Sourdough bread that has a hard crust or a gummy crumb is difficult to be cut cleanly because the hard crust and gummy crumb resists the slicing motion of the knife. Hard crusts and gummy crumb can be avoided by allowing your sourdough bread to be cooled to 32 – 43 Celcius prior to cutting.
How does proper cooling help with producing the cleanest cuts?
As the hot baked loaf leaves the oven, the crust of the loaf is still dry and hard from all the moisture loss during baking, while the crumb of the loaf is still gummy as the starch molecules in the crumb are still in a swollen water-logged state.
If we slice the sourdough bread immediately after it is removed from the oven, we will find that it is difficult to drive the knife through the hard crust. Even when we get past the hard crust, the crumb of the baked loaf will be gummy and gooey, sticking to your knife and causing the slices to be uneven and jagged.
As sourdough bread cools, the hard crusts softens, and the gummy crumb dries out which makes it much easier to produce an even and clean cut.
During cooling, moisture from the swollen, water-logged starch molecules begin to dissipate out of the crumb and into the crust; this is made possible by the moisture gradient between the crust and the crumb – the crust has a lower moisture content than the crumb of the baked loaf.
As water leaves the swollen water-logged starch molecules, the starches undergoes starch retrogradation where it reverts back into a solid crystaline state that is dry, hard and not gummy. The water from the starches then gets absorbed by the crust due to the moisture gradient, which softens the crust considerably.
Proper cooling is essential to allow the moisture in the baked loaf to stabilize, enabling the crust to soften and the crumb to dry out which makes for a clean and effortless slicing of your sourdough bread.
How to know if sourdough bread has been sufficiently cooled?
The best way to determine if your sourdough bread has sufficiently cooled is to use a digital cooking thermometer to monitor its internal temperature; cooling is completed when the internal temperature of your baked loaf has dropped to 32 – 43 Celcius.
At this temperature, moisture in the baked loaf has enough time to sufficiently stabilize.
If you have made an initial cut of the loaf only to find that the crust is still too hard and the crumb too gummy to produce a clean cut, re-wrap the baked loaf to prevent excessive moisture loss, and allow it to cool further before cutting the loaf again.
When to cut open your sourdough bread if you do not own a digital thermometer?
If you do not own a digital thermometer, we can still determine if your sourdough bread has sufficiently cooled, by using time as an indicator. The appropriate cooling time for sourdough bread is dependent on the loaf size, the loaf shape, the room temperature, and the type of flour that you use.
A round sourdough bread of 500g, made with wheat flour, and cooled in a room temperature of 25 Celcius, takes approximately 5 hours to cool. We will use this as a reference point to determine the appropriate cooling times for the different types of sourdough bread below.
- Loaf size – the bigger and heavier the loaf, the longer it takes for it to cool down as the greater mass in the loaf looses heat at a slower pace. Add one hour of cooling time for every additional 100g of weight; if your sourdough is 600g, it will take 6 hours to cool.
- Loaf shape – a long shaped sourdough bread such as the baguette takes a shorter time to cool compared to a round loaf of the same weight, as there are more surface area in a long shaped loaf which causes the loaf to lose heat at a faster rate. Subtract one hour of cooling time if your sourdough is shaped into a long oval shape.
- Room temperature – it takes a shorter time to cool a loaf in a colder room as heat is absorbed by the colder room at a faster rate due to a bigger difference in temperature between the cold room and the hot baked loaf. Reduce one hour of cooling time for every 5 Celcius decrease in room temperature; if room temperature is 20 Celcius, it takes 4 hours to cool.
- Type of flour – flour with a lower protein content contains more starches which are able to hold a lot more moisture and hence requires a longer cooling time for the moisture to dissipate to prevent a gummy crumb. Rye bread for example has a much lower protein content than wheat flour, and requires a cooling time of 24 – 48 hours.
Proper cutting technique for the cleanest and most even slices
1. Use a deep serrated bread knife
The most important tip to making a clean cut on a baked loaf is to use a deep serrated blade as it allows us to saw through the hard crust, and to gently and easily severe the elastic and moist crumb structure in the loaf.
If you are using a smooth blade without any serration, it is still possible to cut through the bread but the cuts wont be clean. The crust is likely to chip, and the elastic crumb will be difficult to cut using the smooth blade causing you to apply additional downward force on the blade, resulting in a jagged cut of the crumb.
2. Do not push down on the knife
A common mistake when slicing through a sourdough bread is to apply too much downward force onto the knife. The serrated blade works best when you are using a forward and backward sawing motion.
The sawing motion and the serrated blade allows the loaf to be cut without too much downward pressure, hence the loaf does not deform during cutting, which will result in an even slice. Take your time on each slice with as many gentle back and forth sawing motion as you need.
3. Keep the knife parallel to the cutting board
Angle the knife such that it is parallel to your cutting board. When the knife is parallel to the cutting board, there is even pressure that is applied on the front and back of the knife, allowing better control of the blade to produce cleaner cuts.
