Trends in the incidence of Fusarium and Microdochium species in UK malting barley: Impacts for malting and brewing quality

Technical Session 05: Malts and Grain Session
David J Cook, University of Nottingham, UK
Co-author(s): Linda Nielsen, University of Nottingham, UK; Simon Edwards, Harper Adams University College, UK; Rumiana Ray, University of Nottingham, UK

ABSTRACT: In 2008, 74% of tested U.K. malting barley samples were infected with Fusarium spp. Reported statistics have shown that the species implicated are diversifying. While due diligence monitoring indicates that mycotoxin levels in U.K. malting barley are below the specified safety limits, the impacts of sub-acute Fusarium infection on the malting and brewing quality of barley are relatively unclear but have been linked variously to a number of key quality parameters such as germinative energy and capacity of the barley crop, brewing malt specifications (e.g., soluble nitrogen, wort FAN, color, and beta-glucan levels), gushing, PYF, etc. The SAFEMalt project (Strategies Against Fusarium Effective in MALTing Barley) is a 3-year multi-partner research initiative spanning the malting barley supply chain from barley breeder through barley grower and merchant to brewer. The project incorporates two annual surveys of U.K. spring malting barleys (2010 and 2011 harvests) and also has retrospective access to U.K. spring barley samples collected for mycotoxin screening between 2007 and 2009. In 2010, species-specific real time PCR analyses identified that the main species present across 88 samples of U.K. malting barley were F. avenaceum, F. langsethiae, F. poae, and F. tricinctum, with each species detected in 80–90% of all samples tested. Retrospective analysis of Fusarium species present in 2007–2009 indicated that the prevalent Fusarium species on U.K. spring barleys differed hugely with harvest year. For example, F. graminearum was identified in all samples analyzed in 2007 and 2008, but in just 9% of samples from 2010. When 2010 samples were germinated (GE 4 mL and GE 8 mL counts) there was a positive correlation between the degree of water sensitivity and the quantity of DNA of Fusarium and Microdochium spp. in each sample (R2 = 0.51; n = 24). This correlation was more pronounced in data relating to a single barley variety (R2 = 0.65; n = 12). A micromalting procedure was developed using 350 g batches of barley in individual steep compartments in a Micromaltings K Steep-Germinator (Custom Lab), this being necessary to investigate the impacts of the Fusarium and Microdochium spp. present without mixing them while steeping multiple samples. The effects of the presence of Fusarium and Microdochium spp. and significant malt and wort quality parameters (friability, alpha-amylase, beta-amylase, wort extract, FAN, beta-glucan, and viscosity) will be presented.

David Cook is a lecturer in brewing science at the University of Nottingham, U.K., and is course director for its innovative e-learning–based courses for brewers. He is engaged in research across the malting and brewing fields, specializing in malting science, flavor formation, stability, and perception. Other current projects focus on biorefining and the use of lignocellulosic waste for bioethanol fermentations and links between crop husbandry, barley microbiology, and the functionality of malts.