Study On Effect Of Dense Phase Carbon Dioxide On The Quality Of Fresh Pear Juice

Consumption of fresh pear juice has been increasing rapidly due to its flavor and nutritional value. At present fruit juice processing widely uses thermal treatment technology to carry on inactivation of microbe and enzyme. The traditional thermal pasteurization processes not only have effect on the fruit juice quality specially freshness, but also have destructive effect on some nutrition ingredient and functionality ingredient. While, non-thermal processing can keep freshness at high limit, and it's better than other methods. The objective of this article was to study effects of DPCD (Dense Phase Carbon Dioxide) on the processing of fresh pear juice, inactivation of microbe and enzyme, and effects on the quality of pear juice at 4℃.(1) More and significantly inactivation of total bacteria counts was achieved at higher pressure, temperature and exposure time (p<0.05). The maximum reduction was 2.664-log at 30 MPa and 40℃for 60 min. The survival curves of total bacteria counts in pear juice against pressure or temperature were fitted by Weibull Model with high regression coefficients, and a value (scale factor) and b value (shape factor) decreased with increasing pressure or temperature.(2) Analysis of first-order reaction kinetic data showed that D value of PPO in pear juice decreased and k value increased with increasing pressure and temperature of DPCD treatment.83.34% of PPO inactivation was achieved at 30 MPa and 40℃for 60min. The ZP and Va value of PPO was 37.88 MPa and -68.67 cm3/mol treated by DPCD with 40℃. The ZT and Ea value of PPO was 86.21℃and 20.19 KJ/mol treated by DPCD with 30 MPa.(3) After DPCD treatment, Brix value and viscosity of fresh pear juice were not significantly changed (p>0.05) and the total color difference (ΔE) value was less than 2. But pH value and L value were significantly reduced (p<0.05). And they were not significantly changed with different treatment (temperature and time). T value decreased and browning degree was inhibited significantly with higher pressure, temperature and exposure time (p<0.05). The average particle size decreased under low temperature low pressure and increased under high temperature high pressure. (4) 30 MPa and 40℃for 60 min was suitable treatment for fresh pear juice. After DPCD treatment, browning degree significantly rose from the fifth week (p<0.05), and the total bacteria counts, pH value, T value were significantly changed (p<0.05) form the sixth week during 8 weeks storage time at 4℃. Brix value and L value of pear juice were not significantly changed (p>0.05). The activity of PPO recorded partly during storage time, but it was at low level. The L data followed first-order reaction kinetics during 8 weeks storage time after DPCD treatment.ΔE value of pear juice treated with 30 MPa and 40℃for 60min was less than 1.5, and the color was not obviously changed during storage time. Incorporation of low temperature, the storage time could reach 6 weeks after DPCD treatment.