Effects on microbial inactivation and quality attributes in frozen lychee juice treated by supercritical carbon dioxide

摘要

In this paper, we described the use of high-pressure carbon dioxide (HPCD) for the inactivation of natural microbes in lychee juice and evaluated its effects on lychee juice quality, compared to a conventional high-temperature, short-time (HTST) method. The HPCD treatments were carried out using a HPCD unit (8 MPa, 36 °C, 2 min), and the HTST was performed at 90 °C for 60 s. The results showed that five log reduction for yeasts and molds and total aerobic microorganisms occurred at 8 MPa for 2 min. And effects of the treatments on pH and concentrations of microbes, organic acids, titratable acidity (TA), total soluble solid (TSS), sugars, polyphenols, color, and free amino acids were also investigated. HPCD could efficiently maintain the concentration of polyphenols and original color at 8 MPa, 36 °C for 2 min. Insignificant differences in colors were observed between unprocessed and HPCD juices, while significant differences were observed between unprocessed and HTST juices. Furthermore, HTST decreased the total free amino acids, whereas HPCD caused a significant increase (increased by 45.92% at 8 MPa) (p 0.05). The increase in total amino acids induced by HPCD treatment is beneficial for nutritional value of commercial ready-to-drink lychee juice. In general, HPCD treatment had less influence on the measured quality parameters of lychee juice than HTST treatment. Therefore, HPCD treatment could be a useful alternative to traditional heat treatment.