GB2156501A - Improvements in or relating to methods of, and apparatus for, the cooling of hot bakery products - Google Patents

Abstract

Apparatus 1 for cooling hot bread loaves 2 comprises a cooling chamber 3 having a loaf intake station 4, a loaf discharge station 5, and a conveyor 6 for causing the loaves 2 to travel through the cooling chamber 3, between the intake and discharge stations 4, 5 in first and second zones, namely upper and lower zones 7 and 8. The apparatus 1 further comprises cooling units 10a, 10b each of which employs cold air to create a cooling atmosphere in each of zones 7 and 8, whereby the ambient temperature of the first zone (7) is substantially less than that of the second zone (8). The internal volume of the first zone (7) is substantially greater than that of the second zone (8). <IMAGE>

Description

SPECIFICATION Improvements in or relating to methods of, and apparatus for, the cooling of hot bak ery products This invention relates to methods of, and apparatus for, the cooling of hot bakery pro ducts.

As used herein, the term "bakery products" includes, for example, bread, bread rolls, pies and cakes. However, the example to be de scribed below relates to the cooling of hot bread loaves.

Most bread cooling systems operate on the established method of causing the loaves to travel through an air conditioned chamber until the loaf's centre temperature has fallen to about 27"C.

The air conditioning takes the form of humidifying an air stream whose temperature is controlled by mixing recycled and fresh air. In winter time a few minutes cooling time may be saved by using only fresh air, whilst in summer the fresh air may become too warm and humid to achieve the desired results, causing problems at the slicing machines.

The warmer the air becomes, the more weight is lost in the form of moisture evaporated, so dough scaling weights have to be increased in hot weather to compensate.

Attempts have been made in the past to reduce cooling times by subjecting the products to reduced pressure or partial vacuum.

This resulted in excessive moisture loss.

However, extended cooling time, usually of the order of 2+ hours, requires expensive, large-capacity machines.

Cooler performance is dependent on climatic conditions, which can lead to poor cooler performance during the summer.

Fairly high product weight-loss can result, especially during the summer months, which increases production costs.

Reduced overall cooling time results in cost savings by employment of smller-capacity, less-expensive machines, fewer loaves being moved around, and reduced production cycles cutting labour and energy costs.

Reduced weight loss results in a saving of expensive raw materials, which form a considerable proportion of the costs of bread making.

The invention also allows the manufacture of uniform products all year round.

It is an object of the invention to reduce overall cooling time and weight loss of bakery products without undue expenditure of energy.

According to one aspect of the present invention, a method of cooling hot bakery products comprises causing the products to travel through a cooling atmosphere, travel taking place in first and second zones, with the ambient temperature of the first zone being substantially lower than that of the second zone, and the volume of the atmos phere of the first zone being substantially greater than that of the second zone.

The ambient temperature of the first zone is preferably of a range 4"C to 6"C inclusive, and that of the second zone of a range 1 4or to 16"C inclusive.

The invention also comprises bakery products cooled by the novel method.

According to another aspect of the invention, apparatus for cooling hot bakery products comprises a cooling chamber having a product intake station, a product discharge station, means for causing the products to travel through the cooling chamber, between the intake station and the discharge station in first and second zones, and cooling means for creating a cooling atmosphere in each zone and operable whereby the ambient temperature of the first zone is caused to be substantially lower than that of the second zone, the volume of the atmosphere of the first zone being substantially greater than that of the second zone.

The travel time ratio of the first and second zones may be, respectively, from 1:1 to 1:4.

However, a 1:1 ratio is preferred.

The cooling means may utilise waste heat from equipment used to bake the bakery products.

Both aspects of the invention will now be described by way of example only, with reference to the accompany drawings, wherein: Figure 1 is a (semi-diagrammatic) side view in medial section, of apparatus for cooling hot bakery products, and Figures 2 to 5 are graphs which illustrate advantages of the invention.

With reference to Fig. 1, apparatus 1 for cooling hot bakery products in the form of bread loaves 2, comprises a cooling chamber 3 of elongate form, having a loaf intake station 4, a loaf discharge station 5, and conveyor means 6 for causing the loaves 2 to travel through the cooling chamber 3, between the intake and discharge stations 4, 5 in first and second zones, namely upper and lower zones 7 and 8 respectively. The apparatus 1 further comprises cooling means 1 Oa, 1 Ob for creating a cooling atmosphere in each of zones 7 and 8, and operable whereby the ambient temperature of the first zone (7) is substantially less than that of the second zone (8). The internal volume of the first zone (7) is substantially greater than that of the second zone (6).

