Abstract:
A continuous dough developing process including the steps of: 
     feeding combined and undeveloped dough to a continuous developing apparatus; 
     feeding oxygen gas to the combined and undeveloped dough as it is fed to the developing apparatus; and 
     mixing within the developing apparatus the oxygen and the dough with a rotor which imparts a shearing action between mixing means and the dough, thereby distributing the oxygen evenly throughout the dough.

Description:
This is a continuation of application Ser. No. 07/427,949, filed Oct. 25, 1989, now abandoned, which in turn is a continuation of application Ser. No. 07/228,272 filed Aug. 4, 1988, now abandoned. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to dough developing, and more particularly to a continuous dough developing process. 
     BACKGROUND OF THE INVENTION 
     Bread has traditionally been made in batch processes. The major processes used in New Zealand are the Bulk Fermentation Process and the Mechanical Dough Development Process. In the bulk fermentation process all the dough ingredients are mixed into a homogeneous mass, without doing an unnecessary amount of work. The dough is set aside for a set period of bulk fermentation. The fermentation time can vary widely but is now commonly two hours. A typical formula is as follows: 
     
         ______________________________________Flour                100     KgWater                59-63   kgYeast                3       kgSalt                 2       kgSugar                2       kgFat                  2       kgPotassium bromate    30      ppm.______________________________________ 
    
