不同品种山药蒸制过程中淀粉消化率及抗氧化活性

本实验以不同品种山药的淀粉相关特性、生物活性成分、抗氧化能力和微观结构为评价指标，研究蒸制时间对铁棍山药、淮山药、糯山药3 种山药的营养品质和抗氧化活性的影响，并探究山药微观结构和品质变化的内在联系。结果表明，蒸制处理后，3 种山药样品中的总淀粉质量分数和抗性淀粉质量分数均显著减少（P＜0.05），但可消化淀粉（快消化淀粉和慢消化淀粉）及表观直链淀粉质量分数显著增加（P＜0.05），同时山药淀粉的持水力增强，溶解度下降。3 种山药中，蒸制15 min的淮山药总可溶性多酚和总黄酮含量最高，分别为1.04 mg/g和0.83 mg/g，同时，其抗氧化能力也最强，铁离子还原力、1,1-二苯基-2-苦基肼（1,1-diphenyl-2-picrylhydrazyl，DPPH）自由基清除率和羟自由基清除率分别为165.56 μmol/g、58.15%和82.26%。扫描电子显微镜观察发现，蒸制后山药样品颗粒呈特征性的块状和不规则的结构，表面粗糙并有裂缝。综合比较，蒸制时间对3 种山药样品的品质特征及活性成分的影响差异较大，蒸制15 min后山药样品的总可溶性多酚和总黄酮含量最高，抗氧化活性也最强，蒸制20 min后山药样品中的可消化淀粉含量较高，而生山药的微观结构特征较好，说明适度蒸制可以提高山药淀粉的消化率和山药的抗氧化能力。

Starch Digestibility and Antioxidant Activity of Different Varieties of Yam during Steaming

In this study, we investigated the effects of steaming time on the physicochemical properties, bioactive components and antioxidant properties of different yam varieties (Tiegun, Huai and Glutinous). The results showed that after steaming treatment, the contents of total starch and resistant starch in the three varieties of yam significantly decreased (P < 0.05), while the contents of digestible starch (fast digestible starch and slow digestible starch) and apparent amylose significantly increased. Meanwhile, the water-holding capacity of yam starch increased and its solubility decreased. Among these varieties, the contents of total soluble phenols and total flavonoids in Huai yam steamed for 15 min were the highest, which were 1.04 and 0.83 mg/g, respectively, and it had the strongest antioxidant capacity with Fe3+ reducing power of 165.56 μmol/g, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging percentage of 58.15% and hydroxyl radical scavenging percentage of 82.26%. Scanning electron microscopic (SEM) analysis showed that the starch granules of steamed yam presented an irregular massive structure with a rough and cracked rough surface. Taken together, steaming time had pronounced effects on the quality characteristics and bioactive components of all the yam varieties. Yam steamed for 15 min had the highest contents of total soluble phenolics and total flavonoids and strongest antioxidant activity. Yam steamed for 20 min had the highest content of digestible starch. The microstructure of yam was damaged by steaming. These results show that moderate steaming can improve yam starch digestibility and antioxidant capacity.