Faculty of Food Technology and Biotechnology, University of Zagreb
Abstract
Ultrasonication is a nonthermal food processing method that is used in several applications (extraction, treatment before drying, freezing, inactivation of microorganisms, etc.) in ultrasound processing. The objective of this study is to investigate the effect of high power ultrasound and pasteurisation on the aroma profile and sensory properties of apple juice and nectar. Samples were treated according to the experimental design, with high power sonicator at ultrasound frequency of 20 kHz under various conditions (treatment time: 3, 6 and 9 min, sample temperature: 20, 40 and 60 °C, and amplitude: 60, 90 and 120 μm). The aromatic profiles of juices showed that, compared to the untreated samples of juices and nectars, ultrasonic treatment led to the formation of new compounds (which were not present in the untreated samples) or to the disappearance of compounds that were found in the untreated samples. Samples treated at the highest amplitude (120 μm) were used for evaluation and comparison with untreated and pasteurised samples using electronic tongue study. Principal component analysis confirmed the results of electronic tongue study, which showed that the ultrasound-treated and pasteurised juices had different scores compared to the untreated samples.Ultrazvuk se može primijeniti kao netermička metoda za ekstrakciju sastojaka, obradu hrane prije sušenja, zamrzavanje, inaktivaciju mikroorganizama i sl. Svrha je ovoga rada bila istražiti utjecaj ultrazvuka velike snage, te postupka pasterizacije na aromatski profil i senzorska svojstva jabučnog soka i nektara. Uzorci su obrađeni ultrazvukom velike snage i niske frekvencije od 20 kHz pri različitim uvjetima (vrijeme tretmana: 3, 6 i 9 min; temperatura: 20, 40 i 60 °C i amplituda: 60, 90 i 120 μm). Iz aromatskog se profila jabučnog soka i nektara može zaključiti da je nakon obrade ultrazvukom došlo do nastanka novih spojeva, a istodobno i do razgradnje nekih spojeva koji su pronađeni u netretiranim uzorcima. Uzorci izloženi ultrazvučnim valovima najveće amplitude (120 μm) uspoređeni su s netretiranim i pasteriziranim uzorcima pomoću elektroničkog jezika. Analizom osnovnih komponenata (engl. principal component analysis - PCA) utvrđeno je da uzorci obrađeni ultrazvukom i pasterizirani sokovi imaju drukčije vrijednosti od netretiranih sokova, što je potvrđeno i senzorskom analizom
