基于均匀板加热法的饲料糊化参数试验研究

Experiment on Feed Gelatinization Parameters Based on Homogeneous Plate Heating Method

提出一种应用铸铝板对饲料样品夹持加热的装置及方法。通过将预调好含水率的饲料密封于自封袋中,夹持于一组平行可控温的铸铝板内,实现对样品的加热。基于一维热传导方程、借助Matlab有限差分法,求解得到样品从室温加热到设定温度的温度曲线,以此评估饲料样品在受热过程中的温度分布情况。结果显示,样品达到温度均匀分布所需的时间尺度远小于样品糊化的时间尺度,可实现对样品热处理时间的准确控制。在此基础上,以育肥猪配合饲料粉料为研究对象,以饲料的糊化温度、糊化时间和饲料含水率为试验因素,以饲料热处理后的糊化度为评价指标,按照三因素五水平二次回归正交旋转组合试验方法,利用Design-Expert软件回归分析和响应面分析法,建立了饲料糊化度与3个因素的二次回归模型(R^2=0. 942 0),并验证了回归模型的有效性。在对饲料样品热处理后的色差分析中发现,在某些条件下,过高的热处理温度并不能提高饲料的糊化度,反而会加剧美拉德反应,导致饲料颜色加深,影响外观质量。

In the study of gelatinization characteristics and kinetics of starchy raw materials, hydrothermal treatment with controllable parameters was needed, but the effect of heating methods on homogenization of temperature distribution of samples was usually neglected. A device and method for clamping and heating feed samples with cast aluminium plates were presented. The moisture-adjusted feed samples were sealed in zip lock bags and clamped in a set of parallel temperature-controlled cast aluminium plates for heating treatment. Based on one-dimensional heat conduction equation, the temperature curves from room temperature to setting temperature were obtained by using the finite difference method of Matlab, and the temperature homogenization of feed samples during heating process was evaluated. The results showed that the device could achieve full homogenization of samples temperature distribution in a short time, and the time scale for achieving homogeneous temperature distribution of samples was much smaller than the gelatinization time scale, which indicated that the time for heat treatment of samples could be controlled accurately. On this basis, taking the formula feed for finishing pigs as research material, the pasting temperature, pasting time and feed moisture were selected as the influencing factors, and the degree of gelatinization was selected as evaluating indicators, thus the quadratic regression orthogonal rotatory combination experiments were carried out. As a consequence, the order of influence of each factor on feed gelatinization degree was feed moisture, pasting temperature and pasting time. A quadratic regression model ( R 2 =0.942 0) for feed gelatinization degree and three factors was established by regression analysis and response surface analysis with Design-Expert software, and the validity of the regression model was verified. In the analysis of chromatic aberration of feed samples after heat treatment, it was found that excessive heat treatment temperature would not increase the gelatinization degree of feed under certain conditions;on the contrary, it would intensify Maillard reaction leading to the deepening of feed color and affecting the appearance quality.