     As fermentation takes place the dough changes slowly from a dense mass lacking extensibility and with poor gas retention properties, into a smooth extensible dough with good gas retention properties. After fermentation the dough is divided into loaf-sized pieces, given an intermediate &#34;proof&#34; of about ten minutes, and then shaped (moulded). 
     The moulding process is vital in producing the correct bubble structure in the dough. If a fine uniform cell structure is desired in the bread, final moulding will be required to expel gas and cause large bubbles to collapse to create many smaller bubbles. The dough is then given a final proof of fifty minutes to expand almost to its full size then baked. 
     During the long fermentation of the fermentation group of processes there is an appreciable loss of flour solids due to their conversion to volatile substances. This loss is economically disadvantageous. In the search for ways of eliminating the need for long periods of fermentation, and also of reducing the loss of flour solids, mechanical dough development was discovered. By this technique, desirable changes in the physical properites of the dough, normally brought about by fermentation, are achieved by a short period of intense mechanical development in the presence of added fat and a moderately high level of a synthetic oxidising agent. 
     In mechnical dough development the initial fermentation step is replaced by a short period of intense mixing in a special high powered batch mixer that imparts between 5 and 12 Wh/kg (Watt-hours per kilogram) of work to all the dough ingredients in two to four minutes. Such mixers are usually operated under a partial vacuum to improve the crumb texture. The dough is then treated as for a bulk fermentation dough, that is, it is divided, given 10 minutes intermediate proof, moulded, given 50 minutes final proof and baked. 
     While this mechanical dough development process succeeds in reducing fermentation time and loss of flour solids, there are still inherent difficulties. The addition of a synthetic oxidising agent (potassium bromate) is undesirable for some markers. 
     The dough from the end of a batch waits longer to be processed than the dough from the start of a batch, leading to changes in dough consistency within batches. The intermediate proof step is still needed. A high-powered motor is required, which is used only intermittently. Further, the process is still a batch process, which is inconvenient for automation. 
     The object of the present invention is to provide a dough development process and apparatus which will go at least some way towards avoiding the above disadvantages. 
     SUMMARY OF THE INVENTION 
     A continuous dough developing process including the steps of: 
     feeding combined and undeveloped dough to a continuous developing apparatus; 
     feeding oxygen gas to the combined and undeveloped dough as it is fed to the developing apparatus; and 
     mixing within the developing apparatus the oxygen and the dough with a rotor which imparts a shearing action between mixing means and the dough, thereby distributing the oxygen evenly throughout the dough. 
     A continuous dough developing apparatus, the apparatus including a generally cylindrical mixer, the inner surface of which has a plurality of inwardly directed pins and an internal rotor positioned within the cylindrical mixer, the rotor having on its periphery a plurality of outwardly extending pins, the internal pins of the mixer and the external pins of the rotor being positioned relative to each other so as to produce in a combined and undeveloped dough to which oxygen gas is fed as it passes through the apparatus a shearing action which thereby mixes the oxygen evenly throughout the dough. 
     With a continuous dough development process, a smaller motor is required to develop the dough compared with that used in a batch mixer and it is not subjected to the strain of frequent stopping and starting. Also, a continuous process ensures that all dough has the same processing time and is therefore of the same consistency. Potassium bromate is not used in the formula but instead oxygen gas is fed into the developing dough to aid oxidation, and is distributed evenly and finely throughout the dough. This allows the dough to be extruded directly into bread tins, without the need for intermediate proof or moulding, and still produces bread similar in character to that produced from the standard mechanical dough development process. The amount of work imparted to the dough can be varied by adding or removing pins from the internal rotor as well as by varying the developer&#39;s speed. The internal rotor is hollow, and open at one end to facilitate the removal or addition of rotor pins without needing to dismantle the developer. With the use of continuous ingredient feeders the process can readily be fully automated. 
     The apparatus consists of a generally cylindrical mixer, the inner surface of which has a plurality of inwardly directed pins and a hollow inner rotor positioned within the cylindrical mixer. The rotor has a plurality of outwardly directed pins. The internal pins of the mixer and the pins of the rotor are positioned relative to each other to produce a strong shearing action on a combined but undeveloped dough. Means are provided for feeding oxygen gas to the dough as it passes through the mixer, and the shearing action mixes the oxygen gas throughout the dough. 
     Further aspects of the invention will become apparant from the following description which is given by way of example only. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a longitudinal section through a developer. 
     FIG. 2 shows a perspective view of the rotor and housing. 
     FIG. 3 shows a detail of a rotor pin. 
     FIG. 4 shows a flow diagram which illustrates a baking process incorporating the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In developing the present invention the applicants realised that an intermediate proof step was usually required to allow the oxidising agents added to bread to act and change the dough structure. This ensured that when moulded the texture in the resulting bread would be fine and uniform. By the use of oxygen gas and ascorbic acid as oxidising agents this oxidation step can be shortened. Oxidation can take place essentially within the developer, so eliminating the need for intermediate proof and moulding. 
     For the oxygen to be effective it must be distributed throughout the dough, and the oxygen bubbles must be finely divided to avoid large holes in the bread. For mechanical dough development to take place the dough should have between 5 and 12 Wh/kg of work imparted to it (the actual amount depending for instance, on the flour used). The mixing action, therefore, must be such as to impart a large amount of work to the dough and at the same time to distribute the oxygen evenly and finely throughout the dough mass. 
     In order to achieve this aim the applicants carried out many trials and have discovered that the use of the apparatus as shown in the drawings achieves this end. 
     The rotor 1 has a plurality of radially extending pins 2. In the example the pins 2 are arranged in four spirals which have the effect of improving dough flow in the direction of arrow 3 for rotation of rotor 1 in the direction of arrow 4. 
     The rotor 1 is mounted within an outer mixer casing 5 which has a plurality of inwardly directed pins 6. The pins 6 of casing 5 may also be in four spiral rows and the spacings between pins 6 and 2 when the rotor 1 is in place is such that a shearing action is created in the dough mixing region between the pins 6 and pins 2. 
     Combined but not developed dough is forced through the mixing space by means of a pump or other suitable apparatus. Oxygen gas is injected into the dough immediately before the first pins at end 7. With the rotor turning at between 100 and 300 rpm a strong shearing action is created between the pins producing intense mixing and at the same time distributing the oxygen throughout the dough. 
     A dough is mixed in order to combine all the ingredients, except oxygen, but not develop them. This mixing can take place in a batch mixer or a continuous mixer. A typical dough formula is as follows: 
     
         ______________________________________Flour             100%Water             60%Yeast             3.5%Gluten            2%Salt              2%Sugar             2%Compound improver 1.25%Ascorbic acid     100 ppm.______________________________________ 
    
