| Among the mushrooms, button mushroom (Agaricus bisporus) has significant importance due to its nutritional, medicinal and organoleptic properties. Button mushrooms contain protein, antioxidants, vitamins C, D and B12, dietary fibers, and polyphenols, and have beneficial effects on health including combating diseases such as diabetics and heart disease. Its production and consumption increases every day, and accounts for approximately32%of total edible mushroom production in the world. It has been observed that mushrooms have3to4days shelf-life at room temperature and up to8days under refrigerator conditions. High respiration rate, dehydration and fast metabolic activities are the underlying reasons for short shelf-life of mushrooms. To solve the short-life problem of button mushroom, this study focused on finding out environment friendly and cheap techniques to prolong the shelf-life of mushroom. In this investigation, some cost effective and environment friendly chemical treatments were used to slow down the deterioration process and enhance the shelf-life of button mushroom during postharvest storage.In the present study, six different composite chemical treatments including (T1) control (water),(T2)1mmol L-1Na2EDTA+10mmol L-1CaCl2,(T3)1mmol L-1Na2EDTA+2.5%CaCl2+0.5%citric acid+2.5%sorbitol,(T4) water,(T5)2.5%CaCl2+0.5%citric acid and (T6)2.5%CaCl2+0.5%citric acid+3%sorbitol were applied as dipping treatment on harvested button mushroom. T1-T3samples were stored at4℃for12days, and T4-T6were stored at12℃for12days.The effects of composite chemical pretreatment on the quality of postharvest button mushrooms were evaluated. The results showed that T3treatment stored at4℃maintained high firmness, color and total soluble protein, and had less weight loss during the postharvest storage. While on other side, T5treatment maintained better firmness, color and total soluble protein and had best performance in reducing the loss of weight among12℃stored samples (P<0.05). These results suggest that the T3at4℃and T5at12℃treatments could be useful in preserving the quality of harvested button mushrooms.The effects of these treatments on antioxdative system and reactive oxygen species (ROS) were further studied in postharvest button mushroom. Results showed that lower levels of hydrogen peroxide (H2O2), hydroxyl radical (OH) and malondialdehyde (MDA) were observed at T3as compared to T1and T2samples which were stored at4℃. Moreover, significantly higher antioxidant enzymes activities i.e., superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD) were observed at T3as compared to T1and T2at the end of storage period (P<0.05). Down regulations in H2O2,-OH and MDA contents were observed, whereas the activities of SOD, CAT, POD and APX were found to increase in T5treated samples stored at12℃. However, T6was found to be more efficient in reducing oxidative stress of button mushrooms within6day, while, T5showed the same effects for12day as compared to T6. These observations suggest that T3at4℃and T5at12℃treatments have the best ability to prolong the shelf-life of button mushroom through reducing oxidative stress.In the second experiment of this study, fresh button mushrooms were harvested and treated with combined chemicals, i.e.,1.5%CaCl2+0.5%citric acid, and stored for16days at12℃. The effects of this combined chemical treatment on firmness, weight, color, cell wall compositions (cellulose and chitin) and cell wall degrading enzymes (cellulase, β-1,3glucanase, chintinase and phenylalanine ammonialyase) were investigated during post-harvest storage. The expressions of major genes (Cel1, Glu1, Chi1and PAL1) involved in cell wall degradation during postharvest storage were also monitored. The results revealed that the postharvest chemical treatment maintained better firmness, weight, color, inhibited cellulase, β-1,3glucanase, chitinase and phenylalanine ammonialyase activities, respectively. However, the expression levels of most of the studied genes were not significantly altered except that of PAL1. These findings showed that the down-regulation of cell wall degrading enzymes with the application of combined chemical treatment was a possible mechanism underlining the delayed softening of button mushrooms. |
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