The purpose of this study was to explore the effect of treatment with dielectric barrier discharge (DBD) plasma followed by complexation with resveratrol on the physicochemical properties and digestibility of green banana starch. The results showed that DBD plasma treatment improved the complexation between banana starch and resveratrol. Compared with unmodified banana starch, the solubility, retrogradation properties, oil-holding capacity, gelatinization temperature (the onset gelatinization temperature (T_o), peak gelatinization temperature (T_p) and conclusion gelatinization temperature (T_c) increased from 64.10, 71.14 and 73.92 ℃ to 70.18, 75.79 and 82.53 ℃, respectively) and digestibility of the complex were significantly improved, while the swelling power and freeze-thaw stability were reduced. Scanning electron microscopy (SEM) showed that DBD plasma treatment produced more starch fragments and etched the starch surface. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) showed that resveratrol combined with banana starch through CH-π bond, which made the structure of the complex more compact and orderly, forming a non V-type inclusion complex with high crystallinity. Therefore, plasma treatment and then complexation with polyphenols can improve the processing properties of banana starch, which will contribute to the development of new health foods.

In this study, to investigate the effects of melatonin on pericarp browning in rambutan fruit, postharvest ‘Baoyan7’ rambutan fruit was immersed in melatonin solutions at varying concentrations for 15 min, air-dried, and then stored at 25 ℃ for 6 days. The results demonstrated that melatonin treatment at each concentration delayed browning and the decline in the chromaticity a^* value of rambutan pericarp, with the most pronounced effect being observed at 0.125 mmol/L melatonin. Physiological and biochemical analyses showed that melatonin treatment at 0.125 mmol/L repressed the increase in relative conductivity (RC) and malondialdehyde (MDA) contents, while retarding the increase in lipoxygenase (LOX), lipase (LPS) and phospholipase D (PLD) activities in rambutan fruit during storage, thereby preserving the integrity of the cell membrane. In addition, treatment with 0.125 mmol/L melatonin increased the contents of nicotinamide adenine dinucleotide (NADH) and flavin dinucleotide (FADH₂), enhanced the activities of energy metabolism-related enzymes including succinate dehydrogenase (SDH), cytochromic c oxidase (CCO), H⁺-ATPase and Ca²⁺-ATPase, and maintained high levels of adenosine triphosphate (ATP) and energy charge, thus improving cellular energy status. Moreover, this treatment enhanced γ-aminobutyric acid (GABA) content, and maintained high activities of glutamate decarboxylase (GAD) and GABA aminotransferase (GABA-T), thus contributing to enhanced cellular energy supply. These findings suggest that melatonin could retard postharvest browning and senescence in rambutan fruit by modulating membrane lipid and energy metabolisms.

We investigated the effect and underlying mechanism of postharvest treatment with 0.5 mmol/L melatonin (MT) treatment 1 h on chilling injury (CI) and ripening of ‘Guifei’ mango fruits during 4 days of shelf life at 25 ℃ after refrigeration at 4 ℃ for 28 days. The results showed that MT treatment markedly decreased CI and enhanced soluble solids content (SSC), respiration rate and ethylene production, while accelerating the decline in hue value and firmness of chilled mango fruits. Compared with the control group, MT treatment promoted the increase in the contents of water-soluble pectin (WSP) and chelate-soluble pectin (CSP) and the activities of polygalacturonase, β-galactosidase and endo-1,4-β-D-glucanase and accelerated the decrease in pectin methylesterase activity, thereby leading to cell wall degradation and fruit softening. Compared with the control group, higher activities of 1-aminocyclopropane-1-carboxylic acid synthase (ACS) and 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) and the expressions of their encoding genes (MiACS and MiACO) were observed in MT-treated fruits. Moreover, MT up-regulated the expression of MiETR1, MiERS1, MiERF1, MiEIN2, MiCBF1 and MiICE1 while down-regulating the expression of MiCTR1. These results indicated that MT treatment could promote the restoration of ripening and reduce CI in mango fruits during shelf life after storage at low temperature.