GB2210768A - The baking of bread and the like dough products - Google Patents

Abstract

In a process for baking bread and the like, the bread is heated to a temperature between 40 DEG C and 50 DEG C in a final prover (14) before transfer to a travelling oven (15). The latter has no static/development section. The higher than conventional entry temperature into the oven reduces the difference between the near-crust temperature and the core temperature, thereby enabling the industry-prescribed core temperature of 96 DEG C to be reached in 12 to 17 minutes. The shorter bake time reduces the weight loss and the weight loss spread, enabling a lower weight dough piece to be used to produce a loaf of a desired weight, e.g. 800g. <IMAGE>

Description

DESCRIPTION THE BAKING OF BREAD AND THE LIKE DOUGH PRODUCTS.

The present invention relates to a process and apparatus for baking dough products, such as bread.

The invention is particularly concerned with continuous bakery lines.

The mass baking of bread is usually conducted on the block transfer principle in which the loaves being baked are transported in baking pans in rows through a wide oven where the loaves are baked by forced convection heating or radiant heating or preferably both types of heating. Because of the nature of such ovens, not all the loaves are necessarily subjected to exactly the same conditions. One particular problem which arises from this is that, not only do the loaves experience a significant weight loss in the oven but they also experience a spread of weight loss. Thus, a standard 800 g white loaf can experience an average weight loss of 70g in the oven and in addition the loaves being baked can exhibit a loss spread of 30 g.

Thus, for an average weight loss in the oven of 70 g the range of weight loss of the loaves is between 55g and 85g.

Amongst the objects of the invention are to reduce the weight loss of the product during the baking process, to reduce the weight loss spread, and to reduce the baking time.

In a continuous baking method for bread or the like dough products in accordance with the invention, the products are raised to a temperature of 40QC to 500C in a humid atmosphere prior to entry into the baking oven.

A prover arranged in advance of the oven can be operated so as to raise the product temperature to 400C to 500C. while maintaining a humid atmosphere around the product. The heat input needed to raise the product to this temperature is applied through the pans in which the product is placed, whereby to avoid the product being subject to draughts which could cause "skinning". Skinning is a result of drying of the surface of the product and can inhibit proper development.

Alternatively, a separate chamber can be disposed between the prover and the oven, such chamber containing an atmosphere of controlled high relative humidity and being adapted to heat the products by convective and/or radiant heat to the said temperature of 400C to 500C such that development takes place in this chamber.

The product thus enters the oven at a temperature of about 400C to 500C, preferably about 440C to 450C, having experienced minimal weight loss during proving and development.

In the oven there is no static section, and the products are subjected to convective and/or radiant heat such that the heat input to the products is relatively high which kills the yeast and raises the near-crust temperature rapidly to the desired final baking temperature, the core temperature closely following the near-crust temperature. Thus, the baking time in the oven need be no more than about 12 to 17 minutes as opposed to a conventional baking time of 22 to 23 minutes for an 800g loaf.

The method of the present invention is thus characterized by a reduced baking time which is accompanied by a reduced weight loss and a reduced weight loss spread.

On leaving the oven, the baked products are preferably subjected to a delay prior to being de-panned and before entering the cooling cycle, whereby the core temperature reaches its final maximum after the baked products have left the oven.

In continuous baking apparatus of the present invention, means are provided for heating the products to a temperature of at least 400C before they enter a travelling oven.

The oven is characterized by the absence of any static section where the products would be subjected to a low heat and no convection so that development could take place.

Preferably the said heating means are such that the products are subjected to a high relative humidity, preferably at least 70%, substantially until they enter the oven.

The oven is preferably of a kind in which the dough products enter the oven and travel through the oven in rows.

The invention is further described, by way of example, with reference to the accompanying drawings, in which: Fig.l is a graph in which the loaf temperature is plotted against time in the oven; Fig.2 is a graph in which the difference between the near-crust and core temperatures is plotted against baking time; and Fig.3 is a block diagram of a bread baking apparatus in accordance with the invention.

Curve A-l in Fig.l shows the rise in near-crust temperature with respect to baking time when the loaves enter the oven at a temperature of about 32us.

The near-crust temperature is the temperature at 5 to 10 mm from the surface of the loaf. Curve A is the core temperature of the same loaf. It will be seen that, whilst the near-crust temperature commences to rise shortly after entry of the loaf into the oven, the core temperature does not begin to rise significantly until at least half of the baking time has elapsed. The reason for this is believed to be that the raised dough is a poor conductor of heat and once the crust has dried, the crust becomes an even poorer conductor so that the core is thermally insulated. It is an industry-set standard that the core temperature should reach 969C as otherwise the bread will be incompletely baked. Thus, the baking time has been dictated by the time taken for the core to reach the prescribed baking temperature.In Fig.l the baking time is illustrated as being typically 22 minutes.

