TECHNICAL FIELD

The invention relates to an arrangement and a method for cooling warm edible products such as freshly baked bread or recently cooked food.

Especially, the invention relates to an arrangement where edible products are cooled in a chamber under sub atmospheric pressure and eventually rehydrated in the same chamber.

BACKGROUND

In the conventional bread baking industry freshly baked breads are allowed to cool on racks somewhere close to the ovens. This is however a time consuming and inefficient way of cooling bread. An effective way of cooling the bread more rapidly is to use vacuum. Today vacuum cooling of bread is widely used. Apart from the fact that vacuum cooling saves time and place, it is also beneficial in view of the properties obtained by the vacuum cooled bread. For example, vacuum cooled bread stays fresher for a longer time than a conventional rack cooled bread.

By lowering the pressure, the boiling point of water is also lowered. A water containing product that is subjected to a negative pressure will lose part of its water content to the surrounding medium. As a consequence of that steam is evaporated from the product, the product will be cooled. In a cooling from 98°C to 28°C as much as 5-6% of the total weight of the product is lost due to the evaporated water.

For a bread product this may typically imply that the water content in the bread after the vacuum cooling is as low as about 8% in the crust of the bread, while the water content is about 47% in the central crumb of the bread and about 45% in the outer crumb. The relatively high water content in the crumb of the bread helps to keep the bread fresh for a long time, and the relatively low water content in the crust of the bread will keep the product crispy for a longer time and it will also help the bread product to preserve its shape for a longer time. A similar effect is achieved in pre-baked products.

For some products this is however not advantageous. In products like sponge cakes, flan cases, swiss roll breads, sliced breads, such as e.g. toast breads, rye bread or wheat bread, it is instead desired to keep the water content as high as possible. For these kinds of breads methods of rehydrating the bread have been elaborated, in which water or steam is sprayed onto the bread during the vacuum cooling or after the vacuum cooling has been concluded.

A problem with these conventional rehydration processes is that it is difficult control the degree of rehydration and that it is likely that most of the steam will stay on the surface of the bread and not penetrate into the crumb of the bread.

Therefore, there is a need of an improved rehydration process that offers better possibilities of rehydrating the bread.

SUMMARY

An object of the invention is to provide an improved arrangement for cooling freshly baked bread.

According to a first aspect the invention relates to an arrangement for cooling freshly baked bread under a negative pressure, which arrangement includes: a vacuum chamber which is adapted for receiving freshly baked bread for the cooling thereof; a vacuum source, such as a vacuum pump, which is connected to the vacuum chamber for exhausting fluid from the vacuum chamber and creating a negative pressure inside it. Further, the

arrangement also includes a steam generator for producing steam under a negative pressure, which steam is essentially free from air, wherein the steam generator is located in connection to the vacuum chamber, such that generated steam may be introduced into the chamber substantially without simultaneous introduction of air.

According to a second aspect the invention relates to a method of cooling freshly baked bread under a negative pressure, which method includes the steps of placing freshly baked bread in a vacuum chamber for the cooling thereof; exhausting fluid from the vacuum chamber by means of a vacuum source and creating a negative pressure inside the vacuum chamber. In a further step, steam is introduced into the chamber, wherein the steam is produced under a negative pressure such that that the introduced steam is substantially free from air when it is introduced into the chamber.

With the arrangement and the method according to the invention the steam will be absorbed by the bread to a much higher degree than in a

conventional re-hydrating process following a vacuum cooling. Further, the method and arrangement is easily adapted to different types products and specifications. Preferred embodiments of the invention and its advantages will be apparent from the detailed description and the dependent claims.

SHORT DESCRIPTION OF THE DRAWINGS

The invention, and further objects and advantages of it, is best understood from the following description with reference to the appended drawings, of which:

Fig. 1 is a schematic illustration of a first embodiment of the arrangement according to the invention;

Fig. 2 is a schematic illustration of a second embodiment of the

arrangement according to the invention; and

Fig. 3 is a schematic illustration of the method according to the invention.

DETAILED DESCRIPTION

The invention relates to an arrangement for cooling freshly baked bread under negative pressure and below the arrangement will be described with reference to figures 1 and 2.

