What Is Phytic Acid?
The Definition
Phytic acid (inositol hexaphosphate) is a natural substance found in plant seeds, nuts, and grains. It serves as the plant's principal storage form of phosphorus. In human nutrition, it is often termed an "anti-nutrient" because it acts as a strong chelator, binding to minerals like iron, zinc, and calcium and preventing their absorption in the digestive tract.
The Science: The Mineral Lock
A grain kernel is a survival capsule. It locks its nutrients away to ensure they are available for the seed's germination, not for your digestion. Phytic acid is the padlock.
When you eat unfermented grains (like commercial yeast bread), the phytic acid remains intact, binding to minerals in your gut and flushing them out of your body.
The Sourdough Solution
To unlock these minerals, you need a key: an enzyme called phytase.
Wheat has endogenous phytase, but it is dormant at neutral pH.
Lactic Acid Bacteria (LAB) in sourdough produce organic acids that lower the dough's pH to roughly 3.5–4.0.
This acidic environment activates the phytase, which degrades the phytic acid, releasing the iron, zinc, and magnesium for absorption [1].
References
Lopez, H. W., et al. (2001). Prolonged fermentation of whole wheat sourdough reduces phytate level and increases soluble magnesium. Journal of Agricultural and Food Chemistry.
Last updated: 6 January, 2026
Pre-shaping is an intermediate step between bulk fermentation and final shaping. The dough is divided and loosely formed into rounds, then left to rest (bench rest) for 15–30 minutes. This step reorganises the gluten network after the division and creates a smooth "skin" on the dough.