technology to optimize baking processes
The way heat transfer takes place drives completely different results on baked goods. The peculiarities of each baked good, throughput requirements, the way consumers perceive the quality of baked goods, sales regulations and sales margins require bakers to pay careful attention when select baking technologies so the balance among conduction, convection and radiation can be properly adjusted to meet market demand.
Out of the three heat transfer modes, convection technologies are relatively easy and cheap to implement in bakery machinery. While convection drives moisture out from dough surface and leads to an even coloring of dough pieces, dough checking due to moisture gradient from dough core to surface is a possibility.
Radiation baking is another opportunity for bakers. While heat transfer rates are correlated to the temperature of the heat source and to the distance between the heat source and the baked goods, any element in a baking chamber contributes to infrared radiation. The high penetrating capabilities of electromagnetic waves, which can easily reach the core of baked goods thus contributing to oven spring, is another upside of radiation baking.
Conduction also contributes to oven spring and development of structure through heat transfer directly to the base of dough pieces, and its effects on products can be optimized through proper steel band design and control of steel band temperatures at the oven infeed.
Several objective parameters may be used to define quality in baked goods. Not all parameters come into play at the same time, which means the definition of quality may differ slightly depending on the baked good itself. Oven spring, crust thickness and alveolation are three parameters strictly correlated to quality, and this is especially true with biological fermentation where the rate at which the “Maillard’s reaction” takes place does impact surface color and Ph of baked goods. For other products, such as chemically leavened cookies, the texture that baked goods achieve at the interface with the oven band is another quality driver as it affects softness and crunchiness of the final product. Moreover, in terms of sales regulation and product “shelf life”, the final humidity level of baked goods is another parameter that bakers need to closely monitor.
How can ovens help achieving quality in baked goods? In the first place, ovens need to generate energy density levels which are coherent with the baked good being processed. For instance, high-energy density ovens such as direct flame ovens would lead to poor results with croissants, while less energy-density-capable ovens, such as cyclothermic ovens, might not be up to baking pizza products. In addition, overall product quality benefits of even humidity distributions and of increases in volume: ovens can help reach these goals when their heat transfer mix includes radiation heat because of the penetration capabilities of infrared radiation.
Let’s look, for instance, at the plot below which shows the radiating heat transfer rates which the TP Food Group has measured with various oven technologies which include TP Food Group’s tunnel, multideck and spiral oven types.
The first thing one can see is that moving away from rotor-design ovens to diathermic oil ovens, the rate in radiation heat transfer increases constantly. It is important to highlight that TP Food Group’s diathermic oil ovens can reach up to 30% of radiating heat delivery.
Figure 1. Heat profile with standard deviation by oven type
The second aspect to mention is that a 30% of radiation heat in the energy mix allows bakers achieve objective quality parameters using less than 8 kW/h of thermal energy. This is an interesting result because of the potential energy savings that industrial bakers can post over the long-life of machinery of this type.
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