---
title: 'Secrets of Sourdough: Science on the SPOT | KQED'
source: 'https://youtube.com/watch?v=y5xOpss4j5E'
video_id: 'y5xOpss4j5E'
date: 2026-06-30
duration_sec: 484
---

# Secrets of Sourdough: Science on the SPOT | KQED

> Source: [Secrets of Sourdough: Science on the SPOT | KQED](https://youtube.com/watch?v=y5xOpss4j5E)

## Summary

This video explores the science and craft behind authentic sourdough bread. Eduardo Morral, founder of Morral's Bread, explains what truly defines sourdough, contrasting it with commercial imitations that use added acids instead of natural fermentation. The video also features insights from a scientist studying the beneficial bacteria, particularly lactobacillus, that create sourdough's unique flavor.

### Key Points

- **Sourdough Defined** [00:00] — Eduardo Morral explains that many breads labeled 'sourdough' are not authentic; they may use added acid rather than natural fermentation. Real sourdough is produced anywhere via natural bacteria and yeast in a starter, resulting in a mild, complex flavor, not just tanginess.
- **The Science of a Sourdough Culture** [01:26] — Eduardo developed an interest in the science of sourdough culture, aiming to return to traditional bread making. A starter is a medium of flour and water where airborne colonize microorganisms, including bacteria and yeast that consume starch and produce gas for rising.
- **Fermentation and Nutrition** [02:10] — Fermentation is a microbial process that makes food more nutritious and digestible. The video highlights lactic acid bacteria, essential for fermented foods like yogurt, cheese, olives, and sourdough bread, which can contain living, beneficial bacteria.
- **Yeast and Bacteria in Sourdough** [03:16] — Sourdough relies on a symbiotic marriage between yeast and bacteria. Unlike baker's yeast (Saccharomyces cerevisiae), sourdough yeast (Candida milleri) works with lactobacillus bacteria (e.g., Lactobacillus sanfranciscensis) to produce acetic acid, giving the bread its sour taste.
- **Baking as Science** [04:25] — Eduardo describes his 15-16 hour baking day as a fusion of physics, biology, and chemistry. He uses wood, flour, water, and salt, and his mixer emulates hand-kneading. The process involves mixing, shaping (about 3 hours), proofing, and baking (3.5 hours).
- **Creativity and Science Intertwined** [06:32] — Eduardo notes that his background in English and science led him to see baking as both creative and scientific. He believes the two disciplines are not mutually exclusive, and he finds beauty in the scientific aspects of bread making.

### Conclusion

Real sourdough is a product of natural fermentation, blending science and craft for a complex flavor. The video shows that authentic sourdough is not merely sour but offers a multidimensional taste.

## Transcript

My name is Eduardo Morral and I'm the founder and owner of
Morral's Bread. I started Morral's Bread back in 2001 along with the with the assistance of my wife who actually was in the bakery with me for the first few years of the business until my daughter was born and it's been 10 years now
that I've been running the business. The idea of sourdough in general can be a little bit confusing to so many people because there are so many breads out there that are labeled sourdough which actually aren't sourdough at all. For a
long time the idea of San Francisco sourdough was just this really sour tasting bread. They didn't have anything to do with natural fermentation. All they were doing was adding some kind of acid to make it this tangy product that
people associated with San Francisco sourdough. The reality of it is that sourdough can be produced anywhere in the world with the bacteria and the yeast and stuff in the sourdough starters and sometimes the natural lemon bread isn't
specifically all that sour. It's a much more mild flavor depending on how much you're fermenting it. I started to develop this interest in the science of a sourdough culture. It was all trying to get back to what bread making has been
for thousands of years. I think that sourdough starters was just the way to do bread up until yeast became commercialized. What starter means to me and what starter is you just take flour and water and you're creating a medium for
these microorganisms that are in the air that we're breathing right now to colonize. They could take a little piece of that dough, mix that into a new dough and that dough would start rising. The bacteria and yeast are doing their job
consuming the starch producing gas for the bread to rise and this is fermentation. It is a form of making food more nutritious and more digestible.
My lab is interested in the beneficial bacteria you find in foods and in our gastrointestinal tracks and a particular we're interested in group of organisms called lactic acid bacteria which are essential for many fermented
plants and dairy foods. Fermented food is actually the result of extensive microbial growth. When you eat yogurt, you're actually eating product made by bacteria in which probably still contains a high amount of living bacteria which
are perfectly harmless and sometimes even helpful. Fermented foods include sausage, salami, cheese, and fermented plant foods like olives and sourdough breads.
Sourdough is really fascinating because it's a marriage between a yeast and a bacteria. There's a difference between the yeast you find in typical supermarket bread and the yeast you find in sourdough bread and supermarket bread just
typically made using baker's yeast or saccharomyces or VCA is able to consume the sugars in the dough for growth. That's different from the yeast you find in sourdough bread, the yeast being Canada, Millerite, and it's dependent on the bacteria you
find in the bread, lactobacillus, sand fans, the senses, or San Francisco for short. To consume the sugar, it's a bit part of it back out and that's what allows the yeast to grow. This lactobacillus species is really only found in
sourdoughs, nowhere else. Like other lactobacillus bacteria produces organic acids as a result of its growth. This particular organism produces a lot of acetic acid, which is vinegar acid. That acid gives the bread a very sour taste.
So my day varies anywhere between 15 to 16 hours. I usually come in the bakery the first thing I do, I start the fire in the oven. And fortunately with the efficiency of these ovens in terms of heat retention, once the fire starts it
goes. I do feel like a scientist sometimes when I bake. I think cooking is you know science to a certain extent. It's taking raw materials. My raw materials being
wood, flour, water, and salt, and you know exerting a force on them. And I start with those things. In 16 hours later I have a complete product, which I can you know then take to the farmer's market and sell to someone. So it's a little bit of
physics, it's a little bit of biology, and that's a little bit of chemistry. It's all rolled into one, no pun intended, with the bread. There's a lot of dough to mix. It'll work that I used to do by hand. I was able to
find the kind of this diving arm mixer that really emulates the way in which bread is hand-needed.
By the time I'm finished mixing and kneading very last dough, the first dough I mixed and kneaded is ready to be shaped. We go through this process of shaping for about three hours.
All the dough is cut and shaped and then I put into the proof box if it's cold in the kitchen. That keeps it warm or not.
As soon as the last doughs are cut and shaped, then the first doughs are ready to go into the oven. Then it's all baking for the next three and a half hours.
I've always been fascinated by science. Both my parents' positions, my brothers you know, as a scientist, and I took science, lots of science classes when I was in college. I was an English major taking all these science classes because I just was
fascinated by that. So it's really interesting that what I do now is both creative and scientific. I don't think that the two are mutually exclusive. I don't think that creativity and science are, you know, these two separate disciplines. I think
they're very much intertwined and I do find the beauty and the creativity and science.
When you taste a bread, it is truly natural that I have a bread. You're like, wow, you know, this isn't just a one-dimensional thing. It's this really round and more kind of
dimensional flavor as opposed to just being sour. A lot of people who say, no, I don't like sour dough. They try my bread and they're just eating it happily and then like, this is sour dough. I'm like, absolutely. This is truly sour dough, real sour dough bread, naturally lemon bread.