本试验旨在研究3种不同生产工艺(钙盐沉淀法、钙盐+钠盐沉淀法和水蒸气法)生产的饲料级磷酸二氢钙(MCP)的质量特性,为MCP国家强制性标准的制定和合理使用提供试验依据。采集全国有代表性地区10个生产厂家的MCP样品,比较3个不同生产工艺间及使用钙盐沉淀法、钙盐+钠盐沉淀法的9个厂家生产的样品间的游离水、结晶水、钙、总磷、水溶性磷含量及钙磷质量比、细度、结晶水个数和pH。结果表明:1)3种生产工艺间比较,水蒸气法的pH显著高于钙盐沉淀法和钙盐+钠盐沉淀法(P<0.05),钙盐沉淀法的pH显著高于钙盐+钠盐沉淀法(P<0.05)。3种工艺的游离水、结晶水、钙、总磷、水溶性磷含量、钙磷质量比和结晶水个数差异均不显著(P>0.05)。水蒸气法的过0.50和0.40 mm试验筛的细度显著低于钙盐+钠盐沉淀法(P<0.05)。2)不同生产厂家间比较,所有样品的游离水含量差异显著(P<0.05),样品4的结晶水含量和结晶水个数显著低于其他各样品(P<0.05),样品5和样品8、9的pH之间差异不显著(P>0.05),但显著低于其他各样品(P<0.05);样品4的各层细度均显著低于其他各样品(P<0.05);样品1、6的钙含量显著高于其他各样品(P<0.05),样品9的总磷含量显著高于样品1、2、4、5、6和7(P<0.05),样品5的水溶性磷含量显著高于其他各样品(P<0.05),样品1的水溶性磷含量显著低于其他各样品(P<0.05),样品1的钙磷质量比显著高于其他各样品(P<0.05),样品9的钙磷质量比显著低于其他各样品(P<0.05)。由此可见,3种生产工艺中,水蒸气法的水溶性磷、游离水、结晶水含量及结晶水个数、pH最高;钙盐沉淀法的水溶性磷、结晶水含量及结晶水个数最低,钙含量和钙磷质量比最高;钙盐+钠盐沉淀法的总磷和各层细度最高。饲料级MCP质量指标因生产厂家及生产工艺的不同而存在极大差异,除国家标准已规定的质量指标外,也应该考虑其中的结晶水含量、结晶水个数、钙磷质量比,同时建议降低对细度的要求。

This study was investigated to research the quality characteristics of feed-grade monocalcium phosphate (MCP) produced by three different production processes (calcium precipitation method, calcium+sodium precipitation method and steam method), and provided an experimental basis for the formulation of the national mandatory standard and the rational use of MCP. The MCP samples were collected from ten manufacturers from the representative areas of China, and the contents of free water, crystal water, calcium, total phosphorus and water-soluble phosphorus, the mass ratio of calcium to phosphorus, fineness, the number of crystal water and pH were detected for comparing differences among the three different production processes and among the samples from the nine manufacturers which used the calcium precipitation method and calcium+sodium precipitation method. The results showed as follows: 1) the comparison of different production processes, the pH of steam method was significantly higher than that of calcium precipitation method and calcium+sodium precipitation method (P<0.05), and the pH of calcium precipitation method was significantly higher than that of calcium+sodium precipitation method (P<0.05). The contents of free water, crystal water, calcium, total phosphorus and water-soluble phosphorus, the mass ratio of calcium to phosphorus and the number of crystal water of the three production processes were not significantly different (P>0.05). The contents of 0.50 and 0.40 mm fineness of steam method were significantly higher than those of calcium+sodium precipitation method (P<0.05). 2) The comparison of different manufacturers, the contents of free water of all samples were significantly different (P<0.05), the content of crystal water and the number of crystal water of sample 4 were significantly lower than those of other samples (P<0.05), and there was no significant difference in pH between sample 5 and samples 8 and 9 (P>0.05), but sample 5 was significantly lower than other samples (P<0.05); all of the fineness of sample 4 were significantly lower than those of other samples (P<0.05); the content of calcium of samples 1 and 6 was significantly higher than that of other samples (P<0.05), and the content of total phosphorus of sample 9 was significantly higher than that of samples 1, 2, 4, 5, 6 and 7 (P<0.05); the content of water-soluble phosphorus of sample 5 was significantly higher than that of other samples (P<0.05), and the content of water-soluble phosphorus of sample 1 was significantly lower than that of other samples (P<0.05); the mass ratio of calcium to phosphorus of sample 1 was significantly higher than that of other samples (P<0.05), and that of sample 9 was significantly lower than that of other samples (P<0.05). It is concluded that in the three production processes, the contents of water-soluble phosphorus, free water and crystal water, the number of crystal water and pH of steam method are the highest; the contents of water-soluble phosphorus and crystal water and the number of crystal water of calcium precipitation method are the lowest, but the mass ratio of calcium to phosphorus is the highest; the contents of total phosphorus and all fineness of calcium+sodium precipitation method are the highest. Because of the different manufacturers and production processes, there are some differences in the quality indicators of MCP. In addition to the quality indicators prescribed by national standards, we should also consider crystal water content, the number of crystal water and mass ratio of calcium to phosphorus, and also propose to reduce the requirements of fineness.