Analysis of Caffeine, Sweeteners, and Other Additives in Beverages by Vibrational Spectroscopy

Abstract

This chapter presents a review of the scientific literature on the use of vibrational spectroscopy, near‐infrared (NIR), mid‐infrared (mid‐IR), and Raman, for the analysis of caffeine, sweeteners, and other additives in beverages and related products. Direct analysis procedures of coffee and tea, for both classification according to precedence or variety and quantitative determination of caffeine, are available. For beverage analysis, caffeine has been determined by direct attenuated total reflection (ATR) measurement or by transmission spectroscopy in the mid‐IR region after extraction with chloroform. Different strategies have been employed for the analysis of sweeteners in beverages and tabletop products, including direct ATR or transmission IR measurements after extraction with an adequate solvent, and also using Raman spectroscopy. Owing to spectral overlapping of characteristic bands of the analytes of interest with other components from beverages and to the high absorption of the sample matrix, many of the developed vibrational‐spectroscopy‐based applications require the use of multivariate calibration through partial least squares (PLS). The future trends for these types of determinations will be based on the use of flow solid‐phase sensors and the automation though flow injection or sequential injection analysis (SIA) approaches.