薯片油炸过程中淀粉-脂质复合物形成与调控机制研究

Fried foods are appreciated by most people because of their unique characteristic including texture and flavor; however, they are increasingly concerned due to excessive intake of fat and energy from them to pose harmful to human bodies. The effect frying technologies, flavor and texture on quality of fried food was focused in former studies, but the interaction of the ingredients from fried food were seldom concerned. Our studies showed that potato starch reacted with different fatty acids to form starch-lipid complexes under deep fat frying conditions, the results showed that the slowly digestible starch and resistant starch were increased significantly in the complexes; potato starch and frying oil were confirmed to form V-type complex compounds during deep fat frying. However, the formation and control mechanism of starch-lipid complexes under potato chip deep fat frying is still lacking. This project will take potato starch and different chain length and unsaturation fatty acid to prepare starch-lipid complex under frying temperatures. The complexes were employed to study the changes in morphological characteristics, crystal structure, and thermodynamic characteristics during deep fat frying process to understand the interactions between starches and lipid. Basing these results, the relationship of structure and characteristic changing of complexes between porosity, lipid migration and distribution, frying oil oxidation will be investigated during potato chip deep fat frying; the relationship of formation conditions of starch-lipid complexes and their structures and characteristics will be analyzed to control the complex formation. Form these results, we hope that can illuminate starch-lipid formation and control mechanism during deep fat frying process and put theory of reference for formation control of starch-lipid complex and frying science.

油炸食品因独特质地和风味而深受人们喜爱，但又担心摄入过多脂肪和热量会对身体造成危害。以往研究主要集中在油炸工艺、风味及质地对油炸食品品质的影响，对油炸过程各组分间相互作用研究较少。项目组前期研究结果表明：马铃薯淀粉与不同脂肪酸相互作用形成复合物，其慢消化淀粉和抗性淀粉显著增加；糊化淀粉与煎炸油相互作用形成V型淀粉-脂质复合物。前人对油炸过程中淀粉与煎炸油形成复合物进行了一定探索，但对其形成与调控机制尚不清楚。本项目以马铃薯淀粉为原料，在油炸条件下与不同脂肪酸制备复合物，分析其淀粉颗粒形貌、分子结构及特性变化，明确马铃薯淀粉与脂质相互作用关系；进而探究薯片在油炸过程中其孔隙度、脂质的分布与迁移、煎炸油的氧化产物与复合物形成的关系；通过对淀粉-脂质复合物形成条件与其结构和特性关系分析，揭示薯片油炸过程复合物形成调控机制；以期为薯片油炸过程淀粉-脂质复合物调控和科学煎炸奠定理论基础。

淀粉和脂质是食品中的两种重要组分，在水性环境中可通过弱相互作用形成淀粉–脂质复合物（以下简称复合物）。以不同淀粉（玉米淀粉、马铃薯淀粉）与脂质（肉豆蔻酸、棕榈酸、硬脂酸、油酸、亚油酸、亚麻酸、单棕榈酸甘油酯和L-抗坏血酸棕榈酸酯）为试验材料，探究淀粉与脂质在高温条件下的复合作用，分析影响复合作用的因素以及复合物的性质和结构特性变化，揭示其形成及调控机制。脂肪酸浓度增加使其与淀粉的复合作用呈先增强后减弱趋势。随处理时间延长和温度升高，复合物呈先增加后减少的趋势。脂肪酸碳链长度增加，复合物减少；脂肪酸不饱和程度增大，复合物增加。脂肪酸链长增加、不饱和程度降低时，复合物热稳定性增强，其中淀粉–硬脂酸复合物的结晶熔融温度（103.16°C）最高。在处理时间、脂肪酸添加量和淀粉浓度条件变化时，复合物增加使抗酶解作用增强。处理温度升高导致样品消化速率增大，其中复合物形成和淀粉糊化程度均影响抗性淀粉含量的变化。处理温度较低时，淀粉–棕榈酸复合物中抗性淀粉含量较高。脂肪酸链长增加和不饱和程度降低时，样品的抗酶解能力增强，其中淀粉–硬脂酸复合物的抗性淀粉含量最高。在复合物分子层次的结构中，淀粉螺旋构象形成并与不同结构脂质复合，脂质疏水碳链的屏蔽作用使淀粉中碳原子化学位移发生偏移，其中C4和C6区域对应的化学位移均向高场移动，并且复合物形成越多时，化学位移值降低越明显。淀粉–亚麻酸复合物样品中C4和C6的化学位移值比对照淀粉分别减小了0.41ppm和0.30ppm。此外，不饱和脂肪酸复合物中双键碳原子与羧基碳原子比例的下降反映出高温处理过程中双键的断裂和氧化分解的发生。在实际油炸过程中研究发现，高温促使形成II型淀粉-脂质复合物，其数量随着油炸温度的升高而减少，随着油炸时间的延长先增加后减少；饱和脂肪酸含量较高的食用油产生的复合物较多，且耐热性好。