This study investigated the effects of postharvest immersion treatment with different concentrations of VB₆ on the quality of pakchoi (Brassica rapa subsp. chinensis) stored at (15 ± 1) ℃. A comprehensive evaluation was conducted using grey relational analysis. The results demonstrated that 200 mg/L VB₆ treatment resulted in the lowest yellowing index and significantly delayed the decline in chlorophyll content. After 8 days of storage, the total chlorophyll content in this treatment group was 44.9% higher than that in the control group. This treatment effectively maintained the levels of antioxidants including ascorbic acid and total phenols (which were increased by 21.6% and 14.9% compared to the untreated control group, respectively), while significantly inhibiting the accumulation of malondialdehyde (MDA) and nitrite (which were decreased by 36.4% and 24.3%, respectively). Furthermore, it enhanced the activities of catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD), and increased the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and total reducing power. Grey relational analysis revealed that the 200 mg/L VB₆ treatment achieved the highest comprehensive score (0.776). It is confirmed that 200 mg/L VB₆ can delay the postharvest senescence of pakchoi through multiple physiological pathways, which provides theoretical support for the development of novel preservation technologies.

This study aimed to investigate the effect of atomized slightly acidic electrolyzed water (SAEW) treatment during vacuum precooling on the quality of Chinese little greens during low temperature circulation and shelf life. The effects of vacuum precooling, vacuum precooling combined with tap water treatment and vacuum precooling combined with SAEW treatment on the appearance quality, nutritional components, antioxidant substances and free radical scavenging capacity of Chinese little greens were analyzed under low temperature ((4 ± 1) ℃) distribution and shelf conditions ((20 ± 1) ℃). The results showed that vacuum precooling + tap water treatment could slow down the yellowing and wilting, maintain higher nutritional quality and antioxidant capacity of Chinese little greens when compared to the control (without vacuum precooling or spraying tap water) and vacuum precooling groups. Furthermore, compared to vacuum precooling + tap water treatment, vacuum precooling + SAEW treatment could delay the yellowing and ageing process, suppress the decline in sensory quality and chlorophyll content, maintain higher titratable acid, soluble protein and soluble sugar contents, and retard the decrease in the contents of bioactive substances such as carotenoids, ascorbic acid, folic acid and total phenols and free radical (1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, hydroxyl radial and superoxide anion radical) scavenging capacity, thereby inhibiting the accumulation of nitrite and malondialdehyde and prolonging the shelf life of postharvest Chinese little greens. It is thus clear that the combination of vacuum precooling with SAEW treatment can effectively relieve the yellowing and ageing process of postharvest Chinese little greens and maintain good commodity characteristics.

To explore the effect of slightly acidic electrolyzed water (SAEW) on chlorophyll degradation in postharvest broccoli, the pattern of changes in the color, total chlorophyll content, chlorophyll derivative content, chlorophyll degrading enzyme activities, and key chlorophyll metabolism-related gene expression of postharvest broccoli after treatment with 50 mg/L SAEW was analyzed. The results showed that SAEW treatment could effectively slow down the degradation of total chlorophyll, maintain the contents of chlorophyll derivatives chlorophyll a, chlorophyll b, chlorophyllide a, chlorophyllide b, pheophorbide a, and pheophytin a, and delay the increase in the activities of chlorophyll metabolizing enzymes, Mg-dechelatase, pheophytinase, and pheophorbide an oxygenase in postharvest broccoli. Meanwhile, it significantly inhibited the expression of the genes encoding chlorophyll b reductase, chlorophyllase 1, chlorophyllase 2, chlorosis protein, pheophytinase, pheophorbide an oxygenase, red chlorophyll catabolite reductase, and aging specific cysteine protease, thereby allowing color protection and freshness preservation. In conclusion, SAEW can be used as an effective method to delay postharvest chlorophyll degradation and inhibit yellowing and senescence in broccoli.

To control the spoilage of fresh-cut chicory caused by microbial contamination of cuts, this study isolated and identified spoilage bacteria from fresh-cut chicory using 16S rRNA gene sequencing and evaluated the bactericidal activity and mechanism of slightly acidic electrolyzed water (SAEW). Five dominant spoilage strains were isolated, including Acinetobacter, Pseudomonas, Serratia, Pectobacterium, and Pantoea agglomerans. After treatment with 175 mg/L SAEW, it was found that the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and half-maximal effective concentration (EC₅₀) of SAEW against these five spoilage bacteria were 43.75–175, 87.5–175, and 28.52–99.54 mg/L, respectively. The results demonstrated that 175 mg/L SAEW exhibited antibacterial effects against all five spoilage bacteria while significantly delaying the decline of ascorbic acid and inhibiting the accumulation of malondialdehyde (MDA). Further analysis revealed that treatment with 175 mg/L SAEW disrupted the cellular morphology and membrane integrity of the spoilage bacteria, causing the cellular surface to become sunken, wrinkled and damaged and leading to the leakage of intracellular nucleic acids and proteins. These findings suggest that SAEW likely exerts its bactericidal effect by damaging the cell membrane structure, thereby resulting in the leakage of intracellular contents.

Melatonin (MT) is a low molecular weight compound with multiple biological functions in plants. It is known to delay leaf senescence in various species. However, no data are available on the MT signaling pathway in postharvest vegetables. This study demonstrates that MT increases cGMP concentration and the expression of the cGMP synthesis gene BcGC1 in pak choi. The cGMP inhibitor LY83583 destroys effect of MT delaying the leaf senescence. LY83583 also prevents MT treatment from reducing the expression of chlorophyll metabolism-related genes (BcNYC1, BcNOL, BcPPH1/2, BcSGR1/2, and BcPAO) and senescence genes (BcSAG12 and BcSAG21). It also inhibits MT from reducing the activity of the key chlorophyll catabolism enzymes Mg-dechelatase, pheophytinase, and pheide a oxygenase. Thus, the ability of MT to maintain high levels of chlorophyll metabolites is also destroyed. The Arabidopsis cGMP synthetic gene mutant atgc1 was used to confirm that delayed leaf senescence caused by MT is mediated, at least in part, by the second messenger cGMP.