OPTICOLD: for an Eco-designed cold chain for fresh cut salad
Résumé
The ANR project OPTICOLD aims to increase sustainability of the cold chain by optimizing the compromise between energy consumption, safety, quality and shelf-life for refrigerated processed food at the level of processing plants. We present here results obtained on spoilage of fresh-cut salad in relation to storage temperature of the raw plant material in the processing plant. Scarole salad heads (Chicorium endivia, var. latifolia) were stored at four temperatures (4, 7, 10 and 12 °C) during 5, 9 or 12 days. The salad heads ability to be processed was estimated by preparing fresh cut salad on a pilot processing line. The end-product was packaged under air in sealed polymeric bags (passive MAP), stored at 4 °C for 7 days. Losses at trimming of the raw material, respiration of processed fresh cut salad, global observations and atmosphere measurements in the packaged fresh cut salad were recorded for all temperatures and durations of raw salad storage. In parallel, texture (puncture and shear tests) and nuclear magnetic resonance (NMR) relaxometry on green leaves were performed on the raw salad heads and the fresh cut product. The three repetitions of this experiment have shown the impact of the origin and/or climactic conditions. Overall, losses at trimming, spoilage of the processed product, respiration of processed fresh cut salad, CO2 in the packaged end-product, increased with storage temperature and duration of the raw material. However, differences between 4°C and 7°C were not significant. Concerning leaves texture, deflection more maximal force was impacted by raw material storage. The NMR results showed that the transverse relaxation signal of leaves changed during salad storage, reflecting modifications in water status and distribution in the tissues and cells, related to the leaf senescence. These changes were amplified for storage temperatures above 7°C and after 5 days of storage. All these data, together with energy consumption of the refrigeration equipment in the plant, are being process to build an inclusive model, to predict impacts on fresh-cut salads and benefices on energy consumption of a modulation of temperatures according storage durations of raw salads.