Research On The Drying Process Of Microelement Molasses Complex As Feed Additives

Microelement is essential nutrient for animals, which is directly or indirectly involved in nearly all the physiological and biochemical processes. Microelement molasses complexes have such virtues as low-cost, nutritious quality and high bioactivity. They have been widely applied in feed additives. However, during drying process of the complexes, it is easily coking and difficult to control because of their stickiness. Currently, hot air drying is used to dry the complexes as a traditional method. Hot-air drying is simple to operate and cost-effective, but it consumes too much time and energy, also can decrease product quality. In this study, microwave drying is firstly applied in drying microelement molasses complexes in order to solve the problems mentioned. Microwave drying theory and quality changes of dried product were explored and better parameters was obtained. Furthermore, comparisons and combinations between hot air drying and microwave drying were conducted.Experimental studies show that:(1) The hot air drying process of microelement molasses complexes was divided into two stages, one was the speed-up stage and the other was the speed-down stage.(2) Microwave drying can obviously increase the drying rate. The drying time of microwave drying was only about6.7%of the Hot-air drying,when the microwave power was400W and The temperature was105℃.(3) The microwave drying process of microelement molasses complexes with low power can be divided into three stages, as the speed-up stage, constant-speed stage and speed-down stage. While the constant-speed stage doesn’t exist when drying microelement molasses complexes with high power. And the drying rate of the complex increases with greater microwave power and a longer drying time, but it decreases with a longer tempering time.(4) The drying process of microelement molasses complexes can be described with Midilli and Kucuk drying models. The model equation is MR=aexp(-ktn)+bt。(5) The effect of hot air drying on the quality of microelement molasses complexes are as followed:caramel content increased appreciably with the increase of hot air temperature. And the caramel content was the biggest when the temperature reached105℃. And after that the caramel content decreased remarkably with the increase of drying temperature. The color value had the same tendency with caramel content. The moisture absorption in different temperature remained9.9～10.5%. With the increase of the initial thickness, caramel content, color value and the moisture absorption decreased.(6) The effect of microwave drying on the quality of microelement molasses complexes was as followed:with the increase of microwave power, caramel content and color value show a trend of firstly increasing and then decreasing. Moisture absorption increase gradually with higher microwave power and its value in high power is bigger than others.with lower microwave power, greater initial thickness, shorter heating time and longer tempering time, the quality of drying products would be better.(7) The study of comparisons among hot air drying, microwave drying and microwave-hot air drying showed that:microwave-hot air drying reduced the phenomenon of uneven heating. And the drying efficiency was significantly improved compared with hot air drying.caramel content and color value of Combined drying product was reduced by19.6%and19.6%respectively than hot air drying product, and the drying time was only about17.8%of the hot air drying time.(8) Microwave-hot air drying was applied to microelement molasses complexes drying process. Considering the average drying rate, caramel content and color value, the optimal technology was obtained by employing quadratic regression orthogonal design of. It indicated that effects of three factors on the index were different, but the impact of transform moisture was the most significant. Meanwhile, regressive equation of each index was significant which was proved by statistical test. The best process conditions were obtained as followed:the early hot air temperature was95℃, dry basis moisture content was7%, microwave power quality was19W·g-1.