| Suma?Perilla frutescens Britt.var.frutescens?is an annual herbaceous plant under the genus Perilla in the Labiatae family.Its seeds are rich in fats and proteins,rich in nutrients,and have multiple functional characteristics.It is a high-quality medicinal and edible specialty crop and an important oil resource.In order to vigorously promote the comprehensive research and development of suma seed oil/protein.In this paper,casein was modified by wet glycosylation and enzymatic hydrolysis technology to study the preparation of suma oil microcapsules;The hydrolytic preparation of suma peptides with different proteases was investigated and the process was optimized.The systematic analysis was conducted to study the taste characteristics,amino acid composition,functional activity and structural sequence information of suma peptides.The main research contents and conclusions are as follows:?1?The effect of sugar type on the modification of casein glycosylation.Glucose with smaller molecular weight in aldose is easier to graft with casein glycosylation,and the degree of grafting is significantly higher than that of ketose?p<0.05?.The grafted products of casein and maltose and dextran 20 000 and 40 000 have good grafting degree and anti-lipid oxidation ability,and the emulsifying activity is significantly increased by 30.14%,42.47%and 52.05%compared with casein?p<0.05?;All have good emulsification stability,of which casein-dextran 40 000 covalent grafts emulsification stability increased by 85.91%compared with casein.The glycosylation grafting modification of casein and dextran or maltose is efficient and easy,and has good anti-lipid oxidation ability and emulsification characteristics.?2?The grafting degree and product characteristics of the product were investigated to determine the different modification methods of casein.Glycosylation grafting:Casein concentration 4%(40 mg.m L-1),protein to sugar mass ratio 3:1,p H8.0,80?reaction for 120 min.Enzymatic modification:Casein concentration 4%?w/v?,enzyme to substrate ratio 1.5%,enzymatic hydrolysis for 20 min.Enzymatic hydrolysis-glycosylation grafting:After enzymolysis according to the enzymatic hydrolysis conditions,the p H of the enzymolysis solution was adjusted to 9.0,the mass ratio of protein to sugar was 4:1,and the reaction was performed at 85?for150 min.The requirements for the modification of casein are not high,the operation is simple,the product performance is good,and the safety is high.?3?Characterization and structure characterization of modified products.After modified by wet glycosylation with maltose,the emulsifying activity and emulsifying stability of casein were significantly improved?p<0.05?,and EAI and ESI increased by 37%and 48%respectively.After modification by casein hydrolysis-glycosylation grafting,the EAI and ESI were significantly improved by 4.37 times and 2.11 times than before grafting?p<0.05?.The SEM,fluorescence and infrared spectroscopy analysis showed that after the protein was grafted through glycosylation,glycosidic bonds and polyhydroxy sugar chains were introduced,forming a relatively smooth and complete structure with the sugar.And after enzymolysis,the amide bond generated by the glycosylation grafting reaction is not broken;under the action of neutral protease,casein and its grafted product will form more micelles.Using casein modified products as microcapsule wall materials,suma oil microcapsules with good embedding rate can be prepared by freeze-drying method.?4?Enzymatic extraction and process optimization of suma peptides.Using soluble nitrogen content and peptide extraction index as indicators,the effects of raw material processing methods and different conditions on the extraction of suma peptides were investigated;the single-dual enzymatic process for direct preparation of suma peptides was optimized.The results show that the best processes for alkaline protease,trypsin,and pepsin are:5%,7%,and 5%enzyme-substrate ratio,respectively,3%feed-liquid ratio,and 50?for 6 h.Under this condition,the peptide extraction indexes were 49.05±0.91%,47.98±0.36%and 44.22±0.87%,respectively.The best process for double enzymatic hydrolysis is 5%feed-liquid ratio,at 55?,trypsin with 3.5%enzyme-substrate ratio is enzymatically hydrolyzed at p H 8.0 for 3 h,and then adjusted to p H 9.5.Using an alkaline protease with an enzyme-substrate ratio of3.5%for 3 hours,the soluble nitrogen content in the enzymolysis solution was significantly higher than that of the single enzyme?p<0.05?.The suma peptide extraction index reached 52.88±0.39%.?5?Characterization and sequence determination of suma polypeptide.Research was conducted around taste characteristics,amino acid composition and content,functional characteristics,peptide sequence information,and interrelationships.The results show that the total amount of amino acids in suma peptides prepared by different enzymatic methods are different,but the proportion is harmonious,and the essential amino acids account for 32.86±0.75%of the total amino acids.It is an active natural protein peptide of high quality and high value.The umami and sweet amino acids in suma peptides account for 60%of the total amino acids,and the taste characteristics of tryptic peptide extraction are more similar to chicken essence.Suma polypeptide has a certain antioxidant capacity,and the polypeptide prepared by alkaline protease and double enzyme method has better antioxidant capacity.A comparative study found that suma peptides extracted by different proteases have different effects on the growth activity of probiotic strains.Among them,the suma peptide extracted by trypsin has a stronger effect on promoting the growth of Streptococcus thermophilus?p<0.05?,while the double enzyme method has a stronger promoting effect on bifidobacteria and Lactobacillus bulgaricus?p<0.05?.Through identification of suma peptides prepared by the double enzyme method,among 96peptide peptides less than 3 k D detected,94%of the peptides have molecular weights between 600-1800 Da and are closely related to their biological activities. |
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