Comparative Analysis of Ultra-high Pressure and Thermal Sterilization of A Blueberry-strawberry-apple Puree
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Abstract:
Using blueberries, strawberries and apples as the raw materials, a blueberry-strawberry-apple compound puree was developed through sensory evaluation. The puree was treated by ultra-high pressure (UHP) and thermal sterilization (TS), respectively. The changes in microorganisms, physical and chemical indicators, color, content of anthocyanins, aroma and rheological properties of the puree before and after the treatment and during 40 days of storage at 4 ℃ were analyzed. The results showed that the total number of bacterial colonies, coliform and mold were not detected in the purees immediately after the two treatments, and the counts of these microorganisms still met the food safety standard limit after 40 days of the storage. The pH decreased significantly after either treatment and during the storage (P<0.05). The total soluble solids did not change significantly after UHP (P>0.05), but increased significantly after TS (P<0.05), with both reaching 7.80 °Brix at the end of storage. After TS, the anthocyanin content in the puree decreased significantly (P<0.05), with insignificant change in the UHP treated samples (P>0.05). During the storage, the anthocyanin content of the UHP treated puree was significantly higher than that of TS group (P<0.05). The maximum ΔE values of UHP and TS were 1.26 and 3.47, respectively, indicating that TS could cause significant color changes in the puree during storage. The results of the electronic nose testing showed that UHP could better retain the aroma components of the puree than TS. The analysis by the rheometer showed that the puree after UHP had better stability during storage. In summary, UHP could better maintain the quality of the blueberry-strawberryapple puree, which was a proper sterilization method for the processing of the puree.
