EFFECTS OF HEAT TREATMENT ON POLYPHENOL OXIDASE ACTIVITY AND TEXTURAL PROPERTIES OF JACKFRUIT BULB

摘要

The jackfruit bulbs were subjected to different heat treatments and the residual polyphenol oxidase (PPO) activity, browning index (BI), the concentration of vitamin C (Vc) and textural properties (TP) after freeze drying (FD) were determined. The results showed that PPO, BI and Vc were 5.83%, 107.69, 4.11 mg/ 100 g and 10.66%, 84.09 and 4.30 mg/100 g at the optimal time or temperature, respectively. The time was significantly negatively correlated to hardness, fracturability, chewiness, resilience and Vc concentration. The temperature was significantly positively correlated to adhesiveness, whereas it was significantly negatively correlated to hardness, gumminess, chewiness, resilience, BI and Vc concentration (P < 0.05). Based on PPO activity, BI, the concentration of Vc and TP, the optimal pre-drying conditions were temperature of 80C and time of 4 min. This paper could provide good guidance for other fruit processing based on the pretreatments of FD jackfruit.