苹果可溶性固形物和糖酸比可见/近红外漫反射与漫透射在线检测对比研究

可溶性固形物和糖酸比是苹果内部品质主要评价指标之一。为此进行苹果糖酸比和可溶性固形物可见/近红外漫反射和漫透射对比检测研究。180个冰糖心和红富士样品被分成建模集和预测集(136∶44)，分别用于建立偏最小二乘模型和验证模型的预测能力。在运动速度5个/秒时，采集了冰糖心和红富士两种样品的可见近红外光谱。漫反射和漫透射可见近红外光谱经多元散射校正、标准正态变量变换、基线校正等预处理后，建立了偏最小二乘回归模型。未参与建模的44个样品用于评价模型的预测能力，经比较，漫透射检测方式优于漫反射检测方式，主要因为漫透射检测方式能更有效地克服杂散光。可溶性固形物模型预测相关系数达到0.936，预测均方根误差为0.476°Brix；糖酸比模型预测相关系数达到0.785，预测均方根误差为10.94。研究结果表明： 应用可见/近红外漫透射光谱技术，可实现苹果可溶性固形物和糖酸比在线检测。为大宗水果内部品质分选提供了技术支持和参考依据。

Comparison of Reflection and Diffuse Transmission for Detecting Solid Soluble Contents and Ratio of Sugar and Acid in Apples by On-Line Vis/NIR Spectroscopy

The soluble solid contents(SSC)and ratio of sugar and acid are main indices for evaluating the quality of apples.Comparison between diffuse mode and transmittance mode was explored for determination of SSC and ratio of sugar and acid using online detection equipment.180 samples of watercore and Fuji apples were divided into the calibration and prediction sets(136:44)for developing calibration models and assessing the performance of the models.The visible and near infrared(NIR)spectra of watercore and Fuji apples were collected at the speed of 5 samples per second.The partial least square regression models were developed with the spectra preprocessed with multiplicative scatter correction(MSC),standard normal variate transformation(SNV),and baseline correction(BC).44 new samples were used to evaluate the predictive abilities of the models.By comparison,the transmittance mode was superior to diffuse model.Because the transmittance mode could restrain stray light more effectively.The prediction correlation coefficients(Rp)of the model of soluble solid contents(SSC)was 0.936 and prediction(RMSEP)of the root mean square errors was 0.476°Brix;The prediction correlation coefficients(Rp)of the model of ratio of sugar and acid was 0.785 and prediction(RMSEP)of the root mean square errors was 10.94;The results showed that online detection of soluble solid contents and ratio of sugar and acid of apples based on Vis/NIR diffuse transmit-tance spectroscopy was feasible.The research can provide technical support and reference basis for grading of mass fruits quality.