【作者】 韩婕妤；

【导师】 沈晓芳；

【作者基本信息】 江南大学 ， 食品科学与工程， 2022， 硕士

【摘要】 奇亚籽含有丰富的多不饱和脂肪酸、膳食纤维、高品质的蛋白质以及多酚等营养物质,近年来受到越来越多人的关注。其食用方式多种多样,包括整颗奇亚籽、奇亚籽油、奇亚籽凝胶、奇亚籽粉。食物的营养价值是由其成分和生物利用率共同决定的,粉碎虽有助于提高奇亚籽的生物利用率,但也造成了营养素的损失,特别是多不饱和脂肪酸。因此,整颗奇亚籽是目前常见的食用方式,可以直接添加到牛奶、果汁等饮品中。但由于奇亚籽很小,添加到饮品中会被吞服,在口腔消化过程中其结构的完整性也不会被破坏。因此,探究整颗奇亚籽在胃肠道的消化过程对其食用和加工有重要意义。本课题采用静态体外模拟消化的方法对整颗奇亚籽在消化过程中的结构、理化以及功能特性的变化进行了探究;通过酶法对整颗奇亚籽的种皮膳食纤维进行了改性处理,结合单因素和响应面实验对改性条件进行优化;并进一步探讨了不同酶法改性对整颗奇亚籽的理化、功能和消化性质的影响。主要研究内容及结果如下:(1)以整颗奇亚籽为研究对象,探究了其在体外模拟消化过程中的营养素降解、结构和功能特性的变化。经胃肠消化后,脂肪和蛋白质的消化率分别为0.46%和11.38%。利用光学显微镜、激光扫描共聚焦显微镜和扫描电子显微镜观察体外消化过程中奇亚籽结构的变化,发现其仍然能够保持结构的完整性,凝胶始终紧密粘附于种皮上,石细胞层是影响营养素释放的主要原因。小肠消化后奇亚籽的持水性和持油性分别为6.37 g/g和3.28 g/g,且傅里叶变换红外光谱表明胃肠消化后的奇亚籽凝胶仍具有多糖的相关特性。为提高其生物利用率,有必要进行预处理。(2)为降低奇亚籽种皮不溶性膳食纤维含量,使整颗奇亚籽更易被人体吸收利用,选用纤维素酶、木聚糖酶和淀粉酶对整颗奇亚籽种皮的不溶性膳食纤维进行了降解。以可溶性膳食纤维得率和奇亚籽含量为指标,利用单因素实验优化了三种酶的实验条件。纤维素酶优化的最佳条件为纤维素酶添加量900 U/g、固液比1:20、p H 5.0、温度50℃、时间6 h;木聚糖酶优化的最佳条件为木聚糖酶添加量900 U/g、固液比1:25、p H 5.0、温度50℃、时间10 h;淀粉酶优化的最佳条件为淀粉酶添加量60 U/g、固液比1:25、p H6.0、温度50℃、时间9 h。结合单因素实验结果,将纤维素酶分别与木聚糖酶和淀粉酶进行复合,采用响应面法进行优化,得到纤维素酶和木聚糖酶复合酶的最佳改性条件为:纤维素酶木聚糖酶配比2.22:1,反应时间8.44 h,反应温度48.7℃;纤维素酶和淀粉酶复合酶的最佳改性条件为:纤维素酶添加量621 U/g,淀粉酶添加量55 U/g,反应时间5.74 h。不同酶法均使奇亚籽不溶性膳食纤维得到了有效降解,以纤维素酶和淀粉酶复合酶优化的效果最佳。(3)对比分析了三种单酶和两种复合酶改性后奇亚籽的理化性质、功能性质和消化性质。五种酶法改性后奇亚籽的脂肪和木质素含量显著上升(P<0.05),蛋白质含量无明显变化(P>0.05),纤维素和半纤维素含量均显著下降(P<0.05);通过扫描电子显微镜的观察得到纤维素酶和淀粉酶改性后奇亚籽表面凝胶量明显降低,红外光谱表明凝胶仍具有多糖的相关特性;纤维素酶改性后奇亚籽的持水性和持油性相对较高,分别为2.91 g/g和1.57 g/g,经体外模拟消化发现,纤维素酶对奇亚籽的结构破坏程度较大,其脂肪酸释放率达2.30%,氨基酸的释放率仅为0.18%。结果表明纤维素酶改性后的奇亚籽不溶性膳食纤维的降解程度最大,并具有良好的理化、功能和消化特性。本论文通过对整颗的奇亚籽进行体外模拟消化研究,发现整颗的食用方式会降低其整体的生物利用率,进一步采用酶法对其种皮膳食纤维进行了改性,优化得到的纤维素酶改性的奇亚籽具有良好的理化、功能以及消化特性,有利于其在食品加工领域的深入开发应用。更多还原

