Determination of Ethanol in Kombucha, Juices, and Alcohol-Free Beer by Enzytec[TM] Liquid Ethanol: Single-Laboratory Validation, First Action 2017.07

• Published in: Journal of AOAC International Vol. 101; no. 4; p. 1101
• Main Authors: Lacorn, Markus, Hektor, Thomas
• Format: Journal Article
• Language: English
• Published: Oxford University Press 01.07.2018
• Subjects: Chemical properties; Composition; Ethanol; Food testing; Juices (Beverages); Low alcohol beer; Measurement; Methods
• ISSN: 1060-3271; 1944-7922
• DOI: 10.5740/jaoacint.17-0466

Enzytec[TM] Liquid Ethanol is an enzymatic test for the determination of ethanol in kombucha, juices, and alcohol-free beer. The kit contains two components in a ready-to-use format. Quantification is based on the catalytic activity of alcohol dehydrogenase, which oxidizes ethanol to acetaldehyde and converts [NAD.sup.+] to NADH. Measurement is performed in 3 mL cuvettes at 340 nm within 20 min. Samples with alcohol contents around 0.5% alcohol by volume need to be diluted 1:20 or 1:50 with water before measurement. Acetaldehyde interferes at concentrations higher than 3000 mg/L, whereas sulfite interferes at concentrations higher than 300 mg/L. The linear measurement range is from 0.03 up to 0.5 g/L ethanol, whereas LOD and LOQ are 1.9 and 3.3 mg/L ethanol, respectively. Kombucha with concentrations between 2.85 and 5.82 g/L showed relative repeatability standard deviation around 1%, whereas juices were below 2%. Results from a reproducibility experiment revealed that at a concentration of 0.1 g/L, the [RSD.sub.R] was at 2.5%, whereas at higher concentrations between 0.2 and 0.3 g/L, coefficients around 1% were obtained. Trueness was checked by using Cerilliant aqueous ethanol solutions and beer with concentration of 0.4 and 4 g/L (BCR-651 and BCR-652). spiking of kombucha and juice samples resulted in recoveries between 95% and 104%. Acceptable stability was found for the whole test kit under accelerated conditions at 37[degrees]C for 2 weeks. the kit is also not susceptible to short freezing--thawing cycles and harsh transport conditions.