Effects of Ultra-high Pressure and High Temperature Short-time Sterilization on the Quality of NFC Orange Juice

In this article, the effect of ultral high pressure processing(HPP, 600 MPa, 1 min) and high temperature short time(HTST, 110℃, 8.6 s) sterilization on microorganisms, basic physical and chemical indicators, color, stability, biologically active ingredients, antioxidant activity and other qualities of not from concentrate(NFC) orange juice were compared at 4℃ storage period, and the sensory evaluation of the sterilized orange junice was carried out at the end of storage. Results showed that, after HPP and HTST treatment, the total number of NFC orange juice colonies, mold and yeast, lactic acid bacteria, psychrotrophic bacteria were reduced to below the detection limit(<10 CFU/mL). After 25 days of storage, microorganisms of HPP-treated orange juice were still not detected, which was according with the national standard of fruit and vegetable juice beverage "NY/T 434-2016". While the total number of colonies and the number of mold yeast of HTST-treated orange juice began to increase at the end of the storage period. HPP treatment had no significant effect on the L^* and b^* values of orange juice color(P>0.05), which significantly increased the a^* value(P<0.05), and the total color difference ΔE was lower than that of HTST treatment. HPP orange juice had lower suspension stability and higher pectin methylesterase(PME) than HTST orange juice. After treatment, the residual PME activities of HPP and HTST orange juice were 92.31% and 14.42% respectively, and were 30.77% and 0.03% respectively at the end of storage period. The suspension stability of the HPP orange juice decreased by 95.45% during storage. And HPP treatment significantly increased the total phenol contents of NFC orange juice by 13.50%(P<0.05), but had no significant effect on vitamin C contents, DPPH scavenging ability, FRAP iron ion reduction ability, and comprehensive sensory evaluation(P>0.05), which was significantly higher than HTST-treated orange juice(P<0.05).In summary, HPP treatment can maintain the nutrition, sensory quality and fresh flavor of orange juice better than HTST treatment, but the inactivation effect of enzymes should be improved.