Vacuum conquers the bakery

VACUUM TECHNOLOGY Screw type technology

Vacuum conquers the bakery Klaus Buhlmann

Baking is one of the oldest activities in the field of artisan food preparation. Flat bread was produced from ground grain and water as early as 8,000 years ago. By comparison, vacuum technology is relatively new. Technically speaking, a vacuum was first generated in the 17th century, and is today an inherent and essential part of industrial practice. Our highly technical world needs vacuum. New technical developments and innovations such as smartphones would not be possible without vacuum technology.

Crispy crust, loose crumb Vacuum technology is now also bringing innovation to the industriallyoriented baking trade. The cooling of baked goods is being revolutionised. In comparison to conventionally cooled baked goods, the advantage of a vacuum-cooled bread is clear from the very first touch. The crust is crispy, the crumb loose. Through the extension of the so-called crusting process, the volume consistency of the baked goods also increased a fact that results in a crust that is stable for longer and brittle, yet soft. This is of advantage as many baked goods tend to loose their form in environments with higher air humidity. A stable volume is not only a win in terms of quality for the customer; it also offers an advantage over the competition in terms of appearance when the baked goods on display not only smell delicious but also look attractive and entice shoppers to make a purchase.

Fewer bacteria in the vacuum

Compact dimensions, more effective area There are other applications of vacuum cooling in baking. Compared to conventional air cooling, the compact dimensions of a vacuum cooling system results in a significant spacesaving – up to one tenth of the floor space previously used. A simple conditioning chamber has a chamber size of around just 120 x 100 centimetres and is approximately 2 metres tall. Vacuum pumps or switch cabinets are function-

Photo©: CETRAVAC

Alongside the advantages to the purchaser that are evident upon first glance, there are a few other important aspects to be considered: By ac-

celerating the process, the time window for the development of bacteria is shortened. In vacuum cooling, the critical temperature range for the growth of mould spores, from 60 ° C to 30 ° C, is cut to two to three minutes, rather than two hours as was previously the case. Cooling in an enclosed chamber also simultaneously serves as a sluice between production and packaging and significantly reduces the risk of airborne bacterial attack and the resulting spore formation. This means that there is no need for a costly sterilisation process following packaging in order to resist the formation of spores. Only pure air and protective gas could further extend the shelf life.

Fig. 1: Vacuum-conditioned bakery products convince through a uniform crumb as well as a larger and dimensionally stable volume

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PROCESS TECHNOLOGY & COMPONENTS 2015


Photo©: CETRAVAC

Future conveying Hygienic pumps – optimized for efficiency

Fig. 2: Batch unit for vacuum conditioning: oven racks enable quick loading.

ally integrated into the system, directly alongside the chamber. The recovered effective space can then be used for additional productions capacities within the company. Breads of various types and sizes can be cooled to 30 ° C within just five to ten minutes. The bakery thus not only benefits from an improvement in quality, but also from increased productivity. The new cooling technology drastically reduces the original cooling phase. Meanwhile, the baked goods are optimally conditioned for the following editing steps – slicing and packaging. The systems commonly used today are designed for a rack trolley with a sheet size of 60 x 100 centimetres. Depending on the product, up to twelve batches or 400– 500 kilograms of baked dough can be conditioned each hour. By comparison, cooling in ambient air can last several hours. Vacuum-cooled baked goods are more quickly and better prepared for the further processing chain.

Vacuum conditioning improves the quality of baked goods The main technical challenges in the vacuum conditioning of

baked goods are two-fold: On the one hand the system manufacturers are required to take the many different bread types in Europe into consideration – in particular those in the German-speaking world. Baked goods are not just baked goods. They all differ. This does not refer merely to the different names used in various regions and dialects. Brötchen, Röggelchen, Semmel, Strippe or, in Swabia, the Seele – all have different recipes and are made with the most varied range of ingredients. If one broadens one's view from the host of typical German breakfast breads to include all of the types of bread found in European baking culture, the differences between various baked goods becomes even more evident: croissant, baguette, roggenbrot or hefezopf with raisins – the unique quality of all of the recipes and properties are reflected in the equipment control system used. The equipment manufacturer must program the corresponding cooling sequences for the respective baked goods into the equipment control system. This requires specific baking expertise and years of experience. Here vacuum technology has almost as much influ-

