Determination of soluble solids content in Prunus avium by Vis/NIR equipment using linear and non-linear regression methods

Victoria Lafuente,Razvan Ghinea,Jesús Val,Angel I Negueruela,Luis J Herrera

doi:10.5424/sjar/2019174-13891

Abstract

Aim of study: Developing models to determine soluble solids content (SSC) in cherry trees by means of Vis/NIR spectroscopy.Area of study: The Spanish Autonomous Community of Aragón (Spain).Material and methods: Vis/NIR spectroscopy was applied to Prunus avium fruit ‘Chelan’ (n=360) to predict total SSC using a range 400-2420 nm. Linear (PLS) and nonlinear (LSSVM) regression methods were applied to establish prediction models.Main results: The two regression methods applied obtained similar results (Rcv2=0.97 and Rcv2=0.98 respectively). The range 700-1060 nm attained better results to predict SSC in different seasons. Forty variables selected according to the variable selection method achieved Rcv2 value, 0.97 similar than full range.Research highlights: The development of this methodology is of great interest to the fruit sector in the area, facilitating the harvest for future seasons. Further work is needed on the development of the NIRS methodology and on new calibration equations for other varieties of cherry and other species.

Highlights

The cherry tree (Prunus avium L.) is one of the leading species of stone fruit worlwide (Bujdosó and Hrotkó (2017)) and, in Spanish Autonomous Community of Aragón (Spain) alone, production reaches114,433 tons (FAOSTAT 2017; http://www.fao.org/home/en/)
Further work is needed on the development of the nearinfrared spectroscopy (NIRS) methodology and on new calibration equations for other varieties of cherry and other species
One example is the nearinfrared spectroscopy (NIRS), which offers a number of advantages over previous techniques: it avoids the destruction of the fruit, provides faster in situ measurement, reduces cost, and determines several quality parameters in a single measurement

Summary

Introduction

The cherry tree (Prunus avium L.) is one of the leading species of stone fruit worlwide (Bujdosó and Hrotkó (2017)) and, in Spain alone, production reaches114,433 tons (FAOSTAT 2017; http://www.fao.org/home/en/). One example is the nearinfrared spectroscopy (NIRS), which offers a number of advantages over previous techniques: it avoids the destruction of the fruit, provides faster in situ measurement, reduces cost, and determines several quality parameters in a single measurement. This technique consists on analysing the behaviour of a light beam incident on the surface of a test sample: part of the incident light undergoes specular reflection and is responsible for the gloss; another part is absorbed selectively by the pigments; while the rest of the incident light is diffusely reflected by the sample, producing the Visible/Near Infrared Reflectance (Vis/NIR) spectra. Near-infrared spectroscopy was widely used to analyse a large variety of fruits and vegetables, such as: apples (Torres et al., 2016), pears (Li et al, 2013), tomatoes (Tiwari et al., 2013), avocados (Clark et al, 2003), oranges (Ncama et al, 2017), and cherries (Escribano et al, 2017)

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