The Great Bread Debate - 🍞 Toast vs. Microwave

When it comes to sourdough bread, one of the things that sets it apart from other types of bread is the presence of beneficial bacteria. These bacteria, known as lactobacilli, are responsible for the fermentation process that gives sourdough its unique flavor and texture. But what happens to these bacteria when you toast or microwave your sourdough bread? Let's find out!

Toasting Sourdoough Bread:

When you toast sourdough bread, the heat does have an effect on the bacteria present in the bread. The high temperatures can cause some of the bacteria to die off, but not all of them. While some lactobacilli may be destroyed during the toasting process, there will still be a significant number of bacteria left in the bread. So, even though toasting may reduce the overall number of bacteria, it doesn't completely eliminate them.

Microwaving Sourdoough Bread:

Microwaving sourdough bread is a different story. The intense heat generated by the microwave can have a more significant impact on the bacteria. The heat can kill off a larger portion of the lactobacilli, resulting in a greater reduction in the number of beneficial bacteria compared to toasting. However, it's important to note that not all bacteria will be destroyed, and some will still remain in the bread.

The Benefits of Sourdough Bacteria:

Now, you might be wondering why these bacteria are so important in the first place. Well, lactobacilli offer several health benefits. They help to break down the complex carbohydrates in the bread, making it easier for our bodies to digest. This can be especially beneficial for individuals with digestive issues or sensitivities to gluten. Additionally, the bacteria produce lactic acid, which helps to lower the bread's glycemic index, making it a better option for those watching their blood sugar levels.

How to Preserve the Beneficial Bacteria:

If you're concerned about preserving the beneficial bacteria in your sourdough bread, there are a few things you can do. First, avoid toasting or microwaving your bread at high temperatures for extended periods of time. Instead, opt for a lower heat setting or a shorter cooking time. This will help to minimize the impact on the bacteria. Additionally, storing your bread properly can also help to preserve the bacteria. Keep your sourdough bread in a cool, dry place, and avoid exposing it to excessive heat or moisture.


While toasting or microwaving sourdough bread may reduce the number of beneficial bacteria present, it doesn't completely eliminate them. There will still be a significant amount of lactobacilli left in the bread, providing some health benefits. To preserve the bacteria, opt for lower heat settings and shorter cooking times when toasting or microwaving your bread. And remember, proper storage is key to maintaining the health of your sourdough bread. Enjoy your delicious and nutritious sourdough treats!

Samantha Dougherty
baking, traveling, photography, gardening

Samantha Dougherty is a professional baker and sourdough enthusiast with over 15 years of experience. She has traveled the world to learn about different sourdough techniques and has a passion for sharing her knowledge with others. Samantha is also the author of the bestselling cookbook, 'Sourdough Delights: A World of Flavorful Breads and Treats'.