The arrangement 1 shown in figure 1 includes a vacuum chamber 2 which is adapted for receiving freshly baked bread. Preferably the vacuum chamber has racks for receiving standard baking plates. In the figure, nine pieces of bread products 20 are distributed on three baking plates 21 which may be located on racks inside the vacuum chamber, or individually mounted in tracks on the inside walls of the chamber 2.

In one embodiment of the invention, the vacuum chamber 2 may also function as an oven, such that the baking of the bread and the cooling of the bread may be performed in the same chamber. In order for the vacuum chamber to also function as an oven some adaptations need to be made to it. Firstly it must be constructed to withstand high temperature and further it needs to be completed with adequate heating elements. These adaptations are however obvious to a person skilled in the art and are therefore not treated in detail in this description, especially since the invention concerns the vacuum chamber, regardless of if it also involves an oven.

In order to create a negative pressure inside the vacuum chamber 2 a vacuum source 3, e.g. in the form of a vacuum pump, is arranged in connection to the vacuum chamber. The vacuum source 3 is used both for exhausting fluid from the vacuum chamber 2 and for creating the negative pressure inside it. Even though the term vacuum is used in this application, there will be no absolute vacuum inside the vacuum chamber. In absolute terms the pressure inside will preferably be kept between 10 and 100 mBar.

An advantageous feature of the arrangement according to the invention is that it includes a steam generator 4 for producing steam to be introduced into the vacuum chamber. Further, the steam is produced under a negative pressure, such that the steam may be essentially free from air when it enters the vacuum chamber 2. When the steam enters the vacuum chamber when there is still a negative pressure inside the chamber, the steam will be able to penetrate deeper into the bread.

Conventionally, when vacuum cooled bread has been rehydrated this has been done after the cooling has been concluded and after or simultaneously as the negative pressure inside the vacuum chamber has been released. Therefore, in conventional arrangements for rehydrating vacuum cooled bread, almost all of the steam or water gets stuck at the outer parts of the crust, whereas the crumb is unaffected by the steam. Instead the negative pressure that has been established in the crumb of the bread will be balanced by the air, which will penetrate into the crumb more easily than the steam.

In the arrangement according to the invention the steam generator 4 is located in connection to the vacuum chamber 2, such that generated steam may be introduced into the chamber without simultaneous introduction of air. This may be achieved in two general manners, which are individually represented in figure 1 and figure 2, respectively.

In the first embodiment of the arrangement according to the invention, which is shown in figure 1 , the steam generator 4 is arranged in a separate chamber, in which the steam is produced under a negative pressure and subsequently introduced into the vacuum chamber 2 in which the bread 20 is being cooled. In this embodiment the steam generator is connected to vacuum source. Possibly, the same vacuum source 3 that creates the vacuum in the vacuum chamber 2 is connected to the steam generator 4. This is the case in the embodiment shown in figure 1, where the vacuum source 3 is connected to the vacuum chamber 2 via first vacuum valve 6 and to the steam generator 4 via a second vacuum valve 7. Further, the steam generator 4 is connected to the vacuum chamber via a steam valve 9.

The steam generator 4 comprises a heating element 1 1 and at least one water nozzle 5 directed towards said heating element 1 1. In the shown embodiment the heating element 1 1 consists of a heating spiral. Other types of heating elements are however also possible. An important feature of the invention is that a negative pressure may be established inside the steam generator 4 before the steam is produced. Hence, in a first step of the steam producing process, the second vacuum valve 7 is opened in order to create a negative inside the steam generator 4 by means of the vacuum source 3. In the following step, after closure of the second vacuum valve 7, steam is produced by spraying water from the nozzles 5 onto the heating element 11 , whereupon the steam valve 8 is opened such that the steam will be sucked into the vacuum chamber 2.

In the second embodiment, which is shown in figure 2, the steps of forming the steam are somewhat different with respect to the first embodiment. In this embodiment the steam valve between the steam generator 4 and the vacuum chamber 2 may be omitted. Instead there is a direct contact between the steam generator 4 and the vacuum chamber 2. In a not shown specific embodiment the steam generator 4 is even an integrated part of the vacuum chamber 2. Either way, the connection between the steam generator 4 and the vacuum chamber 2 will make sure that the pressure will be the same in both chambers. Hence, when water is sprayed onto the heating element 11 the produced steam will directly flow into the vacuum chamber and into the bread product 20.

