Quality evaluation of the physicochemical properties of feed grade phosphates based on principal component analysis

The purpose of this study was to analyze the differences in the physical properties of different feed grade phosphates using principal component analysis (PCA) to streamline the physical properties. The correlation between the different physical properties of different feed grade phosphates was compared; the main components that could represent the physical properties were extracted; the comprehensive score of feed grade phosphates was preliminarily determined; and the evaluation system of feed grade phosphates was established. In this experiment five commonly used dicalcium phosphates (DCP), four calcium phosphates monobasics (MCP) and three monodicalcium phosphates (MDCP) were selected as test materials. Physical characteristics such as moisture, specific surface area, sliding friction angle, angle of repose, apparent density, tapping density, compressibility, water absorption index (WAI), water solubility index (WSI) and swelling power (SP) were measured and analyzed. The PCA method was used to obtain the correlation coefficient matrix, the variance contribution analysis table, the load matrix and the eigenvector of each principal component. The comprehensive score of each sample was calculated. The results showed that: 1) There were certain differences in the physical properties of different feed grade phosphates, namely, the WAI of feed grade phosphates were between 0.28-1.35; the SP were between 0.62-2.40; the WAI and SP of DCP were higher; the WAI and SP of No. 11 (granularity of MCP) and No. 11 (granularity of MDCP) were higher than those of powder; the WSI of DCP were much lower than those of MCP and MDCP; and the angle of repose of DCP were higher, both of which were greater than 40°. The specific surface area of DCP was higher, and the granularities of MCP and MDCP were lower than those of other groups. 2) There is a certain correlation between the physical properties of phosphates in different feed grades. The specific surface area of feed grade phosphate was significantly and positively correlated with the angle of repose (r=0.919, P<0.01). The apparent density was negatively correlated with the specific surface area, sliding friction angle and angle of repose (r=-0.816, -0.809, -0.898, P<0.05). The degree of compressibility was significantly and positively correlated with the angle of repose (r=0.926, P<0.01), the specific surface area (r=0.874, P<0.05), and the apparent density (r=-0.812, P<0.05). The WSI was negatively correlated with the specific surface area and angle of repose and WAI (r=-0.812, -0.810, -0.864, P<0.05). There was a significant positive correlation between SP and WAI (r=0.930, P<0.01), a very significant negative correlation with WSI (r=-0.987, P<0.01), and a significant positive correlation with specific surface area (r=0.801, P<0.05). 3) Through PCA, three active principal components were extracted, and the contribution rates of the first, second and third principal components were 60.07%, 18.10% and 10.10% respectively. The cumulative contribution rate of the three principal components was 88.27%. The scores of the physical characteristics of feed grade phosphates were DCP, MDCP and MCP, and the score of granular phosphate was lower. Based on the comprehensive analysis, considering the physical characteristics of feed grade phosphates, DCP could be preferred for the production of higher quality feed pellets.