| The effects of high pressure homogenization(HPH) on the nature microorganisms in not-from-concentrate(NFC) mango juice and the changes of nature microorganisms during storage of 4℃ and room temperature were investigated, compared with the heat treatment(HT). The effects of HPH on the Escherichia coli(E. coli) inoculated in NFC mango juice were investigated and the inactivation kinetics of E. coli were fitted with Weibull models to predict the inactivation effect in the study. Based on the above results, the effect of HPH on the color, physicochemical properties, bioactive components and antioxidant capacity of NFC mango juice and those changes during storage at 4℃ and room temperature were evaluated. The effects of HPH on turbidity, particle properties, rheological properties and pectin were analyzed, as compared with the HT and untreated samples. The study aimed at pavingthe way for the application of HPH in the processing of mango juice, which with high quality closed to fresh mango juiceand long shelf life. Major conclusions are as follows.(1) HPH significantly affected the inactivation of nature microorganisms. The results showed the reduction of microorganisms was enhanced with the increasing of pressure inlet temperature and the number of passes. The total plate count(TPC), the molds and yeasts(M&Y) were respectively reduced to below 2.0 log CFU/mL and 20 CFU/mL by 1 HPH pass at 190 MPa and 50℃, 1 HPH pass at 40 MPa and 60℃, 2 HPH passes at 190 MPa and 30℃/40℃, 5 HPH passes at 190 MPa and 20℃. The nature microorganism in NFC mango juice by 1 and 3 HPH passes at 190 MPa and 60℃ has been kept stable during the storage of 4℃ for 60 days. The TPC of all samples showed no significant change during storage at 4℃ for 60 days, and the counts were all below 2.0 log CFU/mL, meanwhile the M&Y was not detected. However, the TPC in the samples stored at room temperature grew to about 4.5 log CFU/mL. The E. coli was not detected by 5 HPH passes at 190 MPa and 20℃, 4 HPH passes at 190 MPa and 30℃, 2 HPH passes at 190 MPa and 40℃, which meet the hygienic standard for fruit and vegetable juice. The simplified Weibull models were fitted well under 20-50℃/40-190 MPa/1-5 passes and 20-40℃/190 MPa/1-5 passes(R2>0.92).(2) HPH treatments significantly reduced the L* and b* values and increased the a* value, and △E values were lower than 2, indicating HPH resulted no visible color difference. No significant difference in the physicochemical properties(pH, TSS, TA) and the detectable amount of vitamin C were observed in HPH treated NFC mango juice. Furthermore, HPH treatments enhanced the detectable amount of carotenoids, total phenols and the antioxidant capacity, while HT treatment significantly decreased the bioactive compounds and antioxidant capacity. During storage 60 days of 4℃, the △E values of HPH treated NFC mango juice were lower than 2. The HPH treated NFC mango juices storage of 60 days at 4℃ showed better preservation of bioactive compounds than the ones storage at room temperature and the HT ones.(3) The small particles and the turbidity of NFC mango juice were increased after HPH treatments, which corresponding with the results of microstructure obtained by optical microscopy. The range of the initial particle size of untreated NFC mango juice was 1-1000 μm. The particle size of HPH treated mango juices was lower than 100 μm, and the size of most of particle was between 0.01 μm and 0.1 μm after treated by 5 HPH passes at 190 MPa and 20℃. HPH treatments significantly improved the apparent viscosity, the relative area of thixotropic loop, the storage modulus(G’) and the loss modulus(G’’) of mango juice. HPH treatments can improved the content of water soluble pectin in NFC mango juice. |
PDF Full Text Request