Effects Of Ultra-high Pressure Processing On The Quality And The Safety Of Fresh Carrot Juice

Ultra-high pressure processing can maintain better the sensory and nutrition quality of fruits and vegetables and it also can ensure their safety. In this research, effects of ultra-high pressure non-thermal process technology on quality and safety of fresh carrot juice was studied. By determining the physicochemical and toxicological and microbiological related indexes of untreated and pressurried samples, the sensory and nutrition quality and safety of the samples were analyzed and evaluated, while the parameters related with carrot juice were obtained and the conditions of process and its sterilization were determined. This study provided a reliable basis for standard and safety evaluation of ultra-high pressure fresh carrot juice.The results were summarized as follows:1. The soluble solids content and the color of carrot juice by treated ultra-high pressure had no change significantly, while the pH declined and the stability improved. By the M model of fuzzy mathematics of sensory evaluation, the optimal processing sample was at 500MPa for 10min.2. The content of Vc in carrot juice pressurried decreased significantly, and the retention rate of Vc reached 80.02%-88.92%, while the retention rate of VC was 34.12% in samples processed by thermal methods, which indicated that ultra-high pressure could keep the Vc content in carrot juice better than thermal processing methods.3. Pressure and time had no significant effect onβ-carotene content of carrot juice and different pressure treatments had no significant influence onβ-carotene content of mice serum.4. The trend of the protein content of carrot juice was declined as the pressure increased and its total acid was decrease while its sugar content rose. The treatment of high pressure had no significant effect on the total antioxidant activity of carrot juice; however, the total antioxidant activity of 400MPa's sample was significantly decreased compared with the control group.5. The acute toxicity test indicated that the acute oral maximum tolerant dose (MTD) of carrot juice pressurried for female and male mice was over 21500.00mg/kg bw and the value of LD50 was also over 21500.00mg/kg bw. Therefore, the result indicated that carrot juice pressurried was recognized as a non-toxic substance.6. The 30d feeding tests showed that the body weight, blood biochemical indices and organ growth of mices in each group had no abnormal, indicating that the UHP-treated samples had no significant negative effects on mice. The results suggested that the carrot juice processed by ultra-high pressure was safe.7. The residual bacteria count in carrot juice pressurized at 500MPa for 10min was below 100cfu/mL, the total amount of mold and yeast was<20 cfu/mL, which complied with the national standards of beverage hygienic. And the amount of E. coli and Salmonella also met the national standards.8. The results of morphological and biochemical identification indicated preliminarily that the bacteria isolated from carrot juice was Bacillus cereus. The results of high pressure processing indicated that the lower pressure had no significant effect on the numbers of Bacillus cereus, however, with the pressure increasing, the number of Bacillus cereus decreased, but when the pressure was more than 600MPa, the decreased trend was slowing down and the number tent to stabilization, and this did not meet the standard of none detection. When the suspension of Bacillus cereus had been treated by 600MPa pressure for 10min, the number of Bacillus cereus declined significantly, however, as the treatment time increasing, the number of bacteria had no change obviously. The Bacillus cereus was identified initially as target bacteria of carrot juice processed by high pressure.