Glycosylation Modification Of Flaxseed Protein And Its Application In Gel Delivery System

Flax,commonly known as flax,is widely grown in Ningxia.The by-product of flaxseed after oil pressing is flaxseed cake.The protein content of flaxseed meal is rich,and its nutritional value is comparable to that of soybean protein and pea protein,and it has excellent processing properties,which is of great development value.In this study,the nutritional value of protein in cold-pressed and hot-pressed flaxseed meal was taken as the measuring standard,and the higher nutritional value of flaxseed meal was selected for protein extraction.The extraction process of flaxseed protein was optimized by single factor test and response surface test,and modified flaxseed protein was prepared from the obtained flaxseed protein after glycoylation reaction.The structure,function and volatile flavor components of flaxseed protein were compared before and after modification.At the same time,riboflavin was embedded in the gel matrix with modified linseed protein with the highest grafting degree,and its control and release characteristics on riboflavin were studied in order to design a more effective and safe carrier system for the delivery of bioactive substances.The main research contents and results are as follows:(1)Ultrasonic assisted enzymatic extraction of flaxseed protein.By evaluating the nutritional value of protein in two kinds of flaxseed meal,it was found that the nutritional value of protein in cold-pressed flaxseed meal was better than that in hot-pressed flaxseed meal.Protein was extracted from cold-pressed flaxseed meal by ultrasonic assisted enzyme method.The effects of pH value,ultrasonic temperature,ultrasonic time and enzyme addition on the extraction rate of flaxseed protein were investigated.The extraction process was optimized by response surface test.The extraction rate of protein was 36.31±0.65%with pH 6.0,ultrasonic temperature 47℃,ultrasonic time 70 min and enzyme content 2.5%.(2)Effects of glycosylation modification on structure,function and volatile flavor components of flaxseed protein.The structure,function and volatile flavor components of grafted products of flaxseed protein after glycosylation with four different sugars(glucose,lactose,xylooligosaccharide and maltodextrin)were studied.The results showed that the grafting product of flaxseed protein reacting with xylooligosaccharide had the highest grafting degree and Browning degree.The results of SDS-PAGE,color difference,Fourier transform infrared spectroscopy and thermal stability analysis showed that the glycosylation reaction occurred between flaxseed protein and four kinds of sugars,and the grafted products became dark and yellow in color.The glycosylation could change the structure of protein molecules and improve its thermal stability.At the same time,it can improve the functional properties of protein solubility,oil retention,foaming and foaming stability.The results of GC-IMS analysis showed that the types and contents of volatile flavoring compounds in flaxseed protein were increased by glycation modification.(3)Preparation of modified flaxseed protein gel and its effect on riboflavin release in vitro.The structural properties of the gel prepared from flaxseed protein(FPI)and xylo-oligosaccharide modified flaxseed protein(FPI-XOS)were studied.The results showed that the texture properties and water retention of FPI-XOS gel were significantly improved;By studying the microstructure of the two gel samples,it was found that the gel made by modified flaxseed protein had smooth surface and more compact and uniform structure.The difference of XRD patterns of the two gel samples indicated that the introduction of xylo-oligosaccharide changed the original crystal morphology of linseed protein,which led to the change of gel crystal morphology.It was found that glycosylation modification could improve the encapsulation rate and loading rate of riboflavin in flaxseed protein gel,and effectively reduce the release of riboflavin in simulated gastroenteric fluid.