Study On Preparation Technology And Stability Of Peanut Oil Bodies

Peanut oil bodies exist in peanut seeds as small discrete spherical organelles,a subcellular structure that consists of a triacylglyceride core encapsulated by phospholipids-protein membrane.Peanut oil body emulsions have good emulsifying activity and stability,and their preparation process avoids solvent extraction and homogenization,thus they have a good application prospect in the field of food processing.In this research,preparation technology of peanut crude oil body by the methods of aqueous extraction and enzyme-assisted aqueous extraction were investigated and optimized.The basic properties of crude oil body washed by aqueous solution?ASOB?and crude oil body washed by alkaline aqueous solution?AASOB?were analyzed.The effect of small molecule emulsifier Tween-20 on the stability of peanut oil body was researched for the first time by comparing the effect of Tween-20 on the stability of the simulated emulsions prepared by peanut protein isolate.The results are as follows.On the basis of single factor experiments,Box-Behnken experimental design?BBD?with response surface methodology?RSM?was used for optimization of aqueous extraction of peanut crude oil body when extracted for the first time.The optimal extraction conditions for maximization of oil recovery were NaCl concentration of 1.0 mol/L,sucrose concentration of 0.5 mol/L,pH of 5.0 and grinding time of 10.5 min with the use of colloid grinder.Under these conditions,extraction yield of crude oil bodies of?64.03±0.55?% and oil recovery of?81.59±0.46?% were obtained.Combined with the supernatant fraction of two parts obtained from the second extraction process,the total oil recovery from crude oil bodies extraction was?90.04±0.62?%.The cell wall polysaccharide hydrolyzing enzymes,such as pectinase,cellulose and xylanase,were screened.The results showed that the cellulase had the most significant influence on the oil recovery in comparison of other enzymes.When pectinase,cellulase and xylanase were mixed as 1:4:1?w/w/w?,the highest oil recovery was obtained.On the basis of single factor experiments of enzymatic parameters,orthogonal test was carried out for optimization of enzyme-assisted aqueous extraction of peanut crude oil body when extracted for the first time.The optimum conditions for enzymatic hydrolysis were liquid ratio of 1:7?w/v?,the amount of enzyme addition of 4 %?w/w?,hydrolysis time of 7 h,pH of 5.Under these conditions,extraction yield of crude oil body of?69.2±0.33?% and oil recovery of?89.51±0.65?% were obtained.Oil recovery was 7.92 % higher than that of aqueous extraction of peanut crude oil body when extracted for the first time.The results of variance analysis showed that the liquid ratio was very significant,the amount of enzyme addition was significant,and the hydrolysis time was not significant.Combined with the supernatant fraction of two parts obtained from the second extraction process,the total oil recovery from crude oil body extraction was?94.86±0.51?%.The purity of ASOB and AASOB were improved to some extent compared to crude oil body,and the surface protein load were 9.14 mg/m2 and 5.61 mg/m2 respectively.The difference was significant.Protein distribution by SDS-PAGE electrophoresis indicated that extraneous proteins can be removed by washing with an alkaline aqueous solution;The particle size distribution of ASOB and AASOB was relatively concentrated with little difference,mainly distributed between 1¹0?m.The surface-weighted mean diameters of both oil bodies were around 2 ?m,which indicated that although the surface protein load were different significantly,the average particle size was not affected.The acid?pH 4.5?and alkaline?pH 9.5?emulsions?5% o/w?of ASOB and AASOB were prepared for studying the effect of the hydrophilic surfactant Tween-20 on the stability of peanut oil body.Tween-20 was incorporated at levels ranging from 0 to 2 %.The results show that under acidic and alkaline conditions,M_p/o?the mass ratio of the protein to oil?of ASOB was affected significantly following addition of Tween-20.In contrast,M_p/o of AASOB was unaffected mostly.This paper speculated that the amount of protein adsorbed to the surface of ASOB was much higher than that of AASOB,as a consequence,more protein could be replaced by Tween-20.The proteins that present on the surface of AASOB were mainly oleosins which were closely adsorb to the surface,so that Tween-20 was not easy to replace the proteins;Oil leakage was not occur during the measurement of M_p/o,which indicated that the storage stability of the emulsions could be increased for the sake of the local replacement caused by Tween-20,but thecentrifugal stability was not enhanced.The acid?pH 4.5?and alkaline?pH 9.5?simulated emulsions mixed with Tween-20 which was incorporated at levels ranging from 0 to 2 % were prepared.The particle size distribution of alkaline simulated emulsion without Tween-20 was measured.The effects of Tween-20 on the interfacial M_p/o and stability of the simulated emulsions were studied.The results show that the particle size of alkaline simulated emulsion without Tween-20 was large,mainly distributed in 10¹00 ?m.The M_p/o of acid simulated emulsion interface was not affected by Tween-20,but with the increase of Tween-20,peanut protein isolate adsorbed to the interface of alkaline simulated emulsions could be replaced substantially with the M_p/o dropping sharply to 1.09 mg/g.The protein distribution shown by SDS-PAGE also confirmed this phenomenon;In conclusion,the storage stability of oil body emulsions could be increased but the centrifugal stability of oil body emulsions were not affected for the sake of the local replacement caused by Tween-20.Tween-20 could completely replace the interfacial protein of the simulated emulsions,and drastically reduce the centrifugal stability of the simulated emulsions,but had almost no effect on the storage stability of simulated emulsions.In conclusion,the efficiency of preparation technology of peanut crude oil body has been improved significantly andmechanism of the effect ofsmall molecule emulsifier Tween-20 on the stability of peanut oil body has been further refined.All the findings above provides theoretical foundation for the far-ranging application of peanut oil body in the field of food processing.