Carboxymethyl cellulose and carnauba wax treatments kept the pomegranate fruit (Punica granatum L.) quality during cold storage via improving enzymatic defense system and bioactive compounds

Abstract

The present research was conducted to apply carnauba wax and carboxymethyl cellulose coating on pomegranate fruits to evaluate their effects on the quantitative and qualitative characteristics of the fruits in storage. The experiment was designed with two factors, i.e., the type of coating and the duration of storage. The types of coating were carnauba wax (0.5%, 1%, 1.5%) and carboxymethyl cellulose (0.5%, 1%, 1.5%). Storage lasted for 50, 100, and 150 days after harvest. After immersion and drying treatments, the fruits were packed and transferred to the refrigerator at 4 ± 0.5 °C (relative humidity of 85 ± 5%). The fruits were examined in terms of quantitative and qualitative characteristics after each storage period. Before the analysis, fruits were exposed to physical, physiological, and biochemical characteristics for 3 days at 20 °C after cold storage. The results showed that 150 days after storage, the treatment group of carnauba 1.5% had the largest physiological loss in weight (13.55), pH (5.31), and anthocyanin content (25.77). In the same group of carnauba treatment and after 100 days of storage, measurements indicated the lowest peroxidase activity (0.37), the highest vitamin C content (76.34), and the highest chilling injury. The highest value of firmness of arils (1.81) and fruit skin (7.59) was observed in response to 1% and 0.5% carnauba wax after 100 days of storage, respectively. The control group (distilled water) showed the highest amount of acid (9.48) after 50 days of storage, the highest peroxidase activity (9.75), and the lowest amount of flavonoid (48.61) after 100 days of storage. The amount of soluble solids (17.6) and taste index (3.02) increased through the storage period. Fifty days after storage, the hue and chroma indexes of arils color increased, mostly resulting from the 1.5% carboxymethyl cellulose treatment, although the highest a* arils index was measured at harvest time. The highest hue, chroma, and b* skin index were observed in response to 0.5% carboxymethyl cellulose after 50 days of storage. In general, carboxymethyl cellulose, especially at 1%, was more effective in maintaining fruit weight, pH, vitamin C, acid, phenolic compounds, and fruit lightness, whereas the carnauba wax treatment was more capable of preserving the anthocyanin, flavonoid, and firmness of fruit while minimizing peroxidase and polyphenol oxidase activity. Apparently, carboxymethyl cellulose (1%) worked best with 100 days of storage, whereas carnauba wax (1%) did with 50 days of storage. The present investigation proposed an alternative method to prolong the shelf life of pomegranate fruits during the 150 days of storage.