Spraying glycine betaine on fresh pistachio fruits (Pistacia vera L.) for preservation in cold storage

Oxidative stress occurs during storage, often leading to a decrease in fruit quality and subsequently reducing its marketability. In this investigation, the ability of glycine betaine (GB) to extend the quality and storage of fresh pistachios stored in cold conditions was evaluated. The independent variables in this study were the concentration of GB (0, 5, 10 and 15 mM) and storage period (at harvest, 25, 50, and 75 days after harvest). Over time, the chlorophyll and carotenoid content of both kernels and hulls, as well as phenolics, flavonoids, antioxidant activity, taste, aroma, appearance of shells and hulls, firmness, and overall weight, tend to decrease. However, glycine betaine (GB) significantly prevents these reductions. GB effectively countered the rise in malondialdehyde, ion leakage, and hydrogen peroxide levels in kernels over time. In GB-treated samples, anthocyanin levels initially increased when comparing harvest time in both kernels and hulls, but subsequently decreased. GB enhanced peroxidase activity and suppressed polyphenol oxidase activity. However, contrary to expectation, GB reduces phenylalanine ammonia lyase activity. Overall, higher GB concentrations lead to a more pronounced effect. Based on the results, GB, particularly at a concentration of 15 mM, is recommended for preserving fresh pistachios during cold storage.