Foam
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An important aspect of beer quality is the formation of a stable head of foam when the beer is poured. Lipids are considered to be detrimental to beer foam, while hop derived bitter components and proteins originating from barley are important for the formation of foam. The investigation of which proteinaceous compounds in beer are involved in foam formation has been pursued for decades, mainly by fractionation of beer proteins. At the Carlsberg Research Laboratory another approach was taken. Foam was produced from 15 litres of lager beer in a continuous foam tower by a stream of nitrogen gas. Collapsed foam, rather than beer, was used as a basis for the identification of foam-promoting proteins.

By collecting and fractionating beer foam it has been demonstrated that the foam active proteins are found in fractions with a molecular weight higher than 8000. When such purified fractions are recombined in the same ratio as in beer and added to carbonated water, a nice stable head of "beer foam" is formed when this mixture is poured.

Lipid transfer protein 1 (LTP1), a 10 kDa protein of barley origin, has been identified as the major proteinaceous component in beer foam produced in the foam tower. However, the LTP1 which concentrates in foam is a modified form with a higher foam capacity than the barley type. The transformation of barley LTP1 into the more foam-promoting form takes place during wort boiling and involves an unfolding of the three-dimensional structure.

Polyclonal antibodies have been raised against LTP1 from barley and foam, respectively and ELISA assays have been established for both forms. Likewise, immunological assays have been set up for a number of other foam active components. These assays can be used to quantify the foam promoting components in beer and thus provide a tool for diagnosis of foam problems. Furthermore, it may be possible to optimise the foaming characteristics of beer by selecting raw materials with desirable levels of foam precursors or by tailoring the malting and brewing processes.

Publications:
Sørensen, S.B., Bech, L.M., Muldbjerg,M., Beenfeldt,T., Breddam,K.: Barley lipid transfer protein 1 is involved in beer foam formation. MBAA Technical Quarterly, Vol. 30, No. 4, 136-145 (1993)

Bech,L.M.,Vaag,P., Heinemann,B., Breddam, K.: Throughout the brewing process barley lipid transfer protein 1 (LTP1) is transformed into a more foam-promoting form. Proceedings of the European Brewery Convention Congress, Brussels, 561-568 (1995)

 

 

 

 

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