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Photo©: CETRAVAC


Photo©: CETRAVAC

Half-baked conditioned Kaiser rolls…

Photo©: CETRAVAC

…with simple packaging can be transported to the bakery branch…

tensive cooling, where they can then be stored for up to four days. Thus, deliveries are often made to several branches of a business, spanning large distances. As a result of vacuum conditioning, the products survive delivery to the branches undamaged, without packaging, even in the most varied of weather conditions. In the bakery, the baking of the vacuum-conditioned baked goods is then simply finished off, with baking times reduced on account of the goods being pre-baked. Through the use of the so-called interrupted baking method, and that the deep-cooling logistics and storage previously required within the baking factory and the retail branches, energy consumption can be significantly reduced. The overall energy and logistics costs are thus reduced. The shortened baking process is also much more convenient for staff, as exhaust air and heat generation are significantly reduced. The customer can therefore enjoy fresh, warm bread with the perfect shape around the clock – , instant indulgence, in keeping with the modern lifestyle.

Cooling times reduced, condensation prevented

…where baking will be completed.

The second major technical challenge lies in the technical design of the vacuum cooling and conditioning system.

Here the principle of vacuum cooling is used. At atmospheric pressure, water boils at 100 ° C. If the atmospheric pressure is reduced, the boiling point also falls. If the pressure lies at 42 mbar, water evaporates at just 30 °C. The energy required for the water to boil is drawn from the baked product, which is still almost ovenwarm. Depending on the product, standard cooling times are between 2 and 6 minutes. During this time, the baked good cools evenly across the entire product. The uniform extraction of the water content also prevents possible condensation in the baked good itself, a process often also referred to as gelatinisation. This in turn results in an increase in quality for the bread-lover. The hot (warm) steam produced as a result of the process poses a challenge in the technical design of the vacuum cooling and conditioning system. What is more, the steam is not pure but is rather contaminated with baking ingredients such as flour, yeast, sugar and salt. This is vitally important when selecting the vacuum pump technology. No vacuum pump would withstand contamination with steam and a mushy, sticky-sweet mass in the long-term, and the use of a liquid ring pump should be avoided. In principle these technologies would be ideal, but here the dependency of

ence over the quality of the goods as the baking recipe itself. The vacuum conditioning of baked goods is also ideally suited for the bakery or point of sale concept commonly found today. Baking generally takes place at a decentralised location outside of the town or city. The baked goods are then delivered to points of sale in the city or in shopping malls. The customer's expectation of being able to buy fresh and warm bread rolls at any time of day can be optimally fulfilled with the help of vacuum conditioning.

The key here is so-called pre-baking. Pre-baked goods are conditioned using a vacuum and can then be delivered to the points of sale without in44

Photo©: CETRAVAC

Lower logistics and storage costs

Fig. 3: Two-chamber conditioning unit with optimally integrated oil-free vacuum pumps during assembly.



the final pressure on the water temperature is not conducive to the process. Ultimately, this raises the question as to whether to use a pump with classic, oil-sealed rotary slide technology or modern, oil-free screw technology. At this point it is difficult to name a preference. In principle, both pumps are suitable, however the design of the vacuum cooling system is decisive in making the choice.

The trend points towards dry, screwtype technology Smooth operation comes down to the skill of the equipment manufacturer in implementing the correct measures when it comes to operation and servicing, in order to protect the pump of choice from the mixture of steam and baking ingredients. If you consider the vacuum cooling systems available on the market, there is, however, a notable trend towards the use of oil-free screw technology. This is without doubt on account of the fact that modern screw pumps with frequency converters can be optimally combined and integrated with the equipment control system in a compact manner. With regard to noise emissions, these screw pumps also offer the comfort of low-noise operation. Hygiene regulations in food production also take this factor into ac-

Photo©: Oerlikon Leybold Vacuum

Fig. 4: Modern oil-free, screw-type vacuum pumps with integrated frequency converter are most appropriate for vacuum conditioning of bakery products

count. Many baking companies shun frequent oil changes, which also come with associated costs.

material and energy consumption is huge. The technical and financial prerequisites to market penetration are thus undoubtedly fulfilled.

Profitable vacuum But this is set to change: Upon closer consideration of the new baking technology, it becomes clear that when it comes to the use of a vacuum, equipment manufacturers, producers, bakeries and consumers all reap equal benefit. They all benefit from an increase in quality and productivity, and the potential for improvement with regard to production times, infrastructure personnel, logistics costs and raw

Author: Klaus Buhlmann Market Segment Industry Oerlikon Leybold Vacuum GmbH, Köln

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