4. Brewer’s spent grain—Waste material as potential raw material for a healthy diet

Julia Steiner (1); (1) Technische Universität München, Weihenstephan, Germany

Technical Session 1: Eco-Awareness & Sustainability
Sunday, August 14  •  9:45–11:30 a.m.
Plaza Building, Concourse Level, Governor’s Square 14

Brewer’s spent grain (BSG) is the most abundant byproduct in the brewing industry. It constitutes approximately 85% (w/w) of the total byproducts generated during beer production. Containing beneficial carbohydrates such as arabinoxylan and (1-3,1-4)-beta-D-glucan, upcycling BSG is of great interest for valuable preservation of a former waste material for human nutrition. In addition, sustainability, potential nutritional value, and an attractive price level have made BSG an interesting source for value-added products. Spent grain fiber is difficult to solubilize due to its structure and previous process steps. For this reason the use of hydrothermal treatment (HT) was investigated. It is the aim of this study to break down insoluble polysaccharides and subsequently add them to beverages as an ingredient with health-beneficial attributes. The shift in consumption habits toward functional drinks presents new challenges for the brewing industry. Alcohol-free beverages rich in dietary fiber receive distinctive appreciation and sustained acceptance by the consumer. Due to their origin as natural raw materials and their scientifically proven health-promoting effects, arabinoxylan and (1-3,1-4)-beta-D-glucan offer potential for functional beverages. In 2012, both polysaccharides were registered with the EFSA and may be claimed to deliver health benefits under certain conditions. Currently, HT is gaining increasing importance as an innovative approach for producing fiber-based hydrolysates. In order to solubilize the remaining water-unextractable carbohydrates, BSG was treated with pressurized hot water. Changing permittivity using an increase in pressure and temperature results in modified solubility behavior. In this study, pilot-plant scale trials were carried out to investigate the influence of selected process parameters with respect to solubility behavior and further determine the best process settings for a maximum arabinoxylan and (1-3,1-4)-beta-D-glucan yield. To ensure hydrothermal reaction conditions, temperatures ranging from 160°C to 240°C combined with pressures up to 150 bar were tested. The evaluation of hydrolysis is based on analytical attributes measured using HPLC. Initially, possibly harmful degradation products such as HMF and furfural were quantified. Further research focused on polysaccharide yield, as well as their change in Mw and DP. In batch mode, the change in internal reactor temperature showed the greatest influence on polysaccharide yield. Based on the data analysis an operating window was determined, with HMF and furfural being the limiting factors. At an appropriate combination of variable process parameters a (1-3,1-4)-beta-D-glucan yield up to 9 g/kg (DM) and an arabinoxylan yield up to 15 g/kg (DM) could be achieved, whereby the requirements for health claims were met. Adapting the defined process settings, a large amount of the fiber-rich hydrolysate was produced and subsequently fermented to develop an experimental beverage. For fermentation, Lactobacillus brevis and Lactobacillus plantarum were used, followed by a sensory evaluation. The L. plantarum beverage was preferred since it had a more fruity taste.

Julia Steiner was born in 1984 in Munich, Germany. In 2009 she graduated from the Technische Universität München (TUM) as an engineer with a Dipl.-Ing. degree in food technology and biotechnology. In 2010 she started her career as a Ph.D. student at the Institute of Brewing and Beverage Technology in Weihenstephan (TUM). Julia focuses on complex spent grain components, pursuing the aim to preserve this brewery by-product that is valuable for human nutrition. It is the aim of this study to transfer insoluble dietary fiber fractions into a soluble state in order to add them to beverages as an ingredient with health-beneficial attributes. In addition, Julia is head of sensory at the Institute of Brewing and Beverage Technology. She coordinates and conducts commissioned tastings in the brewing and beverage sector. Furthermore, she educates tasters at the university and is responsible for the training the professional taster panel at the Institute of Brewing and Beverage Technology.