METHOD AND PLANT FOR BAKING USING STEAM

Abstract: A method for producing baked articles comprises the successive steps of mixing a dough, forming the dough, proofing the formed dough, and baking the proofed dough. The formed dough is heated only by steaming thereof as at least a part of at least one of the steps of proofing and baking of the dough. Thus, the steaming may be performed as a start of the proofing of the dough, as a finish of the proofing of the dough, or the whole proofing of the dough may be performed only by the steaming thereof. A plant for producing baked articles comprises a separate housing for heating the formed dough only by steaming thereof as at least a part of the proofing or the backing.

Description: METHOD AND PLANT FOR BAKING USING STEAM The present invention generally is related to baked articles produced by the successive steps of mixing a dough, forming the dough, proofing the formed dough, and baking the proofed dough. The production of baked articles such as bread, croutons and bread crumbs in an industrial scale is still a very labor intensive and time consuming process. Therefore, the main object of the present invention is to improve the prior art processes in order to speed up them by shorting the time period for proofing and/or the time period for baking. According to one aspect of the invention, this object is achieved in that the dough is heated only by steaming thereof during at least a part of at least one of the time periods used by the steps of proofing and baking of the dough. Such heating of the dough during a first part of the time period used for the proofing of the dough results in a considerable reduction of the proofing time, especially if the formed dough is proofed only by the steaming thereof, i.e. when the normal proofing is totally eliminated. Using the heating of the dough during a final part of the time period used for the proofing also results in a reduction of the proofing time by a fast increase of the volume of the dough. These favorable results follow from the use of steaming as single means providing the heat for proofing, which enables proofing at higher temperatures than are normally used, as a consequence of the high humidity generated by this way of steaming. More precisely, the high humidity gives a better heat transfer to the dough and eliminates drying of the surface of the dough. Such drying would result when any other heating means was used and could create an incipient crust that prevents the dough from rising during proofing. Normal proofing of dough containing yeast is performed at temperatures in the interval of 32-42°C. According to the present invention, the proofing temperature may be raised to above about 45°C, but below 65°C, when proofing is performed by means of steaming alone. As a consequence of the raised temperature the proofing time may be so short as about 3 minutes. When using steaming during a first part of the time period used for the baking step, the total baking time may be reduced as a consequence of an improved heat transfer rate. In addition, using steam as a single heating means results in an added moisture retention and a smoother surface which in turn extends shelf life and inhibits mould growth. According to the invention several crust characteristics such as glossiness, smoothness, hardness, thickness, and color may be influenced through a variation of the time of the steaming and the temperature during the steaming. FIG. 1 is a flow chart showing a plant for performing the method according to an embodiment of the present invention. Fig. 1 illustrates a line and the steps performed therealong for producing bread croutons, where in a first step a dough is mixed and then cut into pieces. The dough pieces having a height of 2-4 cm and a temperature of about 30°C are positioned on an impervious conveyor belt and heated by means of a heater positioned below the conveyor belt path such that the dough pieces are exposed to a temperature of about 180°C during a period of about 1 minute. Optionally, heaters positioned laterally of the dough on the conveyor belt may also be used. The heat exposure sets the bottom surface of the dough pieces such that a crust is produced. This crust enables handling of the dough pieces in the remaining process without pans or the like and even carrying them on a foraminous conveyor belt, e.g. a conventional wire or mesh belt following a helical path. Thus, the forming of the crust enables a continuous processing of the dough. Preferably, the dough pieces also are heated from above producing an even top surface on the finally baked dough pieces which facilitates slicing and dicing of the baked pieces into cubes or croutons. Further, this heating produces a small increase of the volume of the dough pieces. The dough pieces are now transferred to a foraminous conveyor belt for transport through a steaming chamber. The steaming chamber is heated by steam only to a temperature of about 65°C. The dough pieces stay in the steaming chamber for about 2-4 minutes and through proofing attain an increasing volume resulting in a height of 6-9 cm. Thus, if the dough pieces are subjected to an atmosphere containing water vapor at or near the saturation point at a temperature higher than about 45°C, the total proof time is greatly reduced. From the steaming chamber the dough pieces are transferred to another foraminous conveyor belt transporting the dough through an oven along a helical path. The temperature in the oven is kept at about 190°C by means of a heated airflow with an addition of steam so as to obtain a vapor by volume of 40-85%. The baking time of the dough pieces in the oven is about 30 minutes. The baked pieces are transferred from the output of the oven onto another foraminous conveyor belt adapted to follow a helical path in a cooler, in which air having a temperature of about 5°C is blown at a speed of about 3 m/s past the baked pieces during about 60 minutes. The cool baked pieces are then transferred to a dicer (or a grinder) and the produced dices finally are dried for 45 minutes in a dryer by an airflow of about 1 m/s and a temperature of 70-150°C. However, the baked pieces may be used without any disintegration, i.e. as ordinary bread loafs . The expert understands that several modifications of the above-described embodiment of a method and a plant for baking using steam are conceivable within the scope of the invention as defined in the appended claims. Thus, steaming may be performed initially during the baking as a separate processing step, e.g. at a tempe- rature of about 90-110°C. Further, the dough may be formed as one or more continuous lengths or sheets on the impervious conveyor belt or may be formed in trays or pans. Finally, it should be noted that each one of the successive steps preferably is performed in at least one separate apparatus, such as a mixer, a sheeter, a cutter, a crust former, a proofer, a steamer, an oven, a cooler, a grinder or dicer, and a dryer.

