Improving spinach quality and reducing energy costs by retrofitting retail open refrigerated cases with doors

The prevalence of open-refrigerated display cases is ubiquitous in retail supermarkets, even in the face of the non-uniform temperature conditions present in these cases. In this paper, the temperature variations (ΔT) of packaged ready-to-eat baby spinach were evaluated for an open display case and a display case with glass doors, in order to assess the advantages of this physical barrier in minimizing ΔT and decay rate, and improving the visual quality of the samples after four days of storage. The two 3.66 m display cases were installed in the same room and conditions were constant at 21 °C and 60-70% of relative humidity, with a thermostat setting for both cases set at 0.6 °C. Results showed that the display case with doors significantly improved temperature uniformity and compliance with the U.S. Food and Drug Administration (FDA) Food Code recommendation of 5 °C or less to prevent microbial pathogen growth in packaged leafy greens. Only 1% of the temperature readings over four days in the case with doors were non-compliant with the FDA Food Code, while 24% of the readings in the open case were non-compliant; mostly recorded by the front positions of the case. The lower temperatures and ΔT of the case with doors were consistent with the higher visual quality scores (P < 0.001) for the baby spinach samples recorded by trained panelists, based on a 9-point hedonic scale, at 7.2 and 6.6 for the case with doors and the open case, respectively. Differences in decay rate were significant (P < 0.001) by the front of the case, with mean values of 8.8% for the open case and 5.5% for the case with doors. Furthermore, operational energy costs were 69% less than the open display case and the cost of door retrofits can be recouped in less than two years by energy savings alone.