Effect of Power Ultrasound Treatment on The shelf Life of Edible Mushroom

Introduction: White edible button mushroom (Agaricus bisporus) is one of the most sensitive postharvest agricultural products physiologically. Poor management and high humidity of freshly harvested horticultural products have reduced their shelf life and thus increased biowastes, so increasing the shelf life of fruits and vegetables to reduce waste is one of the essential goals of postharvest management. The shelf life of button mushrooms with minimal processing is between two and four days at average ambient temperature due to enzymatic browning. A method in increasing the storage of edible mushrooms is using power ultrasonic washing along with other treatments. Ultrasonics is one of the practical methods of non-contact washing of vegetables and fruits with sensitive textures. Ultrasound pretreatment involves immersing the fruit in distilled water or aqueous solution and applying the ultrasound simultaneously. Ultrasound causes a series of rapid contractions and intermittent expansions. The objective of this study was to investigate the effects of using power ultrasound alone and in combination with other treatments such as hydrogen peroxide and ozone on improving the postharvest characteristics of ediblemushrooms.
Materials and methods: In this study, the button fungus (Agaricus bisporus) was used. The fungi were relatively the same size without physical damage and fungal infections. In order to create ultrasonic waves, a Unident Geneve ultrasonic bath machine made in Switzerland with a production power of 100 watts and a frequency of 20 to 35 kHz was used to wash the desired product. The application time of ultrasound for this study was 4 and 6 minutes and it was used at a constant temperature of 20 degrees Celsius. Also, in this research, the ARDA Ozone Plus series ozone generator was used to produce ozone. The amount of ozone produced by this device without oxygen capsule (mgr) is 200 ⁄h. In the present study, the effect of different treatments on increasing the storage of edible mushrooms, physical and chemical properties such as weight loss, pH, stiffness, soluble solids and microbial load were tested.

Results and discussion: Weight loss percentage is one of the most important factors in quality assessment in fruits and vegetables, which is directly related to the amount of moisture content in the samples. During the storage period, the lower the moisture release rate, the smaller this factor becomes, which indicates the retention of moisture in the sample and its quality stability. Comparison of samples During the storage period, there is an increasing trend in weight loss of samples that the amount of weight loss in the control sample is significantly higher than the samples washed by ultrasound. As the amount of maturation due to cell disintegration due to enzymatic activity increases, the firmness of the fruit tissue will also decrease. Tissue loss is the most important change during the storage period of fruits and vegetables and depends on the rate of metabolic changes and water. The reason for the increase in stiffness again is that the fruit and vegetable samples usually start to lose their water gradually. Obviously, this leads to an increase in their stiffness index. Changes in the texture of the fungal cap are an important criterion for determining the quality, amount of metabolic changes and the amount of water in its texture. Decreased strength and softening in the fungal cap tissue is related to the activity of microorganisms and enzyme production. Bacteria with enzymatic activity on the mushroom cause the interstitial material in the mushroom cap to break down and lead to cell destruction, resulting in the loss of tissue and shrinkage. At the end of the twelfth day of storage, the lowest stiffness is related to the ultrasonic treatment of 4 minutes and the highest stiffness is related to the treatment with washing with distilled water for 4 minutes, which shows the highest amount of wood and drying of the fungus. The reason for the decrease in stiffness during the storage period may be due to the breakdown of enzymes, water depletion or degradation of pectic substances in the fruit. The soluble solids from the fungus to distilled water are subjected to ultrasound. The results show that the treatments washed with sonication and hydrogen peroxide have a high performance in terms of microbial load control compared to the control mode and other treatments and have a significant difference at the level of 0.01. Ultrasonic treatment with hydrogen peroxide for 6 minutes of ripple on the first day of storage had 61 and at the end of the storage period had 87.5 cfu / g microbial load.
Coclusion: Ultrasonic washing of agricultural products is one of the ways to increase the shelf life of agricultural and horticultural products. The results of this study show that the samples of mushroom washed with sonication and hydrogen peroxide have a high performance in terms of microbial population control compared to the control mode and other treatments and have a significant difference. Ultrasonic treatment with hydrogen peroxide for 6 minutes on the first day of storage had 61 and at the end of storage period 87.5 cfu / g microbial load. Samples with ozone and ozone-containing treatments combined with sonication with ultrasound have a higher ability to maintain the strength of mushroom tissue. According to the studied treatments and traits, the obtained results show that the sonication treatment with ultrasound with hydrogen peroxide for 6 minutes has the best performance to increase the shelf life of the edible mushroom.