Research On Acylation Modification And Application Of Oat Protein Isolate

As a "super food",oats have adequate sources and good quality of nutrition.However,due to certain limitations of functional properties,oat protein can not meet the food industry and other related industries requires,which makes a great restriction of oat protein application.For the full development and utilization of oat protein,oat protein isolate is modified by succinic anhydride and acetic anhydride in this study.The effect of the functional properties and molecular structure on acylated oat protein isolate and application of acylated oat protein isolate in milk were researched.The results are as follows:Naked oat as raw material was defatted by 1:3(w/v) hexane,oat protein isolate were extracted by the alkali-extraction and acid precipitation method.On the basis of single factor experiment,as the extraction rate for indicator,technological parameters of the extraction of oat protein isolate were determined by Box-Behnken response surface methodology to optimize department conditions following:extraction time 2.5h,extraction temperature 50℃,p H 12.0, liquid-solid ratio 27:1,in this condition the extraction rate of oat protein isolate was 68.91%.The degree of ε-amino acylation sharply increased to about 98.3%(succinylation) and 96.5%(acetylation) then leveled off with the anhydride level increasing from 0 to 0.8 g/g.The degree of ε-amino acylation of succinylation and acetylation showed similar trends,but the active of acetic anhydride was stronger than that of succinic anhydride.Acylation had been basically completed with the anhydride level of 0.8 g/g.The O-acylation distinctly occurred only when the anhydride level was higher than 0.8 g/g.Oat protein isolate was acetylated by succinic anhydride and acetic anhydride. Effects of acylation on functional properties of OPI were studied.The test results showed that isoelectric point of acylated OPI moved to acid migration. Compared to the nature OPI, the solubility, emulsifying activity,foaming capacity of the OPI increased with a increasing anhydride-to-protein ratio,which decreased with the increasing p H.Oil-binding capacity and surface viscosity also improved,but water-binding capacity of OPI decreased.The effect of improvement of succinylation on the functional properties of OPI were greater than that of acetylation under the same reaction conditions.ANS fluorescence probe,Zeta potential,SDS-PAGE,fluorescence spectroscopy and infrared spectroscopy were used to observe the effect on the molecules structural characteristics of acylated OPI.The results showed that the surface hydrophobicity of acylated OPI declined with a increasing anhydride-to-protein ratio,which from 432.4 dropped to 132.5 and 236.2,respectively.Acylation could significantly increase the net negative charge on the protein surface.The greater the degree of acylation,the more the net negative charge increased and the change of Zeta potential of succinylated OPI was slightly larger.Fluorescence intensity of acylated OPI increased and red shift occured.Molecular weight of OPI had increased after succinylation and acylation.The content of β- turn and random coil increased by succinylation and acetylation.The content of α-helical of succinylated OPI significantly reduced.Process conditions of application of acylated oat protein isolate in milk was researched.On the basis of single factor experiment,as sensory score for indicator,technological parameters of process conditions of application of acylated oat protein isolate in milk were determined by response surface methodology to optimize department conditions as following:succinylated OPI amount of 1.3%,complex thickening stabilizer content of 0.18%,milk concentration of 12%, ratio of anhydride to protein of 0.4g/g,sugar content of 4%.Under the optimum department conditions, oat milk double protein dairy product with less precipitation,good sense and texture could be obtained.