Hitherto it was thought necessary to keep the temperature in a final prover immediately in advance of the oven down to 34 0C. To this end, the temperature in the prover has been kept at about 35 0C with a relative humidity of about 85%. Draughts on the dough pieces in baking pans in the prover have been avoided. These features in combination have ensured that the surface of the dough pieces is not dried which would produce skinning.

Hitherto, it was also though-t highly desirable for the oven to have a so-called static section at its entry end wherein the heat input to the loaf is maintained at a fairly low value so that development can continue.

It is a specific object of the invention to reduce the baking time which reduces not only the overall weight loss but also the loss spread, whereby the weight of the input product can be reduced.

Curves B-1 and B relate to a loaf which enters the oven at a temperature higher than conventional, e.g.

450C. Not much difference is seen in the rise of the near-crust temperature as illustrated by curve B-1 as compared with the curve A-l which rises from 320C but it will be seen that the core temperature rise takes place much sooner, the curve B relating to the core temperature being displaced by about six minutes relative to curve A, thus achieving the required core temperature that much earlier.

This effect shows up even more dramatically in Fig.2 where the temperature difference t between the near-crust and the core is plotted against the bake time. This temperature difference approaches 600C at one point, whereas the maximum temperature difference as shown by curve B in Fig.2 is just over 300C for a loaf entering the oven at 450C.

The reduction in baking time reduces the period during which significant weight loss takes place and thereby reduces the actual weight loss and the weight loss spread.

Fig.3 shows a bread baking plant in which the temperature of the product is raised to a temperature of 400C to 500C before it enters the oven.

Referring now to Fig.3 the bread constituents are fed to a dough mixer 10 and thence to a dough divider 11 which divides the dough into pieces of predetermined weight. It is an object of the invention to minimise this predetermined weight in order to render the whole baking process as economic as possible. This predetermined weight must be such that the final weight of the finished loaf is, say, at least 800 g.

From the divider 11 the dough pieces are passed to a first prover 12 and thence to a panner-moulder 13 where the dough pieces which have already risen slightly are placed in individual baking pans. The baking pans are batched in rows and are fed to a final prover 14 where the dough rises to its full extent.

The products to be baked are then transferred to a travelling oven 15 where the pans travel through the oven. After the baked products leave the travelling oven they pass through a dwell section 16 and thence to a de-panner 17. The de-panned loaves are then forwarded to a cooler 18 and then passed on for subsequent handling, e.g. wrapping, and possibly slicing before wrapping. The empty pans are returned to the panner-moulder via a pan temperature controller 19 and a pan greaser 20.

In conventional baking lines, the relative humidity in the final prover is controlled to be between 80 and 90% and the temperature is controlled to be about 320C. to 340C. However, in the apparatus shown in Fig.3 the final prover 14 is operated in such a way the temperature of the products undergoing proving is raised to a temperature between 400C and 500C, preferably 440C or 450C, still at the controlled humidity of between 70% and 90%. Thus, the loaves enter the travelling oven 15 at a much higher temperature than in a conventional bread baking plant whereby the time in the oven 15 can be substantially reduced as described above with reference to Figs. 1 and 2.

The final prover 14 is considered not only to be that part of the plant in which fermentation and consequent development takes place without skinning of the product but also as part of the heat transfer process which previously occurred in the static development section of the oven. Such a section is absent from the oven 15 in Fig.3. If existing provers were simply upgraded or adjusted in an attempt to increase the temperature of the product as it leaves the prover, this would imply much higher air temperatures with consequent undesirable effects, such as "blistering" of the product.

The air distribution method within the final prover 14 is such that air is blown directly at the undersides of the tins in a way and at velocities so as to impose a higher rate of heat transfer to the product than has been achieved in previous production methods. The air temperature is higher than conventional but not so high as would cause blistering. In this way a balance can be achieved between the desired core temperature at exit from the prover, correct development of the product, no skinning and no undesirable side effects such as blistering. This higher heat transfer rate can be applied throughout the final prover or just at an end section thereof.

A further possiblity is to employ a conventional final prover and to dispose a separate treatment chamber between the final prover and the travelling oven wherein a controlled relative humidity of preferably 70% to 90% is maintained and the products are heated to the said higher temperature by microwave, radio frequency or infra-red heating. This ensures that the desired core temperature of 400C to 500 C, e.g. 450C, is reached.

