(1.东北农业大学 食品学院/乳品科学教育部重点实验室, 黑龙江 哈尔滨 150030;2.黑龙江省绿色食品科学研究院, 黑龙江 哈尔滨 150023;3.内蒙古益婴美乳业有限公司, 内蒙古 阿拉善 750308)
(1.College of Food Sciences/Key Laboratory of Dairy Sciences, Ministry of Education, Northeast Agricultural University, Harbin 150030, China;2.Heilongjiang Academy of Green Food Science, Harbin 150023, China;3.Inner Mongolia Yi Ying Mei Dairy Co Ltd, Alashan 750308, China)
通过美拉德反应制备酪蛋白-果胶复合物,研究果胶对酪蛋白的结构和功能特性的影响。以接枝度和褐变指数为响应值,通过单因素实验结合响应面分析确定了制备酪蛋白-果胶复合物的优化工艺条件,以酪蛋白-果胶复合物为壁材制备亚麻籽油微胶囊。研究结果表明,酪蛋白与果胶质量比为3∶1、加热时间为1.5h、加热温度为90℃时,酪蛋白-果胶复合物具有较佳的接枝度,为37.06%±0.80%,褐变指数为1.05±0.014。蛋白质二级结构测定结果显示,与酪蛋白相比,美拉德反应制备的酪蛋白-果胶复合物的α-螺旋、β-折叠和β-转角含量分别下降26.39%、9.21%和2.23%,无规则卷曲含量提高12.43%。酪蛋白-果胶复合物较酪蛋白的功能特性(溶解性、乳化性、热稳定性和抗氧化活性)显著提高。以美拉德反应制备的酪蛋白-果胶复合物为壁材,经喷雾干燥制得亚麻籽油为芯材的微胶囊。研究结果表明,酪蛋白-果胶复合物与亚麻籽油的质量比为 1∶1 时,亚麻籽油包埋率达到最大(77.06%±0.98%),且微胶囊具有完整的球形结构、无破碎现象。相较于游离态亚麻籽油过氧化值[(14.7±0.51)meq/kg],微胶囊化后亚麻籽油经过25℃储存28d的过氧化值仅为(3.82±0.07) meq/kg。研究结果表明,美拉德反应制备的酪蛋白-果胶复合物显著提高了亚麻籽油的抗氧化性。研究结果旨在为基于美拉德反应改性的酪蛋白在食品微胶囊中的应用提供科学依据。
The casein-pectin conjugate was prepared by Maillard reaction, and the effects of pectin on the structural and functional properties of casein was investigated. The optimum process for casein-pectin conjugate was determined by combining response surfaces with single factors taking the grafting degree and browning index as the response values. Flaxseed oil microencapsulation was prepared using casein-pectin conjugate as wall materials. The results showed the optimum process conditions were casein-pectin mass ratio 3∶1, heating time 1.5h, and heating temperature 90℃. The grafting degree of casein-pectin conjugate were 37.06%±0.80% and the browning index was 1.05±0.014. The determination results of secondary structure showed that the α-helixes, β-sheets, and β-turns contents of casein-pectin conjugate was decreased by 26.39%, 9.21%, and 2.23%, respectively, while the random curl content was increased by 12.43%, compared with casein. The functional properties (solubility, emulsification, thermal stability and antioxidant activity) of casein-pectin conjugate were significantly improved compared with casein. Flaxseed oil microencapsulation was prepared by spray drying using casein-pectin conjugate as the wall material and flaxseed oil as the core material. The results showed that the maximum encapsulation efficiency (77.06%±0.98%) was reached at mass ratio of 1∶1 between casein-pectin conjugate and flaxseed oil, and the microencapsulation had a complete spherical structure without fragmentation. In addition, the peroxidation value of free flaxseed oil was (14.70±0.51) meq/kg after stored at 25℃ for 28d, the peroxidation value microencapsulated flaxseed oil was only (3.82±0.07) meq/kg, indicating that the antioxidant activity of flaxseed oil was significantly improved by casein-pectin conjugate. This study aimed to provide a scientific basis for the application of casein in food industry.