Efficacy of blue-diode laser exposure on the postharvest quality maintenance of strawberries

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.