7/28/2014
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