Quantitative visualization of pectin distribution maps of peach fruits

Nan Zhu,Kunsong Chen,Di Wu,Weinan Huang,Yong He

doi:10.1038/s41598-017-09817-7

Abstract

Pectin content is an important quality index of fruits, as pectin content undergoes significant changes during the peach ripening process. The commonly used carbazole colorimetry method measures only the total content value of each kind of pectin for each pulp sample and cannot provide distribution maps of the pectin contents for the whole fruit pulp. This work used the hyperspectral imaging technique to quantitatively visualize the distribution maps of pectin contents inside peach pulp at the pixel level. The protopectin contents were well predicted, with the best residual predictive deviation of 2.264, whereas the predictions of the water-soluble pectin and the total pectin contents were not satisfied. On the basis of the best predictive model, the distribution maps of the protopectin contents were quantitatively visualized. A histogram of an example protopectin distribution revealed the existence of a wide range of protopectin contents in peach pulp. Our results show that hyperspectral imaging holds promise as a powerful alternative to the carbazole colorimetry method for measuring the spatial variations in the protopectin distribution inside peach pulp. The distribution maps could be used as a maturity indicator to understand and evaluate the ripening process of peach fruit in depth.

Highlights

Pectin content is an important quality index of fruits, as pectin content undergoes significant changes during the peach ripening process
The quantitative spectral models were established through multivariate data analysis between the measured visible and near-infrared spectra extracted from the hyperspectral images of the cross-sections for peach pulp and their reference to pectin contents
The results show that the results from the carbazole colorimetry method are not representative for heterogeneous materials, such as peach pulp, because the carbazole colorimetry method can only obtain a total pectin content of a pulp cube

Summary

Introduction

Pectin content is an important quality index of fruits, as pectin content undergoes significant changes during the peach ripening process. The commonly used carbazole colorimetry method measures only the total content value of each kind of pectin for each pulp sample and cannot provide distribution maps of the pectin contents for the whole fruit pulp. Our results show that hyperspectral imaging holds promise as a powerful alternative to the carbazole colorimetry method for measuring the spatial variations in the protopectin distribution inside peach pulp. The distribution maps of pectin contents for peach pulp could provide a detailed understanding the ripening process of a fruit, leading to further optimization of preharvest planting patterns and postharvest storage strategies. The colorimetry method only provides a total content value of each kind of pectin for each pulp sample and cannot provide detailed distribution maps of pectin contents of the fruits. New analytical tools are required to gain knowledge about the pectin spatial distribution for peach fruits to improve our basic knowledge of quality variation during peach fruit development and maturation as well as facilitate the advancement of peach preharvest planting patterns and postharvest storage strategies

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Conclusion