What is Bread Cooling?
Bread cooling is an integral part of high-speed bread production. Bread has to cool before slicing and packaging. Otherwise, the crumb will be warm and gummy. Not only does this cause a problem at the slicer, gumming up the blades and creating downtime cleaning, it also leaves an undesirable moisture condensation inside the package.
Before you speed up or slow down your cooling towers, determine if you have the right conditions for cooling.
During the cooling process, the baked bread loses moisture, dries out and intensifies in flavor. The starches in the loaf start retrogradating, helping setting the crumb texture. The temperature gradient between the crust and the crumb becomes zero with progressive cooling. Depending on the size and shape of the loaf, it may take up to 2 hours for the bread to completely cool. This is critical, as most bakers tend to prolong this process with excessive moisture loss. Using the conditions stated below would help prevent this.
The internal temperature of the bread out of the oven is around 95º C (203º F), and the crust is somewhere around between 150º C (302º F) to 180º C (356 o F).
The internal temperature should be reduced to 35 – 40º C (95 – 104º F) at the end of the cooling cycle. This could be achieved with an external air temperature of 24º C (75º F) and a relative humidity of 85%, with an air movement to produce a 11.1º C (50º F) increase at the exhaust point.
Bread is normally packaged at the legal limit of 38% moisture. A proper cooling method can avoid microbiological spoilage. These are three cooling methods:
- Convection: the simplest method and the most prevalent, though it does not provide accurate control of moisture loss by the cooling loaf.
- Conditioned air: has dry-bulb and wet-bulb temperatures control that will produce effective loaf cooling within 90 minutes.
- Vacuum: accelerates the vaporization of free moisture from the product and loss of the latent heat of vaporization. It’s a rapid method that is suitable for products that are unstable and prone to collapse before they cool.