葵花籽水酶法加工过程中乳状液的形成规律和稳定机理

Enzyme-assisted aqueous processing (EAEP) of sunflower seed is green and safe, and also shows superiority to conventional processes on recovering edible oil, protein and phenolic acids of high quality. However, emulsion is prone to be formed during the process and its hard to accomplish complete demulsification. This limits the free oil yield of the whole process and stands out as an outstanding bottleneck for the industrialization of the EAEP. Considering phenolic compounds such as chlorogenic acid (CGA) would react with protein in aqueous system, especially at high temperature, we developed a mild acid extraction process to remove phenolics before enzymatic processing of sunflower kernel. With dephenolized sunflower kernel as material, the EAEP for simutaneous recovery of oil and protein could still be affected by pH, temperature, particles, protein denaturation and oxidation of residue phenolics. Thus stable emulsion was formed during EAEP. In present study, emulsion will be prepared with typical processes, and the emulsion composition, the interface structure and properties, the phase properties and the stability of emulsion systems under different treatments such as enzyme preparations will be analyzed. Sunflower seed protein, oil, and CGA will be reconstituted in a model system and compared with the naturally formed emulsion for their structure and properties. Based on these studies, the mechanism of emulsion formation as well as its stabilization mechanism could be elucidated. This study is expected to contribute to the industrial exploitation of sunflower seed as well as the aqueous processing technology.

水酶法加工葵花籽具有工艺绿色安全的特点，较传统工艺能更好地开发其所含的高品质食用油、蛋白质和酚酸类物质。但水相取油过程中难免生成乳状液，并不易完全破除，限制了油料中油脂的回收率，阻碍该技术的产业化。鉴于绿原酸等酚酸物质在水相中受热处理时会与蛋白发生不利于其相互解离的反应，我们提出先提取主要的酚酸物质、再以酶法水相加工葵仁回收油脂和蛋白的工艺，实现各组分高值利用。针对脱除酚酸的葵仁，其水相取油过程中仍受到pH、温度、颗粒、蛋白变性、残存酚酸氧化等多种因素的影响，形成稳定的乳化体系。本研究以现有典型工艺获取的乳化体系为研究对象，系统分析葵仁水相取油过程中所生成乳状液的组成成分、界面结构、界面性质、体相性质以及乳化体系在多种酶类等不同外因作用下的变化。通过与重组的蛋白质-油脂-酚酸三元体系的对比，分析两种体系的结构和性质，从而揭示葵花籽水酶法加工过程中乳状液形成的规律以及该乳状液的稳定机理。

葵花籽是高品质食用油、蛋白质和绿原酸的重要来源，采用水媒法加工它具有绿色安全的特点，但加工过程中往往会生成乳状液，限制了油脂的回收，阻碍该技术的产业化。鉴于绿原酸等酚酸物质在水相中受热时会与蛋白发生不利于其相互解离的反应，我们提出先提取绿原酸、再以酶法水相加工葵仁回收油脂和蛋白的策略，以期实现各组分高值利用。.本项目主要研究内容及其结果如下：.（1）开展葵花籽仁预处理对乳状液生成的影响研究，发现葵仁内的多酚类物质主要为绿原酸和咖啡酸，其中游离态绿原酸含量较高，葵仁总绿原酸含量为13.87±0.02 mg/g葵仁。研究建立温和酸溶液浸提整粒葵仁分离绿原酸的工艺，优化条件下绿原酸脱除率可达85.80±1.37%。经脱酚处理，水相提油率可由86.76±0.34%提高至91.32±0.24%。.（2）开展葵仁水媒法加工过程中乳状液生成规律研究，研究发现葵花籽细胞大小约30μm×30 μm，脱酚处理可使葵仁细胞内油脂体聚集，便于提油。发现先初粉后精粉的油料粉碎方法可实现平均粒径更小（19.68μm）、更均匀。研究发现影响水酶法提取葵花籽油的因素（粉碎程度、蛋白酶种类和用量、料水比、酶解时间）中粉碎程度和酶种类较为重要。影响水代法提葵花籽油的因素（粉碎程度、pH、料水比、反应温度和反应时间）中粉碎程度和pH为最主要的。两种工艺较优条件下游离油提取率分别达到92.48±0.82%和87.12±0.41%。尽管水代法乳状液中含有11%的油脂。但随粉碎程度的提升（~20μm）及料水比的降低（1:5 kg/L及以下），乳状液的稳定性显著降低，易于实现破乳。.（3）开展乳状液破除方法研究，发现冷冻解冻与乙醇辅助两种方法破乳率分别可达94.01±0.89%和92.02±1.22%。.（4）开展水媒法加工葵仁各产物的开发研究，发现水媒法提取的蛋白质其SDS-PAGE条带、变性温度、疏水性值均符合预期；所得葵花籽油仅经过简单的脱酸、脱色处理，便可达到国家一级成品葵花籽油各项质量指标要求。.（5）研究发现绿原酸水解酶应用于水代法加工脱酚葵花籽仁工艺时，葵花籽蛋白绿原酸含量由脱酚后的1.77 mg/g降低为0.12 mg/g。功能性质和感官品质显著提升。