Flour 101 for Sourdough Bakers

Sourdough baking starts with three things: flour, water, and salt. But flour, humble as it may seem is where the magic (or the frustration) begins. Whether you're just getting into sourdough or you're deep into hydration tweaks and starter rituals, understanding your flour is essential.

In this deep dive, we’ll break down:

• The different types of wheat flour (and some non-wheat options) 

• How the milling process affects flavor, nutrition, and fermentation 

• Organic vs. conventional 

• What to buy based on your baking goals 

• Amazon affiliate links for my go-to flours (🛒)

This post contains affiliate links, meaning I may earn a small commission at no extra cost to you if you purchase through these links.   

🌾 The Milling Process: Where It All Begins

⚙️ Roller-Milled Flour

Most supermarket flour (even high-end brands) is roller-milled.

How it works: Grain is crushed between steel rollers and sifted, often removing the bran and germ unless labeled “whole wheat.”

Pros:

• Very consistent and shelf-stable 

• Ideal for soft, airy crumb

• Widely available 

Cons:

• Less flavor complexity 

• Lower micronutrient and fiber content (unless whole grain) 

🛒 King Arthur Bread Flour🛒 Central Milling Artisan Baker's Craft

🪨 Stone-Milled Flour

Stone-milling grinds grain slowly between two large stones.

Why bakers love it:It keeps all parts of the grain—endosperm, bran, and germ—intact, which means:

• Full flavor and aroma 

• Faster fermentation due to active enzymes 

• Higher nutrition (more fiber, B vitamins, healthy fats)

Downside: Shorter shelf life. The oils in the germ can go rancid if not stored properly.

🛒 Bob's Red Mill Whole Wheat Flour (Stone-Ground)

🧬 What’s Actually In Your Flour?

Each kernel of wheat contains:

• Endosperm – mostly starch and protein (what white flour is made from) 

• Bran – fiber and minerals 

• Germ – healthy fats, B vitamins, enzymes 

👉 White flour = endosperm only👉 Whole grain flour = all parts of the grain👉 Sifted whole grain flour = some bran removed for better performance but keeps flavor/nutrition.

🔍 Choosing the Right Flour for Sourdough

Let’s break down the most common flours by protein level, fermentation behavior, and ideal uses:

🍞 Bread Flour (12–13% protein)

Best for:

• Tall boules or batards 

• Open crumb, strong gluten structure 

• Long fermentation and cold proofing 

Behavior: Holds shape well during long fermentation. Higher gluten = stronger, chewier bread.

🛒 King Arthur Bread Flour

🛒 Central Milling Organic Bread Flour

🌿 All-Purpose Flour (10–11.5% protein)

Best for:

• Beginners 

• Softer crusts or sandwich-style loaves 

• Blending with whole grain flour 

Behavior: Ferments easily and gives a nice, mild sour flavor, but can spread more in high-hydration doughs.

🛒 Gold Medal Unbleached AP Flour

🌾 Whole Wheat Flour (13–14% protein)

Best for:

• Heartier loaves 

• Adding flavor complexity 

• Feeding your starter 

Behavior: More enzymes = faster fermentation. Absorbs more water (soaks up hydration). Can lead to denser loaves if not mixed with white flour.

🛒 King Arthur Whole Wheat Flour

🌾 Rye Flour (6–9% protein, but high in fermentable sugars)

Best for:

• Very active starters 

• Dense or Northern European-style breads 

• Flavor depth 

Behavior: Low gluten but high enzyme activity = rapid fermentation. Dough can be sticky and slack. Often used in small percentages in wheat breads or as the sole flour in traditional rye loaves.

🛒 Bob’s Red Mill Organic Dark Rye

🧑‍🌾 Ancient Grains: Spelt, Einkorn, Emmer, Kamut

Why use them?

• Nutty, rich flavor 

• Potentially easier to digest for some people 

• Adds variety and nutrition 

Caution: These flours are lower in gluten and tend to behave differently in fermentation—more delicate, prone to tearing, and better suited to blends unless you’re aiming for a dense crumb.

🛒 Jovial Einkorn Flour

🛒 Bob’s Red Mill Spelt Flour

🧂 Bonus: Bleached vs. Unbleached

Always go unbleached for sourdough. Bleaching agents (like benzoyl peroxide or chlorine) can interfere with fermentation and gluten development. Unbleached flour is naturally aged and has better fermentation behavior.

🛒 King Arthur Unbleached All-Purpose

🏷️ Organic vs. Conventional: Does It Matter?

Here’s the short answer: It depends on your priorities.

Organic Pros:

• No synthetic pesticides or fertilizers 

• Often milled slower or in smaller batches

• May retain more enzymatic activity 

Cons:

• Higher price tag 

• Not always more nutritious (especially with white flour) 

What really matters more is the milling method and freshness of the flour—whether it’s organic or not.

🛒 Central Milling Organic Bread Flour

🥖 How I Choose My Flours for Sourdough

👩‍🍳 Final Tips

• Store stone-ground or whole grain flours in the fridge or freezer for longevity. 

• Always check the milling date if you can—fresh flour makes a big difference. 

• Keep a “flour journal” to track how different blends affect your bakes! 

❤️ Want to See These in Action?

Follow along on Instagram where I bake with everything from supermarket staples to fresh-milled rye and share what works (and what definitely doesn’t). And as always, happy baking!