赣州脐橙皮果胶的提取工艺优化及其改性前后理化性质和生物活性的研究

为实现赣州脐橙皮的资源化利用，以超声微波协同萃取法提取赣州脐橙皮果胶（GOP）。采用Box-Behnken试验对工艺参数进行优化，并对获得的果胶进行pH改性，研究改性前后果胶理化性质的变化，进一步研究其体外抗氧化活性，以及对玉米淀粉糊化和体外消化的影响。结果表明，果胶提取的最优工艺条件为:微波功率550 W，微波时间30 min，pH2.4，液料比25.00 mL?g-1，在此条件下，最终GOP得率为18.25%±0.31%。经过改性，其果胶酯化度由74.10%±2.73%下降到33.27%±2.47%、半乳糖醛酸含量由74.65%±1.11%显著（P<0.05）增加至88.19%±2.98%。两种果胶均表现了较良好的抗氧化活性，改性后，果胶的抗氧化能力增强，其浓度为8 mg/mL时，对DPPH、ABTS自由基的清除率分别达到84.35%±0.28%和87.33%±0.43%。果胶的加入显著（P<0.05）提高慢消化淀粉（SDS）和抗性淀粉（RS）的含量，并增加淀粉糊状物中小颗粒的比例，抑制淀粉颗粒的溶胀，从而抑制了淀粉消化。pH改性果胶对淀粉消化的抑制作用优于未改性果胶。本研究为赣州脐橙皮果胶的开发和利用提供理论依据和技术支撑。

Optimization Extraction of Pectin from Ganzhou Navel Orange Peel and Investigation of Its Physicochemical Properties and Biological Activities before and after Modification

In order to realize the resource utilization of Ganzhou navel orange peel, the pectin (GOP) was extracted by ultrasonic-microwave synergistic extraction from Ganzhou navel orange peel. Box-behnken experiment was used to optimize the process parameters. The modified pectin (MGOP) was obtained by pH modification of GOP. The changes of physicochemical properties of GOP and MGOP were evaluated. On this basis, the antioxidant activities and their effects on corn starch gelatinization and in vitro digestion were studied. The results showed that the highest yield of GOP (18.25%±0.31%) was observed under optimal condition (microwave power 550 W, microwave time 30 min, pH2.4, liquid-solid ratio 25.00 mL?g-1. After modification, the esterification degree of pectin decreased from 74.10%±2.73% to 33.27%±2.47%, the content of galacturonic acid increased from 74.65%±1.11% to 88.19%±2.98%, significantly. GOP and MGOP showed good antioxidant activity. After modification, the antioxidant capacity of pectin was enhanced. When the concentration of MGOP was 8 mg/mL, the scavenging rate of DPPH and ABTS free radicals reached 84.35%±0.28% and 87.33±0.43%, respectively. Adding 6% GOP and 6% MGOP could significantly increase SDS to 32.05%±0.65% and 43.83%±0.48%, and RS to 14.61%±1.40% and 19.84%±2.76%, respectively. In addition, the addition of pectin also increased the proportion of small particles in starch paste, inhibited the swelling of starch particles, and thus inhibited the digestion of starch. Compared with GOP, MGOP had more significant effects. The results of this study provided theoretical basis and technical support for the development and utilization of Ganzhou navel orange peel pectin.