Water-soluble propolis extract as a natural preservative for jaboticaba juice

Abstract

This study was focused on the preparation of water-soluble propolis extract as the natural preservative for perishable jaboticaba juice. A successive extraction and alkaline hydrolysis were performed to produce water-soluble propolis extract. The propolis extract was found to have a high content of phenolics and flavonoids, but a low concentration of wax. The hydrolysed propolis extract was added into jaboticaba juice and the treated juice quality was monitored for 2 weeks at 4 °C. The results found that the performance of propolis extract was comparable with chemical preservative, sodium benzoate in similar amount (0.035%) used in the present study. The comparison was performed based on the physiochemical properties such as pH, titratable acidity, browning index and ascorbic acid content of juice. Ascorbic acid was the most reliable parameter to monitor the kinetic degradation of jaboticaba juice. Its degradation followed a first order kinetic model with a lower kinetic constant (0.1912 mg/mL/day) than that of non-treated juice (0.2073 mg/mL/day). The second reliable parameter was titratable acidity which could be used to monitor the rate of acid formation resulting from the breakdown of fruit sugars during degradation. The acidity of juice was slightly increased with storage time following zero order kinetics. The browning index was not suitable for juice quality monitoring as the addition of propolis would reduce flavylium cations of anthocyanins to be colourless. This non-thermal extraction followed by mild alkaline hydrolysis at pH 7.5 could produce good quality propolis extract, possibly as an alternative to chemical preservatives for jaboticaba juice.