Gert de Rouck
KU Leuven, Belgium

SUROWCE I TECHNOLOGIE
Słowa kluczowe: oak wood, maturation, wood extract

Introduction

Wine and spirits are frequently matured in oak wood barrels and this practice is gaining popularity in the brewing industry. Nowadays, oak wood extracts are commercially available and are very promising as an alternative for conventional flavouring in barrels. In this study, the impact of advanced beer flavouring with oak wood extracts on the final flavour characteristics, colloidal and foam stability of the resulting beers was investigated.

Materials and methods

A top fermented beer was produced on a 5 hl scale and six different oak wood extracts were added during maturation at 0.4 g/L: French and American oak (toasted/not toasted), a high vanillin and a high whisky lactone extract. After filtration and packaging, standard beer analyses and sensory evaluations were performed.

Results and discussion

Adding oak wood extracts during beer maturation resulted in a lower protein content, decreased foam stability and improved colloidal stability. The flavour intensity of beers matured with French oak extract is considerably lower compared to beers matured with American oak extract. In contrast to untoasted French oak and toasted French oak extracts, the differences between American toasted and untoasted oak extracts were very clear. Vanilla and coconut aromas were clearly detected in beer matured with toasted American oak extract. Strong vanilla impressions were also found when using high vanillin extract. The extract rich in whiskey lactones resulted in beers with a flavour reminiscent of whiskey barrels.

Conclusions

Advanced flavouring using oak wood extracts during maturation is a valuable alternative to introduce specific woody flavours in specialty beers. Depending on the type of extract, beers were produced with pleasant and distinct vanilla, coconut, woody, or whiskey-barrel-like flavour characteristics.