The impact of traditional wheat landraces on lambic beer production is limited.

As defined by law, at least 30 % of the total amount of starch- or carbohydrate-containing raw materials used for the production of Belgian lambic beers should be unmalted wheat, since this is important for the longevity of the lambic beer production process. Whereas lambic beer brewers in the 19th and 20th century depended on local wheat landraces, supplied by the local farmers, they nowadays use modern wheat varieties that are mainly cultivated for their baking quality and available on the global market. However, it could be assumed that lambic beers made with traditional wheat varieties were characterized by different flavor profiles. To know the impact of those wheat varieties on the growing microbiota and metabolites produced throughout a lambic beer production process, three different productions were assessed as a function of fermentation and maturation time. Two of them were performed with a traditional wheat landrace, namely, Witte van Vlaanderen and Limburgse Rode, and one control was performed with current standard wheat. A multiphasic analysis approach revealed that the impact of the wheat variety on the microbiology and metabolome was limited, although some metabolic differences, such as the concentrations of volatile phenolic compounds and esters, could be linked with the use of the Limburgse Rode wheat landrace. However, the most impacting factor remained the spontaneous origin of the prevailing microorganisms and the environmental conditions, such as temperature, pH, and dissolved oxygen concentration, that are encountered during lambic beer production. Finally, this work allowed to discover a new species, namely, Acetobacter zythi.