Simulation of barrel aging: Effect of stout-type beer maturation with American oak chips pre-soaked in Ruby Port wine

Wood maturation is a traditional process used to modulate the chemical and sensory properties of alcoholic beverages. This study investigated the impact of American oak chips pre-soaked in Ruby Port wine on the maturation of an imperial stout, simulating the effect of barrels with different usage histories. Two conditions were tested: oak chips soaked once (BMOC1) to simulate a first-use barrel and chips soaked three times (BMOC3) to mimic barrels that have undergone multiple uses. Quantitative analyses revealed clear differences in phenolic and volatile composition. After six weeks, BMOC3 showed higher concentrations of key wood-derived phenolics such as vanillic acid, elagic acid, gallocatechin, gallic acid, catechin, eppicathecin, syringaldehyde, and coniferaldehyde, while BMOC1 presented higher levels of hydroxybenzoic acid, protocatechuic acid, and epigallocatechin gallate. In the volatile profile, compounds characteristic of oak maturation, including whiskey lactones and eugenol, were detected only in the oak-treated beers. Aditionally, several esters (ethyl butanoate, ethyl-3-methylbutanoate, ethyl lactate, ethyl decanoate, ethyl phenylacetate, ethyl-3-phenylpropanoate), volatile phenols (4-ethylguaiacol and 4-ethylphenol), citral, and multiple sesquiterpenes (β-caryophyllene, α-humulene, α-muurolene, and α-calacorene) exhibited increased concentrations in BMOC3 after six weeks of maturation. Although the sensory panel described tendencies consistent with the chemical data (e.g., fruity and woody notes in BMOC1, vanilla and coconut nuances in BMOC3), the sensory ANOVA did not reveal statistically significant differences among treatments. Therefore, the sensory results should be interpreted as descriptive trends rather than demonstrable improvements. This approach provides craft brewers with a cost-effective method to introduce barrel-aged characteristics without the need for full-sized barrels, allowing for greater control over the maturation process and flavour development.