Study On Construction And Properties Of Microencapsulation System Of Xylo-oligosaccharide Glycosylated Pea Protein

Theβ-carotene is a representative of fat-soluble bioactive substances that have attracted great attention due to their good biological functions,but their application is limited due to their poor water solubility,easy oxidative degradation and low bioavailability.Microcapsule technology enables the encapsulation of active substances,thereby improving their stability and bioavailability.The properties of the wall material during microencapsulation have an important influence on the stability of the microcapsule.The glycosylated complexes of proteins and polysaccharides have good emulsifying properties and can be used as wall materials to construct stable microcapsule systems.Pea protein isolate(PPI)has attracted attention as a high-quality plant protein with low allergenicity.In glycan donor selection,on the one hand,xylo-oligosaccharides(XOS)can improve the emulsification properties of proteins through glycosylation.On the other hand,it can also be used as a prebiotic,because it is not destroyed by human stomach acid during digestion.And it can protect the modified protein structure from degradation,and play a slow-release effect when used as a wall material.Based on this,PPI and XOS were used as raw materials to prepare pea protein isolate-xylosaccharide glycosylated complex(PPI-MRPS).PPI-MRPS with good emulsification characteristics were selected as the wall material andβ-carotene was used as the fat-soluble active substance model to prepareβ-carotene microcapsules.The performance of the loadedβ-carotene microcapsules was studied,and the main conclusions were as follows:Firstly,the emulsification characteristics were used as the evaluation index to optimize the glycosylation reaction conditions:when the mass ratio of PPI and XOS was 2:1,the reaction temperature was 75°C,and the reaction time was 90 min,PPI-MRPS had good emulsification characteristics,among which the emulsification activity was 12.32 m~2/g and the emulsification stability was 59.64%,which increased by 11.69%and 21.19%,respectively,compared with PPI.At this time,the solubility of PPI-MRPS was 64.58%,and the grafting degree was 14.3%.Further structural characteristics were found to show that the formation of macromolecular substances in SDS-PAGE and the shift of characteristic peaks in infrared spectrum proved that PPI and XOS covalently recomposed.The fluorescence spectroscopy results showed that glycosylation modification caused the spatial structure expansion of PPI,the exposure of tryptophan residues,and PPI-MRPS showed a more suitable conformation at the oil-water interface,showing high emulsification characteristics.Secondly,on the basis of the previous research,the microcapsule system was prepared by using PPI-MRPS with good emulsification characteristics as the wall material andβ-carotene as the core material.When the wall concentration was 4%,the core-to-wall ratio was 1:10,the homogenization pressure was 600 bar and the homogenization time was 2 min,the microcapsule system had a high encapsulation rate and coating efficiency,which reached97.18%and 67.22%.Under this condition,the moisture content of microcapsules was 2.61%,which was easy to preserve.It has better antioxidant activity than PPI microcapsules.Further studies on the environmental stability of PPI-MRPS microcapsules found that after heating and freeze-thaw treatment of PPI-MRPS microcapsules,β-carotene still had high retention rate,and the particle size was small,and there was no obvious aggregation.After salt ion treatment,the particle size of PPI-MRPS microcapsules increased,and slight aggregation and flocculation occurred,among which the influence of divalent salt ions on PPI-MRPS microcapsules was greater than that of monovalent salt ions.After storage at 4°C and 25°C for 25 days,there was no significant change in the particle size of PPI-MRPS microcapsules,and the stability was good.On the whole,PPI-MRPS microcapsules have good processing stability and storage stability.Finally,the in vitro digestion characteristics of PPI-MRPS microcapsules were further studied,and it was found that:after gastric digestion of PPI-MRPS microcapsules,the release ofβ-carotene was less(32%),and the microcapsules had obvious aggregation.When digested in the small intestine for 20 minutes,the release rate ofβ-carotene reached 95%,and only a small amount of oil droplets existed.It shows that most ofβ-carotene is released in the small intestine,and PPI-MRPS microcapsules have a sustained release effect.After gastrointestinal digestion in the model,the release rate of free fatty acids in PPI-MRPS microcapsules reached 96.78%,and the bioavailability ofβ-carotene was 69.1%,indicating that PPI-MRPS microcapsules had high bioavailability.It can improve the utilization of fat-soluble bioactive substances in the intestinal digestive tract.In summary,the microcapsules prepared with PPI-MRPS as the wall material have high encapsulation rate,good processing stability and digestion characteristics.This provides reference for the development of new microcapsule wall materials and the utilization of pea protein isolate.