Study On Freeze-thaw Stability Of Whey Protein Isolate Nanoemulsion Based On Turbiscan Method

Whey protein isolate,as a by-product of cheese industry,has a wide range of raw materials and good functional characteristics,has become an important source of protein in food,medicine and health care products.Whey protein isolate stabilized emulsion is often used in food system,but because of its poor freeze-thaw stability,it has certain application limitations.In this paper,the effects of pH,salt ions and carbohydrate compounds on the freeze-thaw stability of whey protein isolate stabilized nanoemulsion were discussed.The research results of this subject are as follows:1.Freeze-thaw stability of whey protein isolate nanoemulsion with different pH valuesO/W nanoemulsions were prepared by using 1wt% whey protein isolate to stabilize the oil phase of 10% Medium Chain Triglyceride,by high speed shear and high pressure homogenization.The average particle size,zeta-potential and Turbiscan analysis were used as stability indexes to evaluate the freeze-thaw stability of whey protein isolate stabilized nanoemulsions at pH 2-7.After the emulsion was prepared and placed at room temperature for 1 hour,no stratification occurred.After three times of freeze-thaw treatment,the emulsion of pH2.0?3.0 was still a uniform and stable system,while the emulsion of pH4?7 was demulsified after freeze-thaw treatment,and the particle size reached micron level.2.Effects of salts on freeze-thaw stability of whey protein isolate nanoemulsionIn this chapter,a series of concentrations of Na Cl and KCl were added to whey protein isolate stabilized nanoemulsions,and the effects of salt type and ion strength on the freeze-thaw stability of whey protein isolate stabilized nanoemulsions were discussed.Firstly,the particle size of the emulsion without freeze-thaw increased to a certain extent after salt ions were added.Subsequently,the particle size of the emulsion increased significantly after freeze-thaw treatment,reaching hundreds of microns,and the particle size increased with the increase of freeze-thaw times.The absolute value of zeta-potential decreased slightly and the index of milk evolution increased gradually.Turbiscan spectrogram display after 3 times of freezing and thawing process of emulsion has been completely demulsification,speculated that the reason may be that salt ion electrostatic shielding effect weakens the repulsive force between the droplets,the particles used Sheng Ju knot,reunion,the emulsion is in a state of instability,droplet reunion together to form the large droplets,when again the freeze-thaw cycle,the growth of ice crystals leads to interface between the droplets membrane was damaged,make the oil/water two phase separation.3.Effects of sugars on freeze-thaw stability of whey protein isolate nanoemulsionIn this chapter,a series of concentrations of sucrose,trehalose and konjac glucomannan were added to whey protein isolate stabilized nanoemulsions.First of all,after three freeze-thaw cycles in the experimental group with added sucrose,no stratification occurred after freeze-thaw treatment of the added sucrose and the emulsion,according to the appearance chart and the emulsion evolution index.In the experimental group with trehalose,after three freeze-thaw treatments,the particle size of the nanoemulsion added with 4-5% still remained around 200 nm.Finally,the experimental group with KGM was added.After freeze-thaw cycle for 3 times,the emulsion showed a uniform system when the KGM concentration was 0.3-0.5%,showing good freeze-thaw stability.