Novel Combined Use of Red-White LED Illumination and Modified Atmosphere Packaging for Maintaining Storage Quality of Postharvest Pakchoi

摘要

Light-emitting diode (LED) irradiation is a promising way of food non-thermal preservation in recent years, and modified atmosphere packaging (MAP) is a traditional preservation method that can realize long-term storage. To maximize the shelf life of pakchoi and maintain its quality, pakchoi was packaged and stored under modified atmosphere with and without red and white LED illumination. The initial gas partial pressure (kPa) of O-2/CO2 in the three modified atmospheres was 5/10, 5/5, and 10/5. At the end of 30-day refrigerated storage period, LED illumination + 5 kPa O-2 + 5 kPa CO2 showed better effects than other treatments in delaying losses of mass, chlorophylls, soluble sugars, and ascorbic acid and ultimately maintained the package gas partial pressure at O-2/CO2 = 5.11/5.09. Furthermore, the treatment alleviated the accumulation of malondialdehyde, reduced the activity of the polyphenol oxidase and peroxidase, and better maintained DPPH radical scavenging activity. In addition, the combined treatment significantly reduced the amount of soluble quinone accumulated in pakchoi at the end of the storage period. The optimal treatment was effectively distinguished from other treatments by principal component analysis (PCA). The analysis confirmed that the freshness of the jointly treated samples was least different from the start day samples. Through correlation analysis, respiratory rate was highly positively correlated with soluble sugar content, color index, and DPPH radical scavenging activity. In conclusion, the combined treatment of LED irradiation and MAP led to the cumulative effect of different indicators, effectively alleviated the occurrence of browning of pakchoi, enhanced the preservation effect, and extended the shelf life of pakchoi to 30 days.