On the use of combined heat flux measurements and image analysis procedures for the change of scale between industrial and pilot ovens

Abstract

Searching for optimal baking conditions for cereal products in industrial ovens by trial and error is a very costly process. Therefore, a procedure involving a change of scale is often needed, where the baking cycle can be optimized in a much smaller sized pilot oven. The quality and sensory attributes of baked cereal products are linked to the heat flux received by the product during baking. However, the net flux seen by the product can involve complex combinations of heat and mass transfer, chemical reactions and changes in the product over time. A tractable change of scale between the industrial oven and the pilot is based on a simpler flux measurement, which basically takes the process conditions into account. In this article we define baking conditions in the industrial line by measuring the convective and radiative fluxes received by commercial sensors lying on the conveyor belt amongst the products. We show that reproducing these fluxes in a small-sized pilot leads to products with similar color and mass loss to those in the industrial oven. This change of scale (down-scaling) means that baking conditions in the pilot can be optimized with respect to the product properties and the optimized baking cycle can then be replicated in the industrial oven (up-scaling). In order to validate this approach suitable tools are required to quantify the product properties. We highlight the use of image analysis to quantify macroscopic properties (e.g. color) and microscopic properties such as the size distribution of 3D air cells in the bread upon which sensory and mechanical properties depend.