Application Study On Inhibition Of Yoghurt Adhesion Based On Special Wetting Surface

Yogurt is a typical viscous fluid food,there will be about 15%residual adhesion on the surface of packaging materials after eating.This will not only lead to the waste of food resources,but also easy to breed harmful microorganisms,increasing the difficulty of packaging materials recycling.Therefore,reducing the residual amount of yogurt after consumption is an urgent problem to be solved in the dairy industry.Special wetting surfaces can use their own structure and composition to control droplet attachment state.This provides a solution for the adhesion of yogurt droplets on the packaging surface.However,the instability of special wetted surfaces is still a prominent problem in yogurt adhesion,which limits the practical application of special wetted surfaces in yogurt products.In view of the above problems,the purpose of this paper is to construct and characterize the special wettability surface and analyze the influence of the special wettability surface on the physical and chemical indexes of yogurt with the purpose of building durable special wettability surface to inhibit the adhesion of yogurt.The main research contents and results are as follows:（1）Construction of special wettable surfaces.In this study,the effects of the amount of carnauba wax（CW）,silica（Si O₂）and sodium carboxymethyl cellulose（CMC-Na）on the liquid wettability of the surface were investigated.A special wettability surface was constructed by taking the contact Angle and rolling Angle as indexes.The results show that anhydrous ethanol is 100 m L,CW is 3g,Si O₂is 0.9g,as liquid A.When deionized water was 100 m L and CMC-Na dosage was 0.6g,it was used as liquid B.When the volume ratio of liquid A to liquid B is 2:1,the special wettable prepared by spraying method has A contact Angle of（131.34±3.36）°for water,A contact Angle of（141.32±5.43）°for yogurt,A rolling Angle of（7.51±2.86）°,and A residual amount of（3.77±1.99）%.The residual amount of yoghurt was significantly decreased（p<0.05）.（2）Characterization of specially wetted surfaces.SEM results showed that the structure of the special infiltrating surface was similar to that of rose petals,with typical micro-nano structure.The“lift”effect on the yogurt droplets was realized in the structure,and the yogurt adhesion was inhibited by Cassie model.It can be verified that the specially wetted surface is composed of C,O,Si and Na elements by energy dispersive spectrometer（EDS）.Fourier transform infrared spectroscopy（FTIR）analysis showed that the typical absorption peaks of CW(2917 cm^-1,1746 cm^-1),Si O₂(1228 cm^-1and 1044 cm^-1)and CMC-Na(3600 cm^-1)were observed.The results indicate that CW,Si O₂and CMC-Na are compatible together and form special infiltrating surface.The X-ray diffraction（XRD）spectra further confirmed that the special wetting surface was composed of CW,Si O₂and CMC-Na materials.Stability test results show that the specially wetted surface can tolerate lactic acid solution with p H 4.0 and tends to be more stable with time.When the temperature was 80℃,the contact Angle of yogurt on the special wetted surface was（151.36±1.05）°,and the residual amount was（0.10±0.06）%,indicating that the special wetted surface had good temperature stability.（3）Analysis of the influence of special wetting surface on the physical and chemical indexes of yoghurt.A special infiltrating coating was prepared by spraying the inner wall of commercial yoghurt packaging box and compared with uncoated packaging box.The results showed that during the storage period（21 days）,the sensory evaluation,p H value,acidity,soluble solids,fat,protein,viscosity and water holding capacity of yogurt were not significantly affected by the package with special wetting surface（p>0.05）.FTIR analysis of coated yogurt during the storage period showed that the yogurt did not show typical absorption peaks of CMC-Na,Si O₂and CW,indicating that the ingredients of the special wetting surface were not released into the yogurt,which proved that the special wetting surface is suitable for the packaging of yogurt.Through the analysis of contact Angle and residual amount of 15kinds of common yoghurt on special wettability surface,it was found that special wettability surface also had wide applicability,and had good adhesion inhibition effect on yoghurt with viscosity distribution ranging from 95.19 Pa·s to 801.85 Pa·s,and the residual rate ranged from 3.77%to 9.91%.