Preparation Of The Maillard Reaction Products Of Selenium-enriched Peptide Encapsulated By Microcapsules And The Development Of Selenium-enriched Yogurt Melts

Selenium is one of the essential trace elements for the human body.In recent years,the demand for Selenium-enriched products or selenium supplements has gradually increased with the deepening understanding of the relationship between Selenium and human diseases.Selenium-enriched peptides(SP),as a plant derived organic selenium compound,has lower toxicity,higher biological activity,and safety with the wider dosages,compared with inorganic selenium,showing great potential in the development of Selenium-enriched products.However,it exhibited instability in the human gastrointestinal environment,and its structure is susceptible to pH effects,which result in the decreasing or even loss of activity.To date,microcapsules can encapsulate trace amounts of substances(including solids,liquids,and gases)within a polymer matrix,and are widely used in the embedding of different active substances to improve their stability against external factors such as acid,alkali,temperature,and light.Whey protein isolate(WPI)has high nutritional value and is easily uptake by the human body.It can be covalently grafted with polysaccharides(such as dextran)through Maillard reaction to improve its embedding effect as a wall material for microcapsules.In addition,microcapsules encapsulating active substances can be used as food raw materials for the development of functional products to meet the needs of different consumers.Based on this,the aim of this work is to use WPI and dextran as raw materials to prepare polysaccharide-protein complexes through electrospraying as the encapsulation carrier of SP.Furthermore,Maillard reaction is used to regulate the wall structure of microcapsules and the functional characteristics of microcapsules.Finally,based on Maillard reaction,the microcapsule encapsulated SP is used as a Selenium-enriched food raw material for the development of melt bean products,providing a new strategy for the development of Selenium-enriched products.The specific research content and conclusions include the following three sections:(1)The ternary composite microcapsules containing Selenium-enriched peptides(SP)were prepared through electrospraying using dextran(DX),whey protein isolate(WPI)as wall materials.The effects of the concentration and proportion of three materials and the process parameters of electrospraying(such as voltage,receiving distance,flow rate,etc.)on the size of microcapsules and the loading rate of SP were systematically investigated.The results of preparation process optimization showed that the optimized preparation process parameters were 6% DX(w/v),feeding rate Q = 1 m L/h,voltage U = 15 k V,and receiving distance H = 15 cm.When the content of WPI(w/v)was 4–8%,the average diameter of the as-prepared microcapsules was no more than 45 μm and the loading rate for SP ranged from ～46% to ～37%.The DPPH and ABTS free radical scavenging experiments showed that the antioxidant activity of microcapsules increased with the increase of SP content.SP in microcapsules exhibit higher stability under neutral conditions.The results of in vitro simulated gastrointestinal digestion experiments further confirm that microcapsules have certain controlled release properties for SP.The cytotoxicity test results showed that the microcapsule digest had lower cell cytotoxicity.(2)The physical and chemical properties of the as-prepared ternary composite microcapsules was improved via Maillard reaction.Different Maillard products were prepared at various reaction times(0,2,7,and 14 d)through regulating the extent of reaction of DX-WPI and DX-SP.As the reaction time increases,the appearance of microcapsules changed from light yellow to brown with the deepening of the color,and has more protrusions and wrinkles.The increase in the content of intermediates and browning degree of Maillard reaction products improves their thermal stability,but also increases the advanced glycosylation end products,which leads to certain cytotoxicity.In addition,the surface hydrophobicity and improve the antioxidant activity of microcapsules were reduced after Maillard reaction.Results from the simulated gastrointestinal release experiments showed that the release rate of SP in the microcapsules decreased from 94.46± 0.95% to 56.97 ± 0.37% at 120 min after Maillard reaction,which confirmed that Maillard reaction could increase the stability and slow-release characteristics of SP in the microcapsules.In addition,the antioxidant activity and acid-base stability were also improved to a certain extent.Moreover,Maillard products(2 and 7 d)have lower cell cytotoxicity.(3)Selenium-enriched yogurt melts were developed through the enhancement of exogenous selenium methods.Specifically,a single factor experiment was conducted to investigate the effects of egg white,starch,milk powder,and baking temperature on the quality of yogurt melts.The sensory evaluation results showed that when the addition amounts of egg white,starch,and milk powder were 35 g,6 g,and 6 g,respectively,the dissolved bean products prepared at a baking temperature of 120 ℃ had uniform color,full form,rich milk flavor,and excellent taste,with the highest sensory evaluation score.On this basis,the microencapsulates containing SP was added to the yogurt melts as an exogenous selenium fortifier,and the quality of selenium-enriched yogurt melts was further evaluated by sensory evaluation,electronic nose and electronic tongue analysis.The results showed that the sensory evaluation score was the highest when the amount of microcapsules added was 0.3 g,and the impact on the odor and taste of yogurt melts was relatively small.The relevant research results provide a new approach for the development of Selenium-enrich foods.