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The secret of sponge cake production

In households around the globe, convenient products such as mini Swiss rolls, family-size Swiss rolls or layer cakes in all sizes and variations are increasingly popular alternatives to conventional biscuits. To ensure the preparation and processing of suitable light and aerated batter for this type of product, only a certain combination of cake and aeration technologies guarantees perfect quality. Haas offers both the required technologies - batch wise and continuous aeration - and the expertise. One of many tailored solutions Haas has on offer is a combined production line for Swiss rolls and layer cakes.


Superior technology

With Haas technology, a mixing system produces sponge batter which is deposited onto an oven band. After baking and cooling, the sponge mass is conveyed to a finishing table where it is decorated, cut, filled and rolled. By changing the aerated or non-aerated fillings or toppings, a wide variety of products can be created.

At the heart of the finest Swiss roll line lies a continuous aeration technology, complemented by a sponge batter pre-mixing system which can be either manually or automatically fed with ingredients from bulk storage. The deposited sponge batter is baked, cooled and conveyed to the Haas make-up table for decorating, cutting, filling and forming of the final product.

With the range of change parts we offer, a vast range of options are available, from mini Swiss rolls, family-size Swiss rolls and layer cakes to bar cakes with a variety of aerated or non-aerated fillings and/or toppings. With the automatic finishing system for rolling and layering, industrial bakers can obtain a high-capacity production facility with a minimum of manual labour.

Standard components offered with the Haas-Meincke sponge cake lines include premix tanks, a continuous aeration system, closed sheeting manifolds for both batter and fat cream fillings, a turning drum, an indirectly heated convection oven with an individual number of heating zones, an overhead cooling conveyor, a make-up table and much more. Haas experts are on hand for guidance and consultation.


Specifications and unique features

"All continuous aerating systems presently available on the market basically consist of three parts," said Stephan Wimmer, Technology & Support Manager, Haas-Mondomix, explaining the pump, the gas-injection system, and the mixing head (rotor/stator combination). "Continuous aeration systems can be split into two mixing head designs: the flat disc type head and the Haas-Mondomix head. The oldest design is the flat-head, giving centrifugal (radial) flow. The Haas-Mondomix mixing head, however, i.e. the turbine type has an axial flow. It was designed to overcome the shortcomings of the flat disc type," he pointed out.

"The axial turbine type head, like the Haas-Mondomix head, has a sheer force curve which is constant, whereas the centrifugal head shows an increasing sheer force towards the periphery of the head. In fact the sheer force increases at first, then passing the outside of the disc, and the sheer force decreases. Hence, the sheer force of a centrifugal mixing head is described as a Gauss-like curve and is not constant. When increasing the mixing head speed, this Gauss curve becomes even steeper. Although the objective is not to aerate, it is almost inevitable that air inclusions are present in the base mix. The result is a poorer bubble size distribution when the sheer force is not constant, and may result in large undesired voids. The constant sheer force also helps in a better homogenization of the product at lower mixing head rpms. A more stable end product is the result," Stephan Wimmer continued.


The pins used by Haas-Mondomix are especially designed to give the highest possible turbulence, with a minimum of revolutions, which, especially with cake batter, may lead to undesirable gluten formation. If diffusion is to be avoided, foam must be stable, with an even bubble size distribution. Diffusion means that large bubbles collide with small bubbles and then fuse. “Due to the higher membrane pressure of the larger bubble, it is absorbed by the small bubble and the pressure is equalized. When this occurs the product collapses," Stephan Wimmer warned.

Amongst other parameters, the effective volume of a mixing head is an influencing factor to determine the capacity of a machine. For higher capacities, the Haas-Mondomix mixing head is elongated, whilst for a centrifugal mixing head a larger diameter is required. However, this larger diameter means higher sheer force, more temperature pick up, poorer bubble size distribution, which all leads to a bad end product. 

"Since both systems are pressurized, a seal construction for the rotor shaft is required. This seal ensures that no product can escape from the product side to the atmospheric environment. There are many technical solutions to seal a shaft, but its performance depends mainly on the stress to which the shaft is exposed. Haas-Mondomix has developed various solutions to minimize the risk of leaking, in particular the mechanical seal (either single or double) we developed in-house, and a well-balanced rotor contribute to the optimal solution," Stephan Wimmer concluded.


In the Haas Group, this technology is covered by Haas-Mondomix and Haas-Meincke. Both are traditional leaders in this field.