Blue-green light treatment enhances the quality and nutritional value in postharvest Chinese cabbage (Brassica rapa L. ssp. pekinensis)

Abstract

Chinese cabbage is a vital while perishable leafy vegetable. Blue-green light combined treatment was found to be better to retain high nutritional value in Chinese cabbage than blue or green monochromatic light treatments by increasing the contents of soluble protein, indol-3-ylmethyl (I3M), flavonoids, total phenols and carotene. Gene expression study further revealed that blue-green light treatment increased the expression of biosynthetic genes in the metabolic pathways of glucosinolates (BrCYP79B2, BrIGMT1), flavonoids (BrCHS.1, BrF3H, BrCHI) and carotenoids (BrPSY1, BrLCYB, BrLCYE, BrVDE), as well as the light signal master regulator gene BrHY5.2. In addition, the blue-green light treatment up-regulated the activities of antioxidant enzymes, as well as 2,2-diphenyl-1-picrylhydrazyl and ferric-reducing antioxidant power activities, while reducing the levels of superoxide anion, hydrogen peroxide (H₂O₂), polyphenol oxidase (PPO) activity and malondialdehyde (MDA). Overall, our findings confirmed that blue-green light treatment can effectively enrich the nutritional value and prolong the shelf life of Chinese cabbage.

Keywords: Antioxidant activity; Blue-green light treatment; Chinese cabbage; Flavonoids; Glucosinolates.

Graphical abstract

Fig. 1

Schematic diagram of the experimental setup for postharvest light treatment on Chinese cabbage. A. Blue light, green light, and blue-green light combined treatments were used to treat the postharvest Chinese cabbage. B. Treat postharvest Chinese cabbage with 60, 120, and 300 umol m⁻² s⁻¹ light intensities, and take samples at 10 d. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 2

The effects of blue, green, and blue-green light treatment on the color index of Chinese cabbage during storage after harvest. A. Chroma (C*). B. Yellow index (YI). Statistical significant differences between treatment groups at the same period of storage are shown by values with distinct letters (P < 0.05). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 3

The effects of blue, green and blue-green light treatments of postharvest physiological parameters in Chinese cabbage during storage. A. Soluble protein. B. Soluble sugar. C. Total soluble solids. D. Water loss. E. Total flavonoids. F. Total phenolic compounds. Statistical significant differences between treatment groups at the same period of storage are shown by values with distinct letters (P < 0.05). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 4

The effects of blue, green and blue-green light treatments of postharvest antioxidant enzyme activity in Chinese cabbage during storage. A. PPO activity. B. POD activity. C. SOD activity. D. APX activity. E. CAT activity. F. H₂O₂ content. G. MDA content. Statistical significant differences between treatment groups at the same period of storage are shown by values with distinct letters (P < 0.05). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 5

The effects of blue, green, and blue-green light treatments of Chinese cabbage's postharvest total antioxidant capacity. A. FRAP activity. B. DPPH activity. Statistical significant differences between treatment groups at the same period of storage are shown by values with distinct letters (P < 0.05). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 6

The effects of blue, green and blue-green light treatments of postharvest GLS content during storage in Chinese cabbage. A. total GLS content. B. indolic GLS. C. aliphatic GLS. The indolic GLS have inducing 1-methoxyindol-3-ylmethyl (NMOI3M), Indol-3-ylmethyl (I3M), 4-methoxyindol-3-ylmethyl (4MOI3M), and 4-hydroxyindol-3-ylmethyl (4OHI3M). The aliphatic GLS includes (2R)-2-hydroxy-3-butenyl (progoitrin), 4-methylthiopentyl (4MT), 2-hydroxy-4-pentenyl (2-OH-4-pentenyl), 4-pentenyl (4-pentyl), and 5-methylthiopentyl (5MT). Statistical significant differences between treatment groups at the same period of storage are shown by values with distinct letters (P < 0.05). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 7

The effects of blue, green and blue-green light treatments of postharvest carotenoid, flavonoid, GLS metabolism-related gene and resistance-related gene expression pattern in Chinese cabbage during storage. A-H. The transcriptional level of carotenoid metabolism-related genes (BrHY5.2, BrPSY1, BrLCYB, BrLCYE, BrVDE, BrPDS, BrZEP, BrCCD4). I—K. The transcriptional level of flavonoid metabolism-related genes (BrCHS.1, BrF3H, BrCHI). L-M. The transcriptional level of GLS metabolism-related genes (BrCYP79B2, BrIGMT1). N—P. The transcriptional level of resistance-related genes (BrMYB4, BrPIF4, BrMYB12.1). Statistical significant differences between treatment groups at the same period of storage are shown by values with distinct letters (P < 0.05). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 8

Analysis of correlation between physiological indicators, reactive oxygen species metabolism, antioxidant activity, GLS metabolism, carotenoid, flavonoid, GLS metabolism-related gene and resistance-related gene in Chinese cabbage during storage for 21 d. A. Principal component analysis of 12 sample scores diagram from different light-treatment groups B. The correlation network diagram. When comparing the treatment group (blue, green, and blue-green light) to the control group (dark) during storage, asterisks indicate significant changes (*P < 0.05; **P < 0.01; *** P < 0.001). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)