Light-based improvement technology for postharvest fruits and vegetables flavor and regulation mechanism: a review

Fruits and vegetables (FVs) are consumed by humans for the distinctive flavors. Postharvest flavor declines limit its edible and commercial value. Light, as a novel non-thermal technology, is becoming a key strategy for enhancing FVs flavor. This review integrated the light treatment processes, summarized effects, mechanisms and factors of light emitting diodes (LEDs), ultraviolet (UV), pulsed light (PL) and γ-irradiation on FVs flavor. Based on photosensitization, photothermal and photochemical effects, four light treatments demonstrate positive impacts on flavor compounds. They enhance 9%-48% amino acid, 7%-41.5% organic acids and 4%-800% soluble sugar content. LEDs effectively boost the taste and aroma, becoming the most widely researched technology. UV and PL exhibit outstanding effects on aroma release, sweetness enhancement and astringency and bitterness mitigation, with UV also alleviating sourness degradation. γ-Radiation has been less explored, the promotion effect on the accumulation of flavor is observed. Factors such as light quality and dose are not overlooked. Based on the reduction of photothermal effects, future research should focus on elucidating the role of photoreceptors in the transcription regulation and the precise role of energy metabolism or other pathways in regulating flavor by responding to light signals.