Vacuum cooling is taking bakeries by storm

Sometimes when traditional methods of production are replaced by more efficient or more hygienic technology the foods produced lose some of their attractive sensory quality. However, there are examples where modern technology improves products, as is the case with vacuum applications. Drying and deep-frying under vacuum are well-known and successful methods and cooling bakery products using vacuum (vacuum baking) has been experiencing a comeback in recent years.

Vacuum baking or vacuum cooling, oven-hot bakery products has been around for more than 40 years, but it is only today that the technology has reached a level of maturity where it can gain wide acceptance. Patrick Duss, originally a professional baker and confectioner and head of Swiss company Aston Foods, helped the technology achieve a comeback a few years ago and is currently seeing brisk global demand. His Swiss-built systems are in operation in many countries. He considers vacuum baking to be suitable for all types of bakery product with a moisture content of 5% and more. The method offers numerous benefits: bakery products stay fresh longer; have a larger baked volume and more flavour. Freshly sold bakery products stay crustier longer and remain fresh for twice as long.

Raphael Bachmann and Patrick Duss (from left to right).

His favourite customers are medium-sized specialist bakeries. “Decisions are made faster here and process changes are easier to implement,” says Duss. “There are no small craft bakery installations yet because the production processes and volumes are not appropriate. Industrial demand is growing, however. Cost savings are significant. For example, a large commercial business in Austria was able to reduce daily shift work by 2 hours per shift in a two-shift operation. Another customer with 75 shops stated that it was saving over EUR 125,000 a year simply through the reduced baking times for fresh-baked goods in its shops. Added to this were the savings because the infrastructure for deep-frozen goods was no longer needed.”

The highest number of vacuum baking systems are in operation in Switzerland. “Because Swiss bread quality is world class,” reasons Duss, arguing his case for exports with the motto that if the quality of Swiss bakery products can be increased through vacuum baking, then it will satisfy the entire world.

Aston’s strategy was also to target markets close to home first, since response paths are shorter if complications arise. This has proven its value. “We encountered problems with several components at the beginning,” explains Duss. “These have now been solved and Aston Foods’ vacuum systems currently have an availability of 99.68%. The remaining 0.32% results from idle times due to maintenance work. Even 24-hour operation is no problem for the systems.

Energy savings - a major argument

Significantly increased demand is coming from countries which have decided to phase out nuclear power since vacuum baking can greatly reduce energy costs. Countries without a logistics infrastructure for deep-frozen goods are also queuing up. “Innovative businessmen are the people most interested,” explains Duss.

Small craft businesses with fewer than five employees are not yet benefiting as they do not generally achieve the production volumes for a reasonable amortisation period. Duss also sees limits due to the physical properties of some types of product. Because the external pressure is lowered, pressure within the bakery products increases. Compact (non-porous) bakery products increase in size considerably or form cracks. This can happen in the case of unsuitable products such as baked cheesecake or, conversely, with very un-porous meringues whipped up with air - air expands greatly in the vacuum. And the effect is too slight for small items such as honey ring-biscuits or shortbread. Since these items are too small, the hot baking tray, which remains hot despite the vacuum, reheats the products that the vacuum has cooled down. In contrast, the bases for chocolate marshmallows, Linzer tarts, Danish pastries and sponge cake are ideal thanks to their porosity.

Practical experience at Bachmann’s bakery

Users of innovative technology frequently do not wish to be named because of the high market advantage. However, three Swiss bakeries are the exception. Bachmann in Lucerne, Pfyl in Hedingen and Steiner in Wetzikon all work with the Aston vacuum cooling system. The medium-sized Bachmann installed a double Vacuum oven from Aston at the beginning of 2010. Raphael Bachmann, co-owner of the bakery has had a positive experience and confirms “positive customer reaction and an increase in the sale of bread by 18% in the first year. Bread is crustier and stays fresh and crisp longer. Bread is 1-2% moister. And part-baked bread has a drier crust.”

He has not noticed any increased loss of flavour compared with normal cooling. And there is even less moisture loss since the vacuum system only cools down to room temperature. Additional advantages that Bachmann mentions are a 20-40% shorter baking time, which lowers overall energy requirements and frees up baking capacity, shock cooling of half-baked bread is no longer necessary, pre-packed small loaves, croissants and cakes remain mould free for twice as long as when they are packed in a clean room. There is only a minimal amount of extra handling that results from the extra work step and the use of transport trolleys. The space required is similar to that of a rack oven but less space is required thanks to increased oven capacity.

“The vacuum is extremely flexible,” praises Bachmann, “The only disadvantage is the capital investment required and the effort involved in acquiring the necessary expertise.” His business uses vacuum baking for all yeast-raised pastries and a second system for filo pastry products and sponge cakes has been ordered.

What is vacuum baking?

Baking products turn brown and crusts form at the end of a conventional baking process when water, caught in the surface of the dough, evaporates. This occurs relatively slowly and requires a great deal of heat. Fully baked bread must then cool down to moderate temperatures (or be shock frosted) before it can be handled, which also requires time and energy. Both processes - the drying of the crust and cooling - can be expedited through vacuum baking. It is not the thermal baking that takes place in the vacuum but the subsequent cooling.

However, the term ‘vacuum baking’ is often used in everyday practice. It is an enthalpy cooling process. The reduction in pressure causes the boiling point of the water, caught in the product, to decrease and, because it evaporates, it removes heat from the product, i.e. vaporisation enthalpy takes place. In practical terms, the bread is removed after baking for a shorter period in the conventional oven and immediately transferred hot to the vacuum chamber where the crust can form completely (through drying only and not browning) and the bread can cool down. This normally happens in batches.

“Baking times can be cut by between 30 and 50%,” promises Aston CEO Patrick Duss, “and energy costs decrease by 60% since shock frosting and freezer logistics are no longer necessary.” Pre-baked items coming hot out of the oven cool down to 25° in the vacuum chamber in 3 minutes.

However, it is important that they are transferred from the oven to the vacuum chamber within 30 seconds or they may collapse due to their surfaces still being soft. Looking at the process as a whole, from baking, cooling and storing to final baking at a branch, “The total loss from baking and cooling is only 12% with vacuum cooling, which compares with 25% when shock frosting,” explains Duss. “This makes bread moister and it stays fresh longer.”

Greatly reduced baking times

Aston claims that packed bread can be stored for up to four weeks without the risk of mould since the vacuum uses sterile air. And bread can be cut to make sliced bread in four minutes after baking. Duss recommends this method for large-scale specialist and industrial bakeries and assures that capital investment will be amortised in 18 months. A batch vacuum chamber has a capacity of 6,800 bread rolls per hour, “freeing up 30% of baking capacity at the same time,” emphasises Duss. Continuous vacuum systems with a capacity of over 44,000 items are also available.

A further use for vacuum baking is the production of crustless bread, for example for fashionable English triangular sandwiches. The usual process is to bake the bread with a crust and then cut the crust off, resulting in considerable waste. Alternatively, a microwave oven may be used. Aston Foods AG has developed a third approach to producing crustless bread in conventional ovens with vacuum baking. The bread in the baking tin is transferred to the vacuum chamber immediately after baking (without vacuum), where it is ‘finished’ or ‘gelatinised’.

Enthalpy cooling lowers the core temperature in the baked product to 28° in three minutes, meaning that it can be removed from the tin. The loaves no longer need to be stored in an acclimatised room for 16 hours and the bread can be sliced and packed immediately.

Aston Foods Ltd.

www.astonfoods.com

The Australian/New Zealand contact for Aston Foods is Heinz Frunz (heinz.frunz@astonfoods.com).