UCC Library and UCC researchers have made this item openly available. Please let us know how this has helped you. Thanks! Title Development of a toolbox for the reduction of hordeins in barley malt beers Author(s) Taylor, Joshua P. Publication date 2016 Original citation Taylor, J. P. 2016. Development of a toolbox for the reduction of hordeins in barley malt beers. PhD Thesis, University College Cork. Type of publication Doctoral thesis Rights © 2016, Joshua P. Taylor. http://creativecommons.org/licenses/by-nc-nd/3.0/ Item downloaded http://hdl.handle.net/10468/3241 from Downloaded on 2021-10-04T08:07:22Z Ollscoil na hÉireann THE NATIONAL UNIVERSITY OF IRELAND Coláiste na hOllscoile, Corcaigh UNIVERSITY COLLEGE CORK SCHOOL OF FOOD AND NUTRITIONAL SCIENCES DEVELOPMENT OF A TOOLBOX FOR THE REDUCTION OF HORDEINS IN BARLEY MALT BEERS Thesis presented by Joshua P. Taylor BSc (Hons) Biotechnology Under the supervision of Prof. DSc. Dr. Elke K. Arendt For the degree of Doctor of Philosophy (PhD in Food Science and Technology) Head of School - Prof. Yrjö Roos January 2016 ii Table of Contents Table of Contents ......................................................................................... iii Abstract ......................................................................................................... 1 Acknowledgements ....................................................................................... 3 Declaration .................................................................................................... 4 Chapter 1: Introduction ................................................................................. 5 Introduction ............................................................................................................. 6 Literature cited ......................................................................................................... 9 Chapter 2: Literature review – Gluten-free beer .......................................... 11 Abstract .................................................................................................................. 12 Introduction ........................................................................................................... 13 Conclusion and future trends ................................................................................ 38 Literature cited ....................................................................................................... 41 Chapter 3: A Fundamental Study on the Relationship between Barley Cultivar and Hordeins in Single Cultivar Beers .............................................. 51 Abstract .................................................................................................................. 52 Introduction ........................................................................................................... 53 Materials and methods .......................................................................................... 55 Results .................................................................................................................... 57 Discussion ............................................................................................................... 65 iii Conclusions ............................................................................................................ 71 Literature cited ....................................................................................................... 73 Chapter 4: A study on Malt Modification, used as a Tool to Reduce Levels of Beer Hordeins ............................................................................... 76 Abstract .................................................................................................................. 77 Introduction ........................................................................................................... 78 Materials and methods .......................................................................................... 79 Results and discussion............................................................................................ 83 Conclusion .............................................................................................................. 94 Literature cited ....................................................................................................... 95 Chapter 5: Reduction of Hordein content in beer by applying Prolyl- endoprotease to the malting process ........................................................... 98 Abstract .................................................................................................................. 99 Introduction ......................................................................................................... 100 Materials and methods ........................................................................................ 102 Results and discussion.......................................................................................... 105 Conclusion ............................................................................................................ 119 Literature cited ..................................................................................................... 120 Chapter 6: Fundamental study on the impact of silica gel and tannic acid on hordein levels in beer .................................................................... 123 Introduction ......................................................................................................... 125 Materials and methods ........................................................................................ 127 iv Results and discussion.......................................................................................... 131 Conclusions .......................................................................................................... 146 Literature cited ..................................................................................................... 148 Chapter 7: Fundamental Study on the Impact of Transglutaminase on Hordein Levels in Beer ............................................................................... 152 Introduction ......................................................................................................... 154 Materials and methods ........................................................................................ 156 Results and discussion.......................................................................................... 161 Conclusion ............................................................................................................ 177 Literature cited ..................................................................................................... 179 Chapter 8: Overall discussion and conclusion ............................................. 184 Overall discussion and conclusion ....................................................................... 185 Literature cited ..................................................................................................... 201 v Abstract Gluten sensitive consumers and people suffering from coeliac disease account for up to 6% of the general population (Catassi et al., 2013). These consumers must avoid foods which contain gluten and related proteins found in wheat, rye or barley. Beer is produced from barley malt and therefore contains hordeins, (gluten like proteins). Beers labelled as gluten-free must contain below 10 mg/kg hordeins (10 mg/kg hordeins = 20 mg/kg gluten under current regulations) to be considered safe for gluten sensitive consumers. Currently there are a limited number of methods available for reducing beer hordeins, the studies outlined in this thesis provide a range of tools for the beverage industry to reduce the hordein content of beer It is well known, that during malting and brewing hordeins are reduced, but they still remain in beer at levels above 10 mg/kg. During malting, hordeins are broken down to form new proteins in the growing plant. Model malting and brewing systems were developed and used to test, how the modification of the malting process could be used to reduce beer hordeins. It was shown, that by using a controlled malting and brewing regime, a range of barley cultivars produced beer with significant differences in levels of hordeins. Beer hordeins ranged from 10 mg/kg to 60 mg/kg. Another study revealed that when malting was prolonged, to maximise breakdown of proteins, beer hordeins can be reduced by up to 44%. The natural breakdown of hordein during malting enhanced in a further study, when a protease was added to support the hordein degradation during steeping and germination. The enzyme addition resulted in a 46% reduction in beer hordeins 1 when compared to the control. All of the malt treatments had little or no impact on malt quality. The hordein levels can also be reduced during the beer stabilisation process. Levels of beer hordein were tested after stabilisation using two different concentrations of silica gel and tannic acid. Silica gel was very effective in reducing beer hordeins, 90% of beer hordeins were removed compared to the control beer. Beer hordeins could be reduced to below 10 mg/kg and the beer qualities such as foam, colour and flavour were not affected. Tannic acid also reduced beer hordein by up to 90%, but it reduced foam stability and affected beer flavours. A further study described treatment of beer with