Abstract: In this study, the pH-differential method and a fully automatic colorimeter together with the degradation kinetics model were used to examine the effects of low acyl (LA) and high acyl (HA) gellan gum on the thermal stability of anthocyanins from passion fruit peel (PFP) in model beverages in the presence of ascorbic acid, which were heat-treated at 85 ℃ for 0, 1, 2, 3, 4 or 5 h. The anthocyanin components of PFP were identified by ultraperformance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (UPLC/Q-TOF-MS). The results showed that during the heat treatment, the anthocyanin contents in four model beverage systems, i.e., PFP, PFP + VC, PFP + VC+ LA and PFP + VC + HA, showed downward trends, and the degradation of anthocyanins conformed to a first-order kinetic model. The half-lives of anthocyanins in the four systems were 308.44, 155.09, 189.69 and 217.92 min, respectively. Low concentration (0.2%–0.5%) of gellan gum could improve the stability of anthocyanins, and the interaction between HA and anthocyanins was stronger than that between LA and anthocyanins. With increasing heating period from 1 to 5 h, the L* value increased significantly whereas the a* and b* values decreased significantly (P < 0.05), but greater changes in all these parameters were observed between 0 and 1 h. Four anthocyanins from passion fruit peel, namely cyanidin-3-glucoside, cyanidin-3-glucose, cyanidin-3-rutinoside and paeoniflorin-3-glucoside, were identified.

Key words: low acyl gellan gum, high acyl gellan gum, ascorbic acid, passion fruit peel, anthocyanins, thermal stability