The cooling atmosphere is cold air. The intake station 4 accepts bread loaves 2 direct from the oven (not shown) in which they are baked.

The cooling chamber 3 is divided internally by wall means including a partition 11 so as to define upper and lower levels which form, respectively, the first and second zones 7 and 8. The conveyor means 6 operates continuously so as to pass the loaves 2 around a circuit commencing from the intake station 4, along the (upper) first zone 7, then down to the (lower) second zone 8, and finally along zone 8 to the discharge station 5, as indicated by arrows 12, 13, 14.

The conveyor means 6 of this example is of the form disclosed by British Patent Specification No. 1,044,290, to which reference is directed. However, it will be appreciated that other suitable forms of conveyor means may be employed.

The intake and discharge stations 4, 5 employ pusher units 15, 1 6 to unload and load loaves 2 from and on to belt conveyors 17, 18.

The cooling chamber 3 further comprises an atmosphere re-circulating passage 20 connecting one common end of the zones 7 and 8 with an exhaust duct 21. An extraction fan 22 is disposed within the passage 20. Shutters 23, 24 control outflow of cooling air from zones 7 and 8. A shutter 25 controls outflow of air from the discharge side of fan 22 to atmosphere.

A fresh air inlet passage 30 connects the other common end of zones 7 and 8 with an inlet duct 31 provided with a control shutter 32. A shutter 33 controls flow between the upper portion of the passage 30 and the lower portion thereof. The upper and lower portions of the passage 30 house the cooling means 1 Oa and 1 Ob respectively. A shutter 34 controls air flow between passages 20 and 30.

Airflow control movement of each of the shutters 25, 32, 33, 34 is controlled automaticaly by cooling means 1 Oa and/or cooling means lOb, by conventional control means, not shown. The shutters 23, 24 are manually set at the commissioning stage and are nor mally not adjusted thereafter.

Cooling means 1 Oa comprise a humidifying water spray unit 40, an air cooler unit 41 and an airflow discharge fan 42. Cooling means lOb comprise a humidifying water spray unit 45 and an airflow discharge fan 46.

In operation, air enters the upper portion of the passage 30 to be humidified and chilled by units 40, 41. The chilled, humid air, cooled by units 40, 41 to 4"C-6"C (inclu sive), is blown by fan 42 along the upper portion of the cooling chamber 3, i.e. along the first cooling zone 7. The flow of chilled air passes over the moving loaves 2, whereby the hot bread is instantly chilled on its outer surface.

This action reduces the amount of latent heat removed from the bread, with a corre sponding reduction in moisture loss.

The cooling conditions are maintained for 50% of the cooling cycle, i.e. throughout the first cooling zone 7, whereby the outer layer of each loaf 2 is kept at a low temperature so that heat is absorbed from the centre of the loaf. This means that heat lost from the bread is in the form of sensible heat.

It is considered unnecessary to maintain cooling at 4"C-6"C for more than 50% of the cooling cycle, as excessive cooling will overcool the bread and will thus be uneconomic.

After passage through the first cooling zone, the loaves 2 are caused to travel through the second cooling zone, i.e. zone 8.

Here the loaves 2 are exposed to an increased temperature, (14 C-16 C inclusive), which causes the surface layers of the loaves to warm up prior to discharge and subsequent slicing.

Humidity levels may be varied in either cooling zone, but it is desirable to maintain these at a high level in order to produce a crust suitable for slicing. However, automatic humidity control allows complete flexibility, particularly in the second cooling zone.

Any ratio may be used for the time relationship between the first and second zones. In the present example a 1:1 is employed. Up to 1:4 will produce some advantages but there is no advantage in going beyond 1:1 in favour of the first zone, as this will produce overcooling, with little reduction in cooling time or weight loss. Similarly, cooling temperatures lower than 4-6"C and/or 14-16"C are considered to produce little advantage for a considerable increase in capital and operating costs.

The majority of the heat is taken from a loaf 2 during travel through the first zone 7. Thus in order to maintain the temperature conditions required, most of the air circulating through the cooling chamber 3 passes through zone 7. When the outside air temper ature is below the return air temperature, outside air can be used in the cooling process.

Part or all of the refrigeration requirement of cooler unit 41 can be supplied by absorption units heated by waste heat derived from ex haust gases emitted by the associated baking oven. Thus the prevention of over-cooling, the use of cold outside air and refrigeration from recovered heat ensure that energy consump tion is kept to a low level. It also ensures that the cooler produces the same effects all the year round and is independent of the prevail ing climatic conditions.

