Tang in sourdough comes from organic acids produced during the long, mixed fermentation carried out by lactic acid bacteria and yeasts. Lactic acid gives a gentle acidity while acetic acid delivers the sharper, vinegar-like note; their balance changes with the strains present and the fermentation environment. Marco Gobbetti at the University of Bari has synthesized decades of microbiology and biochemistry showing that heterofermentative lactobacilli convert sugars into both lactic and acetic acids, and that their metabolic pathways shift according to available carbohydrates and redox conditions. Ilenia Cocolin at the University of Turin has demonstrated through molecular analyses that each starter culture develops a characteristic consortium of Lactobacillus species and Saccharomyces or non-Saccharomyces yeasts that together shape the acid profile and aromatic volatiles of the dough.
Microbial ecology and process control
Interactions among microorganisms, dough hydration, temperature and salt produce the sensory fingerprint of a sourdough loaf. Michael Gänzle at the University of Alberta has described how lower fermentation temperatures and higher hydration favor acetic acid formation by promoting heterofermentative metabolism, while warmer and faster fermentations favor lactic acid. Bakers who maintain cool, slow fermentations tend to cultivate a tangier crumb. The presence of specific bacteria such as Lactobacillus sanfranciscensis, historically associated with certain regional traditions, also contributes distinctive acid and aroma metabolites tied to local microbial heritage.
Cultural, nutritional and territorial impacts
The tang of sourdough is not merely a flavor note; it reflects cultural practices and influences shelf life, texture and nutrition. Traditional starters carried across generations embed local flour microbiota and milling practices, creating territorial signatures found in communities from San Francisco to European villages. Research compiled by Marco Gobbetti at the University of Bari and investigations by Ilenia Cocolin at the University of Turin link prolonged lactic fermentation to slower starch gelatinization and changes in protein structure that can affect digestibility and preservation. For bakers and consumers the tang signals a living process, one shaped by microbial ecology, regional ingredients and deliberate choices about time and temperature, and it is these combined factors that make sourdough uniquely variable and culturally resonant.
