Are microbes at the root of red wine’s peppery flavor?

Terroir—from the French word for soil—describes how local soil, climate, and geography affect the flavor of wine. Research at an Australian vineyard suggests that microbes in the soil make their own important contributions to terroir, changing the flavor of the wines made from the grapes that are grown there (Front. Microbiol. 2019, DOI: 10.3389/fmicb.2019.01607). Australia’s Victoria wine region has a cool climate and produces distinctive peppery wines from the Syrah grape, known locally as Shiraz. This spicy flavor is thanks to the sesquiterpene molecule called rotundone. But rotundone levels vary among vines, even in the same vineyard. Sequencing the DNA of soil microbes from one vineyard, Gupta Vadakattu at the Commonwealth Scientific and Industrial Research Organisation in Urrbrae and coworkers found higher rotundone concentrations in grapes grown in soil that had a high bacterial diversity but low fungal diversity. While it’s not clear exactly how the bacteria are influencing the wine’s rotundone levels and flavor, the researchers suggest that winemakers seeking to make a spicy red may have to care for their soil microbiome as well as their grapevines in future.