PHYSIOCHEMICAL PROPERTIES AND DETERMINATION OF BIOGENIC AMINES IN KOREAN MICROBREWERY BEER PRODUCTS

Study on the shift of ultraviolet spectra in aqueous solution with variations of the solution concentration

In this study, we mainly focused on predictable regularities of the red shift of ultraviolet spectra for β-phenylethylamine (PEA), NaCl and NaOH in aqueous solution. The absorption peaks of the UV spectra near 191 nm of NaCl, NaOH and PEA in aqueous solution moved in the direction of a red shift while the molar absorption coefficient at the peak increased regularly with the increasing solution concentration. These shifts were obtained for solutions with concentrations ranging from 3.68 to 1000 mmol/L for NaCl, from 0.762 to 2000 mmol/L for NaOH, and from 0.0515 to 8.91 mmol/L for PEA. The plots of the logarithm of the solution concentration for NaCl and PEA versus the absorbance at 191 nm and at the peak were linear, and the plots of the logarithm of the solution concentration for NaCl and PEA versus the wavelength at the peak (shifted from 191 nm) were also linear. In addition, the plots of the logarithm of the solution concentration for NaOH that ranged from 0.762 to 1.96 mmol/L versus the absorbance at 191 nm and at the peak were linear as well as the plots of the logarithm of the solution concentration for NaOH that ranged from 1.96 to 2000 mmol/L versus the wavelength at the peak. The slopes of the absorbance at 191 nm of PEA, NaCl and NaOH were somewhat similar to the absorbance at the peak separately, whereas the slopes of the wavelengths at the peak were different from them. Finally, in order to obtain the predictable regularity of the red shift of the UV spectrum for the mixture, 22 ternary mixtures were prepared. The results indicate that the inhibiting effect of hydroxide ions (OH-) caused the wavelength near 206 nm to remain unchanged when the solution concentration of NaOH in the mixture was more than 0.762 mmol/L.

Hydrogel-Based Sensors for Ethanol Detection in Alcoholic Beverages

A fast and reliable determination of the ethanol concentration is essential in the analysis of alcoholic beverages. However, different factors like pH value or salt concentration can influence the ethanol measurement. Furthermore, analytical figures of merit for the alcohol sensor, such as limit of detection, sensitivity and measurement uncertainty, are necessary for the application. In this paper, a detailed sensor characterization of a novel sensor based on ethanol-sensitive poly acrylamide hydrogels will be presented. The resulting swelling pressure of the hydrogel was transformed via a piezoresistive pressure sensor into a measurable output voltage. These kinds of sensors can be used over a large measuring range, up to 50 vol% ethanol and more, with a high sensitivity. In the range from pH 7.4 to 4, the pH value had no influence on the sensor signal. Higher salt concentrations can slightly influence the measurement. The detection limit amounts to 0.06–0.65 vol% ethanol. The concentration of a vodka sample was determined with a sufficient measuring uncertainty.

Health effects and occurrence of dietary polyamines: a review for the period 2005-mid 2013

This review continues a previous one (Kalač & Krausová, 2005). Dietary polyamines spermidine and spermine participate in an array of physiological roles with both favourable and injurious effects on human health. Dieticians thus need plausible information on their content in various foods. The data on the polyamine contents in raw food materials increased considerably during the reviewed period, while information on their changes during processing and storage have yet been fragmentary and inconsistent. Spermidine and spermine originate mainly from raw materials. Their high contents are typical particularly for inner organs and meat of warm-blooded animals, soybean and fermented soybean products and some mushroom species. Generally, polyamine contents range widely within the individual food items.