     For optimum bread quality the dough temperature as it leaves the developer should be 32° C. To achieve this the dough water temperature is adjusted so that the amount of work given will raise the dough temperature to 32° C. Formulae for carrying out such calculations are readily available. A standard form of the calculation is as follows: 
     
         [2×32-(WI×1.33)]-FT=Required water temperature 
    
     Where 
     WI=work input in Wh/Kg 
     FT=flour temperature in degrees celsius. 
     The combined ingredients are placed in the hopper of a pump which then forces the dough, at a constant rate, through the continuous developer. The production rate is determined by the pumping rate. 
     The operation of the developer can best be described by referring to FIGS. 1, 2 and 3. The present developer consists of a hollow inner rotor 1 of 135 mm external diameter and 500 mm length. Four spirals of 10 mm diameter pins 2 protrude 30 mm with approximately 20 mm between each pin. FIG. 3 shows details of a rotor pin and its screw mounting. 
     To decrease the amount of work given to the dough the pin can be unscrewed and a blank pin 11 screwed in to fill the hole. The spirals of pins turn one quarter turn along the length of the rotor. The rotor is contained in an external housing tube 5 of 160 mm internal diameter of the same length. Four spirals of identical pins 6 protrude into the space between the rotor and the housing. The outer spirals are of opposite pitch to the rotor spirals. The rotor is turned in the direction of arrow 4 at a rate of 150 rpm by a 3-phase motor 9 through a gearbox 10. The rotor speed can be varied but below 100 rpm the oxygen is not well incorporated and above 200 rpm the resulting bread is of inferior texture and volume. Oxygen is injected into the developer directly adjacent to the first row of pins 12, through a 0.5 mm diameter nozzle 13. When the dough was pumped through the developer in the direction of arrow 3 at a rate of 400 kg/hour an oxygen flow rate of 6 L/minute (at standard pressure) was used. This gave an oxygen proportion of 0.9 liters per kg of dough which was approximately 1.4 liters per kg of flour. 
     As has been noted for optimum development a mechanically developed dough should receive a work input of between 5 and 12 Wh/kg, the optimum value varying for individual flours. To achieve variable amounts of work input, the number of pins on the rotor and the rotor speed can be varied. It is intended the main adjustment shall be made by varying the number of pins protruding from the inner rotor, which can be done while the rotor is stationary. Fine adjustment of work input while the mixer is working can then be achieved by adjusting the rotor speed. This can most readily be achieved by use of a speed controller attached to the motor. To facilitate the removal of rotor pins the inner rotor is hollow and open at end 8 so that the pins can be removed without dismantling the mixer. 
     This has the added advantage of allowing easy replacement of pins as they become worn. 
     The developed dough is extruded out of the end of the developer. From here as shown in FIG. 4 the dough can be divided and directly placed into bread tins or can be passed on to the traditional make up plant of divider, intermediate prover and moulder. The process can be automated by incorporating a computer controller adapted to control and monitor the input of ingredients, operation of the process and quality of the resultant output. This includes control of the operation of the mechanisms incorporated--in the baking process shown in FIG. 4. 
     For full scale commercial production the developer would need to be able to produce up to 6000 kg of developed dough an hour. To scale up the present design to produce this amount of dough it is envisaged the mixer would have the following dimensions. The internal rotor will have a diameter of 200 mm and a length of 1000 mm. The four spirals of 10 mm diameter pins will protrude 99 mm with approximately 30 mm clearance between each pin. The spirals are to be of the same pitch to give one half turn along the length of the rotor. The rotor will be contained in an external housing of 300 mm internal diameter. Four identical spirals of pins will protrude from the housing into the space between the rotor and housing. The housing spirals will be of opposite pitch to those of the rotor and the rotor will be turned at between 100 and 200 rpm. 
     Due to possible differences in mixing efficiencies the optimum rotor speed may be different and the amount of oxygen injected may need to be varied from the present rate of 0.9 L/kg of dough. Possibly more than one injection point may also need to be used. 
     A particular embodiment of the invention has been described herein by way of example and it is envisaged that improvements can take place without departing from the scope and spirit of the appended claims.