USWBSI Abstract Viewer

2021 National Fusarium Head Blight Forum


Plenary Session Speaker

Invited Presenter

Challenges and Mitigations of Fusarium Impacts in Malting and Brewing

Authors & Affiliations:

Xiang S Yin, Rahr Corporation. Shakopee, MN, USA

Corresponding Author:

Xiang S Yin
Rahr Corporation
xiangsyin@rahr.com

Abstract:

In the malting and brewing industries, the impact of scab is far more than just management of food safety. Several key aspects of the impact lead to serious consequences to the processes and quality of the product. 1) Viable fungal hyphae on barley grains taken into the malthouse can proliferate further in the germination stage of the malting process causing uncontrolled out-of-specification increase of DON in the finished malt. 2) Certain polypeptides, also known as hydrophobins, secreted by some Fusarium species can survive the brewing and fermentation processes to the packaged beer and exhibit gushing propensity of beer upon opening the containers. 3) The action of antifungal response of barley when infected, can adversely produce high molecular weight substances impeding performance of yeast (also of fungal nature) in the brewery causing hung fermentation, known as the Premature Yeast Flocculation (PYF) phenomenon. The mechanisms may involve the multiple steps of interaction between pathogens and host plant, and the metabolites in turn affect the microorganisms on the plant or in later processes in the malting and fermentation media. Fusarium may also contribute to barley dormancy, malt flavor profile, and hydrolytic enzyme activities in some cases. After harvest and during storage, usually over the period of several months, the dominant form of microflora on the barley changes from the field fungi to storage fungi because of the shift in environmental conditions, such as temperature, kernel moisture, and storage time. With malting barley of average quality, the total plate count per gram (TPC/g) or colony-forming units per gram (CFU/g) of all viable microorganisms is in the order of millions. In most cases, bacteria were most prevalent, followed by yeasts, and then molds. The malting plant configuration, e.g. floor malting vs. tower malting, may have a strong influence on the types and proportions of microflora present due to the variation in moisture and temperature cycles employed, which in turn influence the flavor or quality of the finished malt. The change in microflora load on barley during malting could be up to a two-log increase (in CFU/g) during steeping but malt kilning under heat results in only limited reduction of the high CFU/g counts from germination. Options for managing the fusarium growth during germination are restricted as the germination capacity of the kernels should not be negatively affected, and the profile of flavor and taste of product should be preserved. Effects of selected physical and chemical treatments have been studied and recommendations are provided for practical applications.


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