Interactions of Linearly Polarized and Unpolarized Light on Kiwifruit Using Aquaphotomics.

Damenraj Rajkumar,Andrew Mcglone,Harpreet Kaur,Rainer Künnemeyer,Jevon Longdell

doi:10.3390/molecules27020494

Abstract

Near infrared (NIR) spectroscopy is an important tool for predicting the internal qualities of fruits. Using aquaphotomics, spectral changes between linearly polarized and unpolarized light were assessed on 200 commercially grown yellow-fleshed kiwifruit (Actinidia chinensis var. chinensis ‘Zesy002’). Measurements were performed on different configurations of unpeeled (intact) and peeled (cut) kiwifruit using a commercial handheld NIR instrument. Absorbance after applying standard normal variate (SNV) and second derivative Savitzky–Golay filters produced different spectral features for all configurations. An aquagram depicting all configurations suggests that linearly polarized light activated more free water states and unpolarized light activated more bound water states. At depth (≥1 mm), after several scattering events, all radiation is expected to be fully depolarized and interactions for incident polarized or unpolarized light will be similar, so any observed differences are attributable to the surface layers of the fruit. Aquagrams generated in terms of the fruit soluble solids content (SSC) were similar for all configurations, suggesting the SSC in fruit is not a contributing factor here.

Highlights

Preference for high-quality fruit has propelled the development of non-destructive techniques for postharvest fruit grading
The final decision before purchasing fruit depends upon consumers, the development of instruments used to mimic human judgement is important [1]
Unpolarized light is used in near-infrared spectroscopy (NIRS)

Summary

Introduction

Preference for high-quality fruit has propelled the development of non-destructive techniques for postharvest fruit grading. The final decision before purchasing fruit depends upon consumers, the development of instruments used to mimic human judgement is important [1]. One such technique uses near-infrared spectroscopy (NIRS), which has seen success in predicting fruit internal qualities such as soluble solids content (SSC) and dry matter content (DMC) by utilizing multivariate and statistical analyses such as principal components analysis (PCA) and partial least squares regression (PLSR) to create prediction models [2]. Polarized light may offer advantages as suggested by some recent studies on pears and apples [6,7]

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