Effect of high hydrostatic pressure on microbial load and quality parameters of grape juice

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Gıda Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2010

Öğrenci: MECNUN MERT

Danışman: HAMİ ALPAS

Özet:

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.