Suitable Sanitizing Agent and Pre-Conditioning Temperature to prolong Shelf Life of Minimally Processed Onion (Allium cepa L.) and Green Pak Choy (Brassica rapa cv Chinensis)
Z. Othman, R. Mustaffa, C.O. Dali and H. Mohamad
Book of Abstract. APEC Symposium on Assuring Quality and Safety of Fresh Produce, August 1-3, 2005, Bangkok, Thailand. 76 page.
2005
บทคัดย่อ
Suitable Sanitizing Agent and Pre-Conditioning Temperature to prolong Shelf Life of Minimally Processed Onion (Allium cepa L.) and Green Pak Choy (Brassica rapa cv Chinensis)
Peeled onion and green Pak Choy (GPC) was treated with different sanitizing agents: 150 ppm hydrogen peroxide (HP), 100 ppm chlorine (from sodium hypochloride) (CHL) and distilled water (as control A). After washing, the sample was pre-conditioned at different temperatures (2°C and 5°C) for 20 hr. Minimally processed onion and green Pak Choy without pre-conditioning (processed immediately after washing) were used as control B. After 20 hr, the pre-conditioned samples were removed from cold room for minimal processing. The processed samples were packed in polypropylene (PP) container and stored at 2°C for 30 days. Physical and chemical analyses were carried out daily for samples kept at room temperature and every 3 days for samples stored at 2°C. Washing treatment showed more beneficial effect in MP green Pak Choy but not suitable for MP onion. Washing was able to reduce the CO2 concentration and percentage weight loss and effective in maintaining chlorophyll content in MP green Pak Choy. In contrast, sanitizing agent caused an increase in CO2 concentration, percentage weight loss and pH of MP onion. Pre-conditioning at 2°C and 5°C reduced CO2 concentration, percentage weight loss and pH and maintained significantly the chlorophyll content of MP green Pak Choy. Pre-conditioning at 2°C showed a better effect on reducing CO2 concentration of onion and maintaining ascorbic acid and chlorophyll contents in green Pak Choy as compared to samples pre-conditioned at 5°C. Pre-conditioned at 5°C showed a significant effect in reducing percentage weight loss and ethylene production rate of MP onion and pH of MP green Pak Choy. Hydrogen peroxide as sanitizing agent combined with pre-conditioning at 5°C was the best method of maintaining freshness and prolonging shelf life of MP onion and green Pak Choy from 20-25 days and 10-14 days, respectively.