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Abstract: Fresh mushrooms (Agaricus bisporus) are highly perishable. They should be consumed or processed promptly after harvest (KOMANOWSKY et al., 1970). While being transported or displayed for sale, mushrooms should be kept under refrigeration. Black stems and opened veils are corrected with dehydration. According to WRIGHT (1954) reported that about ten times of respiration ratio would be taken place in mushrooms as stored at the temperature from 32°F to 50°F. Browning in mushrooms is partially caused by oxidation of phenol substances which catalysed by enzymes. The phenoloxidase system in mushroom tissues consists of several forms, each exhibits different catalytic and physical properties as described by MALLETTE and PARSON (1949). YAMAGUCHI and HUANG (1970) found that an inactive or latent form of O-diphenoloxidase in mushrooms could be reactivated by 0.1% of sodiumlauryl sulgate, the latent form constituted about 45% of the total O-diphenoloxidase. For better quality retention, mushrooms before freezing, drying or freeze-drying may be treated with salt, ascorbic acid, EDTA or metaphosphorus acid as recommended by TRESSLER et al. (1968). FANG et al. (1971) reported that freeze-dried mushrooms can be produced successfully by procedures in which the activity of polyphenoloxidase was controlled by treated with 200 ppm SO2 and the freezing process was done by dipping in food grade Freon-12 at -22°F. Blanching is one of available methods to control the activity of mushroom enzymes, but under- or over-blanching could cause the mushroom products in poor quality. Compensation is necessary by treated with enzyme inhibitors. The present work is to investigate the activities of polyphenoloxidase and peroxidase in mushrooms, and selection of their inhibitors and control of their activities by blanching method were carried out.
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