Swiss bakery optimises operations with vacuum cooling system

Busch Australia Pty Ltd

By Uli Merkle*
Monday, 01 April, 2019

Swiss bakery optimises operations with vacuum cooling system

Fleur de Pains, a medium-sized bakery and patisserie in western Switzerland, values high-quality baked goods, patisserie and confectionery products.

All goods sold at Fleur de Pains’ 21 shops are handmade in Crissier, near Lausanne, using traditional methods. In addition to this craftsmanship, the consistent high quality of the baked goods is made possible by modern vacuum cooling, which rapidly cools the products after they are baked, preparing them for further processing or sale.

To guarantee quality, Managing Director Stéphane Simon repeatedly tested and changed the manufacturing process. The most difficult aspect was creating a firm bread crust and consistent texture of rolls and croissants on humid days.

In 2015, Swiss company Aston Foods implemented a vacuum cooling system to improve quality and reduce cooling time after baking. The vacuum chamber is connected to a vacuum pump located in a separate room and is designed to accommodate a manually loaded transport rack. Baked goods are placed in the vacuum chamber immediately after baking where they are cooled to 30–35°C within one to three min.

After cooling, the goods can be removed and eaten almost immediately or processed further. When the vacuum cooling system was introduced, Simon deliberately did not inform customers or employees of the new system so he could test whether there would be a reaction from consumers. Positive feedback quickly came from all shops. The customers praised the bread crust, its refined colour and more homogeneous formation of pores, and the associated greater volume.

Vacuum cooling explained

The principle of vacuum cooling baked goods has been well known for decades but could not be technically implemented in a satisfactory way. Working closely with Busch, Aston Foods optimised the vacuum cooling process by incorporating Busch’s dry COBRA screw vacuum pumps into its cooling systems.

Unlike oil-lubricated rotary vane vacuum pumps, which were often used while vacuum cooling systems were first being developed, COBRA vacuum pumps operate without the need for oil or other operating fluid in the compression chamber. This means that water vapour, which can be sucked into the system during the cooling process, cannot mix with any operating fluids and condense in the vacuum pump in the process. The high pumping speed of the vacuum pump in the low pressure range makes it possible to set up the vacuum pump 20 m from the actual vacuum chamber in an adjacent room.

Due to the elimination of oil, and thus the risk of forming an emulsion with the condensate, all maintenance work required for oil-lubricated vacuum pumps, such as regular oil and filter changes, becomes unnecessary. Both COBRA vacuum pump screw rotors avoid contact with themselves and the housing, resulting in no wearing parts. This is an important benefit for Simon because, despite the improvement in quality, he has no additional costs. Maintenance of the entire vacuum cooling system is only performed once a year by service technicians from Aston Foods.

Maintenance and other benefits

Aston Foods CEO Christian Vetterli confirmed that the yearly maintenance effort for the system only takes two to four hours and, although the system at Fleur de Pains operates for two shifts six working days per week every year, the only maintenance the vacuum pump requires is cleaning the inlet filter and exchanging the gear oil.

For Fleur de Pains, converting to a vacuum cooling system has brought further advantages: the time for baked goods to cool has reduced from several hours to one to two min, depending on the product. During conventional cooling, baked goods are exposed to various environmental influences like humidity and ambient temperature, which have an uncontrollable influence on quality. With vacuum cooling, the process after baking is precisely fixed and independent of all external conditions.

“The process requirements for vacuum cooling are demanding,” said Vetterli, “but thanks to the integrated control and reliable vacuum technology, it is perfectly manageable.”

Fleur de Pains installed a total of 150 programs for cooling its various products. In doing so, the exact cooling procedure for each product is individually defined and can be replicated. The programs were finely adjusted during the initial phase and can now be easily started with the press of a button.

The two deciding factors during the cooling process are the time and the progression of pressure in the vacuum chamber. The cooling process begins at atmospheric pressure and, after a predefined progression, reaches a vacuum of 30–50 mbar. This process can be repeated within the cooling period and, depending on the product, can pass through different vacuum levels. The COBRA screw vacuum pump works reliably at all vacuum levels, from atmospheric pressure to far below one mbar. According to Vetterli, “It is important that the predefined vacuum level and the pressure profile are precisely maintained. In the process, it is not a matter of achieving the highest possible vacuum. It is more about achieving the right vacuum level or precisely maintaining the predefined pressure profile.”

With the introduction of the vacuum cooling system, Simon was able to achieve a significant and consistent quality improvement for his baked goods. The genuinely positive reactions of customers in his shops are the best evidence of this.

*Uli Merkle, Busch Dienste GmbH

Image credit: © Ryzhov

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