Improving temperature management and retaining quality of freshcut leafy greens by retrofitting open refrigerated retail display cases with doors

Authors: XIE, YURUI - University Of Florida; BRECHT, JEFFREY - University Of Florida; ABRAHAN, CAROLINA - University Of Florida; BORNHORST, ELLEN - US Department Of Agriculture (USDA); Luo, Yaguang - Sunny; MONGE-BRENES, ANA LORENA - Iowa State University; VORST, KEITH - Iowa State University; BROWN, WYATT - California State University

Submitted to: Journal of Food Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/2020
Publication Date: 7/31/2020
Citation: Brecht, J., Xie, Y., Abrahan, C., Bornhorst, E., Luo, Y., Monge-Brenes, A., Vorst, K., Brown, W. 2020. Improving temperature management and retaining quality of freshcut leafy greens by retrofitting open refrigerated retail display cases with doors. Journal of Food Engineering. https://doi.org/10.1016/j.jfoodeng.2020.110271.
DOI: https://doi.org/10.1016/j.jfoodeng.2020.110271

Interpretive Summary: The US Food Code requires temperature control for packaged fresh-cut leafy greens for improved food safety. However, the temperature fluctuation during retail store display negatively impacts the integrity of the cold chain. In this study, researchers at the USDA, University of Florida, and Iowa State University partnered with a retail chain in Florida to retrofit existing open vegetable display cases with doors, and monitored the display temperature profile over 5 months. Results showed an overall temperature decrease in the fresh-cut produce after retrofitting the open case with doors. This led to the increase in thermostat setting, which translates to the reduction in operational energy. Packaged salads also showed reduced quality deterioration after storing in the temperature conditions simulates the case with doors than those in the open case. Research information benefits consumers, retail industry, and the produce industry, in developing and implementing cost-effective solutions to improve food safety and quality.

Technical Abstract: Open refrigerated display cases in supermarkets are prevalent in the United States despite being prone to temperature fluctuations. We collaborated with a chain retailer in Florida to retrofit existing open vegetable display cases with doors, and monitored the display temperature profile over 5 months. Quality evaluations were performed on baby spinach, spring mix, and chopped romaine lettuce after storage under simulated open and closed case conditions. Doors improved spatial and temporal temperature uniformity in whole and fresh-cut vegetable cases. Optimal storage temperature for ready-to-eat produce (=5 °C) was recorded over 98% of the time after door installation versus 49 ~ 88% before retrofitting. An overall temperature decrease in the fresh-cut produce case from 3.62 to 0.66 °C necessitated a thermostat setting adjustment of +1.1 °C to avoid freezing of salad product. Elevated headspace CO2 concentrations and higher populations of aerobic bacteria, yeasts and molds were found under open display conditions for one or more salad products tested. Baby spinach leaves from the open case environment were lighter green and more yellowish in color. Electrolyte leakage and ascorbic acid content of the three salad types were similar between the open and closed door displays. Superior overall visual quality and stronger purchase intent were found for baby spinach and spring mix samples from the closed display case. These products had less severe off-odor and discoloration, and crispier texture than those held in the open case. The decreased overall temperature and improved temperature uniformity in closed display cases, along with better produce quality and potential energy savings, may encourage retailers to consider retrofitting open displays with doors or purchasing closed displays.