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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/9864

Title: Pilot Scale Freeze-Drying of Pomegranate Juices and Roselle Extracts
Authors: B.H. Hassan
A.S. Al-Khalifah
تاريخ النشر: 18-ديس-2010
Abstract: A series of experimental test runs were conducted to investigate the possibility of freeze-drying strength (17 ºBrix) and concentrated (34 ºBrix) pomegranate juices and similar concentrations of Roselle extracts using a pilot scale freeze-dryer. The investigation included determining suitable process conditions and relevant chemical composition and physical properties of the original liquid products and the produced freeze-dried powders. The time required to reach freezing temperature of -25ºC for both pomegranate juices and roselle extracts was about 80 min. which is considered as a slow freezing process resulting in large ice crystals. Temperature of the primary freeze-drying phase was kept constant at 40ºC because of the high sugar content of the pomegranate juices. The primary freeze-draying times were 40 and 48 h for single and concentrated pomegranate juices, and 5 and 8 h for the single and concentrated roselle extracts, respectively. Secondary drying of juices and extracts was carried out by raising the pattern temperature from -40ºC to +25ºC. Attempts were successful to produce freeze-dried powders from single strength pomegranate juice and both concentrations of roselle extracts. The high sugar content of the 34 ºBrix pomegranate juice was primarily responsible for the difficulties to freeze-dry it. The results of chemical analysis indicated that roselle extract of 17 ºBrix is a very good source of vitamin C as having a four times concentration of ascorbic acid as compared to the 17 ºBrix pomegranate juice. The bulk density of powder produced from 34 ºBrix roselle extract was higher than the one obtained from the 17 ºBrix. Hygroscopicity data showed tendency of the 34 ºBrix roselle powder to absorb more moisture than the 17 ºBrix roselle powder. Two models describing the hygroscopic behavior of freeze-dried pomegranate and roselle were given
URI: http://hdl.handle.net/123456789/9864
يظهر في المجموعات:College of Foods And Agricultural Science

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