【Abstract】 In recent years,chia seed has attracted more and more attention due to its polyunsaturated fatty acids,dietary fiber,high-quality protein,and polyphenols.The culinary uses of chia seeds were equally diverse,including whole seeds,seed oil,seed mucilage and seed flour.It is well known that the nutritional value of food not only depends on its composition but also its bioavailability.While seed flour could improve bioavailability,it also leads to a loss of nutrients,especially polyunsaturated fatty acids.Hence,the whole chia seed is a common way to consume,which can be added directly to milk,juice and other drinks.However,chia seeds are so small that can be swallowed when added to drinks.And the structural integrity of seeds could not be destroyed during oral digestion.Therefore,it is of great significance to explore the changes of whole chia seeds during gastrointestinal digestion for consumption and processing.In this study,the changes of structure,physicochemical properties and functional properties of whole chia seeds during digestion were investigated by static in vitro digestion method.Then,the dietary fiber of seed coat was modified by different enzymatic methods,and the modification conditions were optimized by single factor experiment and response surface experiment.The effects of different enzymes on the physicochemical,functional and digestive properties of whole chia seeds were further studied.The main studies and results are as follows:(1)The nutrients degradation,structural and functional characteristics of whole chia seeds during simulated in vitro digestion were investigated.After gastrointestinal digestion,the digestibility of lipid and protein was 0.46% and 11.38%,respectively.The microscopic results(optical microscopy,laser scanning confocal microscopy and scanning electron microscopy)demonstrated that the seeds remained intact after digestion,and the mucilage adhered tightly to the seed coat during digestion.The reason affecting the nutrients release was the existence of sclereid layer.The water holding capacity and oil holding capacity of seeds accounted for 6.37g/g and 3.28 g/g after intestinal digestion.Fourier transform infrared spectroscopy indicated that chia seed mucilage still had polysaccharide properties after gastrointestinal digestion.In order to improve bioavailability of chia seeds,pretreatment is important.(2)In order to reduce the content of insoluble dietary fiber in chia seed coat and make the whole chia seed easier to be absorbed and utilized by human body,the dietary fiber of whole chia seed was modified by cellulase,xylanase and amylase,respectively.Taking the soluble dietary fiber yield and chia seeds content as index,the experimental conditions were optimized by single factor experiment.The optimal conditions of cellulase were as follows: cellulase enzyme addition 900 U/g,solid-liquid ratio 1:20,p H 5.0,50℃,6 h.The optimal conditions of xylanase were as follows: xylanase enzyme addition 900 U/g,solid-liquid ratio 1:25,p H 5.0,50℃,10 h.The optimal conditions of amylase were as follows: amylase enzyme addition 60U/g,solid-liquid ratio 1:25,p H 6.0,50℃,9 h.Based on best modification conditions of three single factor experiments,cellulase was chosen to combine with xylanase and amylase,respectively,and further optimized by response surface methodology.Firstly,compound cellulase and xylanase.The optimal conditions were as follows: the ratio of cellulase to xylanase was 2.22:1,the reaction time was 8.44 h,and the reaction temperature was 48.7℃.Secondly,compound cellulase and amylase.The optimal conditions were as follows: cellulase addition was 621 U/g,amylase addition was 55 U/g,and reaction time was 5.74 h.The results showed that enzymatic modification of chia seed insoluble dietary fiber was effective,and the complex enzyme of cellulase and amylase was the best.(3)The physicochemical properties,functional properties and digestive properties of chia seeds modified by enzymes were compared and analyzed.The results showed that the contents of fat and lignin were significantly increased(P<0.05).And there were no significant differences(P>0.05)in protein contents.At the same time,the contents of cellulose and hemicellulose were significantly decreased(P<0.05).The mucilage of chia seeds modified by cellulase and amylase decreased significantly by scanning electron microscope.And the Fourier transform infrared spectroscopy showed that the mucilage still had the polysaccharides properties.The water holding capacity and oil holding capacity modified by cellulase were relatively higher,which was 2.91 g/g and 1.57 g/g,respectively.After simulated in vitro digestion,the structure of chia seeds modified by cellulase was the most damaged,and the release rate of fatty acids was 2.30% and that of amino acids was only 0.18%.The results showed that cellulase could degrade more insoluble dietary fiber,and exhibited good functional and digestive properties.In conclusion,we found that the consumption of whole chia seeds would reduce their overall bioavailability by simulated in vitro digestion.The dietary fiber of seed coat was further modified by different enzymatic methods.The chia seeds modified by cellulase had excellent physicochemical,functional and digestive properties,which was beneficial to its further development and application in the field of food processing.更多还原