Abstract 118
Recent discoveries in beer foam
J. Amer. Soc. Brew. Chem. 72 (2): 79-87, 2014.
K.J. Siebert
Combinations of ovalbumen, isoalpha acid, and ethanol were prepared in buffers of different pH and foamed. A response surface model of foam height was constructed (R2 = 0.876). This indicated that intermediate ethanol levels lead to the best foam, with poorer foam at higher and lower ethanol contents, and that increasing pH led to poorer foam. When ethanol was added to non-alcoholic beer the effect on foam was somewhat similar to the model system. When a lager was adjusted in pH, the foam increased with increasing pH, opposite to the model system. Dimethyl formamide, dioxane and NaCl solution were each added to the model system and beer. Salt greatly reduced foam in the model system, indicating mainly ionic interaction. DMF caused the largest reduction in commercial beer foam, indicating a hydrogen bonding mechanism. Barley lipid transfer protein 1 (LTP1) and proteins Z4 and Z7 have been associated with beer foam. Ovalbumen has considerable similarity to proteins Z4 and Z7, but is quite different from LTP1. A crude extract of barley LTP1 behaved much like beer in the buffer model system. The results suggest greater involvement of LTP1 than the other two proteins in beer foam.
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