Vacuum Conquers The Bakery

Baking is one of the oldest activities in the field of artisan food preparation. Flat bread, for example, was produced from ground grain and water as early as 8,000 years ago. Vacuum technology by comparison is relatively new to the baking industry. Technically, a vacuum was first generated in the 17th century and is today an inherent and essential part of industrial practice, particularly the advanced technological industry. New technical developments and innovations such as smartphones would have been impossible without vacuum technology.

Vacuum technology is enabling new innovation to the industrially oriented baking trade and revolutionising the way baked goods are cooled. In comparison to conventionally cooled baked goods, the advantage of vacuum conditioned pastries 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, resulting in a stable crust which has a longer shelf-life, and a texture that is brittle yet soft at the same time. This is advantageous as many baked goods tend to lose their form in environments with high air humidity.

A baked product with consistent volume is not only an important quality factor for the consumer; it also offers an advantage over competitors in terms of appearance. The baked goods on display do not only smell delicious but also look attractive, thus enticing shoppers to make a purchase.

Along with the advantages mentioned, there are a few other important aspects to be considered. By accelerating the process, the time window for the development of bacteria and mould is minimised.

In vacuum cooling, baked goods are cooled in an enclosed chamber. The process reduces the duration of critical temperature range for the growth of mould spores (60 deg C to 30 deg C) from two hours with conventional cooling methods to approximately 2-3 minutes. Cooling in an enclosed space also serves as a sluice between the production and packaging phrases which significantly reduces the risk of airborne bacteria contamination, resulting in less spore formation. This means that there is no need for a costly sterilisation process following packaging in order to resist the formation of spores.

Depending on the product, up to 12 batches, or 400–500 kg, of baked dough can be conditioned per hour. With ambient cooling, it may take several hours for it to cool. With vacuum technology, however, it takes just 5–10 minutes to cool products to 30 deg C. Therefore, the bakery not only benefits from an improvement in quality, but also from increased productivity.

There are other applications of vacuum conditioning in baking. Compared to conventional air cooling, the compact dimensions of a vacuum cooling system results in a significant space saving— up to one tenth of the floor space previously used.

A simple conditioning chamber has a chamber size of around 120 cm x 100 cm and is approximately two metres tall. Vacuum pumps or switch cabinets are functionally integrated into the system, directly alongside the chamber. The recovered effective space can then be used for additional productions capacities within the company.

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 cm x 100 cm.

Since the baking time is significantly reduced, vacuum conditioned baked goods can be quickly and better prepared for further processing chain.

There are two main technical challenges in the vacuum conditioning of baked goods. Firstly, manufacturers are required to take into consideration the many different pastries in Europe. 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. For example in Germany, Brötchen, Röggelchen, Semmel, Strippe or, in Swabia, the Seele, all have different recipes and are made with a wide variety of different ingredients.

Look beyond Germany and into the rest of Europe and the differences between various baked goods become even more evident. For example, croissant, baguette, Roggenbrot or Hefezopf with raisins. Not only are they made of different ingredients, they also differ in terms of texture, volume, size and presentation. Although all of these unique recipes and properties can be customised in the cooling equipment control system, they are not pre-set into the system. Thus, an experienced equipment manufacturer with specific baking expertise must program the corresponding cooling sequences for the respective baked goods into the equipment control system.

Vacuum technology has almost as much influence over the quality of the baked products as the recipe itself. Baking under vacuum is also ideal for the local bakery or at a point-of-sale.

Baking generally takes place at a decentralised location outside a town or city. The baked goods are then delivered to points-of-sale in the city or in shopping malls. Traditionally, retailers find it cost ineffective and difficult to meet customer’s expectation of being able to buy fresh and warm bread rolls at any time of day. Now, however, this is easily managed with the help of vacuum conditioning through pre-baking.

Pre-baked goods, which were partially baked and vacuum conditioned in the factory, can be delivered to the points of sale without intensive cooling, and can be stored for up to four days. Therefore, deliveries are often made to several branches of a business, spanning large distances. As the product is more stable, coupled with a longer shelf-life, deliveries can be made to locations of further distance without being damaged, even in the most varied weather conditions. .

At the bakery or retail store, pre-baked products are then ‘finished off’, with baking times reduced as the goods were already partially baked in the factory. 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 also therefore minimised.

Another advantage of the shortened baking process is that it helps create a more comfortable working environment for staff, as exhaust air and heat generation are significantly reduced. Consumers can therefore enjoy fresh, warm bread with the perfect shape around the clock—instant indulgence, in keeping with the modern lifestyle.

The second major technical challenge lies in the design of the vacuum cooling and conditioning system. Physical law dictates that the lower the atmospheric pressure, the lower the boiling point becomes. In nature, water has a boiling point of 100 deg C. However, water in a vacuum has a lower boiling point as the surrounding atmospheric pressure is much lower. For example, if the pressure lies at 42 mbar, water will evaporate at just 30 deg C.

The energy required for the water to boil is drawn from the baked product, which is still almost oven warm. Depending on the product, standard cooling times are between two and six minutes. During this time, the baked goods cool evenly across the 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.

However, the steam produced as a result of gelatinisation poses a challenge in the technical design of the vacuum cooling and conditioning system. Additionally, the steam is not pure but is contaminated with baking ingredients such as flour, yeast, sugar and salt. This is vitally important when selecting which vacuum pump technology to use. No vacuum pump can withstand contamination with steam and the formation of 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 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 reference. In principle, both pumps are suitable, however the design of the vacuum cooling system is decisive in making the choice.

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 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, screw pumps also offer the comfort of low-noise operation. Hygiene regulations in food production also take this factor into account. Many baking companies shun frequent oil changes, which also come with associated costs.

After taking a closer look at 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 benefits.

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