The quality and shelf-life of pressure processed (150, 200 and 250 MPa at 25 and 35° / C for 5, 10 and 15 minutes) orange, tomato and carrot juices were compared to fresh and thermally pasteurised (60° / C for 5, 10 and 15 minutes and 80° / C for 1 minute) juices. Treatments were capable of microbial inhibition of juices to non-detectable levels. The change in ascorbic acid content of HHP treated juices was not statistically significant (p> / 0.05). Both heat treatments at 60 and 80° / C, displayed a significant loss and induced a decrease in the free radical scavenging activity but was not affected by HHP treatments. Pressurization at 250 MPa at 35° / C for 15 minutes and thermal pasteurization at 80° / C for 1 minute and stored at 4 and 25° / C for shelf-life analysis. HHP treated juices showed a small loss of antioxidants (below 10%) at both storage temperatures whereas the loss is higher (about 30%) in the heat treated juices through shelf life (30 days). The pressurized juices, stored at 25° / C, contained ascorbic acid better than heat treated ones after 30 days. The total color changes were minor (& / #8710 / E=10) for all pressurized juices but for heat pasteurized samples, higher as a result of insufficient antioxidant activity. The pH of juices was not affected by treatment, storage temperature or time. HHP yielded a better product, regarding the studied parameters of the juices compared to the conventional pasteurization. Therefore, HHP treatment (250 MPa, 35° / C for 15 minutes) can be recommended for industrial production of fresh fruit and vegetables.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12606513/index.pdf |
| Date | 01 August 2005 |
| Creators | Dede, Saner |
| Contributors | Alpas, Hami |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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