Effect of high hydrostatic pressure (HHP) processing on physicochemical properties, bioactive compounds and shelf-life of pomegranate juice

The aim of the present study was to evaluate the effect high hydrostatic pressure (HI-IF) processing (350-550 MPa for 30, 90 and 150 s) on microbial quality as well as physico-chemical and bioactive compounds of pomegranate juices during 35 days of storage at 4 degrees C. Antioxidant activity, phenolic content and color values (L*, a* and Delta E) were determined. The microbiological results showed that HHP-treatment at or over 350 MPa for 150 s resulted in a reduction of the microbial load around 4.0 log cycles, and were sufficient to keep microbial populations investigated below the detection limit during the whole storage period. Therefore, these treatments were able to extend the microbiological shelf-life of pomegranate juice stored at 4 degrees C for more than 35 days. All HHP-treated samples showed a slight reduction in antioxidant capacity during storage time. Phenolic content increased significantly (p<0.05) between 3.38% and 11.99% for treated samples with 350 MPa and 550 MPa at day 0. The Delta E values, which are an indicator of total color difference, showed that there were significant differences (p<0.05) in color between untreated and treated samples and showed a significant decrease (p<0.05) in Delta E values during storage time. The highest color difference was obtained at day 35 for 550 MPa for 90 s. These results clearly demonstrate that the color stability of pomegranate juice depends on the processing conditions. During the first 15 days. the pH, degrees Brix and titratable acid were not significantly affected by high pressure processing. Industrial relevance: This paper provides information of storage stability of pomegranate juice after pressure treatments which is quite scarce. In database collected, criteria for commercial production of high quality pomegranate juice with safety requirements could be established. (C) 2011 Elsevier Ltd. All rights reserved.