近红外光谱技术无损检测火龙果有效酸度

Non-destructive Measurement of the Active Acidity of Pitaya by Near-infrared Spectroscopy

火龙果是一种有益于人类健康的水果。本文利用Field Spec 3便携式地物波谱仪采集350~2500 nm波段的光谱数据,通过多种预处理方法、连续投影算法（SPA）优选波长、偏最小二乘回归（PLSR）等分析方法,建立了火龙果有效酸度预测模型。实验结果表明：原始光谱经过Savitzky-Golay卷积平滑法（SGS）,建立的PLS模型最优,其RCV为0.8862,RMSECV为0.1535;联合SPA算法,利用优选出的25个变量建立的PLS模型,其预测相关系数（RP）为0.8702,预测均方根误差（RMSEP）为0.1682,其模型的预测精度高于原始光谱2151个变量建立模型。比较分析了果皮对模型精度的影响,对光谱数据进行最佳Normalize预处理后,完整果PLS模型的RP为0.8151,果肉PLS模型RP为0.8583,说明果皮存在对模型有影响,但可以进行光谱优化减小影响。本研究结果表明基于近红外光谱技术联合连续投影算法的漫反射无损检测火龙果有效酸度含量具有可行性。

Pitaya is a fruit that exhibits health benefits.The Field Spec 3 spectroradiometer was used to collect spectral data of pitaya in the wavelength range of 350~2500 nm.Multiple pretreatments,successive projections algorithm（SPA）,and partial least squares regression（PLSR） were adopted to establish the active acidity prediction model for pitaya.The experimental results showed that the optimal partial least squares（PLS） model was established after the original spectrum was processed by using the Savitzky-Golay convolution smoothing method（SGS）.The correlation coefficients of cross-validation（RCV） and root mean square error of cross-validation（RMSECV） were found to be 0.8862 and 0.1535,respectively.In combination with SPA algorithm,the preferentially selected 25 variables were used to establish the PLS model with a correlation coefficient of prediction（RP） of 0.8702 and a root mean square error of prediction（RMSEP） of 0.1682.The predictive accuracy of the model was higher than that of the model constructed by using 2151 variables from the original spectrum.The effect of the fruit peel on the model accuracy was analyzed.After the optimal normalization pretreatment of spectral data,the RP of the whole fruit PLS model was 0.8151 and that of the RP of the fruit flesh PLS model was 0.8583,which showed that the fruit peel affected the model,but the effect could be reduced by spectral optimization.The results obtained indicate that it is feasible to use diffuse reflectance based on near infrared spectroscopy combined with SPA for the non-destructive measurement of the active acidity of pitaya.