Similarly, the core temperature can be raised partially or wholly by such means prior to entering the proving chamber.

The products begin to bake immediately they enter the travelling oven 15 which has no static section and are subjected to full treatment to kill the yeast and commence baking proper. Because the dough products enter the travelling oven at a relatively high temperature, less heat is put into the products in the oven, the core to near crust temperature difference is reduced and the baking time is substantially reduced.

When the products leave the travelling oven after a baking time of 12 to 17 minutes, the core temperature is at 960C but still noticeably below the near-crust temperature and is still rising. To permit the core temperature to reach the final baked tenperature the baked loaves are not immediately cooled but instead are allowed to travel through the dwell section 16, which is simply an extended conveyor run, before they reach the de-panner 17. The dwell or holding time is preferably about two minutes.

Hitherto, it was believed that the employment of too high a core temperature on leaving the prover would lead to an-excessively coarse crumb structure of the loaf, as a result of which the loaf would be liable to collapse after it leaves the oven. However, it has been found that, by omitting the static/ development section and using generally lower oven temperatures than conventionally used, whereby the core temperature does not lag far behind the near-crust temperature, an even bake crumb structure is achieved and the loaf collapse is not experienced.

In the case of production of round-topped loaves, it has been the practice to use the steam supplied in te static/development section of the oven to glaze the top of the bread. This glazing, which is to improve the appearance of the product, is achieved in that the skin temperature is rapidly raised in a very humid atmosphere to cause gelatinization of the starch. Because the static/development section is omitted from the oven used for carrying out the present invention, separate means are provided when glazing is desired for applying the glazing treatment. Such means can comprise a separate section in advance of the oven, steam being applied to the top of the product in each section. When baking in tins with lids and for other processes in which glazing is not required, such extra section can be omitted.

However, the provision of a glazing section adds to versatility in that the plant can be used for a full range of varieties of bread manufacture, both open-top and lidded and both white and brown bread.

It is conventional practice for the mixing of the dough in the mixer 10 to be conducted under vacuum as otherwise the resulting baked product has too large a pore size. The vacuum is believed to extract oxygen and carbon dioxide from the dough as it is being mixed and thus prevents any effective development during mixing. Surprisingly, it has been found that, when using the baking method and apparatus according to the invention, it is unnecessary to carry out the mixing under vacuum, thereby considerably reducing the cost of the dough mixer.

Although the present invention has originally been intended, inter alia to reduce the weight spread when baking bread in wide travelling ovens, the invention is also useful, particularly from the point of view of reduced baking time and reduced weight loss stemming therefrom, in baking processes on which the product items are transported in single file through the oven.

Claims (14)

1. A continuous process for the baking of bread and the like dough products, in which such products are raised to a temperature of 400C to 500C in a humid atmosphere prior to entry into a baking oven.

2. A process as claimed in claim 1, in which the products are raised to the said temperature between 4CUC and 50 C in a final prover disposed in advance of the baking oven.

3. A process as claimed in claim 2, in which heat is supplied to the dough products in the final prover by directing hot air against the bottoms of baking pans in which the product is disposed.

4. A process as claimed in claim 1, 2 or 3, in which the dough products enter the baking oven at a temperature of about 440C or 450C.

5. A process as claimed in any preceding claim, in which the dough products are immediately subjected in the baking oven to full heating by convection and/or radiation sufficient to terminate development.

6. A continuous baking apparatus for the baking of bread and the like dough products, comprising a travelling oven and means in advance of the oven for heating the dough products to a temperature between 400C and 500C.

7. A baking apparatus as claimed in claim 6, in which the heating means are adapted to subject the dough products to a relatively high humidity while they are being heated before entry into the oven.

8. A baking apparatus as claimed in claim 7, in which the heating means comprises a final prover.

9. A baking apparatus as claimed in claim 8, in which means are provided in the final prover for directing heated air against the undersides of baking pans in which the dough products are disposed.

10. A baking apparatus as claimed in any of claims 6 to 9, in which the travelling oven is adapted to apply a full heat input into the dough products immediately on entry into the oven.

11. A baking apparatus as claimed in any of claims 6 to 10, in which a glazing section is disposed in advance of the travelling oven.

12. A baking apparatus as claimed in any of claims 6 to 11, in which the products to be baked are transported through the travelling oven in rows extending widthwise of the oven.

13. A continuous baking process substantially as herein described with reference to the accompanying drawings.

14. A continuous baking apparatus constructed and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.