Post‐harvest application of micellar pomegranate peel extract ( MPPE ) enriched starch‐casein composite coating to preserve the plum ( Prunus salicina L.) fruit during cold and ambient storage

Abstract

The present investigation applied a new coating (taro starch-casein composite enriched with micellar pomegranate peel extract (MPPE)) to mature plum (Prunus salicina L.) fruits in a randomized factorial design with five replicates. Results showed that, during storage of 20 days at 5 and 23°C, a recognizable reduction in weight and firmness loss with a stable respiration rate of coated plums than uncoated ones (4.5% and 8.4% at 5 and 23°C respectively) were noticed. The coating provided appealing optical properties with exceptionally controlled changes in pH and acidity of plums. The coating significantly reduced the change in total soluble solids (TSS) at the end of storage which was 9 and 11.67°brix compared to uncoated fruits (11.83 and 13.08°brix) at 5°C and 23°C, respectively. Moreover, the loss of bioactives (polyphenols, flavonoids, antioxidant capacity, and ascorbic acid) was arrested due to bioactive coating. A slight rise in total anthocyanins, carotenoids, and reducing sugars was observed at 23°C. However, they were efficiently suppressed in coated fruits stored at 5°C. Microbial growth was also effectively controlled in coated plum fruits. Overall, the results suggested that applying MPPE starch-casein composite coating on plum fruits exhibited a noticeable shelf life of ≥20 and 14 days at 5 and 23°C, respectively, over uncoated fruits (about 12 and 8 days). Novelty impact statement Plum fruit is a nutritionally rich climacteric fruit. However, it is very prone to deterioration and thus a quick loss in its quality. Many postharvest practices, such as irradiation, controlled and modified atmosphere storage, and chemical and thermal treatment have been used. However, these methods affect the nutritional value of fruits. The biodegradable bioactive coating is one of the cost-effective ways for the shelf-life extension of fruits. In this regard, natural bioactive and antioxidant-rich MPPE enriched starch-casein composite acts as a barrier against moisture loss and gas exchange and provides a glossy appearance to the fruits. Moreover, the bioactive coating provides excellent pathogen resistance with effective retention of bioactive compounds. Using the finding of this study, the application of MPPE enriched starch-casein composite coating to plum fruits stored at ambient (23°C) and cold (5°C) storage can extend the postharvest shelf-life of plum, save cost and energy, and open the global marketing window for plum fruits. MPPE-taro starch-casein composite coating was successfully used to prolong the postharvest life of plum fruits as well as to minimize fruit processing industrial waste by utilizing pomegranate peel as a source of a bioactive ingredient. Physical (color, firmness, and weight loss), chemical (pH, acidity, and TSS), and bioactive (polyphenols, ascorbic acid, carotenoids, and anthocyanins) properties of plums were found to be retained with the application of coatings during storage. The composite coating containing natural bioactive compounds can be used as an effective alternative to synthetic preservatives with an eco-friendly approach.