During storage of beer, proanthocyanidins (PA) originating from barley and hops form precipitates with proteins. This haze development is normally avoided by using different methods for stabilising the finished beer to ensure a brilliant look and long shelf-life of the product. A similar or even better haze stability of the beer can be obtained by the use of PA-free malt.

Proanthocyanidins belong to the flavonoid group of polyphenols and occur in the testa layer of the grains of all traditional barley varieties. PA-free barley was unknown until 1974, when the first PA-free barley mutant was detected at the Carlsberg Laboratory. Beer brewed with malt from this mutant has a dramatically improved haze stability.

Intensive efforts have been made to breed PA-free malting barley varieties at Carlsberg Plant Breeding. The breeding program has been based on chemically induced mutations in the pathway of proanthocyanidin biosynthesis.

Yield performance and disease resistance of the PA-free barley lines have improved a lot in recent years and PA-free varieties are now comparable with the traditional malting barley varieties on the market.

Extensive malting and brewing trials in production scale, especially with the PA-free variety Caminant, have shown that PA-free barley can be malted and brewed to meet the breweries´ quality specifications. The haze stability of unstabilized PA-free beers has been excellent and it is possible to mix PA-free and traditional malt in the proportions 1:1 and still obtain a beer with satisfactory haze stability without technical stabilization.

Proanthocyanidin-free barley varieties on national variety lists in 2001.

1. Chamant (Denmark)
2. Prominant (Denmark)

Publications.

1. Wettstein, D. von, Jende-Strid, B., Ahrenst-Larsen, B. and J.A. Sørensen (1977). Biochemical mutant in barley renders chemical stabilization of beer superfluous. Carlsberg Res. Commun. 42:341-351.
2. Wettstein, D. von, Nilan, R., Ahrenst-Larsen, B., Erdal, K., Ingversen, J., Jende-Strid, B., Kristiansen, K.N., Larsen, J., Outtrup, H. and S.E. Ullrich (1985). Proanthocyanidin-free barley for brewing: Progress in breeding for high yield and research tool in polyphenol chemistry. MBAA Tech. Q. 22:41-52.
3. Erdal, K. (1986) Proanthocyanidin-free barley – Malting and brewing. J. Inst. Brew. 92: 220-224.
4. Jende-Strid, B. (1997). Proanthocyanidin-free barley – A solution of the beer haze problem. Proceedings of the European Brewery Convention Congress, Maastricht 1997, 101-106.

Proanthocyanidin-containing and proanthocyanidin-free barley kernels, stained with vanillin-HCL The red colouring indicates the presence of proanthocyanidin.