Insufficient cooling causes a gummy crumb
The firm crumb structure of our sourdough bread is made up of gluten and starches. As our freshly baked loaf leaves the oven, the starches are swollen with water and is in a gelatinized state. As the hot loaf cools, the water leaves the gelatinized starches and is absorbed by the dry crust, which causes the starch molecules to dry out and recrystalize, setting itself into a firm crumb structure. This process is known as starch retrogradation.
If we do not allow enough time for our loaf to cool, the water in the swollen starches have not dissipated sufficiently and the starches are still in a gelatinized state which has a gel like consistency. The resulting crumb will be gummy and gooey from the high quantity of gelatinized starches.
Excessive amylase enzymatic activity causes a gummy crumb
Gummy sourdough bread can also be caused by excessive amylase enzymes activity that breaks down too many of the structurally important starch molecules in the crumb of the bread into non-structural simple sugar, imparing the setting of a firm crumb structure, resulting in gumminess.
The crumb of a sourdough bread is made up of the gluten network, starches and simple sugars.
The gluten network gives your bread its strength and contributes to the crumb structure when baked. Similarly starches recrystalizes during cooling, which is hard by nature and also contributes to a firm crumb texture. Simple sugar on the other hand does not contribute to the formation of the crumb structure.
As amylase enzyme activity increases, too many structurally important starch molecules are broken down into simple sugars, reducing the number of starches that would recrystalize and contribute to a firm crumb structure, resulting in gumminess. This is commonly known as ‘starch attack’ in rye breads.
Amylase enzymatic activity is important for fermentation as it breaks down the complex starch molecules into simple sugar which is consumed by yeast and bacteria in the dough to undergo fermentation. Without amylase enzymes, fermentation will be severely impaired.
Amylase enzymatic activity is only menacing when it is present at very high levels. At moderate levels, there would be enough starch molecules left in the dough once baked to recrystalize and set into a firm crumb. When baked and eaten, they produce a moist crumb that melts in your mouth but is not gummy.
Sweet and fruity smelling sourdough is a sign that your bread will turn out gummy
Starches are converted into simple sugars by amylase enzymes that is found naturally in flour. In a well balanced dough, yeast undergoes fermentation at a rate which consumes all or most of these simple sugars, and leaving very little residual simple sugars in the dough at the time of the bake.
When the activity of amylase enzyme is unusually high, there is an accumulation of these sweet smelling simple sugars in the dough. These simple sugar that smell sweet and fruity can be used as an indicator of the rate of amylase enzymatic activity.
If your sourdough smells excessively fruity, it is a sign that amylase enzymatic activity is excessively rampant and your crumb will turn out gummy.
4 Ways to Prevent a Gummy Crumb in Sourdough Bread
To prevent a gummy crumb, we have to ensure that amylase enzymatic activity is kept at a moderate level to prevent excessive decomposition of the structurally important starch molecules, and at the same time sufficient cooling is required to allow the remaining starch molecules to retrograde, which dries out and form a firm crumb structure.
1. Increase acidity of dough through use of higher quantity of pre-ferments
It was discovered that amylase activity comes to a grinding halt in an acidic environment at a pH value of 5 – 3.5 . We can increase the acidity of our sourdough through the use of pre-ferment at more than 30% of total flour. The higher the quantity of pre-ferment that is used in the dough, the more acidic the dough becomes.
Pre-ferments are basically sourdough starters that have been build up with flour and water over 2 – 3 feedings to a desired weight. Typically pre-ferments are called for in the range of 15-20% of the weight of total flour used, but if you find that your sourdough bread is gummy, you can increase the amount of pre-ferment up to 35%. Any higher, the sourdough may be too acidic and tastes too sour.
2. Accelerate bulk fermentation and proofing time
Amylase enzymes starts metabolizing once water is incorporated with the flour. The longer the dough takes to enter the oven and finish baking, the more starch molecules are being broken down by these amylase enzymes.
We can reduce how much starch molecules these amylase enzyme break down by controlling the duration of the baking process. By accelerating the bulk fermentation and proofing time, we can reduce the length of time amylase enzyme remains active, reduce the amount of starch molecules that are broken down and hence reduce the risk of gumminess in the crumb.
3. Ensure oven temperature is accurate
Home ovens are notoriously inaccurate in temperature control; temperature can deviate by as much as 10 – 20 Celcius from the readings that is displayed. The problem comes when you are baking at too low of a temperature.
When the oven temperature is lower than intended, amylase enzymes in the dough remain active for a longer period of time which allows it to breakdown more starch molecules in the dough into simple sugar, releasing all that moisture that the starch was holding back into the dough causing it to be gooey and gummy.
Get yourself an accurate oven thermometer and place it in the oven when it is preheating. Once the oven stop heating up, check to see if the temperature of your oven corresponds to the temperature readings of the oven thermometer.
4. Ensure sufficient cooling
As the baked loaf leaves the hot oven, starch molecules are swollen with water and exists in a gelatinized state which we commonly describe as being gummy. When baked loaf is sliced without sufficient cooling, the crumb of the loaf will be gummy and difficult to slice through.
Cooling is completed when the baked loaf reaches an internal temperature of 32-43 Celcius. If you do not own a digital baking thermometer, you can simply alow your sourdough bread to cool for about 4-5 hours which is usually sufficient for most sourdough bread.
Cooling times is dependent on the size of the loaf, shape of the loaf, the room temperature and the type of flour used. I have written a comprehensive guide which explains how all these factors affect cooling times.
If you would like to learn more, read Proper Cooling to get the Cleanest Cuts on Sourdough Bread.
