Journal otApplied Sciences Research, 9(8): 5323-5336, 2013 ISSN 1819-544X This is a refereed journal and all articles are professionaiiy screened and reviewed ORIGINAL ARTICLES Effects of thermosonication on apple and guava juices quality ‘Salab M. Saad, ‘Ibrahim M. Abd Elaleem, 1Farahat Foda All Foda, 2Hesham A. Eissa, 2GM. Abdelmoniem and 2Wafaa A. Ibrahim. 1Chemisrry Department, Faculty ofAgriculture, Benha University, Egypt 2Food Technology Department, National Research Centre, 12622 Cairo, Egypt. ABSTRACT Apple and guava juice samples were sonicated with processing variables of amplitude levels (21, 30 and 40%), temperature (20, 35 and 50 °C) at a constant frcquency of 20 kHz, sonication times (2, 5 and I O mm) and pulse duration of 5 s on and 5 s off. The effects of sonication on the quality of apple and guava juice were studied for selecting physicochemical properties such as Hunter colour values (L*, a* and b*), turbidity, pH, tittratable acidity, total soluble solids, and ascorbic acid content. Hunter colour values (Le, a* arid b*), pH, °Brix. titratable acidity, cloud value and browning index were measured. Ascorbic acid content was found to be lower in samples treated with sonication than in the control. Retention of quality parameters was observed at the maximum treatment conditions of 40% amplitude level for 10 mm, indicating stability of colour during sonication. Colour changes observed during sonication were subtle (TCD from O to 6.88 in apple juice and from o to 1.68 in guava juice). Colour values (L*, a*, b*), total colour difference (TCD), chroma, hue angle, browning index, ascorbic acid and turbidity were influenced by both ultrasonic amplitude level and treatment time, with the effects observed being either individual or interactive. A sonication treatment was demonstrated to be an effective technique to investigate the influence of sonication on colour and quality retention. Sonication could be employed as a preservation technique for apple and guava juice processing where colour and quality retention is desired. Key words: apple, guava. juice, sonication, colour, turbidity, quality, vitamin C.