S17 - Session O2 - New applications of infrared spectroscopy to detect and bridge the variability before and after apple processing.

Authors: Weiji Lan *, Benoit Jaillais, Catherine Renard, Alexandre Leca, Songchao Chen, Sylvie Bureau

How to face the variability of horticultural materials and optimize their processing into food products? The challenges here were to show how visible-near infrared (VIS-NIR) and mid-infrared (MIR) spectroscopy coupled with advanced chemometrics can i) highlight the large variability of raw apples and processed purees, ii) predict puree quality from spectra of raw apples, and iii) provide new solutions to formulate constant fruit products. Experimental trials were designed to modulate factors in orchards (varieties, agricultural practices), during storage at 4°C (0-6 months) and processing (temperature, grinding and refining) in order to modify properties and composition of apples and/or purees. The inter-batch variability of apples and the intra-batch variability between individual apples intensively changed the cooked purees. The good linear correlations of titratable acidity (R 2 > 0.91), soluble solids content (R 2 > 0.79), dry matter content ((R 2 > 0.72)) and physical properties (textual and rheological parameters (R 2 > 0.79)) were observed before and after apple processing. Therefore, VIS-NIR and NIR techniques allowed to estimate puree characteristics from spectra acquired non-destructively on corresponding apples such as viscosity (R 2 > 0.82), cell wall content (R 2 > 0.81), dry matter content (R 2 > 0.83), soluble solids content (R 2 > 0.80) and titratable acidity (R 2 > 0.80). MIR spectroscopy was the best tool to detect the variability of purees and can assess their biochemical (soluble solids, acidity, dry matter) (R 2 > 0.84), rheological (viscosity and viscoelastic moduli) (R 2 > 0.84) and textural (particle size and volume) properties (R 2 > 0.82) using different cooking conditions based on spectra of raw apple homogenates. Besides, MIR spectroscopy can guide puree formulation from spectra of single-variety purees. Our innovative approaches could provide objective data to better manage apples and to adapt processing conditions according to their initial properties. The ultimate goal is to improve the quality of fresh and processed fruits while reducing losses.