Study on browning and the activity of related enzyme of Tricholoma giganteum and Agaricus bisporus during storage

Tricholoma giganteum and Agaricus bisporus were stored in 12 °C, relative humidity 90%. The changes in browing and the activities of polyphenol oxidase (PPO), Tyrosinase (Tyr) and Laccase of T. giganteum and A. bisporus were investigated. The results showed that: PPO activity of T. giganteum decreased during storage. PPO activity of fresh T. giganteum was 138.89 U/mL and it decreased to 120.67 U/mL on day 7. PPO activity of A. bisporus rose rapidly, the highest activity was 4840 U/mL on day 7 after storage. Tyr activity of T. giganteum was obviously lower than that of A. bisporus. Tyr activity of fresh T. giganteum and A. bisporus were 0.56 and 1.14 U/mL respectively. Tyr activity of T. giganteum decreased during storage and it decreased activity of 39.29% on day 7. Tyr activity of A. bisporus rose rapidly and the highest activity was 6.05 U/mL on day 7. Laccase activity of T. giganteum was obviously higher than that of A. bisporus, the highest activity was 1.57 U/mL on day 4, followed by a decrease in activity on day 5. But Laccase activity of A. bisporus changed small during the whole storage and the highest activity was below 0.1 U/mL. The browning of T. giganteum was very slow and it was 3.26% on day 7. A. bisporus brown fast and the browning was 51.23% on day 7.