Abstract:
The effect of hot water treatment on microbiological quality of fresh-cut 'Kimju' and 'Pan Srithong' guava was investigated. Guava fruit, cv. 'Kimju' and 'Pan Srithong' were treated with hot water at 40, 50 and 60°C for 10 and 30 minutes. Fruit was cooled in sterile water at 5°C for 5 minutes and cut into 2 cm3 cubes, then packed in foam tray and wrapped with polyvinylchloride (PVC) film. Total microbial count, coliforms, lactic acid bacteria and fungi were enumerated after processing and during storage at 10°C for 6 days. Vitamin C content and disorder were determined for quality changes of fresh-cut guava as affected by the heat treatment. The results showed that the hot water treatment significantly reduced total microbial and coliforms counts of 'Kimju' cultivar, with the reduction was increased with higher temperature and longer immersion time. Lactic acid bacteria and fungi were below the detection level during 4 days of storage at 10°C, thereafter they were increased at day 6 of storage. Vitamin C content of 'Kimju' and 'Pan Srithong' guava cubes at the initial day of storage was in the range of 0.8- 1.1 and 0.5-0.9 mg/100 g fresh weights, respectively. After storage at 10°C, vitamin C content was slightly decreased in 'Kimju' cultivar, whereas it was slightly increased in 'Pan Srithong' cultivar. Browning development as indicated disorder was observed on the surface of both cultivars during storage. Browning development increased with an increase in temperature and time. Hot water treatment at 50°C for 10 and 30 minutes could be used to maintain quality and minimized microorganism of fresh-cut guava.
