Straw mushrooms (Volvariella volvacea (Bull ex Fr.) Sing) are an edible tropical fungus and a popular ingredient in various East Asian dishes. The straw mushroom fruiting body is white with a short stipe and large cap, and it is cultivated mainly in Southeast Asian countries 1. Thailand produced approximately 66,000 tons of straw mushrooms worth 3,630 million Baht in 2009 2. Straw mushrooms require hot, humid growing conditions and are widely grown in central Thailand provinces such as Saraburi, Angthong, Ratchaburi and Nakhon Ratchasima. These mushrooms typically contain 85-90% moisture and rapidly transpire 3. The mushrooms are harvested at the button stage when they are considered to have the best flavour and texture. Commercial production methods yield a fruiting body with a light-coloured cap, which ages rapidly after harvest. The major postharvest problem that limits the shelf life of straw mushroom at ambient temperatures (25-34ºC and 60- 70% RH) is browning of the cap/cut surface and shrivelling related to water loss. As a result, most of the fresh straw mushroom market is domestic because of its postharvest life of only 1-2 days. Browning disorders in agricultural products are normally induced by dehydration, mechanical injury or wound deterioration4. Polyphenol oxidase (PPO) is the major enzyme involved in browning reactions. PPO catalyses the oxidation of phenolic compounds to