Isochoric freezing and isochoric supercooling as innovative postharvest technologies for pomegranate preservation

Abstract

In the present study, the effect of isochoric supercooling at − 2.5 °C and isochoric freezing at − 2.5 °C/12 MPa on the qualitative attributes of arils from whole pomegranates (cv. “Wonderful”) and fresh-cut arils preserved for 30 days was investigated and compared with cold storage at 5 °C/95% RH and isobaric freezing at − 2.5 °C/0.1 MPa. Mass, total soluble solids (TSS), titratable acids (TA), pH, color, texture, microstructure and phytochemical components including anthocyanin and ascorbic acid contents were determined. Isochoric supercooling of whole pomegranates led to color and texture retention, and increased levels of total anthocyanins, ascorbic acid content and antioxidant activity. In addition, isochoric supercooling inhibited mesophilic aerobic bacteria growth and led to significantly lower counts of yeast and molds in comparison with cold storage at 5 °C. On the other hand, isochoric freezing was the most effective technology to inhibit bacterial, yeast and fungal growth and to increase ascorbic acid content. However, this technology caused some loss in texture. Isochoric supercooling was also the most effective preservation technology for fresh-cut arils to minimize loss in textural and color properties. In addition, mesophilic aerobic bacteria, yeast and mold counts were significantly lower in comparison to cold storage at 5 °C. These findings suggested that isochoric supercooling can be beneficial as a postharvest technology to extend shelf life for at least one month and maintain physicochemical quality of whole pomegranates and fresh-cut pomegranate arils.