Abstract
The kinetics for enzymatic browning of pulp samples from six apple cultivars (Fuji, Mutsu, Orin, Tsugaru, Jonagold, and Kogyoku) were examined. Reflectance was used to measure the extent of enzymatic browning and was evaluated by the Hunter color scale. The time-course plot of the color difference(ΔE)was related to the extent of browning and could be expressed by the equation, ΔE=B (1-exp (-kt)), where B and k are fitting parameters and t is the time in min. The B and k values were calculated by the non-linear least-squares method and respectively applied to the extent of browning and the browning rate constant. The rate and extent of browning were high with the Fuji, Mutsu, and Orin pulp samples, and low with Tsugaru and Jonagold. Although Kogyoku showed a low browning rate, the extent of browning was high. The rate of browning was influenced by the ascorbic acid content and polyphenol oxidase (PPO) activity in the pulp. The extent of browning and PPO activity showed good correlation. However, there was no correlation between the chlorogenic acid content and the extent of browning with the six apple cultivars.
