Emphasis on near infrared lasts for long, but new technology in the infrared area (both mid infrared or MIR and Near Infrared or NIR) open new applications. A user guide has been built in order to help the food engineer to choose a technique able to help him in his process control, especially according to his on-line constraints and on his performances requirements. This chart has been applied to two examples : the constituent analysis of a fermentation thanks to Mid infrared spectrometry and the non destructive ultrafast measurement of sugar in fruits thanks to a diode array spectrometer. In the first experiments, good accuracies were obtained, which makes of MIR a potential tool for rapid process control. In the second example, fiber optics are used in order to optimize the throuput of the optical system and to allow multiplexing. The cost of this apparatus would be so low that it could be available even by small conditionning stations. Abstract of the paper N° 920602. / L'intérêt de la spectroscopie proche infrarouge existe depuis longtemps mais les nouvelles technologies dans le domaine infrarouge (à la fois moyen et proche infrarouge) ouvrent de nouvelles applications. Un guide a été construit de manière à aider l'ingénieur agro-alimentaire à choisir la technique la plus appropriée pour l'aider dans le contrôle de procédé, notamment en fonction de ses contraintes en ligne et des performances requises. Ce guide est appliqué à 2 exemples : analyse des fermentations par moyen infrarouge et mesure rapide du sucre dans les fruits. Abstract de la communication N° 920602