| Sturgeon is the largest freshwater fish,which is rich in nutrients and full of "treasures".During the processing of sturgeon,a large number of scraps such as abdominal waste is produced,which are rich in nutrients such as lipids and proteins,especially n-3 polyunsaturated fatty acids,so they can be used as an excellent source of fish oil.However,fish oil is poor in stability,and its quality is often degraded due to oxidative deterioration.In addition,fish oil has an unpleasant fishy smell,which leads to its limited application.The emulsion system can effectively protect fish oil and conceal its undesirable flavor,which is conducive to expanding the application of fish oil in functional foods.In this study,a double-enzyme method was used to extract sturgeon fish oil from the abdomen scraps of sturgeon.The refined fish oil was used as the oil phase to prepare the fish oil Pickering emulsion gel stabled by Zein-Lysine(Lys)-Konjac glucomannan(KGM)ternary composite particles and explored its stabilization mechanism.In addition,?-carotene was loaded into Pickering emulsion to study the stability and bioavailability of ?-carotene in different environmental conditions and simulated digestion processes.The results obtained are as follows:(1)The basic composition of sturgeon belly was analyzed,the experimental enzymes were screened,the optimal extraction process of fish oil was established using single factor orthogonal optimization experiment,and the relevant physical and chemical indexes of refined fish oil were determined.The results showed that the experimental enzymes were neutral protease and papain,the optimum reaction pH was7,the ratio of material to liquid was 1:2,the enzymatic hydrolysis temperature was50?,papain: neutral protease was 1:1,and the total amount of enzyme added was 1.5%,enzymatic hydrolysis for 3 h,the highest extraction rate at this time was 83.54±1.14%.Crude fish oil became refined fish oil through degumming,deacidification,decolorization and deodorization.The water and volatile matter were 0.08%,the acid value was 0.6 mg KOH/g,the peroxide value was 4.2 meq/kg,the iodine value was 167g/100 g,and the appearance was bright yellow,clear and transparent.Among the fatty acid components,n-3 polyunsaturated fatty acids(n-3 PUFA)content was 7.18%,n-6polyunsaturated fatty acids(n-6 PUFA)content was 23.92%,of which EPA content was2.84% and DHA content was 3.54%.(2)The anti-solvent method was used to prepare the stable fish oil Pickering emulsion of Zein-lysine-KGM ternary composite particles(ZLKCPs).The preparation process of the emulsion was optimized and its structure was characterized.It was found that at pH 8.0,the Pickering emulsion prepared with concentrations of 2%(w/v)ZCPs,0.2%(w/v)Lys,0.4%(w/v)KGM and a water-to-oil ratio of 1:1 showed gelatinous.It had the smallest droplet size and could be stable for 30 days or more.Furthermore,the reaction sequence and reaction time of ZCPs,Lys and KGM have a significant impact on the stability of the emulsion.According to FE-SEM observation,a single ZCPs was spherical with uneven size and adhesion,while the addition of Lys and KGM significantly changed the morphology of ZCPs.The main driving forces between ZCPs,Lys and KGM might be electrostatic interactions,as well as hydrogen bonding and hydrophobic interactions.After adding Lys,the ?-helix of Zein molecule increased and the spatial structure stretched.The CLSM image showed that the composite particles were adsorbed on the oil/water interface as a Pickering stabilizer and were filled in the water phase,providing steric hindrance between the oil droplets.After adding enough KGM,the ZLKCPs emulsion formed a gel network structure,and the apparent viscosity and elasticity of the emulsion increased.(3)The effects of pH conditions,salt ion concentration and temperature on the storage stability of the emulsion were explored,and the protective effect of the emulsion on ?-carotene(?-CE)and the interaction between the emulsions and ?-CE in simulated gastrointestinal digestion were studied.The results showed that: Pickering emulsion stabilized by ZLKCPs had the strongest stability under weak alkaline conditions of pH8.0.The emulsion was demulsified at a low temperature of-20?.After heat treatment at 37? for 24 h,the emulsion droplets increased,and a water layer was deposited at the bottom.Under other temperature treatment conditions(4??25? for 24 h,65?for 30 min,90? for 3 min)the emulsion could remain stable.The retention rate of ?-CE loaded in ZLKCPs emulsion was significantly higher than that of bulk oil during the period of UV light irradiation and static storage.After adding ?-CE,the primary and secondary oxidation products of the emulsion during storage were reduced.In the process of in vitro simulated digestion,the particle size of the emulsion changed with the change of the digestion environment;compared with bulk oil,ZLKCPs emulsion had a slow-release effect on free fatty acid(FFA),and the emulsion system improved the bioavailability of ?-CE. |
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