Soy Protein Spray Coating Dispersions Rheological Parameters On The Impact Of Sprayability

Under the support of the key project of Tianjin natural science fund(15JCZDJC34100) “Study of the rheological behavior of soy protein spray coating dispersions(SPSCD) and its regularity of spray atomization”, the rheological properties of different formulation SPSCD and their sprayability were studied, and the impact of the spraying parameters on spray conditions were also investigated in this thesis.The main content and work are as follows:1) The influence of different soy protein spray coating dispersion(SPSCD)concentration and spraying conditions on the atomization angle and atomization overall morphology was studied to evaluate atomization performance. The high-speed camera was used to collect images of spraying and then the spray angle was calculated through the image processing function of MATLAB software.The effect of the concentration and process parameters on spray angle was also analyzed according to the “response surface methodology”. When the hydraulic pressure was big and the air pressure was small, poor atomization was resulted. With the increase of air pressure, the better atomization performance was reached. In the aspect of single factor, concentration and air pressure have a significant effect on the spray angle. The relative model among spray angle, process parameters and concentration had been established by analysis software. The optimal spraying condition: the spray angle of SPSCD was up to 81.4690°, when the concentration of SPSCD was 11.13%,the air pressure was 0.2 MPa, and the hydraulic pressure was0.164 MPa.2) The influence of SPSCD components on the rheological behaviour was investigated.SPSCD shear viscosity was falling with the increase of the shear rate. It showed the non-newtonian characteristics, namely the phenomenon of shear thinning.The results of parameter estimation for Herschel-Bulkley’s model of steady-state rheological properties showed that consistency coefficient increased with the increase of the samples’ concentration and the viscosity was greater. All of the groups of SPSCD presented non-newtonian fluid properties because of the flow index was less than 1. Analysis of variance(ANOVA) showed that soy protein concentration and sodium carboxymethyl cellulose had significant influence on storage modulus. Soy protein concentration, soy protein concentration x glycerin, soy protein concentration2 and poly-carboxylic salt2 had a significant effect on the loss tangent. The regression models of consistency coefficient, flow index, storage modulus and loss tangent with relation to SPSCD components were established respectively. It will be a reference for the performance of the SPSCD which was prepared with different ratio of additives.3) In the process of temperature which increased from 20 ℃ to 80 ℃, 4 kinds of concentration of SPSCD, among which soy protein is 20 g, 30 g, 40 g and 50 g respectively,had a change that the apparent viscosity increased with the increase of the samples’ concentration under the same test temperature. When the temperature gradually rose to80 ℃, soy protein degenerated in the process so that made SPSCD’s viscosities of various concentration droped and reached the minimum. Whin Four kinds of concentration of SPSCD, storage modulus G’ was less than loss modulus G", which indicated that viscosity properties were stronger than elastic properties during this period of temperature change of soy protein spraying liquid.4) SPSCD was a kind of composite macromolecule polymer which included soy protein isolate and additive, whose internal structure is not easy to remain stable. There was no regularity of the influence of storage time on apparent viscosity of the SPSCD.But the longer we saved, the medium of spraying liquid was not easy to maintain its state of suspension. The precipitation phenomenon would appeared, which will influence the spraying effect. In terms of coating process, SPSCD should be sprayed within the reasonable time according to the different performance to so as not to affect the effect of the stability of the SPSCD when it flows through the nozzle. The performance of the SPSCD of20 g soy protein isolate was more unstable than those of 30 g soy protein isolate and40 g soy protein isolate in the same storage temperature.