Arabinoxylans and fructans in the malting and brewing process

Nutrition/Health Session
Moritz Krahl, Radeberger Gruppe, Frankfurt am Main, Germany
Co-author(s): Werner Back, TU München, Freising, Germany

ABSTRACT: Nowadays our nutrition is mainly based on only three cereals: wheat, rice, and corn. They contribute over 75% to the world’s starch production. At the same time diseases caused by wrong or unbalanced diets are becoming a severe problem in Western countries. In this regard the enrichment of soluble dietary fiber in the malting process with the objective of providing their health-beneficial effects to the consumer is a possible approach to better nutrition. Arabinoxylan (AX) and fructan, two health-beneficial dietary fiber fractions have been measured during the entire malting and brewing process. The total AX in barley, wheat, rye, triticale, oats, and spelt wheat did not change during the malting process. Water-extractable arabinoxylans (WEAX) increased during malting, and the influence of the germination parameters time, temperature, and moisture content was determined for each of the cereals. The malting process is influenced by the quality of the raw material and by several process parameters (e.g., moisture, temperature, and time); in addition changes in dietary fiber content depend on the same variables. To reduce the necessary number of trials for the evaluation of optimal conditions we used software for the design of experiments. This software supports several different statistical approaches like various factorial designs or response surface methods (RSM). With RSM the interactive effects of various process conditions are modeled empirically. WEAX increased during germination in all malted cereals. Kilning had no effect on the amount of WEAX in most cereals. Only in rye did WEAX content increased by 30% during kilning. At the same time the viscosity of Congress wort decreased. The probable explanation for this phenomenon is a cleaving of diferulic acid-bridges by the heat of the kilning process. These cross-linkages have been found only in WEAX of rye. Using optimum malting parameters WEAX can increase up to threefold the level found in unmalted kernels. Malting did not affect the fructan content of most cereals, so no losses of this dietary fiber fraction were observed. In spelt wheat the fructans increased during standard malting, and the final level was 67% higher than in the raw material. During the brewing process only mashing had an influence on AX content. During lautering, wort boiling, fermentation, and storage no changes were observed. Fructans were not influenced by mashing, wort boiling, and lautering. During fermentation and storage more than 90% of the fructans found in cooled wort were fermented by the yeast. The experiments showed that malting is an effective way to enrich WEAX in cereals and fructans in spelt wheat. In the brewing process the final WEAX concentrations depend on the raw materials and not on the mashing parameters.

Moritz Krahl was born in Schwetzingen, Germany. After passing the German Abitur (A levels) in 2000, he began studying brewing and beverage technology at Technische Universität München in Weihenstephan, Germany. In 2004 he graduated with a B.S. degree and in 2005 with a Dipl.-Ing. (graduate engineer) degree. From 2005 to 2010 Moritz worked on his Ph.D. on “Functional Beverages Based on Malted Cereals and Pseudocereals” at the Institute for Brewing and Beverage Technology in Weihenstephan. From 2010 to 2011 he worked as head engineer for plant and process optimization for MEG. In October 2011 Moritz joined the Radeberger Group with key responsibility in product and process development for new beverages.