Effects of vibration stress on the browning and antioxidant capacity of Agaricus bisporus

Agaricus bisporus is one of the most popular foods rich in nutrition and with unique flavor among the edible fungus. However, the edible part of A. bisporus is prone to water loss and mechanical damage during the process of postharvest transportation, thereby leading to browning and decay, due to its high water content without the protective tissue in the outer skin. This study aims to explore the effect of vibration stress on the storage quality of A. bisporus during logistics and transportation for better cushioning packaging, and then to determine the relationship between browning degree and antioxidant capacity of A. bisporus after vibration stress treatment. W192 strain of A. bisporus was treated in a simulated transportation vibration with different duration times (0, 8, 16, and 24 h) at the frequency of 3.33 Hz, and then stored at 4℃ for 15 days. The results showed that the browning degree of A. bisporus cap was aggravated under vibration stress, where the brightness (L*) in the vibration treatment group was generally lower than that in the control group (P < 0.05) during the storage. After 15d of storage, the browning index (BI) and total chromatism (ΔE) of samples treated by the vibration for 24 h were 1.53 and 1.57 times higher than that in the control, respectively. Vibration treatment increased the permeability of cell membrane, thereby accelerating the consumption of non-enzymatic antioxidants, such as phenols, vitamin C, and glutathione (GSH), particularly for better activities of ascorbate peroxidase (APX), peroxidase (POD), and superoxide dismutase (SOD). Compared with the vibration treatment, the activities of APX, POD, and SOD changed more slowly in the control group, indicating that the higher activities had remained during the later stage of storage. The activities of catalase (CAT) and glutathione reductase (GR) were usually higher in the control group than those in the vibration treatment (P < 0.05) during storage, indicating that the enzyme activities decreased fast, as the duration of vibration stress increased. After 15d of storage, the 1,1-Diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging rate of samples treated by vibration for 24 h was also significantly lower than that in the control (P < 0.05). Correlation analysis showed that there was a great significance between the antioxidant capacity and browning index of A. bisporus under vibration stress. More importantly, the antioxidant capacity of A. bisporus was proportional to the browning degree after vibration treatment. As such, a relatively lower browning was achieved under the stronger antioxidant capacity of A. bisporus after vibration treatment. Therefore, it can be inferred that the damage of A. bisporus caused by vibration stress was a cumulative process, where the mechanical damage was greater for the longer transportation vibration. Correspondingly, shorter transportation and reasonable preservation were recommended for the higher antioxidant capacity of A. bisporus. Particularly, the reduction of relative friction between mushroom bodies and cushioning packaging can be expected to minimize the vibration damage during transportation. The finding can also provide a sound reference for the development of logistics and transportation packaging in most vegetables.