The effect of postharvest fumigation treatment with hydrogen sulfide on the quality and antioxidant characteristics of edible white button mushroom (Agaricus bisporus) during shelf life

Button mushrooms are very popular and account for 30 % of the world's mushroom production (Royse, 2014). It has been reported that the Agaricus bisporus mushroom has a shelf life of one to three days at 20−25 ºC, five to seven days at 4 ºC (Diamantopoulou & Philippoussis, 2015; Jiang, 2013). Throughout the short shelf life of white button mushrooms (Agaricus bisporus), a few quality degradation processes emerge, including moisture loss, discoloration as browning, texture changes, off-flavor, and nutritional loss, reducing their economic value (Ding et al., 2016). This phenomenon is accompanied by the increase of reactive oxygen species (ROS) levels, due to the decline of the ROS scavenging power of the cell. Numerous studies have been performed on maintaining the postharvest quality of fresh mushrooms and postponing their deterioration (Zhu et al., 2021; Zhang et al., 2020; Shekari et al., 2021; Liu et al., 2019). Extensive investigations reported that the role of hydrogen sulfide (H2S) as an endogenous gaseous signaling molecule primarily acts on the regulation of physiological functions associated with nitric oxide (NO), carbon monoxide (CO), and H2O2 in animals and plants (Hancock and Whiteman, 2016; Beltowski, 2019). Zheng et al. (2016) stated that postharvest exogenous H2S treatment of fresh-cut apples mitigated enzymatic browning. In the present investigation, NaHS solution as an H2S donor was applied to fumigate edible white button mushrooms (Agaricus bisporus) in the postharvest and its effects on cap browning index, percent open caps, weight loss, dry matter, firmness, ascorbic acid, total phenol, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging in edible white button mushroom during shelf life for 6 days was evaluated.

Fresh button mushrooms were selected on the basis of the uniformity of maturity and size. Sodium hydrosulfide (NaHS) was applied as an H2S donor. Each treatment was implemented in three replications. To prepare the solution, NaHS was dissolved in 200 mL of distilled water in 3 L sealed containers at room temperature, then mushrooms were exposed to 0 (control; distilled water), 0.25, 0.5, 0.75, 1, 1.25, and 1.5 mM NaHS for 20 min. Afterward, treated mushrooms were maintained for 6 days at shelf life. Samplings of mushrooms were taken at 0, 2, 4, and 6 days after treatment. To calculate the browning index (BI), photographs of edible mushroom samples were taken on sampling days and L, a and b were calculated in Photoshop software environment (Aghdam et al., 2019). Percent open caps were measured according to Jiang et al's (2011) method. Weight loss was measured according to the method of Sing et al (2016). Dry matter was measured according to Kalberer's (1991) method. The firmness of the mushrooms was measured by a digital firmness tester by the method of Nasiri et al (2017). A spectrophotometric procedure described by Terada et al (1978) used for the determination of ascorbic acid content. Total phenolics was measured with using the Folin–Ciocalteu reagent by Singleton and Rossi (1965) method. DPPH radical was used to measure of scavenging activity according to the method of Dokhanieh & Aghdam (2016). Data were analyzed using SAS software and the comparison of means was performed using Tukey’s test for p < 0.05. Graphs were drawn using Excel software.

Our results showed that the cap browning index of mushrooms treated with 0.5 mM NaHS as donor H2S was significantly lower than that of control samples during 6 days of shelf life. Similar results were observed regarding color retention of strawberry and broccoli fruits treated with NaHS donor H2S during the postharvest period (Molinett et al. 2021; Hu et al. 2012; Li et al. 2014). The percentage of weight loss and cap opening of mushrooms treated with 0.5 mM NaHS was significantly lower, and the percentage dry matter and firmness was higher compared to the control mushrooms. The high dry matter content of mushrooms is related to their lower weight loss (Loon et al. 2000). The results of the present experiment are consistent with the results of Ni et al.'s (2016) studies, which showed that fumigation with H2S reduces the weight loss of grape bunches by increasing firmness and preventing senescence. Also, the use of NaHS treatment in strawberries caused a higher firmness of its fruits due to the decrease in the activity of pectin methylesterase and polygalacturonase enzymes (Molinett et al. 2021; Hu et al. 2014). Since H2S reduced the water loss rate of mushrooms treated with 0.5 mM NaHS, the percent cap opens of these mushrooms was much lower and their ascorbic acid content was higher compared to the control treatment. The lower decrease of ascorbic acid in button mushrooms treated with 0.5 mM NaHS donor H2S can be attributed to its the antioxidant effects, which causes a decrease in physiological activities related to senescence. The use of 0.5 mM NaHS treatment led to an increase in total phenol in button mushrooms. A similar increase in total phenolic content along with maintaining quality has also been reported in hawthorn and apple fruits treated with H2S during storage (Aghdam et al., 2018; Zheng et al., 2016). In this experiment, DPPH radical scavenging activities were higher in button mushrooms treated with 0.5 mM NaHS donor H2S compared to the control group during shelf life, which indicates that DPPH radical scavenging is improved after H2S fumigation.

In summary, in this experiment, the positive effect of postharvest NaHS treatment as H2S donor on the quality and antioxidant characteristics of edible white button mushroom during shelf life for 6 days was observed. The results of our study showed that postharvest H2S fumigation treatment of button mushrooms with 0.5 mM NaHS led to a reduction in postharvest senescence with delayed cap browning, lower percentage of open caps, lower weight loss and higher firmness than the control during the shelf life, which is probably related to maintaining the stability of the cell membrane during shelf life. In addition, button mushrooms fumigated by H2S showed increased antioxidant capacity and DPPH radical scavenging during shelf life, which was caused by increased accumulation of phenolic compounds and ascorbic acid in these mushrooms. In general, it can be concluded that the use of postharvest H2S fumigation treatment of the button mushrooms by maintaining the quality and antioxidant characteristics can be a suitable method to delay postharvest senescence and increase the shelf life of edible white button mushroom.