| Lipase has the advantages of efficient conversion in food production and is widely used in the development of natural flavors,nutrients,biodegradable polyesters,structural lipids,etc.However,the low catalytic efficiency of the lipase two-phase interface is also in food processing.Most studies still use chemically modified nanoparticles to construct emulsions,which link particles and lipases through non-covalent interactions.In this paper,a highly efficient food-grade particle-stable Pickering emulsion was constructed and applied to two-phase biotransformation to promote efficient enzymatic conversion of fat-soluble ingredients.Several natural emulsifiers were evaluated for the formation of enzyme-containing particles.The catalytic efficiency of food-grade emulsions provides a new way for the application of lipases in green food processing,and provides new ideas and methods for the development of enzyme interface microreactors and the improvement of food flavor and nutrition.The main findings of this paper are as follows.(1)A Pickering emulsion catalytic system was prepared using chitosan nanogels as particle emulsifiers.The colloidal properties of the chitosan nanogels such as potential,morphology,surface wettability interface properties,and particles and lipase were studied.The interactions between the chitosan nanogel — stabilized composite Pickering emulsions were investigated for their catalytic activity,cycle utilization,p H stability,and reverse stimulus response.When the p H value is 6.5,the chitosan nanogel has a particle size of about60 nm and is positively charged.It binds negatively charged lipases through non-covalent forces such as electrostatic interactions and hydrogen bonding.Chitosan gum has better Hydrophilicity is conducive to the formation of(o / w)Pickering emulsion.Covalently labeled lipase can effectively adsorb on the surface of emulsion oil droplets.The colorimetric determination of p — nitrobenzene palmitate hydrolysate and p-nitrophenol shows that the compound Pickering emulsion system can effectively improve the catalytic activity of lipase,and the system shows strong stability in the range of p H 1.5—7.5 After 13 batches of repeated experiments,the catalytic activity of the system can still maintain more than 55% of the initial activity.In situ reverse application experiments show that the free fatty acid obtained bylipase-catalyzed hydrolysis has an in situ modification effect on chitosan nanogels,which is beneficial to reverse the Pickering emulsion of lipase stimulation response.(2)A hydrophobic modified chitosan modified enzyme-loaded gelatin microspheres were prepared by emulsion template method,and microspheres were used as emulsifiers,n-hexane was used as oil phase,and deionized water was used as water phase to construct(o/ w)Pickering.Emulsions were studied for the possibility of enzymatic reactions at the two-phase interface of Pickering emulsions.Unmodified chitosan particles(CS?0C)have poor surface wettability.The potential is not affected after modification of fatty carbons of different carbon chain lengths(heptanal,nonanal,undecanal),and the surface wettability is improved.The three-phase contact angles are 43.35 °(CS?0C),60.7 °(CS?hep),65.85 °(CS?non),and 67.35 °(CS?und).The wettability of the gelatin microspheres obtained by further modification of the hydrophobically modified chitosan is also The three-phase contact angles were improved to 22 °(CS?0C),62.15 °(CS?hep),68.05 °(CS?non),and 74.02 °(CS?und).The gelatin-loaded enzyme microspheres were used as particle emulsifiers to stabilize the Pickering emulsion.Among them,the emulsion droplet size is about 30—150 ?m,the emulsified layer is dense and delicate,and the two-phase interface reaction area is large;the in vitro hexyl caproate synthesis reaction was used to study the enzymatic catalysis of the two-phase interface,and undecaldehyde modified chitosan.The gelatin microspheres have a stable emulsion with a catalytic efficiency of 87.8%.At the same time,the emulsion can effectively separate the product(the upper n-hexane layer))and the substrate(the gelatin layer and the water layer)by centrifugation.The enzyme has good stability,and the reaction conversion rate after the eight recovery is still about 52% of the initial reaction,indicating that the gelatin microspheres can effectively protect the lipase from the influence of organic reagents,which is conducive to recycling applications.(3)A food-grade Pickering emulsion system stabilized with zein — gel composite colloid-loaded enzyme particles was prepared.The surface wettability,interfacial adsorption capacity,and Pickering emulsion system of the composite colloidal particles were investigated.Hydrolytic activity and stability.At p H 8.0,zein and gelatin are mixed in a 1: 1ratio combined by non-covalent methods such as electrostatic interaction and hydrogen bonding.The obtained colloidal particles have good surface wettability,strong interfaceadsorption capacity,and stable particle picking.The emulsion particle size is small,the distribution is concentrated,and the stability is good;the colorimetric determination of p—nitrobenzene palmitate hydrolysate,p—nitrophenol,shows that compared with free enzyme,Pickering emulsion has a strong ability to adsorb lipase at the oil-water interface,and the enzyme catalytic activity High,hydrolysis and high temperature resistance. |
PDF Full Text Request