草莓的光学特性及其与可溶性固形物含量和含水率的关系

Optical Properties of Strawberry Fruit and Their Relationship with Soluble Solids Content and Moisture Content

为了解水果的光学特性及其与可溶性固形物含量和含水率的关系,本实验采用单积分球技术搭建光学特性测量系统,并对系统进行了验证;进而以‘红颜’、‘甜香’和‘章姬’草莓为对象,测定950~1650 nm波长范围内草莓的光吸收系数μa和约化散射系数μ’s,分析光学参数与草莓可溶性固形物含量和含水率间的关系;建立基于光学参数谱预测草莓可溶性固形物含量和含水率的偏最小二乘模型。结果表明,该系统测量μa和μ’s的平均相对误差分别为8.23%和3.71%;整个波长范围内,μa在975、1197 nm和1411 nm波长处存在峰值,而μ’s基本随波长的增大而减小;草莓的μa与可溶性固形物含量呈负相关,而与含水率呈正相关,且吸收峰处出现相关系数极值;基于μa谱所构建模型具有最好的预测可溶性固形物含量(rp=0.815、预测集均方根误差(root mean squares error of prediction,RMSEP)=1.153%)和含水率(rp=0.757、RMSEP=1.280%)的能力,说明可溶性固形物含量和含水率主要影响草莓的吸收特性,基于吸收特性可以更好地预测草莓的内部品质。

To understand the optical properties of fruits and their relationships with soluble solids content(SSC)and moisture content,a single integrating sphere system for the measurement of optical properties was established and validated.Furthermore,the absorption coefficientμa and reduced scattering coefficientμs’of the fruit of the strawberry cultivars‘Hongyan’,‘Tianxiang’and‘Zhangji’,were measured over the wavelength range of 950–1650 nm.The relationships of optical properties with SSC and moisture content were analyzed,and partial least squares models to predict SSC and moisture content based on optical properties were established.The results showed that the average relative errors of the system forμa andμs’were 8.23%and 3.71%,respectively.Over the investigated wavelength range,μa had peaks at 975,1197 nm and 1411 nm,andμs’generally decreased with increasing wavelength.μa had negative correlation with SSC but positive correlation with moisture content.Moreover,extreme correlation coefficients were observed at the absorption peaks.The models established based on the spectra ofμa had the best capability in predicting SSC(rp=0.815,root mean squares error of prediction(RMSEP)=1.153%)and moisture content(rp=0.757,RMSEP=1.280%),indicating that SSC and moisture content mainly affected the optical absorption property of strawberry fruit,which allowed good prediction of the internal quality of strawberry fruit.