Our cake quality varies when we change from one type of oven to another even when the ovens register the same temperature
Ovens, even those of the same make and model, vary in their ability to deliver heat to the product. The temperature setting indicated on dials or displays are indications of the actual air temperature rather than a measure of the heat available for baking.
During baking heat is transferred to the product in one of three ways:
• Convection, the transfer of heat in fluids, achieved by the colder fluid carrying away heat from a hotter surface which sets up convection currents.
• Conduction, the passage of heat through a medium, from hot to cool regions, the heat being passed on from molecule to molecule, e.g. hot pan to cooler bread dough.
• Radiation, the transfer of heat from hot surfaces without the need for a transferring medium, e.g. the heat we receive from the sun.
Ovens used in bakeries use all three heat transfer mechanisms though the balance between the three varies with oven type. For example, in a deck oven conducted and radiant heat dominate, while in a rack oven convection and to a lesser extent radiation dominate.
The thermostat fitted to an oven senses and controls the temperature of the oven by calling for more or less heat accordingly. Occasionally this may be at fault and may not be working accurately or may be controlling the temperature at a point that does not coincide with the position of the cakes in the oven. For specific temperature settings in your oven it is advisable to bake the products at several different temperatures to find the ideal settings for your oven. You should try to make sure that the oven has a reasonably similar load for each trial otherwise you will get variable results. Try adjusting temperatures in 5 °C steps, above and below your current settings, so as to avoid making products that would not be acceptable for sale.
It would be wise to check that a consistent temperature is being delivered for consecutive bakes in case you have a problem with burners or heating elements. You may find that the oven is not fully recovering its heat load between bakes of successive batches. If this is the case you should consult your equipment supplier. On the other hand it may be that the time between bakes is so long that ' flash' heat builds up in the oven. This is associated with the radiant heating component in the oven and often leads to burning of the product crust. Since most products are baked to a particular colour and shape, the temptation in these circumstances is to lower the oven temperature for the next bake. You should avoid this if possible. If you are about to use an oven that has been standing empty but heating for a period of time and you suspect there may be problems with flash heat, we suggest that you inject a burst of steam into the chamber. The evaporation of the water will remove some of the excess heat and readily escapes when you open the oven door or damper. If you use the latter remember to close it again when you load the product into the oven otherwise you could end up drying the product out unnecessarily.
Variations in oven humidity can also lead to variability for some products. For example, Swiss rolls benefit from humidity in the oven as the water vapour keeps the crust moist and so aids the rolling process post-baking.
While your problem is associated with cakes you might like to note that the same rules will apply to almost all baked products.
10.24 We are encountering an intermittent fault with our round high-ratio cakes in that a shiny ring with a pitted appearance is seen on the cake surface. What factors are likely to give rise to this fault?
This fault is caused by the batter viscosity being too low during the early stages of baking. As the product is heated the viscosity of the batter helps to trap the gases produced by the raising agents. If the batter is too fluid, i.e. low in viscosity, then the structure, which is not set, allows gases to escape and these burst through the forming crust, leaving behind the pitted surface appearance.
The shine on the ring suggests that the sugar level in the recipe is too high. High levels of sugar delay the gelatinisation of the starch and so the batter is kept fluid for longer.
An increase in viscosity can be achieved in any of the following ways:
• Reduce the water content of the batter.
• Increase the flour-damaged starch. Damaged starch will hold more water, thus making the batter more viscous.
• Extend the mixing time but avoid over-mixing.
• Reduce the recipe sugar level.
Continue reading here: How important is the temperature of cakes at the point of wrapping
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