The effect of postharvest treatments of melatonin and γ-aminobutyric acid on improving antioxidant activity and reducing browning of fresh cut button mushroom (Agaricus bisporus) during cold storage

Production and consumption of button mushroom is increasing in many parts of the world due to their good nutritional value and desirable medicinal properties, but because these types of mushrooms do not have a protective outer coating, they have a short shelf life, and during the postharvest, the quality of button mushrooms decreases due to water reduction, color change, texture change, reduction of taste and nutritional value, which limits its economic value, so the application of postharvest treatments can preserve the nutritional value and improve the shelf life of these mushrooms. Therefore, this study aimed to investigate the effect of postharvest treatments of melatonin and γ-aminobutyric acid (GABA) on the storage life and nutritional quality of fresh cut button mushrooms.

The postharvest treatments used in this experiment included melatonin (10 μM) and GABA (1 mM) and control (distilled water), which the mushrooms were immersed in a solution of these treatments for 5 minutes, and after drying at room temperature (24 ± 1), the mushrooms were placed in sealed containers and stored in a cold store at 4 °C with a relative humidity of 90 ± 5%. The samples were taken on days 0, 5, 10, and 15 days after treatment, and to measure browning index, hydrogen peroxide accumulation, the activity of cell membrane degrading enzymes and antioxidants enzymes were used.

The results showed that postharvest application of melatonin and GABA in fresh cut button mushrooms caused a delay in browning of slices of button mushrooms compared to control mushrooms and on the 15th day of storage, browning index in mushrooms treated with melatonin, GABA, and control was 45.78, 40.01, and 90.5%, respectively. Accumulation of hydrogen peroxide in melatonin and GABA treated mushrooms was significantly reduced compared to control mushrooms due to increased activity of the antioxidant enzymes superoxide dismutase, ascorbate peroxidase, catalase and glutathione reductase, and the highest hydrogen peroxide accumulation (51.35 μ mol g-1 FW) was obtained on the 10th day of storage in control samples. Membrane stability increased in melatonin and GABA treated mushrooms due to decreased activity of lipoxygenase and phospholipase D enzymes in these mushrooms. GABA treatment also showed better results than melatonin in most of the studied traits.

In general, according to the results of the present study, melatonin and GABA can used as an effective and safe method in maintaining nutritional quality and improving the shelf life of fresh cut button mushrooms during cold storage. Also, due to the better results provided by GABA in most of the studied traits and its cheapness compared to melatonin, it is recommended to use GABA in fresh cut mushrooms postharvest to maintain the quality of the mushrooms.