Use of NIR spectroscopy on fresh apples to determine the phenolic compounds and dry matter content in peel and flesh

Vincent Baeten,Marc Lateur,Pascal Dupont,Pierre Dardenne,Audrey Pissard

doi:10.25518/1780-4507.16241

Abstract

Description of the subject. The article deals with the use of near-infrared spectroscopy (NIR) on fresh apples to determine the phenolic compounds and dry matter content in peel and flesh powders. Objectives. The aim is the rapid and non-destructive determination of these nutritional parameters. Method. Two hundred twenty-nine fruits from 20 varieties were analyzed with NIR spectroscopy and reference methods. Results. Great variability of total phenolic compounds (TPC) in peel and flesh powders was observed among varieties. The dry matter (DM) content also differed greatly between peel and flesh. Calibration and validation models showed high coefficients of determination for the TPC content, which were slightly higher for the peel than for the flesh (R² val = 0.91 and 0.84 respectively). For the DM content, high coefficients of determination and ratios of prediction to deviation (RPDs) were also observed (R² val = 0.94, RPD = 4.8 and R² val = 0.94, RPD = 4.9 for the peel and flesh respectively). Conclusions. Calibration and validation models allow quantitative predictions to be made for TPC and DM content. They confirm the potential of NIRS for predicting the polyphenol content and highlight its potential for determining the DM content, a parameter often neglected in research into apple quality.

Highlights

There has been an increasing appreciation and understanding of the link between dietary fruit and health benefits for humans (Hyson, 2011)
Total phenolic compounds show great variability among the varieties maintained in the collections of the CRA-W (Table 1)
The average ratio was 3.8, which means that total phenolic compounds are on average almost four times higher in peel than in flesh

Summary

Introduction

There has been an increasing appreciation and understanding of the link between dietary fruit and health benefits for humans (Hyson, 2011). The average consumption of apples in the EU is 15 kg per person, and apple consumption is declining in Europe, worldwide consumption of apples is growing As they are commonly eaten, in Europe and North America, in various forms (e.g. fresh fruit, juice, cider, compote) and throughout the year, they constitute a large contributor of phytochemicals in the human diet. Polyphenol content and composition depend on variety, fruit maturity, agricultural practices, growing year, storage period and processing (Awad et al, 2000; Van der Sluis et al, 2002; Markowski & Plocharski, 2006; Lata, 2007). Higher concentrations of total phenolic compounds have been found in the peel than in the flesh, and some compounds (quercetin glucosides) have been found mainly in the peel (Awad et al, 2000; Van der Sluis et al, 2002; Verberic et al, 2005). Hydroxycinnamic acids, in particular chlorogenic acid, have been found in higher concentration in the flesh than in the peel in all varieties (except ‘Reinette Russet’) (Khanizadeh et al, 2007). Awad et al (2000) showed the low level of chlorogenic acid in the peel compared to the core area

Methods

Results

Discussion

Conclusion