Role of Beer Lipid-Binding Proteins in Preventing Lipid Destabilization of Foam

Abstract

The negative effect of fatty acids on the foam stability of beer has been assessed. Long-chain fatty acids are far more damaging than short-chain fatty acids on the foam stability of beer at the concentrations employed. Polypeptides have been isolated from an all malt beer by hydrophobic interaction chromatography. Using this technique five groups of polypeptides were isolated, group 1 being the least hydrophobic and group 5 the most hydrophobic, all of which exhibited similar polypeptide compositions by SDS-PAGE. All five hydrophobic polypeptide groups bound [(14)C]linoleic acid; however, group 5, the most hydrophobic group, bound the most linoleic acid. Groups 1 and 5 were titrated with cis-parinaric acid (CPA) to produce binding curves, which were compared with a binding curve obtained for bovine serum albumin (BSA). Groups 1 and 5 both produced binding curves that saturated at approximately 5.5 microM and 4 microM CPA and had association constants (K(a)) of 6.27 x 10(7) and 1.62 x 10(7) M(-1), respectively. In comparison, BSA produced a binding curve that saturated at 6 microM CPA and had a K(a) of 3.95 x 10(7) M(-1). Further investigation has shown that group 1 is pH sensitive and group 5 pH insensitive with respect to lipid binding. The lipid-binding activity of group 5 was also shown to be unaffected by ethanol concentration. Linoleic acid (5 microM) when added to beer resulted in unstable foam. Group 5 was added to the lipid-damaged beer and was shown to restore the foam stability to values that were obtained for the control beer. It has therefore been demonstrated that proteins isolated from beer have a lipid-binding capacity and that they can convey a degree of protection against lipid-induced foam destabilization.

Polipeptídeos e proteínas com influência na qualidade da espuma da cerveja e métodos analíticos utilizados no seu estudo

“…A adição destas proteínas exógenas, à cerveja, atenua o efeito negativo dos lípidos sobre a espuma da mesma 40 . Pensa-se que as puroindolinas do trigo se ligam aos lípidos livres, impedindo assim a destabilização da espuma 40,41 . No entanto, a informação disponível acerca deste grupo de proteínas é reduzida.…”

“…Uma vez que a SDS-PAGE separa as proteínas segundo o seu peso molecular, é muitas vezes utilizada na caracterização dos polipeptídeos e proteínas da cerveja 5,19,38,41,45,46 e da espuma 5,11,25,27,29 , assim como dos seus percursores da cevada e do malte 34 . A caracterização destas biomoléculas pode ainda ser complementada com a determinação dos pontos isoeléctricos, utilizando a focagem isoeléctrica (IEF) 21,22,47 .…”

Characterisation of sparkling cider by the yeast type used in taking foam on the basis of polypeptide content and foam characteristics

“…The presence of polysaccharide-polypeptide complexes at the protein isoelectric point improves foam stability, since interactions increase and electrostatic repulsions decrease, thus facilitating the formation of a viscoelastic film that reduces drainage of the liquid film. Moreover, the effect of foam-negative materials such as fatty acids may be inhibited by various proteins isolated from beer which can bind lipids and improve foam stabilization (Cooper, Husband, Mills, & Wilde, 2002). On the other hand, Mangas, Moreno, Rodríguez, Picinelli, and Suárez (1999) reported the effect of methanol (a molecule linked to pectic substances in apples) and acidic polysaccharides on cider foam stability, which could be related to an increase in viscosity that reduces drainage of the liquid film (Prins, 1988), and also indirectly reduces the degree of disproportionation of bubbles (Ostwald ripening) (Bamforth, 2004).…”

Prediction of beer foam stability from malt components

“…Furthermore, Bamforth and Milani (2004) demonstrated that the beer foam stability is dependant not only on the level of the individual foam-promoting polypeptides but also on the balance between the polypeptides derived from albumins and hordeins. However, malt is not the source of proteins, only but also of other foam-positive and foam-negative components, such as β-glucan, melanoidins, polyphenols, and lipids (Lusk et al 1995;Dickie et al 2001;Cooper et al 2002;Evans & Sheehan 2002). It is commonly known that lipids damage the beer foam (Dickie et al 2001;Cooper et al 2002;Van Nierop et al 2004).…”

“…However, malt is not the source of proteins, only but also of other foam-positive and foam-negative components, such as β-glucan, melanoidins, polyphenols, and lipids (Lusk et al 1995;Dickie et al 2001;Cooper et al 2002;Evans & Sheehan 2002). It is commonly known that lipids damage the beer foam (Dickie et al 2001;Cooper et al 2002;Van Nierop et al 2004). By now the data have not been conclusive in identifying the roles of other malt factors in producing stable beer foam.…”