| This study took the enrichment of the protein-active ingredient emulsion delivery system as the starting point,and aimed to expand the application range of fish roe.We constructed a Pseudosciaena crocea roe protein isolate oil-in-water emulsion delivery system,which is of great significance for enriching the research results in related fields and filling the gap of fish roe utilization.Firstly,we used Pseudosciaena crocea roe as experimental materials to extract Pseudosciaena crocea roe protein isolate(PRPI)with 0.6 M sodium chloride solution.A series of analysis and detection of the molecular weight distribution,emulsification,and amino acid composition of PRPI were carried out by means of high performance liquid chromatography,nano LC-ESI-MS/MS system,circular dichroism and medium-infrared spectroscopy.The results showed that PRPI contained higher levels of glutamic acid(11.48%),lysine(9.86%)and cysteine(9.03%).Its protein components were concentrated around 66.4 to 116 kDa.The results indicated that most of the protein components were Vitellogenin.PRPI had good emulsifying activity and emulsion stability under neutral and alkaline conditions,so pH 7 and 8 were chosen as alternative conditions for subsequent aqueous phase construction.Secondly,PRPI was dispersed in a phosphate buffer solution of two pH conditions(pH 7 and 8)as an aqueous phase for constructing the emulsion.We explored the effect of different oil ratios(2%,3%,4% and 5%)and the concentration of benzyl isothiocyanate(BITC)in the oil phase(2,3,4 and 5 mg/mL)on emulsion stability.The average particle size,zeta potential,BITC retention rate and confocal laser scanning microscopy(CLSM)images were used as evaluation indicators.The results showed that the stability of the emulsion system under pH 8 was significantly better than that of pH 7.After storage for 14 days at 20 °C,the average particle size of the pH 7 emulsion system was 1362.28±132.07 nm,which was 4.51 times that of the pH 8 emulsion system.What's more,the zeta potential of the pH 8 emulsion system was as high as-25.57±1.66 mV,while the zeta potential of the pH 7 emulsion system was only-18.47±2.06 mV.The CLSM images also showed a very pronounced flocculation in the pH 7 emulsion system.Moreover,emulsion system with the condition of pH 8 and 5% oil phase has good stability and it can embed more active ingredients than the 2% oil phase,thus having higher delivery efficiency.In addition,when the initial oil phase concentration of BITC was 5 mg/mL,the remaining amount after storage was the highest.Results of the stability test of the emulsion system indicated that 5 mg/mL protein used to emulsify 5% v/v oil(5 mg/mL BITC)in water at pH 8 is the optimized construction condition.Thirdly,we used Tween as the water phase control,medium chain triglyceride(MCT)as the oil phase control to explore the effects of storage temperature as well as time,environmental pH,salt ion and freeze-thaw on the stability of PRPI emulsion.The results showed that the higher ambient temperature has a certain negative impact on the stability of the emulsion.The specific performance was: after 14 days of storage at 20 °C,the average particle size of the PRPI emulsion was 310.62±6.32 nm,which was 17.46% higher than that of the 0th day,but the growth rate is far lower than MCT emulsion;The PRPI emulsion can maintain stability under non-acid conditions,and the salt ions as well as freeze-thaw had a certain impact on its steady state,resulting in a significant agglomeration of droplets within the system.Finally,this study used the simulated in vitro digestion model and the rat intestinal perfusion model to explore the fat-soluble active ingredient release mechanism of the PRPI emulsion system.Compared with the other two emulsions,the PRPI emulsion had a more obvious protective effect on the BITC.After the simulated digestion,the retention rate of BITC was as high as 75.93±7.17%;Both atomic force microscopy images and CLSM images showed that the simulated digestion process has a greater impact on proteins.However,with the exposure of oil droplets in the small intestine phase,the PRPI emulsion had a higher release rate of free fatty acids(99.13±2.49%),and BITC can be fully released,making its bioaccessibility as high as 77.32±5.36%.At the same time,animal experiments showed that PRPI emulsion had better slow release effect.In summary,PRPI emulsion had good stability and superior fat-soluble active ingredient delivery effect.This study provides a reference for the release of fat-soluble active ingredients in other aquatic protein source emulsion systems,and provides a scientific theoretical basis for enriching the mechanism of food dispersion system and promoting the development of emulsion system in food. |
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