Degradation kinetics of bioactive compounds and antioxidant activity in strawberry juice concentrate stored at high and low temperatures

Abstract

In this study, changes in ascorbic acid (AA), phenolics, anthocyanins (ACNs) and antioxidant activity (AOA) were monitored during storage at - 25, 4, 10 and 20 degrees C to observe the stability of bioactive compound in strawberry juice concentrates (SJCs). Half-life periods (t(1/2)) for ACN and AA degradations were 7.9 and 50 days at 20 degrees C, respectively. On the contrary, much higher t(1/2)values were found for the reduction in AOA and phenolics, i.e. 251 and 430 days at 20 degrees C, respectively. AOA and phenolics were more stable during storage than AA and ACNs.p-Coumaric acid was the major phenolic identified in SJC.p-coumaric acid (33.8%), catechin (23.1%), vanilic acid (18.6%) and epicatechin (16.1%), which constituted 91.6% of phenolics in SJC, followed by chlorogenic acid (4.9%) and caffeic acid (3.2%). Chlorogenic acid was the least stable phenolic in SJC stored at 20 degrees C. Strong correlations were found between AOA and ACNs (r = 0.99), phenolics (r = 0.94) and AA (r = 0.92) in SJC stored at 20 degrees C. Significant ACN and AA degradations occurred at storage temperature as low as 4 degrees C. Therefore, storage at - 25 celcius was suggested for SJC to maximize the stabilities of especially ACNs and AA in SJC.