Mixing and kneading: Set-up for continuous processes

© RBS

Reading Bakery Systems Exact HDX Continuous Mixer

All set for continuous mixing and kneading

Continuous dough production is designed with volume and efficiency in mind. Requirements stemming from the product characteristics, the manufacturing needs, the facility and equipment line-up will influence how continuous mixing and kneading should be set up.

+A continuous kneading and mixing process ensures all types of ingredients are mixed and kneaded in the optimum sequence to produce the desired product with consistent characteristics while saving time, resources and minimizing waste.

For the production of buns and rolls, such a system is the Exact HDX Continuous Mixer, developed by Reading Bakery Systems, which can process from 2,000 pounds per hour up to 15,000 pounds of dough per hour. It offers a number of features that make it well suited for these products: + The mixer has a two-stage design. In the first stage, the dough is mixed up to the clean-up stage (the point in the process where the moisture is completely distributed, but the development of the dough is only beginning). At this point, the dough will feel tacky but will not stick to the hand. The second stage is designed for the high-speed development of the dough. “Because the two units have independent drives, the two stages can be mixed at different mixing intensities. This makes the HDX Mixer very versatile,” highlights Jim Warren, vice president of Exact

Mixing at Reading Bakery Systems. + Both stages are designed to optimize the ability to cool the dough. Highly-developed doughs such as those typically used for buns and rolls can sometimes require temperatures lower than 70°F for mixing. To control the temperature, all internal surfaces are suitable for glycol solution cooling:

“The glycol (or chilled water) circulates in the mixer jacket and within the mixing shafts. The actual temperature is adjusted by either adjusting the temperature of the glycol or by changing the rate of circulation of the glycol,” Warren illustrates.

Moreover, the characteristics of the dough have been taken into consideration in the design of the HDX Mixer. Dough with hydration ratios of 60% and higher generally requires a great deal of shear to be developed to the required level. The key to success is to apply energy in a way such that the gluten strands are formed without shearing or shortening the strands, which is what the HDX is designed to do, he explains.

Diosna

ContinoMIXX

© Diosna

Zeppelin CODOS®NT

© Zeppelin

Exact Mixing

The company was founded in 1992 in the U.S. and became a part of Reading Bakery Systems in 2008. Between 1992 and 2008, four initial families of mixers were developed. These mixers allowed RBS to mix a wide variety of doughs from snack products, sweet goods, pizza, cookies and crackers to batters, and flat breads. In 2012, RBS joined AMF as part of the Markel Food Group. AMF specializes in the production of bread and bun equipment. This led to the development of the HDX Mixers, a fifth mixer family, which are specifically designed for these types of high development doughs.

Buns and rolls with the HDX Mixer

The equipment from Exact Mixing streamlines necessary processes for efficiency. The workflow is synchronized so that the dough is made at the same rate it is used, to avoid the accumulation of large batches of doughs that would need to be stored. Also, the dough exits from the mixer at a rate that allows it to be moved directly to the divider on a belt, without the need for resizing equipment or a dough pump.

All these processes are automatically synchronized so that a single operator is needed to oversee mixing and forming. To optimize the HDX Mixer’s settings, the primary adjustment will be in the speed of the mixer and developer shafts. “From recipe to recipe, the process may require more or less development or mixing due to specific requirements,” Warren explains. Other potential adjustments can include temperature settings, the location of the ingredient infeed, and controlling the quantity of the product in the mixer.

To control the temperature of the finished dough, the equipment offers three possibilities: coolant system adjustments, controlling the ingredient temperatures and the speed of the developer shaft (the last method is used less than the other two, because the manufacturer may not want to change the product’s development level). “The coolant properties can be easily automated, and it is the most common method used to control the finished dough temperature. This can be done best by adjusting the rate of coolant dough through the mixer jacket,” the specialist illustrates. Dough hydration is controlled by balancing the amount of moisture added to the dough and the speed of the mixer and development shafts.

Processes are automated to guarantee consistency; all process variables, including individual ingredient input rates, temperatures, development levels, and other inputs are constantly measured, compared to set points and automatically adjusted to assure the dough leaving the mixer meets set requirements consistently. In addition, the downstream equipment and dividing hopper levels are monitored and the mixer output automatically adjusted to match the rate needed.

For process safety, parts in motion are completely enclosed, and operations can be managed remotely. Food safety is also guaranteed since the dough is never exposed to the environment.

Kneading with continoMIXX

The continuous dough production system continoMIXX made by DIOSNA is recommended for any products using wheat. It features two independently adjustable tools and ensures optimal kneading, even when sizeable amounts of

The continoMIXX

Three different sizes are available: + Small: 1,500 - 3,000kg of dough per hour + Medium: 2,500 - 5,000kg of dough per hour + Large: 4,000 - 8,000kg of dough per hour

residual doughs are added back into the system. “Due to the mechanical decoupling of the two tools (paddle drive and screw drive), the speeds can be set separately,” R&D Constructor Stefan Bensmann, DIOSNA, explains. Different types of dough can be kneaded using the same tools, which ensures fast recipe changes while reaching maximum flexibility in hourly performance and kneading intensity. Its design is also mindful of the space it occupies and it supports increased water absorption, which is beneficial in terms of volume, flavor and ingredient costs.

