| As the world’s second largest food product,wheat is rich in nutrients such as starch,fat,protein,minerals,thiamine,riboflavin,niacin,vitamin A and vitamin C.Processing wheat directly into whole wheat flour can retain the nutrients in it as much as possible;however,storage stability has always restricted the development of the whole wheat flour industry.As a non-thermal food processing technology,pulsed electric field has the characteristics of short processing time,low energy consumption,environmental protection and little influence on the quality of the treated materials.Moisture content is an important factor in the process of pulsed electric field treatment.Therefore,the paper firstly studied the water absorption kinetics of wheat.Next,the water content,electric field intensity,pulse frequency,pulse width and treatment time were used as variable parameters,and the effect of wheat lipase activity as reference index on the passivation of wheat lipase by pulsed electric field was studied,and optimize the process by response surface analysis.Finally,the influence of pulsed electric field on the properties of wheat gluten was explored,which provided a reference for the changes of the components in the pulsed electric field.It also provided a theoretical basis for the utilization of pulsed electric field in gluten modification.The main findings are as follows:(1)The Peleg equation model can be used to describe the relationship between moisture content change and temperature and time during wheat soaking.M is the moisture content,M0 is the initial moisture content,T is the temperature,t is the soaking time,and the water absorption kinetic equation of wheat established at 10 ℃～50℃ is:M=M0+t/[-0.00007T+0.0071+(-0.0001T+0.0085)t],the influence of temperature on the rate constant K1 was further explained by the Arrhenius equation.The water absorption activation energy of wheat during the soaking process was 11.891 kJ/mol.(2)The results of single factor test showed that the 4 factors of moisture content,electric field strength,pulse frequency and treatment time had significant effects on the pulsed electric field blunt enzyme effect(P<0.05),while the pulse width was not significant(P>0.05).On this basis,the response surface analysis method is used to optimize the design,and the optimal process conditions are obtained:moisture content 295 g/kg,electric field strength 12.5 kV/cm,pulse frequency 316 Hz,pulse width 4μs,processing The time is 5 min 15 s.Under the above parameters,the actual wheat lipase activity inhibition rate is 50.39%,so the pulsed electric field can effectively passivate the wheat lipase activity.(3)Under the optimal blunt enzyme condition,the pulsed electric field had a certain effect on the functional properties of gluten,and the solubility and oil retention rate were significantly increased(P<0.05).By studying the rheological properties of wet gluten,it is concluded that the wet gluten has a more stable structure after the pulsed electric field treatment.The apparent viscosity of the protein solution is studied,and it is concluded that the pulsed electric field treatment does not change the molecular shape of the gluten protein.Thermal characteristics studies showed that the thermal stability of the fascia after pulsed electric field treatment was significantly decreased(P<0.05),and the heat sensitivity was increased.(4)After the pulsed electric field treatment,the gluten structure was extended,the disulfide bond was broken,and more small molecular weight proteins were formed.The free sulfhydryl content in gluten increased by 25.2%and the total sulfhydryl content decreased by 46.9%;gluten protein The hydrophobicity of the surface was reduced by 47.5%.The microscopic morphology showed that the treated wet gluten had a more stable network structure;the composition of the secondary structure of the glutenamide I band changed,and the β-fold content increased by 12.9%,α-The spiral and β-turn content were reduced by 14.7%and 74.1%,respectively;the conformation of gluten did not change significantly. |
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