Extending The Shelf-life Of Mushroom By Vacuum Cooling

Vacuum cooling is a rapid cooling technique extensively used for cooling some agricultural and food products. Due to the advantages of quick cooling, easy operation, no constraint of packing containers and efficient energy usage, the vacuum cooling technology is now gradually applied to the precooling treatment of agricultural products. Vacuum cooling is rapid and cools mushrooms uniformly within a stack, but the capital and operating costs are high and weight losses are incurred. Consumption of mushrooms has been increasing substantially due to their delicacy, flavor and nutritional value. Mushrooms are excellent source of several essential amino acids, vitamins (B2, niacin, and folates) and minerals (potassium, phosphorus, zinc and copper). Mushrooms have a short shelf life of 3-4 days compared to most vegetables at ambient temperatures because that they have no cuticle to protect them from physical or microbial attack or water loss.Firstly, the optimum vacuum cooling parameters of mushrooms were obtained by the response surface analysis under various conditions for the color and content of soluble solids. The optimum vacuum cooling techniques of the mushrooms were determined by the physiological changes.Secondly, with the increasing emphasis on quality of fresh horticultural produce,"cool-chain distribution", the movement of produce from the point of packaging to that of retail sale in refrigerated transport, has been widely adopted. To extend the shelf life of mushrooms after vacuum cooling, experiments were carried out to evaluate the effects of different storage conditions on weight loss, the respiration rate, soluble solid content, membrane permeability and degree of mushrooms browning. To investigate the influence of storage conditions on the properties of mushrooms, mushrooms were stored in three different conditions: (1) cold room, (2) hypobaric room, and (3) modified atmosphere packaging (MAP). The results showed that the optimum storage condition was modified atmosphere packaging (MAP). Additionally, a combination of 15KPaCO2+10KPaO2 was the optimum gas composition for mushrooms after vacuum cooling. And the optimum store temperature was 0°C.Thirdly, though a lot of works have been done on production of oxidants and antioxidant activity during senescence, little is known about the effect of vacuum cooling treatment as a factor that affects antioxidative mechanisims in mushrooms stored under modified atmosphere packaging. The results indicated that there were some effects of vacuum cooling treatment on the lipid oxidation (MDA levels), superoxide anion generation and antioxidant enzymes system of the mushrooms. The treatment of vacuum cooling had a positive influence on prolong the shelf life of the mushrooms stored under MAP.Furthermore, vacuum cooling resulted in a small decrease in the quality of the mushrooms. And light microscope and scan electron microscope were used to observe the...