Browsing by Author "Manninen, Jenny"

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    Characterisation of barley-associated biofilms and their impact on wort separation
    (2016-02-02) Manninen, Jenny; Laitila, Arja; Kemian tekniikan korkeakoulu; Nordström, Katrina
    Wort separation is one of the rate-limiting steps in breweries. Weak filtration performance may have its origin in the malting of barley. Malting conditions favour the growth of indigenous microbiota and the biofilm formation under the husk of barley. The exposed starchy endosperm of naturally split barley has been observed to potentially induce biofilm formation retarding wort filtration performance. A better understanding of the role of bacteria in biofilm formation during malting is needed in order to possibly control the phenomenon and to improve the wort filtration performance. This thesis aimed to answer what are the the key barley-related microbial factors influencing wort separation and which barley-associated bacteria could have an impact on the wort separation efficiency. To our knowledge, next-generation sequencing was used for the first time in this thesis to explore the bacterial communities of barley of the same variety, but grown in geographically different locations – South Africa, Sweden, France and Argentina. Furthermore, the biofilm formation was first induced in laboratory scale malting trials by gently damaging the barley just prior to malting. Then the bacterial growth was suppressed with antibiotics and Lactobacillus plantarum VTT E-78076 starter cultures during steeping. The bacterial communities of the Overture barleys were surprisingly similar and dominated by Gammaproteobacteria. Damaging barley just prior to malting lead to remarkable decreases in wort filtration performances. The indigenous bacteria embedded in amorphous slime colonised the exposed endosperm during malting. 12 % of damaged grains decreased the amount of separated wort up to 25 % with over 10 % lower extract yields. The abundance of Leuconostoc and its bacterial polysaccharides was the main potential reason for the decreased filtration performances. The wort filtration rate was significantly improved by suppressing the bacterial growth during malting: up to 90 % of the wort could be separated in only 15 minutes of Bücher filtration. L. plantarum added as a starter culture showed great potential to inhibit the growth of all the biofilm-forming bacteria in malting and thus improve the already good filtration performance. Bacterial biofilms proved to be one of the key factors influencing wort separation.
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    Heraproteiinien funktionaaliset ominaisuudet, erottaminen ja käyttö
    (2013-04-21) Manninen, Jenny; Lehtikari, Leena; Kemiantekniikan korkeakoulu; Fabricius, Gunilla