Here’s mushroom spoilage up-close and personal:
“Mushroom spoilage mechanisms include dehydration, enzymatic browning and bacterial growth. Mushrooms have a shorter shelf life than most ready-to-use vegetables because their respiration rate is rapid and they have no barrier to protect them from water loss or from microbial attack. Enzymatic browning occurs when the enzyme, tyrosinase, makes contact with its substrate and initiates a series of reactions which produces brown melanin pigments. Contact between the enzyme and its substrate can occur when mushrooms are bruised, cut, or damaged by microbial growth. Microbial spoilage of mushrooms is usually due to the growth of pseudomonad bacteria. As these bacteria grow, they break down the mushroom fibres which softens the mushroom and leads to enzymatic browning. The major species responsible for this is Pseudomonas tolaasii which produces a toxin that lyses mushroom cells. The resulting brown pigments and surface lesions are symptoms of the disease, “bacterial blotch”. Growth of pseudomonad bacteria also causes slime to form on the mushroom surface. Chilled storage (4°C) of mushrooms from harvest to cooking helps to maintain good quality (Gormley, 1975) by reducing the rate of bacterial growth and enzyme activity.”
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