UV‐C treatment inhibits browning, inactivates Pseudomonas tolaasii and reduces associated chemical and enzymatic changes of button mushrooms

Abstract

BACKGROUND Button mushrooms with completely white appearance are popular with consumers. However, button mushrooms are susceptible to infection with Pseudomonas tolaasii, which results in browning. This study evaluates the effects of ultraviolet‐C (UV‐C) treatment on the inactivation of P. tolaasii in vitro and in vivo and on the physiological and chemical changes of button mushrooms during storage for 21 days at 4 °C. RESULTS UV‐C doses of 0.5 to 9.0 kJ m−2 resulted in 3.91–6.26 log CFU mL−1 reduction of P. tolaasii populations in vitro, and UV‐C treatment reduced P. tolaasii populations inoculated on mushroom cap surfaces and browning severity. Moreover, P. tolaasii increased polyphenol oxidase (PPO) activity, and decreased phenylalanine ammonia‐lyase (PAL) activity, the accumulation of phenolics and contents of brown melanin precursors, including γ‐l‐glutaminyl‐4‐hydroxybenzene (GHB), γ‐l‐glutaminyl‐3,4‐dihydroxybenzene (GDHB), and tyrosine in button mushrooms. UV‐C treatment was found to reduce the negative changes due to P. tolaasii infection. CONCLUSION These results indicated that the application of UV‐C treatment inhibited browning, inactivated P. tolaasii and reduced P. tolaasii – associated chemical and enzymatic changes of button mushrooms. © 2021 Society of Chemical Industry.

Enhancement of quality and self‐defense capacity of Agaricus bisporus by UV‐C treatment

“…This finding was in agreement with our previous research that a reduction of PPO activity can cause an elevation in the accumulation of GHB and GDHB. 5 Our examination also revealed that UV-C-treated button mushrooms maintained a greater degree of whiteness. UV-C improved the antioxidant properties of button mushrooms TPC and PAL activity of button mushrooms According to reports, the primary non-enzymatic antioxidant components of mushrooms are phenolic compounds, which have a crucial function as ROS scavengers.…”

“…Our previous studies 5,10 found that UV-C irradiation at 1.0 kJ m −2 dose could not only achieve the desired germicidal effect but it could also better maintain the quality of A. bisporus during storage. Therefore, 1.0 kJ m −2 UV-C was selected in this study.…”

“…Determination of γ-26 glutaminyl-4-hydroxybenzene (GHB), γ-glutaminyl-3,4-dihydroxybenzene (GDHB) and tyrosine Brown melanin precursors (GHB, GDHB and tyrosine) were extracted and then measured based on our former report. 5 The conditions of high-performance liquid chromatography (HPLC, Ssi Evans 1500, PA, USA) to quantify these extracts were: C18 column (250 mm × 4.6 mm, 5 μm), solvent gradient as follows: 0-40 min, 5-46% solvent B (10% acetonitrile in 1.8% (v/v) trifluoroacetic acid) and 95-54% solvent A (1.8% (v/v) trifluoroacetic acid), 30 °C, 1.0 mL min −1 (flow rate) and 10 μL (injection volume). Tyrosine, GHB and GDHB were observed at 230 nm and 245 nm for each injection.…”

“…On the one hand, UV-C with its wellknown antiseptic property could reduce the Pseudomonas tolaasii population, which is the main pathogen responsible for browning in grown mushrooms. 5 On the other hand, UV-C might effectively regulate browning-related enzyme activities. 17…”

“…This agrees with studies 8,9 reporting that there was corresponding proof that UV-C stimulated the formation of protective secondary metabolites, primarily phenolic, which increased disease resistance. Besides, UV-C radiation effectively inhibited browning lesion progress on the mushroom surface 5,10 and improved the associated defensive enzyme expression in fruits. 11 The change in mushroom quality is highly associated with its browning metabolism and cell oxidation conditions; however, there is no systematic study of the possible induced mechanisms of UV-C on self-defense capacity of postharvest button mushroom.…”