SMLR Method to Obtain the Representative NIR Wavelengthin Determining the CGA and Trigonelline in Coffee Beans

Abstract

Coffee from diverse place will serve a diverse flavor, especially the accidity and bitternes, could be easily detected by human’s sense of taste. This is due to the differences of the chemical content, in this case the chlorogenic acid (CGA) and trigonelline, inside the green beans. In coffee industry the assesment of coffee quality usually done by the sertified cupper. However, the cupper could not provide the exact concentration inside and the information only determined by the chemical method such as the LCMS method. These method are expensive, time consuming and destructive the opposite with the need of industries. Near Infrared Spectroscopy (NIRS) method could be used to answer the requirement. In this study, the CGA and trigonelline concentration in coffee beans could be determined by several most representative NIR wavelenght. A hundred samples (96 grams coffee beans) were subjected to NIR measurement in the wavelength of 1000 – 2500 nm, followed by the chemical analysis by LCMS method, then calibrated by the Stepwise multiple linear regression (SMLR) method to obtain the representative NIR wavelength. Result showed that the NIR spectroscopy could determined the CGA concentration by using 24 NIR wavelenghts indicated by high r, RPD and consistency value of 0.949, 2.59 and 88.78%, respectively. However, the trigonelline could not be assesed by the SMLR method due to its small amount and its chemical bounding inside the beans.