Effect of high hydrostatic pressure (150-200-250 MPa) on the microbial load and quality parameters (pH, color, 5-hydroxymethylfurfural-HMF) of white (Sultaniye) and red (Alicante Bouschet) grape juices with combination of temperature (20-30-40° / C) and holding time (5-10-15 min) was studied. Increased pressure and temperature showed significant effect on microbial reduction in white and red grape juices (p< / 0.05). The effect of pressure and time on pH drop was found to be insignificant (p> / 0.05). HHP resulted in E< / 1 for white grape and E< / 7 for red grape juice samples. Shelf life analysis for HHP treated white grape juice (200 MPa-40° / C-10min) and red grape juice (250 MPa-40° / C-10min) revealed no microbial growth up to 90 days when stored at 25° / C. Although HMF formation was observed in industrially manufactured, pasteurized samples (65° / C for 30 min), no HMF was detected in HHP treated white and red grape juices. HHP at the suggested conditions can be recommended as a better production alternative to heat treatment for white and red grape juice with respect to microbial load and studied quality parameters even at temperatures lower than required for pasteurization.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12611536/index.pdf |
| Date | 01 January 2010 |
| Creators | Mert, Mecnun |
| 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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