Study On The Preparation Of Instant Egg White Powder By Ultrasonic Wave And Its Change Law Of Solubility

Egg white powder is a protein powder that is dehydrated and dried after treatment of egg white and contains the same type of protein as fresh egg white.The high protein content and the low moisture content of the solid powder facilitates transportation and storage.Therefore,it is widely used in the food industry.It can be used not only for the production of high-protein nutritional products,but also for the improvement of food texture and food flavor in food processing.It is a common functional ingredient.Because the protein in the egg white is in a close-packed colloidal form,large molecules are easily formed between the proteins.Therefore,the common egg white powder obtained after spray drying has poor fast dissolving properties and is easily lumped into clumps,which hinders the application and promotion of egg white powder in food processing.In this paper,ultrasonic pretreatment of egg white was used to improve the fast dissolving performance of egg white powder.The effect of ultrasonic treatment on the protein structure of egg white powder was studied.The effect of storage conditions on the fast dissolving properties and protein structure of egg white powder was also investigated.The main results are as follows:(1)Using fresh egg white as a raw material,it is modified by ultrasonic treatment and spray dried to make egg white powder.It is hoped that the solubility of egg white powder can be improved and an instant egg white powder can be prepared.The three conditions of ultrasound time,ultrasonic power,and concentration of egg white during the study were selected as experimental factors.Dispersibility,solubility,and stability coefficient were used as evaluation indicators for rapid dissolvability.Ultrasonic treatment conditions were optimized through single-factor and orthogonal experiments.The optimal ultrasonic treatment conditions were as follows: ultrasonic time 10 min,ultrasonic power 120 W,and ultrasonic egg white concentration 50 %.The average dispersibility of egg white powder prepared under this condition was 56.67 s,reduced by about half compared to the non-ultrasound group.The average solubility was 93.56 g/100 g.The stability factor is 97.29 %.The egg white powder obtained after optimizing the ultrasonic conditions has a better instant solubility.(2)The effects of ultrasonic treatment and spray drying on protein structure of egg white powder were studied,and the effects of spray drying and ultrasound on the preparation of instant egg white powder were compared.The results show that ultrasonic and spray drying do not change the primary structure of the protein,but ultrasonic cavitation can destroy some large protein aggregates with a molecular weight greater than 100 kDa.The porous particles formed by spray drying after ultrasonic egg white liquid are more favorable for water absorption and dissolution,and the particles are more uniform and smaller,and are easy to disperse.The particle size distribution of egg white powder solution shows that compared with the original egg white freeze-dried powder,ultrasonic treatment and spray drying will reduce the particle size of the solution.Comparing the two egg white lyophilized powders,we can see that the proportion of particles in the ultrasonic group with a particle size greater than 1000 nm decreased from 39.16 % to 13.64 %;but the ultrasound group samples distributed to a smaller particle size range,accounting for 42.26 % less than 10 nm,35.13 % of the particle size distribution is between 140-530 nm;in the non-ultrasonic egg white powder solution,only 33 % is less than 10 nm and 35.29 % is distributed between 340-1000 nm.From the results of circular dichroism spectra,surface hydrophobicity,and thiol content,it can be seen that ultrasound can disrupt protein aggregation,expand the protein molecular structure,facilitate the formation of soluble protein aggregates,and spray-drying make the powder particles more easily dispersed.It can effectively increase the solubility of the protein,and the combination of the two processes improves the fast dissolving performance of the egg white powder.(3)The egg white powder was prepared after the ultrasonic treatment of egg white at different times to study the fast dissolving properties and structural changes of the egg white powder.The results showed that the rapid dissolving performance of egg white powder was best at 10 min.The results of SDS-PAGE showed that the ultrasonication of macromolecules would form soluble aggregates during the appropriate time;the scanning electron microscopy showed that the particle size of egg white powder decreased as the ultrasonic time increased.At 10 min,the particle size distribution in the solution also indicates that the particle size distribution is smaller at 10-15 min.Zeta potential results showed that the absolute value of the potential decreased after ultrasonication for more than 20 min,and the solution stability also decreased;with the extension of the ultrasonic time,the surface hydrophobicity index of egg white powder first increased and then decreased,reached the maximum at 10 min and 15 min,respectively.1.17 and 1.18,only 0.86 at 25 min ultrasound.The results of circular dichroism spectra showed that the prolongation of the ultrasound time led to a disordered protein structure.The ?-helix and the ?-turn and random coils increased with ultrasound at 25 min,indicating that the protein was unfolded and aggregated simultaneously.(4)The quality changes of two groups of egg white powders obtained without ultrasound and ultrasonic egg white under different storage conditions were studied.The results showed that the instant characteristics of both egg white powders were attenuated during storage.When stored at 4 °C for 60 days,the dispersion of egg white powder in the ultrasound group increased by 84.14 %,while that in the non-ultrasonic group increased by 23.64 %.At the temperature of 25 °C,the egg white powder of ultrasonic group increased by 58.66 % for 60 days and 20.91 % of the non-ultrasonic group.When the egg white powder was stored at 37 °C,the dispersion time of ultrasonic group increased by 70.20 %.In the non-ultrasonic group,the dispersion increased by 25.73 %.The solubility of egg white powder as a whole showed a downward trend.After 60 days of storage,the solubility of the egg white powder in the ultrasound group decreased to about 88 g/100 g.The non-ultrasonic group still had a solubility of 90 g/100 g or more.The results of electron microscopy showed that the powders before and after storage at different temperatures changed.The non-ultrasonic powders generally aggregated,the particles swelled,and the surface depressions became lighter;the ultrasound group accumulated severely at the low temperature of 4 °C storage,and the powder particles deformed when the temperature was high,even broken.The average particle size of the two egg white powders increased to varying degrees during storage.The average particle size of the solution in the ultrasonic group and the non-ultrasonic group increased first and then decreased at 4 °C and reached the maximum at 40 days,561 nm and 470 nm respectively.The average particle size of the solution in the ultrasonic group at 25 °C for 20 days reached the maximum and increased by 429 nm.The average particle size of the solution at 37 °C increased first and then decreased,and the increase was as high as 382 nm at 20 days.The solution particle size fluctuates significantly when stored at higher temperatures.Egg white powder had browning obviously when the storage temperature was higher.At 37 °C,the b* values of the ultrasonic and non-ultrasonic egg white powders increased by 3.29 and 2.83,respectively,and the L* value decreased,which was darker than that of other groups.The results of free sulfhydryl and endogenous fluorescence spectra demonstrated that the internal conformation of egg white powder was continuously changed during storage.It is suggested that ultrasonography destroys the relative stability of the protein structure,and that the intramolecular and intermolecular interactions of proteins during storage result in solubility and change in powder morphology.