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    Laser light as a novel postharvest strategy to suppress chlorophyll degradation and oxidative stress in pakchoi (Brassica rapa subsp. Chinensis)
    (2026-01-01)
    Wen, Bo
    ;
    Kang, Chuankai
    ;
    Yang, Ting
    ;
    Zhan, Qi
    ;
    Chen, Tingyuan
    Short-term diode laser light irradiation is an emerging physical treatment for preserving quality and enhancing oxidative stress resilience in postharvest commodities. Rapid deterioration, including leaf yellowing, is a major factor limiting the postharvest shelf life of pakchoi. This study investigated the effects of short-term exposure to blue (450 nm) and red (660 nm) diode laser light on quality maintenance, oxidative stress mitigation, and chlorophyll metabolism in pakchoi stored at 20 °C for 5 days. The results demonstrated that 660 nm red laser irradiation significantly maintained visual quality and green coloration while reducing weight loss more effectively than 450 nm blue laser light and the untreated control. Both laser treatments reduced respiration rates and ethylene production and induced partial stomatal closure. Additionally, both treatments regulated oxidative stress responses by lowering malondialdehyde (MDA) content, lipoxygenase (LOX) activity, and reactive oxygen species (ROS) accumulation (H₂O₂ and O₂⁻), while enhancing both enzymatic and non-enzymatic antioxidant systems. The red and blue laser treatments also preserved total chlorophyll content by suppressing the expression of chlorophyll degradation genes (BcPAO, BcNYC1, BcPPH1) and upregulating chlorophyll biosynthesis genes (BcCAO, BcCHLH). Among the treatments, the 660 nm red laser exhibited the strongest effects, as confirmed by higher maximum quantum efficiency of PSII photochemistry (Fv/Fm) values and principal component analysis (PCA). Overall, these findings demonstrate that 660 nm laser irradiation synergistically modulates chlorophyll metabolism and antioxidant defense, offering an effective and practical physical strategy to extend the postharvest shelf life of leafy vegetables.
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    Efficacy of blue-diode laser exposure on the postharvest quality maintenance of strawberries
    (2024-12-01)
    Cui, Shijiang
    ;
    Supapvanich, Suriyan
    ;
    Xiao, Yinghui
    ;
    Zhang, Weiyan
    ;
    Li, Junbing
    The purpose of this research was to evaluate the impact of postharvest laser irradiation on strawberry visual quality and texture. In preliminary studies, strawberries were exposed to diode laser radiation for 2.5 or 5 min at wavelengths of 405, 450 and 660 nm. The treatment at 450 nm for 2.5 or 5 min kept the visual appearance without deterioration after storage at 20 °C, 70% RH, for 4 d. The diode laser at 450 nm was selected to screen the exposure duration, and 2 min of exposure preserved a desirable visual appearance without decay during storage at 20 °C, 70% RH, for 6 d. Subsequently, the impacts of a diode laser at 450 nm for 2 min on the quality and softening of strawberries during storage at 4 °C for 14 d were observed. The laser treatment delayed strawberry softness and visual fungal development and maintained total acidity level, but had no effect on the total soluble solids content and BrimA value during storage. The membrane degradation of the laser-treated fruits was retarded, due to the inhibitions of the increases in malondialdehyde levels, phospholipase-D (PLD) activity and FaPLD gene expression. The activities of cell wall hydrolases such as polygalacturonase (PG) and β-galactosidase (β-Gal) activity and the expressions of FaPG1 and Faβ-Gal1genes were suppressed by the laser treatment. The laser treatment had no effect on the cellulase activity. These findings show that diode laser irradiation is a promising postharvest approach for efficiently preventing strawberry softness and deterioration.
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