We aimed to purify polyphenols from distiller’s grain extract using macroporous resins and to identify its polyphenolic components. The influence of operational parameters on purification efficiency was investigated. The polyphenolic composition was analyzed by ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) and then quantified by UPLC-MS using authenticated standards. The results showed that the optimal purifying conditions were D101 resin with a dosage of 3 g, four hours adsorption, three hours desorption time, and 60% ethanol as the eluent, producing the highest purification rate of 51%. The purified distiller’s grain extract exhibited stronger antioxidant activity than the unpurified extracts, which was assessed using DPPH and ABTS methods (IC₅₀ DPPH = 34.03 and 16.21 μg/mL, respectively; IC₅₀ ABTS = 20.31 and 5.73 μg/mL, respectively). UPLC-MS results indicated that (−)-epicatechin is the major compound found in distiller’s grain extract which was quantified as 562.7 μg/g extract, followed by ferulic acid (518.2 μg/g), p-hydroxybenzoic acid (417.7 μg/g), caffeic acid (217.1 μg/g), syringic acid (158.0 μg/g) and quercetin (147.8 μg/g). Two compounds, vanillic acid (66.5 μg/g) and gallic acid (41.4 μg/g), were found in lower concentrations. The findings of this study suggest that purification of polyphenolic compounds from distiller’s grain by macroporous resins is feasible, providing a new and effective method for the secondary use of distiller’s grain resources.

To improve storage of peach fruit, the effect of slightly acidic electrolyzed water (SAEW) dissolved without and with Ca(NO₃)₂ (at concentrations of 0.5, 1, and 2%) on fruit browning, antioxidant system, tissue Ca²⁺ content and distribution, metabolism of cell wall polysaccharides, and related modifying enzymes was evaluated at 25°C for 8 d. Results showed that Ca(NO₃)₂ and SAEW had synergistic effects on reducing ethylene production, respiration rates, and browning index; inhibiting the accumulation of free radicals and lipid peroxidation, and polyphenol oxidase activity; maintaining fruit firmness and higher levels of phenolic compounds, enzymatic and non-enzymatic antioxidants; increasing tissue Ca²⁺ content and distribution; and delaying the disassembly of cell wall polysaccharides and activities of cell wall-modifying enzymes. These results revealed that 1% Ca(NO₃)₂ in SAEW treatment has potential as a commercial cleaning process to extend fruit life, through suppressing browning and solubilization of pectin, protecting the antioxidant system, and facilitating Ca²⁺ absorption.

The effect of post-harvest application of methyl jasmonate (MeJ) on reactive oxygen species, antioxidant systems, and cellular structure in Chinese winter jujube (Ziziphus Jujuba Mill.) at the major ripening stages of green maturity (GM) and half-red maturity (HM) were investigated. Jujube fruit at each ripening stage were treated with 0, 50, 100, and 200 μmol l⁻¹ MeJ for 24 h, then stored at 20 ± 2°C for shelf-life testing. Thereafter, changes in firmness, color, respiration rate, superoxide anion (O₂⁻), hydrogen peroxide (H₂O₂), malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), ascorbic acid (AsA), and glutathione (GSH) were measured at 4-d intervals for up to 8 d. Results showed that, in comparison with control fruit, MeJ treatment effectively suppressed the decrease of firmness, color, and respiration rate, inhibited the production of O₂⁻ and accumulation of H₂O₂ and MDA, maintained higher activities of SOD and CAT and contents of AsA and GSH, and preserved the integrity of cell membranes and organelles. The degree of maturity influenced the benefits of MeJ application. The 100 μmol l⁻¹ MeJ treatment had a positive impact on antioxidant systems for GM fruit, whereas a MeJ concentration below 100 μmol l⁻¹ was found to extend the shelf life of HM fruit.