| Popis: |
The quality and shelf-life of high pressure processed (HPP) Valencia and Navel orange juices were compared to fresh and thermally pasteurized juices. The juices were pressure processed at 600 MPa, 20 °C for 60 s and stored at 4 and 10 °C for up to 12 weeks. The microbiological, physical, chemical and nutritional properties of the juices and pectin methyl esterase (PME) activity were analyzed at regular intervals. HPP of the juices reduced the microbial load to non-detectable levels immediately after processing. Storage of the juices at 4 °C kept the microbial load below the limit of detection for at least the first 4 weeks of storage, and then to less than 2 log 10 cfu/ml for up to 12 weeks. PME was not completely deactivated in the Valencia juice (pH 4.3) by HPP or thermal treatment (65 °C, 1 min). In the Navel juice (pH 3.7), PME was reduced significantly with thermal treatment (85 °C for 25 s) and with HPP. Other orange juice quality parameters (°Brix, viscosity, titratable acid content, alcohol insoluble acids, browning index and color), ascorbic acid and β-carotene concentrations of the juices were not significantly affected by HPP. |
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