Potential of Laser Induced Breakdown Spectroscopy for analyzing the quality of unroasted and ground coffee

Abstract

Coffee is an important commodity and a very popular beverage around the world. Its economic value as well as beverage quality are strongly dependent of the quality of beans. The presence of defective beans in coffee blends has caused a negative impact on the beverage Global Quality (GQ) assessed by cupping tests. The main defective beans observed in the productive chain has been those Blacks, Greens and Sours (BGS). Chemical composition of BGS has a damaging impact on beverage GQ. That is why analytical tools are needed for monitoring and controlling the GQ in coffee agro-industry. Near Infrared Spectroscopy (NIRS) has been successfully applied for assessment of coffee quality. Another potential technique for direct, clean and fast measurement of coffee GQ is Laser Induced Breakdown Spectroscopy (LIBS). Elements and diatomic molecules commonly present in organic compounds (structure) can be assessed by using LIBS. In this article is reported an evaluation of LIBS for the main interferents of GQ (BGS defects). Results confirm the great potential of LIBS for discriminating good beans from those with BGS defects by using emission lines of C, CN, C2 and N. Most importantly, some emission lines presented strong linear correlation (r > 0.9) with NIRS absorption bands assigned to proteins, lipids, sugar and carboxylic acids, suggesting LIBS potential to estimate these compounds in unroasted and ground coffee samples.