Rapid and mobile determination of alcoholic strength in wine, beer and spirits using a flow-through infrared sensor

<p>Abstract</p> <p>Background</p> <p>Ever since Gay-Lussac's time, the alcoholic strength by volume (% vol) has been determined by using densimetric measurements. The typical reference procedure involves distillation followed by pycnometry, which is comparably labour-intensive and therefore expensive. At present, infrared (IR) spectroscopy in combination with multivariate regression is widely applied as a screening procedure, which allows one to determine alcoholic strength in less than 2 min without any sample preparation. The disadvantage is the relatively large investment for Fourier transform (FT) IR or near-IR instruments, and the need for matrix-dependent calibration. In this study, we apply a much simpler device consisting of a patented multiple-beam infrared sensor in combination with a flow-through cell for automated alcohol analysis, which is available in a portable version that allows for on-site measurements.</p> <p>Results</p> <p>During method validation, the precision of the infrared sensor was found to be equal to or better than densimetric or FTIR methods. For example, the average repeatability, as determined in 6 different wine samples, was 0.05% vol and the relative standard deviation was below 0.2%. Accuracy was ensured by analyzing 260 different alcoholic beverages in comparison to densimetric or FTIR results. The correlation was linear over the entire range from alcohol-free beers up to high-proof spirits, and the results were in substantial agreement (R = 0.99981, p < 0.0001, RMSE = 0.279% vol). The applicability of the device was further proven for the analysis of wines during fermentation, and for the determination of unrecorded alcohol (i.e. non-commercial or illicit products).</p> <p>Conclusions</p> <p>The flow-through infrared device is much easier to handle than typical reference procedures, while time-consuming sample preparation steps such as distillation are not necessary. Therefore, the alcoholic strength can be economically and quickly controlled (requiring less than 60 s per sample). The device also gives the opportunity for mobile on-site control in the context of labelling control of wine, beer and spirits, the process monitoring of fermentations, or the evaluation of unrecorded alcohols.</p

NMR-based metabolomics: quality and authenticity of plant-based foods

Nowadays metabolomics is a widely accepted approach in several scientific disciplines, especially in food science. The possibility to identify a wide range of metabolites (untargeted analysis) allowed to evaluate various food characteristics, regarding quality, adulteration, geographical origin, as well as secondary species-specific metabolites endowed with nutraceutical properties. In the present chapter, latest findings of plant-based foods investigated by NMR-based metabolomics are presented. Almost all of the recent studies were focused on quality assessment and authenticity; different aspects such as geographical origin, metabolic modifications upon stress, nutraceutical properties, and fraud detection are described as well. The here reported plant-based foods are balsamic and traditional balsamic vinegars, cereals, cocoa, coffee, fruits, legumes, spices, vegetables and vegetable oils, wine, beer, and spirits. A brief paragraph is concerning organic and conventional foods, which is a new growing scientific field of interest for researchers encouraged by the increasing consumers’ demand. The results here reported testify the capability and the power of this approach thus endorsing NMR spectroscopy as a valid alternative or complement to the chemical and physical analysis nowadays routinely applied for the quality assessment