Novel application of CO2-assisted high pressure processing in cucumber juice and apple juice

A novel technique of CO2-assisted High Pressure Processing (CO2-HPP) was originally applied to cucumber juice at pH 5.81 and apple juice at pH 3.83. CO2-HPP was carried out with CO2 of 0.98 mmol/container assisted 600 MPa/3 min. The changes of microorganism, enzymes and quality characteristics were discussed during 15 days of storage (4 degrees C). Compared with HPP, CO2-HPP enhanced inactivation effect on total aerobic bacteria (TAB) in cucumber juice with 0.604 log(10) CFU/mL extra reduction. During storage, CO2-HPP showed remarkable inhibition on the growth of TAB and lactobacillus in cucumber juice with 1.25 and 0.72 log(10) CFU/mL lower than HPP-treated samples. Similarly, TAB and yeast and molds (Y&M) in CO2-HPP treated apple juice were 0.51 and 0.53 log(10) CFU/mL lower than HPP-treated samples at the end of storage. Denaturation of polyphenol oxidase in apple juice was enhanced by CO2-HPP with only 0.5% residual activity left which contributed to stable contents of ascorbic acid and total phenol, while it was 87.0% in HPP-treated juice. However, lipoxygenase in CO2-HPP treated apple juice was 31.86% higher than that in HPP-treated samples leading to better flavor in CO2-HPP treated samples. CO2-HPP could be an alternative technique in production of high quality juice.