Claims: CLAIMS 1. In a method for producing baked articles by the 5 successive steps of mixing a dough, forming the dough, proofing the formed dough, and baking the proofed dough, the improvement comprising heating the formed dough only by steaming thereof during at least a part of at least one of the time periods used by the steps of proofing and 0 baking of the dough. 2. A method as claimed in claim 1, wherein the steaming is performed during a first part of the time period used for the proofing of the dough. 3. A method as claimed in claim 1, wherein the 5 steaming is performed during a final part of the time period used for the proofing of the dough. 4. A method as claimed in claim 1, wherein the formed dough is proofed only by the steaming thereof. 5. A method as claimed in any one of claims 1-4, 0 wherein the steaming is performed initially during the baking as a separate processing step. 6. A method as claimed in any one of claims 1-4, wherein the formed dough is proofed above about 45°C by the steaming. 5 7. A method as claimed in claim 5, wherein the proofed dough is steamed at about 90-110°C initially during the baking. 8. A method as claimed in claim 1, wherein the steaming for the proofing is performed in a separate -0 housing. 9. A method as claimed in claim 1, wherein the dough is transferred by a foraminous conveyor belt through each one of the proofing and baking steps. 10. A method as claimed in claim 9, wherein the dough is formed on an impervious conveyor belt and is heated at least from below for forming a crust supporting the dough on the foraminous conveyor belt in each one of the proofing and baking steps. 11. A method as claimed in claim 10, wherein the dough is formed as a continuous length on the impervious conveyor belt. 12. A method as claimed in claim 10, wherein the dough is positioned as separate pieces on the impervious conveyor belt. 13. A method as claimed in claim 10, wherein each one of the successive steps is performed in at least one separate apparatus. 14. A method as claimed in claim 9, wherein the dough is formed in pans or trays supporting the dough on the foraminous conveyor belt in each one of the proofing and baking steps. 15. In a plant for producing baked articles by the successive steps of mixing a dough, forming the dough, proofing the formed dough, and baking the proofed dough, the improvement comprising a separate housing for heating the formed dough only by steaming thereof during at least a part of the time period used for the proofing of the dough. 16. A plant as claimed in claim 15, further comprising another separate housing for heating the proofed dough only by steaming during a first part of the time period for the baking of the dough.

Inventors: HYLLSTAM MARI, JARA BRUCE C, PAAHLSSON STEN, HYLLSTAM, MARI, JARA, BRUCE, C., PAAHLSSON, STEN
Applicants: FRIGOSCANDIA EQUIPMENT AB
Application year: 1999
Main classification: A21C8
IPC codes: A21C13, A21D8