Effect of Storage Temperature on Degradation and Antioxidant Activity of Anthocyanin in Community-Produced Mao Juice from Sakon Nakhon Province, Thailand

Abstract

This study examined the influence of storage temperature and duration on anthocyanin degradation and antioxidant activity in Mao juice, a community-produced beverage from Antidesma thwaitesianum in Sakon Nakhon Province, Thailand. Four commercial samples were stored at 4°C and 30°C for 35 days. Anthocyanin content was determined by the pH differential method, while antioxidant activity was assessed using ABTS and FRAP assays. Results showed that Sample A had the highest initial anthocyanin content at 4 °C (41.74 mg/L), decreasing slightly to 40.24 mg/L. At 30 °C, anthocyanin degradation was more pronounced, with Sample A declining from 36.06 to 33.89 mg/L, Sample B from 21.87 to 18.86 mg/L, and Samples C and D dropping from 1.03 to 0.70 mg/L and 0.76 to 0.53 mg/L, respectively. Degradation followed first-order kinetics, with rate constants ranging from 1.0×10⁻³ to 10.9×10⁻³ day⁻¹ and half-lives between 99.0 and 9.1 weeks. Sample A was the most stable (k = 1.0×10⁻³ day⁻¹ at 4°C), while Sample C degraded fastest at 30 °C. Antioxidant capacity was highest in Sample A at 4°C on day 0 (1,286.17 mg Trolox/100 mL, ABTS assay), decreasing to 1,240.16 mg by day 35, compared with 1,184.46 mg at 30°C. FRAP values showed parallel trends, with Sample A declining from 826.56 to 811.55 mg Trolox/100 mL at 4°C and from 770.80 to 750.38 mg at 30 °C. The greatest antioxidant loss occurred in Sample B at 30°C (k = 10.0×10⁻³ day⁻¹). Overall, cold storage was shown to preserve Mao juice stability and functional quality, providing practical guidance for local producers to extend shelf life.