Study On Preparation And Bioavailability Of β-carotene Pickering Emulsion Delivered By Mulberry Leaf Protein

β-carotene is the main source of vitamin A precursors and is important for maintaining human health.β-carotene structure is very unstable,and it is easy to be oxidized and decomposed or isomerized under certain conditions such as heat treatment and light.It is slightly soluble in oil,and the bioavailability ofβ-carotene can be significantly improved by co-ingestion with lipids.Therefore,Pickering emulsion loaded withβ-carotene can improve its stability and increase its bioavailability.Since mulberry leaves have been listed as"medicinal and edible"plants,the development of related health products has attracted more and more scholars’attention.Mulberry leaves are rich in protein,which is a high-quality plant protein resource.At present,the comprehensive development and utilization of mulberry leaf protein at home and abroad is still in its infancy,and the comprehensive utilization rate of mulberry leaf resources is low.Protein particles are often used as one of the natural stabilizers for Pickering emulsion due to their amphiphilic properties,but different drying treatments will affect the structure and properties of proteins.Therefore,the effects of different drying treatments on protein structure and nutritional value of mulberry leaves were studied in this paper,and Pickering emulsion containingβ-carotene was prepared by using mulberry leaf protein to investigate its effects on bioavailability ofβ-carotene.This paper mainly obtains the following research results:1.The effects of different drying methods on extraction rate,amino acid composition,active substances,in vitro digestibility,functional and structural properties of mulberry leaf protein were studied.The results showed that compared with fresh mulberry leaves,the two drying methods had no significant effect on the amino acid composition of the protein extract of mulberry leaves.Vacuum freezing-drying method could significantly improve the protein extraction rate of mulberry leaves,reaching 68.89%,and better retain some active substances in the extract,while hot air drying could improve the gastrointestinal digestibility of mulberry leaf protein to 66.41%.Therefore,more suitable mulberry leaf drying method can be selected according to the use of the product;In addition,hot air drying can improve the solubility,emulsification(62.53 m~2/g),water absorption(3.46 g/g)and oil absorption(2.04 g/g)of mulberry leaf protein.However,compared with vacuum freeze-drying,hot air drying has greater damage to protein structure,most of mulberry leaf protein is degraded,and the content of hydrogen bond,ionic bond and sulfhydryl group is greatly reduced.The results showed that the hydrophobic interaction(95.19%)and surface hydrophobicity(50.25μg)were stronger,which proved that vacuum freeze drying could reduce the influence on protein structure to a greater extent.2.Stable Pickering emulsion was prepared by using mulberry leaf protein.The effects of different protein concentration and oil content on Pickering emulsion were studied,and the optimal preparation concentration and oil phase volume fraction were selected.The results showed that with the increase of protein concentration,the particle size of emulsion decreased,the absolute value of zeta potential increased,and the milk chromatography index decreased slightly.With the increase of oil content,the particle size of emulsion increased gradually,zeta potential did not change significantly,and the milk chromatography index decreased significantly.Finally,the optimal protein concentration of Pickering emulsion was 1.5%and oil phase volume fraction was 0.7.3.Pickering emulsion loaded withβ-carotene was prepared from mulberry leaf protein.The stability ofβ-carotene Pickering emulsion prepared by mulberry leaf protein extracts obtained by different drying methods was studied,and the bioavailability ofβ-carotene Pickering emulsion was simulated by gastrointestinal digestion in vitro.Compared with hot air drying and vacuum freeze-drying,Pickering emulsion prepared with fresh mulberry leaf protein extract has the best properties,good storage and thermal stability,and the highest bioavailability ofβ-carotene(12.15～19.01%).It was proved that drying could reduce the stability of Pickering emulsion prepared by mulberry leaf protein to a certain extent,and hot air drying had more effect on the emulsion.In addition,the stability of Pickering emulsion and the bioavailability ofβ-carotene(15.70-19.01%)were significantly improved by adding 0.1% Guar gum.