Determination by near infrared microscopy of the nitrogen and carbon content of tomato (Solanum lycopersicum L.) leaf powder.

Gauthier Lequeue,Vincent Baeten,Xavier Draye

doi:10.1038/srep33183

Abstract

Near infrared microscopy (NIRM) has been developed as a rapid technique to predict the chemical composition of foods, reduce analytical costs and time and ease sample preparation. In this study, NIRM has been evaluated as an alternative to classical chemical analysis to determine the nitrogen and carbon content of small samples of tomato (Solanum lycopersicum L.) leaf powder. Near infrared spectra were obtained by NIRM for independent leaf samples collected on 216 plants grown under six different levels of nitrogen. From these, 30 calibration and 30 validation samples covering the spectral range of the whole set were selected and their nitrogen and carbon contents were determined by a reference method. The calibration model obtained for nitrogen content proved to be excellent, with a coefficient of determination in calibration (R2c) higher than 0.9 and a ratio of performance to deviation (RPDc) higher than 3. Statistical indicators of prediction using the validation set were also very high (R2p values > 0.90). However, the calibration model obtained for carbon content was much less satisfactory (R2c < 0.50). NIRM appears as a promising and suitable tool for a rapid, non-destructive and reliable determination of nitrogen content of tiny samples of tomato leaf powder.

Highlights

For four decades, the food sector has adopted near-infrared (NIR) based techniques for the quantitative control of raw materials and final products
NIR spectra of food products include mainly absorption bands characteristic of O–H, C–H, N-H, S-H and C-C groups. These bands are the result of the interaction between photons and matter. These interactions occurring in the NIR region of the electromagnetic spectrum induce vibration transitions in the second, third or higher excited states or overtones, as well as combinations derived from fundamental vibrations that occur in the MIR region[5,16,17]
Comparison between the near-infrared spectra of one of our samples analyzed by NIR microscopy (NIRM) instrument and by near-infrared spectrometry (NIRS) classical instrument with the attribution of the main infrared bands (A–G)

Summary

Introduction

The food sector has adopted near-infrared (NIR) based techniques for the quantitative control of raw materials and final products. These techniques offer the possibility to investigate simultaneously physical, biological and nutritional features of complex matrices, require small sample amounts and simple small preparation, and involve small analytical costs and times[1,2,3,4,5,6]. Because NIRM results can be shared in networks of laboratories[28], the technique has been validated at European level[27]

Methods

Results

Conclusion