Determination of Free Tryptophan in Beer Samples by Capillary Isotachophoretic Method

Deep Eutectic Solvent Based Reversed-Phase Dispersive Liquid-Liquid Microextraction and High-Performance Liquid Chromatography for the Determination of Free Tryptophan in Cold-Pressed Oils

A fast and straightforward reversed-phase dispersive liquid-liquid microextraction (RP-DLLME) using a deep eutectic solvent (DES) procedure to determine free tryptophan in vegetable oils was developed. The influence of eight variables affecting the RP-DLLME efficiency has been studied by a multivariate approach. A Plackett-Burman design for screening the most influential variables followed by a central composite response surface methodology led to an optimum RP-DLLME setup for a 1 g oil sample: 9 mL hexane as the diluting solvent, vortex extraction with 0.45 mL of DES (choline chloride-urea) at 40 °C, without addition of salt, and centrifugation at 6000 rpm for 4.0 min. The reconstituted extract was directly injected into a high-performance liquid chromatography (HPLC) system working in the diode array mode. At the studied concentration levels, the obtained method detection limits (MDL) was 11 mg/kg, linearity in matrix-matched standards was R² ≥ 0.997, relative standard deviations (RSD) was 7.8%, and average recovery was 93%. The combined use of the recently developed DES -based RP-DLLME and HPLC provides an innovative, efficient, cost-effective, and more sustainable method for the extraction and quantification of free tryptophan in oily food matrices. The method was employed to analyze cold-pressed oils from nine vegetables (Brazil nut, almond, cashew, hazelnut, peanut, pumpkin, sesame, sunflower, and walnut) for the first time. The results showed that free tryptophan was present in the range of 11-38 mg/100 g. This article is important for its contributions to the field of food analysis, and for its development of a new and efficient method for the determination of free tryptophan in complex matrices, which has the potential to be applied to other analytes and sample types.

Developing colloidal structure of beer by grain organic compounds

The present article introduces the problem of determining the general structure of beer as a complex system of related biomolecules. The objective was to establish the correlation of various quantities of organic compounds in beer formulation. The research featured samples of filtered pasteurized beer obtained from a retail chain shop in Moscow (Russia). The experiment relied on standard research methods, including instrumental methods of analysis, e.g., high-performance liquid chromatography (HPLC). The obtained experimental data underwent a statistical analysis using the Statistica software (StatSoft, 2016). The research established the correlation between the type of grain (barley or wheat malt) and the content of organic compounds, e.g., β-glucan, polyphenols, soluble nitrogen, etc. The research also revealed some patterns in the distribution of proteins, which served as a framework for the system of organic compounds. The distribution of thiol proteins proved to depend on the dissolution degree of the grain and was different in barley light, barley dark, and wheat malt samples. The fraction distribution of β-glucan depended on the color of the malt. In light beer samples, it concentrated in high- and medium-molecular fractions of nitrogenous substances, in dark beer – in low-molecular fractions (≤ 63%). Initial wort density and alcohol content affected the amount of catechins and total polyphenols. Nitrogenous compounds depended on the color, initial extract, and alcohol content. The nitrogenous structure and other organic compounds of beer proved to depend on protein substances. The research also revealed a number of factors that affected the fraction distribution of biomolecules in different beer sorts.

Recent progress in analytical capillary isotachophoresis (2018 - March 2022)

This review brings a survey of papers on analytical capillary and microchip isotachophoresis published since 2018 until the first quarter of 2022. Theoretical papers extending fundamental knowledge include those on computer simulations that remain an important research tool useful in the design of electrolyte systems. Many papers are focused on instrumental aspects where new media including microfluidic devices and their hyphenation to various detection techniques bring remarkable results. Papers reporting analytical applications demonstrate the potential of contemporary analytical isotachophoresis. Although it is not being used on a mass scale, its special features are attracting continued interest resulting in applications of isotachophoresis both as a stand-alone analytical method and as a part of multidimensional separation techniques.

Molecular Networks and Macromolecular Molar Mass Distributions for Preliminary Characterization of Danish Craft Beers

Beer is one of the most widely consumed beverages containing up to 200,000 unique small molecules and a largely uncharacterized macromolecular and particulate space. The chemical profiling of beer is difficult due to its complex nature. To address this issue, we have used various state-of-the-art methods to determine the physicochemical characteristics of beer. Specifically, we have successfully generated an LC-MS-based molecular network with minimal sample preparation to profile indoles in beer and confirmed their presence using 1H-NMR. In addition, we have identified different macromolecular signatures in beer of different colors by utilizing AF4-MALS. These preliminary findings lay the foundation for further research on the physicochemical nature of beer.

Simple extraction procedure for free amino acids determination in selected gluten-free flour samples

The simple extraction of flours samples followed by free amino acids determination procedures was studied and optimised. The conditions of amino acids derivatisation reaction with ninhydrin for chromatographic determination of free amino acids sum was discussed. The developed method was processed in terms of linearity, precision, accuracy, and limits of detection and quantification. Moreover, capillary isotachophoresis and HPLC methods were applied for individual free amino acids determination. The proposed extraction procedure is simple, fast and convenient for different flours samples. Studied procedures were used for free amino acids determination in twelve gluten-free flour samples (corn, oat, soy, rice, pumpkin, millet, peanut, hemp seed, buckwheat, amaranth, pea and chickpea) and the obtained results were compared with wheat flour.