Coffea arabica var. laurina authentication using near infrared spectroscopy : [C311]

On the island of Réunion, a project designed to develop a high added-value coffee brand was launched in 2002. The project focused on Coffea Arabica var. Laurina called 'Bourbon Pointu', and set out to determine growing practices and post-harvest treatments enabling the production of an inimitable coffee. The project involved the development of 106 experimental cultivation plots. The first phase of the project, from 2002 to 2007, was used to establish technical/commercial references for the production and processing of high added-value "grands crus" coffees. Soils were characterized and farms potentially suitable for the production of quality coffee were identified. Over that period more than 1126 samples were collected and analysed in diffuse reflectance from 1100 nm to 2500 nm using a NIRSystem FOSS 5000 spectrometer (Port Matilda, USA). In that way, a Near Infrared (NIR) spectral database specific to Bourbon Pointu (BP) coffees was compiled. A principal components analysis was performed on the spectral database in order to calculate Mahalanobis distances from the average spectrum for each spectrum and then fix boundaries for the population. Based on these results, samples differing from pure BP, such as "Bourbon rond", were removed from the database. The database was constructed by removing samples corresponding to abandoned trials such as certain post-harvest treatments or fertilizer tests. This led to a specific database for BP comprising 670 spectra of green coffees. From that collection, 250 random samples were analysed at the CIRAD laboratories, using reference methods, for their caffeine, chlorogenic acids, trigonelline, fat, sucrose and moisture contents. Those values were added to CIRAD's Arabica NIR database to develop specific calibration for BP coffees using Partial Least Squares Regression. This approach revealed that it was possible to authenticate BP coffee from Réunion using NIRS fingerprinting. The calibrations developed in this study made it possible to quantify the content of 6 major quality-related chemical compounds in BP green coffee. (Résumé d'auteur