Simplified process of extraction of polyphenols from agroindustrial grape waste

Abstract The extraction, and stability of polyphenols from the grape residue were studied. The extractions were performed following the Box-Behnken design, and the surface response methodology was used to model the extraction of total anthocyanins (TA), flavonols (TF), and phenolics (TP). The extraction was optimized simultaneously by the desirability function. The degradation kinetics of monomeric anthocyanins, and the increase in polymeric color were modeled under refrigeration conditions. The extraction with a temperature of 60 °C, solid:liquid ratio of 1/25 g/mL, and time of 80 min, maximized the recovery of TA (30.96 mg/100 g), TF (73.34 mg/100 g), and TP (856.78 mg EAG/100 g). The degradation of monomeric anthocyanins, and the increase in polymeric color followed a kinetic first-order reaction, with reaction rates (k) of 4.10 x 10-3 days-1, and 3.46 x 10-3 days-1, respectively. The half-life (t1/2) of anthocyanins was 169 days. The ethanol-citric acid solution allowed polyphenols to be efficiently extracted from the grape residue, and had a positive effect on the stability of anthocyanins.摘要 本研究针对葡萄果渣中多酚类物质的提取工艺及其稳定性展开探究。实验采用Box-Behnken设计开展提取操作，并借助响应面法分别建立总花色苷（total anthocyanins, TA）、总黄酮醇（flavonols, TF）与总酚（phenolics, TP）的提取模型；采用综合满意度函数对提取工艺进行多目标同步优化。此外，本研究在冷藏条件下，对单体花色苷的降解动力学及聚合色的变化过程进行建模分析。结果表明，当提取温度为60℃、料液比为1/25 g/mL、提取时长80 min时，TA、TF与TP的得率可达最优，分别为30.96 mg/100 g、73.34 mg/100 g与856.78 mg EAG/100 g。单体花色苷的降解及聚合色的提升均符合一级动力学反应规律，其反应速率常数（k）分别为4.10×10^-3 d^-1与3.46×10^-3 d^-1，花色苷的半衰期（half-life, t1/2）为169天。乙醇-柠檬酸溶液可高效从葡萄果渣中提取多酚类物质，且对花色苷的稳定性具有积极作用。