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

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.