Further, in a not shown embodiment of the invention, steam or hot water may be introduced directly into the vacuum chamber 2 from nozzles arranged inside the vacuum chamber 2.

In all of these embodiments the rehydration may be pressure controlled, such that the steam introduction into the vacuum chamber may be interrupted at a product specific pressure. Hence, it will be possible to control the relative water content in both the crust structure and the crumb of the bread.

Also, as a further step, steam may be introduced during the vacuum cooling process in order to reduce the loss of water and to improve the formation of a softer crust.

The degree of moisture in the bread does not only have an impact on the final product. In addition, it is also of importance for the subsequent process steps. For example the formation of cracks in the crust will be reduced or even totally eliminated if the steam pressure is controlled to not sink below a certain value. By cutting the surface of the bread product a lower weight loss in the crumb may be attained. This means that the packed product will have a higher weight, which is an advantage in most aspects.

In the following, the method according to the invention will be described with reference to the schematic stepwise illustration shown in figure 3. In this illustration necessary inventive steps are provided in closed rectangles, while advantageous but not necessary method steps are provided in dashed rectangles.

In a first step (A) freshly baked bread products are provided into the vacuum chamber. In a second step (B) a negative pressure is established inside the vacuum chamber, in order to cool the bread products by evaporation of water from them. Further, in an optional step (C) the core temperature of the bread product may be monitored by means of a temperature sensor 12, i.e. a thermometer, that is provided into core of the bread product, or where applicable, one of the bread products 20. Preferably, the humidity inside the vacuum chamber 2 is monitored in another optional step (D) by means of a humidity sensor 13, i.e. a hygrometer, and preferably the pressure inside the vacuum chamber 2 is monitored in yet another optional step (E) by means of a pressure sensor 14.

By means of these three sensors the cooling process may be monitored and controlled throughout the whole cooling process and individually adapted to the type of product that is being cooled and to the desired properties of the cooled bread products.

The pressure and the humidity may be controlled jointly or separately, and these values will of course influence the core temperature of the bread product. The actual controlling of the parameters is of course something that is individually performed for each type of product and is based on theoretical and empirical parameters. In a specific embodiment of the invention, both the monitoring and the controlling of the processing parameters is performed automatically by means of a processing unit that is programmed to keep the pressure, humidity and core temperature within threshold values.

When, the core temperature of the bread has reached below a certain threshold value or when the bread product 20 has been cooled for a predetermined amount of time, steam will be introduced into the vacuum chamber 2 in an inventive method step (F) .

The first vacuum valve 6 should preferably be held closed as the steam is introduced into the vacuum chamber 2, such that the steam is absorbed by the bread product 20 and does not escape from the chamber 2 through said first valve 6. Further, the pressure may be controlled to a certain

predetermined value before steam is introduced into the vacuum chamber 2. Preferably, steam is introduced into the chamber until a certain

predetermined threshold parameter is reached. This predetermined

threshold parameter may be the monitored pressure value, the monitored humidity value, the monitored core temperature value, or any feasible combination of these parameters.

The vacuum cooling process is completed by the introduction of fresh air into the vacuum chamber 2 via the air valve 8. As the steam is introduced into the vacuum chamber the pressure will increase as function of how much steam that is introduced, which of course is product dependent and controllable such that the bread product 20 attains the desired water content. There is however still a negative pressure inside the vacuum chamber after that the steam introduction is completed. This negative pressure is levelled out by the introduction of fresh air into the vacuum chamber 2.

An advantage of introducing the steam into the vacuum chamber 2 before the pressure is levelled out is that the steam will be absorbed by the bread to a much higher degree.

Above, the invention has been described with reference to specific

embodiments. It is, however, obvious to a person skilled in the art that other embodiments may be used to achieve the same result within the scope of the invention. Hence, the invention is not limited by these embodiments; instead it is only limited by the appended claims.