An interesting case of kneading optimization contributing to the overall efficiency is when residual doughs are added. In the case of uniform return dough (laminated dough, for example), it is added directly to the kneading chamber and the kneading process is adjusted accordingly. In the case of non-uniform return doughs, they are placed into a storage container and continuously added from there in smaller quantities (adjustable). “The gentle addition of return dough is absolutely necessary for large quantities of return dough to prevent the deterioration of the final dough quality,” explains Bensmann.

Another interesting feature is how the two independently adjustable tools work (for feeding and kneading). The specialist shares the details: “In the process patented by DIOSNA, it is possible for the first time to separate the energy translation from the conveying effect in the continuous kneading process. In the past, increasing the rotational frequency of the kneading tools increased both the feed rate and the kneading energy. Now, it is possible to control these parameters individually via two independently coaxial kneading tools.”

The so-called paddle tool, which is arranged centrally in the middle of the continoMIXX, is used exclusively for applying the necessary kneading energy without conveying the dough. “It can be conditionally controlled via a frequency-controlled drive in the range of 20-70Hz, which allows maximum flexibility in the targeted addition of kneading energy,” the specialist adds. The infeed rate, respectively the hourly output of the kneading plant, is realized via the externally arranged screw tool. Due to the specific arrangement of the crescent-shaped elements of the tool, the dough is conveyed and also permanently pressed into the effective kneading zone between the paddle and screw tool. This tool is also conditionally infinitely variable in the range of 20-70Hz and also offers the possibility of specifically controlling the filling level of the machine trough. If the hourly output of the metering systems remains constant and the speed of the screw tool is reduced, the filling level of the machine increases, for example. This measure would have a direct influence on the kneading energy applied to the dough without increasing the conveying effect.

To automate workflow, the continoMIXX records weight data and the parameters of the kneader at all times. In case of deviations from presets, the system will automatically issue warnings, error messages, or even shut down the entire plant if the tolerance values are exceeded.

More power, less space

With a capacity range between 500 and 6,000kg/h, the newgeneration CODOS®NT from Zeppelin Systems brings improvements in capacity and efficiency over its predecessor. Its benefits include tight temperature control, raw material accuracy, low energy and maintenance requirements. It can save up to 15% floor space because it is equipped with a new drive technology that is smaller in size and better positioned, and up to 25% in weight, compared to the previous model. The gearbox and motor block have been resized and better positioned for efficiency, and the drive technology also helps optimize operation control. The servomotor has very high torque compared to the previous technology, which also contributes to saving energy and space. It is also more

flexible and easier to operate, as it requires fewer controls. Also, the design features make it easier to operate and maintain without having to dismantle the shaft, such as a light hood for fast access to change seals, bearing or couplings. These are the only parts that are regularly exchanged, which implies minimal maintenance costs. Requirements for a more hygienic design were also incorporated, and can also include a fully-automated cleaning system.

As the mixer operates continuously, the system is required to handle all types of ingredients over time, according to the recipes. It incorporates mixing, blending and metering units and synchronizes several processes. The dry ingredients (flour, salt) are collected in a blender, where the minor and micro ingredients are then conveyed, after scaling. “In a very short time, the dry ingredients are blended completely into a premix which is conveyed continuously into the mixer,” explains Thomas Ismar, director technology, Zeppelin Systems. The dry and the liquid ingredients are brought together and hydrated in the Dymo Mix high-speed mixer. There are several ways to control the temperature during the continuous mixing process in the CODOS®NT system: + Conditioning of the temperature of the raw materials (for example, laminated dough for croissants requires a cold

dough; in this case, the flour is brought to 18°C and even lower with ice water alone. Alternative cooling solutions such as CO2 or ice are not needed, resulting in important savings in the cooling process. For hamburger buns, a warm dough of around 30°C is required, so the flour does not need cooling in this case.) + The energy of the mixing process also contributes to the temperature of the dough. The speed of the mixing tools is not related to the production capacity (unlike extrusion systems where they are directly proportional), which is only dictated by the ingredient infeed. By adjusting the speed of the tools, the CODOS®NT system provides the option of having low or high energy mixing. The temperature of the dough during mixing can rise by 1-10°C depending on this parameter, making the system very flexible to various requirements. + The system itself is also double jacketed so it can be easily cooled or heated to the desired temperature.

The same system can be used for doughs with vastly different requirements and characteristics; it is ideal for the whole range of doughs, whether they need high-energy infeed like sandwiches and buns, or low-energy infeed such as pastry or some cookie doughs. +++

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