Maintaining quality of not from concentrate peach juice by high pressure carbon dioxide treatment

Abstract: In the juice industry, thermal treatment is the most common and least expensive technology for pasteurization or sterilization. Unfortunately, the method easily leads to degradation of some product qualities as well. HPCD (high pressure carbon dioxide) has been reported as an alternative cold pasteurization technique for foods, since it could effectively inactivate microorganisms and enzymes in liquid food. Some detrimental effects of HPCD on food quality have been reported. But compared to traditional techniques, HPCD avoids drawbacks such as lack of retention of flavor, denaturation of nutrients, of production of side toxic reactions, as well as changes in physical, mechanical, and optical properties of the material involved in the treatment. In this study, the effects of HPCD on NFC (Not from concentrate) peach juice quality were investigated, and temperature, pressure, and time were proposed as the main parameters. The pH value and the total soluble content of untreated NFC peach juice were 3.82 and 10.3°Brix, respectively. HPCD had no effect on the pH values and total soluble contents. This was possibly attributed to a lower pH (3.82) in the original juices. At this pH the carbonic acid formed by CO2 dissolution into juices with difficultly dissociated into free hydrogen ions, because the dissociation constants of carbonic acid and bicarbonate were pKa=6.57 and pKa=10.62, respectively. The L, a, b values of color parameters was decreased while browning degrees were increased in HPCD-treated juice, possibly due to the non-enzyme browning during HPCD. Thereafter, it was found that the polyphenol oxidase was susceptible to HPCD. The main phenolic compounds in the NFC juice were (+)-catechin, chlorogenic acid, neochlorogenic acid, and ferulic acid measured by HPLC, and the results showed that HPCD had no effect on the phenolic compounds. Moreover, the antioxidant capacities of NFC juice after HPCD were enhanced with increasing treatment time measured by FRAP and DHHP, possibly due to the extraction of antioxidant substances and inhibited oxidation of phenolic compounds in NFC peach juice. HPCD was expected to be an alternative technology for NFC juice processing, which could better maintain the quality of NFC juice.