Application of Multispectral Imaging to Determine Quality Attributes and Ripeness Stage in Strawberry Fruit

Wei Chen,Changhong Liu,Xuzhong Lu,Fei Ma,Lei Zheng,Jianbo Yang,Wei Liu,Sara Amancio

doi:10.1371/journal.pone.0087818

Abstract

Multispectral imaging with 19 wavelengths in the range of 405–970 nm has been evaluated for nondestructive determination of firmness, total soluble solids (TSS) content and ripeness stage in strawberry fruit. Several analysis approaches, including partial least squares (PLS), support vector machine (SVM) and back propagation neural network (BPNN), were applied to develop theoretical models for predicting the firmness and TSS of intact strawberry fruit. Compared with PLS and SVM, BPNN considerably improved the performance of multispectral imaging for predicting firmness and total soluble solids content with the correlation coefficient (r) of 0.94 and 0.83, SEP of 0.375 and 0.573, and bias of 0.035 and 0.056, respectively. Subsequently, the ability of multispectral imaging technology to classify fruit based on ripeness stage was tested using SVM and principal component analysis-back propagation neural network (PCA-BPNN) models. The higher classification accuracy of 100% was achieved using SVM model. Moreover, the results of all these models demonstrated that the VIS parts of the spectra were the main contributor to the determination of firmness, TSS content estimation and classification of ripeness stage in strawberry fruit. These results suggest that multispectral imaging, together with suitable analysis model, is a promising technology for rapid estimation of quality attributes and classification of ripeness stage in strawberry fruit.

Highlights

Strawberry fruit (Fragaria6ananassa Duch.) is an economically important fruit which is more popularly consumed fresh, as well as used for garnishing cakes and pastries, flavored for juices and milk products, and processed into jams and other products
In despite of ripeness stage, the reflectance curves of strawberry fruit were rather smooth across the entire spectral region
Anthocyanins and chlorophyll which represent the color characteristics in the strawberry fruit have previously been identified at around 520 and 680 nm wavelength, respectively [33,34]

Summary

Introduction

Strawberry fruit (Fragaria6ananassa Duch.) is an economically important fruit which is more popularly consumed fresh, as well as used for garnishing cakes and pastries, flavored for juices and milk products, and processed into jams and other products. Together with the recent attention for food quality and safety, technologies for estimating the fresh quality of strawberry fruit are being sought [1]. Internal quality attributes such as firmness, sweetness, acidity and flavor are very important in the quality evaluation industries. Since the strawberry is a non-climacteric fruit, in order to achieve good quality, it is essential to harvest at the optimum stage of ripening [2]. Standard methods for these quality measurements are mostly destructive, slow, and prone to operational error. In order to overcome these disadvantages, nondestructive methods, especially those based on optical properties, are urgently required

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Conclusion