Studies on reduction of microbial load in the refrigerated fresh-cut pineapple wedges by pretreatment processing

Pineapple is one of the most important fruits grown in Taiwan, and the demand for fresh-cut pineapple wedges is growing. However, high amount of total plate counts has been limiting its marketability. Thus, this study was aimed to look for methods that can reduce the microbial load in refrigerated fresh-cut pineapples effectively. Chlorine dioxide and ozone were used in this study. In the first part, pineapple wedges were immersed into 50 ppm chlorine dioxide solution with ultrasonication and with or without vacuuming for 2.5 or 5 mins. In the second part, pineapples were treated with gaseous ozone (0.93 or 1.11 ppm) with or without vacuuming or repeated vacuuming for 30 mins. After these treatments, the microbial load was evaluated. The effects of chlorine dioxide and ozone on physical properties of fresh-cut pineapples during storage were also investigated. The results showed that vacuum-infiltration with chlorine dioxide solution or gaseous ozone can effectively reduce the microbial load in pineapples. Meanwhile, there is no significant effect on the physical properties of fresh-cut pineapples under refrigerated storage. In conclusion, we propose to use vacuum-infiltration with microbicides, such as chlorine dioxide and ozone, as pretreatment in the processing of refrigerated fresh-cut fruits to reduce the microbial load.