title: Impact of different wort boiling temperatures on the beer foam stabilizing properties of lipid transfer protein 1.
abstract: Beer consumers demand satisfactory and consistent foam stability; thus, it is a high priority for brewers. Beer foam is stabilized by the interaction between certain beer proteins, including lipid transfer protein 1 (LTP1), and isomerized hop alpha-acids, but destabilized by lipids. In this study it was shown that the wort boiling temperature during the brewing process was critical in determining the final beer LTP1 content and conformation. LTP1 levels during brewing were measured by an LTP1 ELISA, using antinative barley LTP1 polyclonal antibodies. It was observed that the higher wort boiling temperatures ( approximately 102 degrees C), resulting from low altitude at sea level, reduced the final beer LTP1 level to 2-3 microg/mL, whereas the lower wort boiling temperatures ( approximately 96 degrees C), resulting from higher altitudes (1800 m), produced LTP1 levels between 17 and 35 microg/mL. Low levels of LTP1 in combination with elevated levels of free fatty acids (FFA) resulted in poor foam stability, whereas beer produced with low levels of LTP1 and FFA had satisfactory foam stability. Previous studies indicated the need for LTP1 denaturing to improve its foam stabilizing properties. However, the results presented here show that LTP1 denaturation reduces its ability to act as a binding protein for foam-damaging FFA. These investigations suggest that wort boiling temperature is an important factor in determining the level and conformation of LTP1, thereby favoring satisfactory beer foam stability.
authors.affiliation: The South African Breweries Ltd., Sandton, South Africa. sandra.vannierop@sabreweries.com
authors.forename: Sandra N E
authors.initials: SN
authors.lastname: Van Nierop
authors.forename: David E
authors.initials: DE
authors.lastname: Evans
authors.forename: Barry C
authors.initials: BC
authors.lastname: Axcell
authors.forename: Ian C
authors.initials: IC
authors.lastname: Cantrell
authors.forename: Marina
authors.initials: M
authors.lastname: Rautenbach
mesh_terms: D000531:Altitude; D001515:Beer / Q000032:analysis*; D002352:Carrier Proteins / Q000032:analysis / Q000737:chemistry*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D050556:Fatty Acid-Binding Proteins; D005230:Fatty Acids, Nonesterified / Q000032:analysis; D005511:Food Handling / Q000379:methods*; D006358:Hot Temperature; D011487:Protein Conformation
chemical_list: D002352:Carrier Proteins; D050556:Fatty Acid-Binding Proteins; D005230:Fatty Acids, Nonesterified; C422456:Ltp1 protein, barley