基于电学特性的生鲜牛乳蛋白质含量检测仪研究

Design of Protein Content Detector for Raw Milk Based on Electrical Properties

为了提供一种操作简单、成本低廉且便于现场检测的生鲜牛乳蛋白质含量检测仪器,基于农业物料的电学特性设计了扫频范围为1~100 MHz的牛乳蛋白质含量检测仪。该检测仪的硬件系统由STM32单片机、扫频信号源模块、检测模块、信号处理模块和输入输出模块组成。基于MDK 5.0环境,利用C语言开发了检测仪的软件,主要实现系统初始化、频率扫描、数据采集、串口发送、按键处理和结果显示等功能。以生鲜牛乳为研究对象,分析了蛋白质含量与1~100 MHz范围内199个采样点的输入、输出信号的幅值,以及输入与输出信号相位差之间的关系,基于采集的信号建立了牛乳蛋白质含量的偏最小二乘模型,该模型决定系数为0.835。对仪器检测精度进行了测试,本检测仪蛋白质含量绝对测量误差范围为-0.11~0.12 g/(100 g),平均绝对测量误差为0.01 g/(100 g),检测时间小于2 min,可以快速、有效地检测生鲜牛乳中的蛋白质含量。

Protein content is one of the most important quality indicators of milk. The traditional methods used to measure the protein content of milk have the advantage of high precision,but the measurement procedures are tedious and time-consuming,and the measurement equipment are expensive. In addition,these methods cannot be used in filed or in-suit. Therefore,developing a kind of portable milk protein content detector which is simple in operation and low in cost,and could be used in-suit measurement,will be appreciated by milk producers,processers and consumers. Since the values of electric parameters of milk are affected by protein content,a portable protein content detector over the frequency range of 1 ~100 MHz was developed. The hardware of the detector consisted of a STM32 single chip microcomputer,a frequency sweep signal source module,a detection module,a signal processing module,and an input and output modules. The software,developed under the development environment of MDK 5. 0 by using C language, realized the functions of initialization, frequency sweep, data sampling, serial port transmission,key processing and result display. Fresh raw milk were used as samples to analyze the relationship between the protein content and the obtained data,i. e.,the amplitudes of input and output signals,and the phase difference between the input and output signals. The partial least squares model was established to predict the protein content based on obtained data. The results showed that the model had a determination coefficient of 0. 835,the absolute measurement error of-0. 11 ~ 0. 12 g/( 100 g),and the average absolute error of 0. 01 g/( 100 g). Moreover,the measurement could be realized in2 min. The developed detector made the detection of protein content of fresh raw milk realized quickly and effectively.