The occurrence and structural heterogeneity of arabinoxylan in commercial pilsner beers and their non-alcoholic counterparts

Ascorbic acid-mediated reduction of arabinoxylan viscosity through free radical reactions

Arabinoxylan (AX) is a potential natural food additive that can enhance the textural properties of food. However, the addition of ascorbic acid (AA) can easily lead to a decrease in the viscosity of AX, which poses a challenge in the development of AX-rich foods. Therefore, the purpose of this study is to elucidate the mechanisms behind the reduction in AX viscosity in the presence of AA. The results indicated that AA could reduce the apparent viscosity and molecular weight of AX without significantly affecting the monosaccharide composition, suggesting a potential mechanism related to the cleavage of AX glycosidic bonds. Interestingly, free radicals were present in the reaction system, and the generation of free radicals under different conditions was consistent with the reduction in apparent viscosity of AX. Furthermore, the reduction in AX apparent viscosity by AA was influenced by various factors including AA concentration, reaction time, temperature, pH, and metal ions. These findings suggested that the mechanism of AX degradation may be due to AA-induced free radical generation, leading to non-selective attacks on glycosidic bonds. Therefore, this study revealed that the potential mechanism behind the reduction in AX viscosity induced by AA involved the generation of ascorbic acid radicals.

Arabinoxylans: A review on protocols for their recovery, functionalities and roles in food formulations

Arabinoxylans (AXs) are compounds with high nutritional value and applicability, including prebiotics or supplementary ingredients, in food manufacturing industries. Unfortunately, the recovery of AXs may require advanced separation and integrated strategies. Here, an analysis of the emerging techniques to extract AXs from cereals and their by-products is discussed. This review covers distinct methods implemented over the last 2-3 years, identifying that the type of method, extraction source, AX physicochemical properties and pre-treatment conditions are the main factors influencing the recovery yield. Alkaline extraction is among the most used methods nowadays, mostly due to its simplicity and high recovery yield. Concurrently, recovered AXs applied in food applications is timely reviewed, such as potential bread ingredient, prebiotic and as a wall material for probiotic encapsulation, in beer and non-alcoholic beverage manufacturing, complementary ingredient in bakery products and cookies, improvers in Chinese noodles, 3D food printing and designing of nanostructures for delivery platforms.

Advancing Quantification of Water-Extractable Arabinoxylan in Beer: A High-Throughput Approach

Water-extractable arabinoxylan (WEAX) may cause major problems during clarification processes in a brewery owing to its ability to form gel networks. However, high WEAX contents can also enhance the nutritional quality of the final product as they play an important role in the human diet. Therefore, precise quantification of WEAX is required. Current methods are very time- and resource-consuming as well as limited in the number of samples and in some cases provide low accuracy. Thus, a reproducible high-throughput method for the quantification of WEAX optimized for beer was developed, reaching recovery rates (RRs) of almost 100%. The assay is based on Douglas's colorimetric method. Hydrolysis was conducted using glacial acetic acid to induce the formation of red color complexes resulting from the interaction between pentose degradation products and phloroglucinol. The method was successfully transferred to a multi-mode microplate reader to minimize the loss of color intensity over time and to obtain a high throughput. By using 96-well plates, up to 40% of the previous analysis time could be saved, and a larger number of samples could be analyzed in one batch. The collected data determined xylose as an optimal calibration standard due to high accuracy and reproducibility. The respective AX control standards showed RR within the range of 95-105% without exception. To validate and show the ruggedness of the modified method, WEAX concentration in seven commercial German beers (e.g., lager, pilsner, wheat beer, non-alcoholic beer) was quantified. Interfering hexose sugars that lead to measurement errors when analyzing samples with high amounts of fermentable sugars (e.g., non-alcoholic beer produced by limited fermentation) were eliminated by Saccharomyces diastaticus fermentation. Further investigations were carried out by means of LC-MS in order to obtain additional information about the reddish product in the hydrolyzed samples. In this context, C16H12O6 could be identified as one of numerous condensation products, contributing to the coloring. The collected data showed the impact of diverse factors on the measured AX concentration and helped optimize the experimental procedure for a high sample throughput with precise and highly reproducible results. The proposed quantification method should be primarily used in completely fermented finished beer to emphasize the time aspect. Wort samples and non-alcoholic beer produced by limited fermentation can be also analyzed, but only after fermentation with S. diastaticus.