U.S. flag

An official website of the United States government


Main content area

Quality characteristics of pomegranate juice concentrates produced by ohmic heating assisted vacuum evaporation

Sabanci, Serdal, Cevik, Mutlu, Cokgezme, Omer F, Yildiz, Hasan, Icier, Filiz
Journal of the science of food and agriculture 2019 v.99 no.5 pp. 2589-2595
anthocyanins, antioxidant activity, color, electric potential difference, electrochemistry, electrodes, energy efficiency, evaporation, hydroxymethylfurfural, juice concentrates, odors, ohmic heating, pH, pomegranate juice, processing time, sugar content, sugars, titanium, titratable acidity, total soluble solids, volatile fatty acids
BACKGROUND: Vacuum evaporation (VE) process is widely utilized in fruit juice evaporation to preserve quality attributes of final product. However, it has some disadvantages such as possible degradation of aroma components or volatile fatty acids due to long process time, and low energy efficiency of process. Pomegranate juice having 17.5% total soluble solid (TSS) content was evaporated to 40% TSS by ohmic heating assisted vacuum evaporation (OVE; 7.5, 10 and 12.5 V cm⁻¹) and VE in the present study. The effects of the evaporation methods on pH, titratable acidity and colour values, antioxidant activity (AA), total monomeric anthocyanin (TMA), total phenolic content (TPC), hydroxymethylfurfural (HMF) and invert sugar content of pomegranate juice concentrates were compared. RESULTS: The colour properties, TMA, TPC and AA values of pomegranate juice concentrates evaporated by OVE were more influenced than those evaporated by VE. The degradation of sugars was minimized for OVE processes at high voltage gradients (10 and 12.5 V cm⁻¹), and HMF content of pomegranate juice concentrated by OVE was lower than VE. CONCLUSION: It is thought that electrochemical reactions occurred because of the use of titanium electrodes during the OVE process caused these quality changes in pomegranate juice concentrates having high acidity. Hence, it was concluded that the utilization of relatively more electrochemically inert electrodes should be investigated in further studies to better evaluate the of influence of OVE method on quality attributes of different fruit juices. © 2018 Society of Chemical Industry