What Is Lactic Acid?

The Glossary

18 Jan

The Definition

Lactic acid is an organic acid produced by Lactic Acid Bacteria (LAB) during the fermentation of carbohydrates. It is responsible for the mild, creamy, yogurt-like acidity in sourdough bread. It lowers the pH of the dough, activating enzymes and extending shelf-life by inhibiting mould growth.

The Flavour Profile

Lactic acid is less volatile and perceived as "softer" on the palate compared to acetic acid. Maintaining a warmer starter (26°C+, ~79°F) tends to favour homofermentative bacteria that produce primarily lactic acid, resulting in a milder loaf.

Last updated: 6 January, 2026

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31 August 2026

What Is A Lame?

31 August 2026

A lame (pronounced "lahm") is a baker’s tool consisting of a double-edged razor blade mounted on a handle. It is used for "scoring"—slashing the top of the proofed dough just before baking. It is not merely aesthetic; it is a surgical intervention to control expansion.

31 August 2026

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What Is Retarding?

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Phytic acid is a natural substance found in plant seeds, nuts, and grains, and 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.

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7 May 2026

What Is The Float Test?

7 May 2026

The Float Test is a common method used to determine if a sourdough starter or leaven is ready to use. It involves dropping a teaspoon of starter into a glass of water; if it floats, it is deemed "ripe."

7 May 2026

Organic AcidsFlavor ProfileMicrobiologyBacterial Fermentation

The Pact

The Lectin Defense: Fermentation as a Chemical Shield

In the world of diet culture, lectins—specifically Wheat Germ Agglutinin (WGA) found in whole grains—have become a villain. They are accused of binding to the gut lining, causing "Leaky Gut," and triggering systemic inflammation.

Post-Antibiotic Recovery: Rebuilding the Microbiome with Fibre Diversity

A course of broad-spectrum antibiotics is like a forest fire. It burns down the infection, but it also incinerates the "old growth forest" of your beneficial microbiome. Species like Bifidobacterium and Lactobacillus are often collateral damage.

The Retrograde Method: Freezing and Toasting for Maximum Prebiotics

This guide details The Retrograde Method—a specific protocol of cooling, freezing, and toasting designed to manipulate starch crystals. It turns a standard slice of sourdough into a high-performance delivery system for Resistant Starch (Type 3).

Stress Baking Psychology: Mindfulness and Tactile Therapy

"Stress baking" is often dismissed as a quirky coping mechanism or procrastination. But psychologists and occupational therapists view it differently. They see it as a legitimate form of sensory regulation.

Enzymatic Shearing: How Protease Cuts Gluten (The Scissors)

When a baker talks about "strength," they are usually talking about elasticity—the ability of dough to snap back. This is the hallmark of commercial yeast bread. It is rubbery, tight, and resilient. But a sourdough baker looks for something else: Extensibility. The ability to stretch without tearing.

Meet The Yeast: The Sprinter vs. The Marathon Runner

In the world of baking, the word "yeast" is used carelessly. We treat the beige granules in a packet and the wild population in a sourdough starter as if they are the same organism just living at different speeds. They are not.

Sugar Hunters: How Amylase Unlocks the Grain

Microbes are hungry. To survive, they need sugar. But flour is not sugar. It is starch—long, complex chains of glucose molecules locked together in granules. For a yeast cell, a starch granule is like a boulder. It is too big to eat. Before the yeast can feast, someone has to break the rock. This is the job of Amylase.

The Invisible War: Phages

You can see mold. You can smell kahm yeast. But the most lethal predator in your sourdough starter is entirely invisible. They are Bacteriophages (or simply "Phages"). They are viruses that hunt bacteria. And in the dense microbial city of a sourdough culture, they are the apex predators.

Troubleshoot: The "Fool's Crumb"

In the pursuit of the "Instagram Crumb"—that wild, open lattice of air pockets—many bakers fall into a specific trap. You slice the loaf and see massive, cavernous holes. You celebrate. But when you eat it, the bread is heavy, chewy, and dense.

