Effect of cinnamic acid on shelf life and quality of button mushroom at postharvest period

Button mushroom (Agaricus bisporus L.) is one of the most popular and widely consumed edible mushrooms that is grown all over the world. However, button mushrooms have a short shelf life of about 3 to 4 days after harvest and lose their commercial value within a few days due to browning of the tissue, water loss, aging and microbial attack. Tissue browning is caused by the activity of polyphenol oxidase (PPO) in plastids on phenolic compounds in the vacuoles as a substrate. Therefore, enzymatic browning is intensified by the loss of membrane integrity due to aging and tissue deterioration and as a result of physical connection between the enzyme and the substrate. The use of some techniques such as the chemicals and physical treatments gives promising results in delaying Browning and increasing the shelf life of edible mushrooms. Cinnamic acid (CA) is an organic acid that occurs naturally in plants and has low toxicity and a wide range of biological activities. Cinnamic acid and its derivatives are widely used in food industry. This compound acts as an inhibitor of polyphenol oxidase activity. On the other hand, cinnamic acid in low concentration has been proposed as an activator of the antioxidant system and its positive effects on reducing the effects of environmental stresses in various plants have been proven in several experiments. Therefore, in the present study, the effect of cinnamic acid treatment on reducing the browning of the tissue and maintaining the quality of white button mushrooms in the post-harvest period has been investigated. 

Treatments included exogenous application of cinnamic acid at four levels (control, 100, 200 and 400 μM trans cinnamic acid) and storage time at five times (0, 4, 8, 12 and 16 days after storage). Cinnamic acid treatment at the mentioned concentrations was applied by top application 24 hours before mushroom harvest. Distilled water was used for control treatment. At the time of picking, infected, very large and small mushrooms were removed and the same mushrooms with a cap diameter of 40 to 45 mm were collected for each experimental treatment. After harvesting, the mushrooms were placed in a polyethylene box covered with cellophane and after weighing, they were transferred to an incubator at 4°C. In the post-harvest period, different traits were measured with a four day interva.

The results showed that by increasing storage time, the activity of polyphenol oxidase and peroxidase increased and consequently the browning of the tissue also had an increasing trend. Also, with increasing storage time, weight loss percentage, hydrogen peroxide and malondialdehyde increased and total phenol and total antioxidant capacity were decreased. The use of cinnamic acid treatment in all three concentrations (100, 200 and 400 μM) reduced the activity of peroxidase and polyphenol oxidase activities and reduced tissue browning. The application of cinnamic acid also improved the quality traits of edible mushrooms such as total phenol, total antioxidant capacity and visual quality index. These findings suggest that application of cinnamic acid, especially at a concentration of 400 μM, could have the potential of inhibiting tissue browning and thus maintaining the mushrooms quality at the postharvest period