It will be appreciated that movable shutters 25, 32, 33, 34 are operated so as to provide, together with fixed shutters 23, 24, control of cooling air.

With reference to Figs. 2 to 5: Figure 2. As the average air inlet tempera ture for the first and second zones 7, 8 is reduced, so the cooling time is also reduced, until a temperature of approximately 10"C is reached. At this point relatively large changes in air temperature produce only relatively small reductions in cooling time. The reason for this is apparent from Fig. 3.

Figure 3. This graph shows that the total heat extracted from the loaves 2 increased significantly when the cooling time is below 80-90 minutes, which corresponds to 10"C in Fig. 2. This implies that times above 90 minutes do not involve over-cooling the crust, whereas to cool in less than 90 minutes more heat must be extracted than is necessary. It is possible to calculate the amount of heat that has to be removed from a loaf in order to cool its centre to 27"C, a desirable temperature.

When this is done uniformly throughout an 800g loaf, 1 73 kJ have to be removed. In order to cool more quickly it is necessary to cool the loaf surface to below 27"C, which necessitates removing more heat than the minimum. It is important that as much heat as possible is removed in the form of sensible heat rather than latent heat of evaporation as weight loss must be kept as low as possible.

It is clear from Fig. 3 that the shorter cooling times are associated with lower evaporative or weight loss, which fact is confirmed by Fig. 4.

Figure 4. This graph shows that the colder the average air inlet temperature, the lower the bread weight loss. However, as has been shown, over-cooling results in an excessive heat loss which means that the economies of weight savings are outweighed by the costs of handling the heat load. The greatest economies occur when an average inlet temperature of 10 > C is employed, which corresponds with the minimum time atainable and enables cold outside air to be used or at least part of the cooling effect for most of the year.

Figure 5. This graph illustrates that there is little advantage in extending the first zone cooling time beyond a 1:1 ratio as there is little improvement in the total cooling time, i.e. less than 90 minutes, for what has already been shown as uneconomical over-cooling.

Claims (11)

1. A method of cooling hot bakery products comprising causing the products to travel through a cooling atmosphere, travel taking place in first and second zones, with the ambient temperature of the first zone being substantially lower than that of the second zone, and the volume of the atmosphere of the first zone being substantially greater than that of the second zone.

2. The method claimed in Claim 1, wherein the ambient temperature of the first zone is of a range 4 C to 6 C inclusive.

3. The method claimed in Claim 1 or 2, wherein the ambient temperature of the second zone is of a range 14"C to 16"C inclusive.

4. The method of any one of Claims 1, 2 or 3, wherein the cooling atmosphere is a recirculated atmosphere.

5. Apparatus for cooling hot bakery products, comprising a cooling chamber having a product intake station, a product discharge station, means for causing the products to travel through the cooling chamber, between the intake station and the discharge station in first and second zones, and cooling means for creating a cooling atmosphere in each zone and operable whereby the ambient temperature of the first zone is caused to be substantially lower than that of the second zone, the volume of the atmosphere of the first zone being substantially greater than that of the second zone.

6. Apparatus as claimed in Claim 5, wherein the travel time ratio of the first and second zones is, respectively, from 1:1 to 1:4.

7. Apparatus as claimed in Claim 5 or 6, provided with means for utilizing waste heat employed to bake the products.

8. Apparatus as claimed in claim 6 or 7, wherein the cooling atmosphere is cold air, and means are provided for recirculating the cold air through the first and second zones.

9. Apparatus as claimed in any one of Claims 5 to 8, wherein the cooling means comprise a cooler, a himidifier and a fan.

1 0. Apparatus as claimed in any one of Claims 5 to 9, wherein the chamber is divided into upper and lower levels.

11. Apparatus as claimed in any one of Claims 5 to 10, provided with recirculating means operable whereby the cooling atmosphere is recirculated through the cooling chamber, means allowing a controlled outflow of atmosphere from the cooling chamber and means allowing a controlled inflow of fresh air into the cooling chamber.

1 2. A method of cooling hot bakery products substantially as hereinbefore described with reference to the accompanying drawings.

1 3. Apparatus for cooling hot bakery products substantially as hereinbefore described with reference to the accompanying drawings.

1 4. Any novel subject matter or combination thereof, including novel subject matter herein disclosed, whether or not within the scope of or relating to the same invention as any of the preceding claims.