Authentication of Agave Products through Isotopic Intramolecular ¹³C Content of Ethanol: Optimization and Validation of ¹³C Quantitative NMR Methodology

Abstract

Agave syrup has become a popular sweetener among consumers because of its low glycemic index and pleasant taste, but substitution by cheaper sugar syrups makes it vulnerable to fraud. A 13C site-specific natural isotopic fractionation (SNIF)-NMR approach had been developed to allow the detection of C4 plants (cane, maize) in agave products, with the drawback of a long NMR acquisition time. In this work, an INEPT (insensitive nuclei enhanced by polarization transfer) pulse sequence was implemented to significantly reduce acquisition time while accurate and reproducible results are obtained. Apparent site-specific isotopic deviations were correlated to values acquired with single pulse method. The analytical method was validated following the normative procedure NF V03-110, from sample preparation to data correction. With a single pulse method as a reference, performances were at least equally good and measurement time was halved, opening new methodological ways for isotopic ratio monitoring of carbon in the ethanol molecule by NMR, also applicable to fermented and fermentable beverages. In parallel, the method was extended to agave inulin characterization after a preliminary controlled hydrolysis.

Agave Syrup: Chemical Analysis and Nutritional Profile, Applications in the Food Industry and Health Impacts

“…As a tool to prevent adulteration in ASs and to control their authenticity, Portaluri et al, (2021) [ 12 ] developed an approach to detect C4 plants called the 13C site-specific natural isotopic fractionation (SNIF)-NMR approach. After obtaining ethanol from the sugar fermentation of several ASs, it is analyzed via the optimization of a method based on an insensitive nucleus enhanced by a polarization transfer (INEPT) pulse sequence for 13C SNIF-NMR to reduce the acquisition time; it produces reproducible and reliable results.…”

“…The results also show that maize and cane are converted into sugar syrups, masked by the glucose-fructose ratio. This suggests the probability of using ASs for adulteration [ 12 ].…”

“…Gut microbiome growth is not the same for all bacteria [ 12 ]. There are three Firmicutes, Proteobacteria and Bacteroidetes phyla, along with five other minor phyla (Tenericutes, Actinobacteria, Cyanobacteria, Defferribacteres, Verrucomicrobia) that dominate the caecal microbiota of mice.…”

Application of 13C Quantitative NMR Spectroscopy to Isotopic Analyses for Vanillin Authentication Source

“…Furthermore, its determination gives the most important information concerning falsifications, adulterations, and fraud in food products [6]. For example, this method is the official method applied by the IOV (International Organization of Vines and Wine) [7] to quantify the sugar added into wine [8,9]. Isotope ratio mass spectrometry (IRMS) is the official methodology for the analysis of carbon stable isotope ratio due to its high accuracy (0.1‰) and sensitivity (up to 0.01‰) [10].…”