Studies on Coffee Roasting Process by Means of Nuclear Magnetic Resonance Spectroscopy

Abstract

The chemical composition of coffee has been widely investigated, focusing the attention both on main components and trace compounds. Most of these studies have been performed by using liquid and gas chromatography, eventually combined with mass spectroscometry. These techniques, although straight and effective, are time demanding due to the sample pretreatments. Here, we propose high‐resolution‐magic‐angle spinning nuclear magnetic resonance spectroscopy (HR‐MAS NMR), a system capable of acquiring highly resolved NMR spectra of gel‐like and suspension samples. This approach allowed us to determine the chemical composition of coarsely ground coffee beans of two varieties: Arabica and Robusta. Variation of the concentration of relevant species was monitored as a function of roasting temperature, from green beans to completely roasted. The HR‐MAS NMR tool demonstrated to be very powerful for quick chemical composition determination, opening up possibilities for novel applications of this approach in food quality control. PRACTICAL APPLICATIONS Food quality control needs novel and press‐button applications. High‐resolution‐magic‐angle spinning nuclear magnetic resonance contains such requirements, since it can analyze suspension and gel‐like samples, providing a chemical characterization with minor, or, in most cases, no chemical and physical pretreatment operations. The application proposed here concerns the examination of relevant molecules in coffee beans as a function of the roasting temperature. This can be used for a quality check of the final product, and such approach has a general suitability, being functional for almost all foodstuff, fresh and transformed.

Coffee fermentation and flavor – An intricate and delicate relationship

“…Currently, multiple-SPME method which involves the extraction of one coffee sample with multiple SPME fibers followed by a one-time injection of all the volatiles extracted into the GC instrument is explored and developed so as to enhance the sensitivity of SPME (Lee, Lee, Lee, & Buglass, 2013). With the advancement of analytical technologies, analytical techniques such as two-dimensional gas chromatography coupled to either MS or flame ionization detector (FID) (Chin, Eyres, & Marriott, 2011) and nuclear magnetic resonance (NMR) spectroscopy (Ciampa, Renzi, Taglienti, Sequi, & Valentini, 2010) have been used for headspace and compositional analysis of roasted coffee aroma. However, only a fraction of the odorants detected from coffee aroma were determined to be character-impact odorants with flavor dilution (FD) values in the range of 16-2048.…”

Traceability of Italian garlic (Allium sativum L.) by means of HRMAS-NMR spectroscopy and multivariate data analysis

“…Furthermore, the full width at half height of most signals is in the order of about one Hertz, therefore comparable to the one obtained from liquid sample equivalent. The chemical composition of some foodstuff have been determined by means of 1 H HRMAS-NMR: cheese, (Shintu, Ziarelli, & Caldarelli, 2004) fish, (Nestor et al, 2010) coffee, (Ciampa, Renzi, Taglienti, Sequi, & Valentini, 2010) wheat, bread and flour (Brescia et al, 2007;Sacco et al, 1998;Sacco, Brescia, Buccolieri, & Jambrenghi, 2005), sweet pepper (Ritota, Marini, Sequi, & Valentini, 2010).…”

HRMAS-NMR spectroscopy and multivariate analysis meat characterisation

“…It offers the opportunity of measuring samples without any chemical and/or physical preparation, by producing highly resolved spectra. While HRMAS-NMR has been extensively used in medicine and related fields (Rocha et al, 2010;Wang et al, 2003), its application in food characterisation is still in its infancy, and few studies have been reported (Valentini et al, 2011), mainly referring to fresh vegetables (Perez, Iglesias, Ortiz, Perez, & Galera, 2010;Ritota, Marini, Sequi, & Valentini, 2010) and processed materials (Ciampa, Renzi, Taglienti, Sequi, & Valentini, 2010;Consonni, Cagliani, & Cogliati, 2011;Shintu & Caldarelli, 2005, 2006. Brescia et al (2002) reported a preliminary study on meat composition by HRMAS-NMR.…”