Scoring Mechanics: Functional Expansion vs. Decorative Art

Scoring is the act of creating a controlled weakness in the "skin" of the loaf. Without it, the massive pressure of oven spring will find its own way out, usually rupturing the loaf in an ugly "blowout" at the bottom [1]. There are two types of cuts: Functional and Decorative.

The "Scrapings" Method: Zero Waste Maintenance

Standard sourdough maintenance protocols are inherently wasteful. The classic "1:1:1" feeding ratio—where you discard half your starter to feed the rest—is a relic of a time when flour was cheap and understanding of microbiology was poor. Over the course of a year, a conscientious home baker following these rules will throw away kilograms of high-quality grain.

Tactile Metrics: The Windowpane, The Poke, The Jiggly Test

The only reliable clock is the dough itself. To read it, you must stop looking and start touching. These are the three Tactile Metrics that every sourdough baker must master to judge the invisible biology of the jar.

Red Fife: The Time Capsule

Red Fife is Canada's oldest wheat. Unlike modern "monoculture" wheat, Red Fife is a landrace, meaning there is significant genetic diversity within a single bag of flour. This diversity translates directly to the palate.

Sugar: The Metabolic Accelerant

Sugar is viewed by many purists as a "cheat." But biologically, it is simply high-octane fuel. While flour starch must be broken down by amylase before the yeast can eat it, sugar provides an immediate, ready-to-eat feast.

Milk: The Chemical Softener

Water is neutral. Milk is complex. By swapping water for milk (as in Shokupan or Sandwich Bread), you introduce three new variables: Fat, Protein (Casein), and Sugar (Lactose).

Butter: The Gluten Lubricant

Butter is the bridge between bread and pastry. In small amounts, it softens. In large amounts (like Brioche), it transforms the dough into a foam-like structure that is more air than wheat.

Gas Retention: Why Weak Gluten Networks Leak CO2

You can have the most active starter in the world, pumping out massive amounts of Carbon Dioxide (CO2). But if your dough cannot trap that gas, your bread will be a brick. This is the principle of Gas Retention.

Thermal Death Curves: What Happens at 60°C?

When you slide a loaf into a 250°C oven, you are subjecting the microbial city inside to a rapid climate change. For the first few minutes, the yeast and bacteria actually work faster (the "Oven Spring"). But as the internal temperature rises, they hit a wall. This is the Thermal Death Curve.

Altitude Baking: Adjusting Pressure Variables

At high altitudes, the air pressure is lower. This invisible change alters the behaviour of every gas bubble and water molecule in your dough. To bake successfully, you must adjust your variables to match your environment.

The Ear: The Physics of Differential Expansion

The ear is more than decoration. It is functional physics. It is the visual proof that your loaf expanded to its maximum potential before the crust hardened. To get an ear, you must master the forces of Tension and Differential Expansion.

What Is Lactic Acid?

The Definition

The Flavour Profile

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The Pact: Sourdough Protocols

Explore the science

The Body

The Microbes

The Method

The Ingredients

The Chemistry

Join The Resistance.

They Bake for Aesthetics. We bake for biology 💁‍♀️.

CITIZEN SCIENCE FOR STEWARDS OF SOURDOUGH

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CITIZEN SCIENCE FOR STEWARDS OF SOURDOUGH |

The Pact

The Protocol

The Science

The Glossary

The Resistance

What Is Lactic Acid?

The Definition

The Flavour Profile

What Is Wild Yeast?

What Is Scoring?

Get the app

The Pact: Sourdough Protocols

Explore the science

The Body

The Microbes

The Method

The Ingredients

The Chemistry

Join The Resistance.

They Bake for Aesthetics. We bake for biology 💁‍♀️.

CITIZEN SCIENCE FOR STEWARDS OF SOURDOUGH

|

CITIZEN SCIENCE FOR STEWARDS OF SOURDOUGH | CITIZEN SCIENCE FOR STEWARDS OF SOURDOUGH |

The Pact

The Protocol

The Science

The Glossary

The Resistance

CITIZEN SCIENCE FOR STEWARDS OF SOURDOUGH |