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Rene Meira Medina, Executive Vice President Gericke USA | October 11, 2021
I recently received a request for a quotation from a food technologist for a blender. His task is to develop a new version of a best-selling product, but with cleaner labels, and all-natural and functional ingredients. The new formula requires the content of several of these ingredients to range from 20% to close to or less than 1%, and the mixer in their test laboratory cannot consistently produce a uniform mixture. When the number of ingredients is close to 20% of the mixture-usually called micro-ingredients-or close to or less than 1%-called micro-ingredients-many types of mixers are usually struggling to solve the uniformity problem of the final product. However, these micro-components are not only difficult to mix uniformly, they are usually more expensive than traditional components, and their delicate and sensitive characteristics usually require special consideration during processing. Unfortunately, more and more product development professionals in the food, beverage, and nutrition industries are learning about these issues through costly trial and error.
Although most pharmaceutical processors have been mixing very small amounts of active ingredients (API) and flavors with various large amounts of excipients for many years, consumer demand for nutritional supplements and healthier foods and beverages has surged. Inexperienced companies process micro-ingredients to develop new products that meet this demand. These probiotics, herbs, spices, trace elements and/or other healthier ingredients may provide medicinal or preventive health benefits (and key marketing benefits) and are usually used as trace ingredients without affecting the required Function. However, many of these ingredients, such as flaxseed and soy protein, usually need to be masked by the main ingredients due to their taste and texture. Even if the content in the mixture is slightly higher, it will have a negative impact on consumer acceptance.
When the formula needs to mix one or more micro-ingredients, certain types of mixers can be designed to integrate them evenly better than other types of mixers. Simultaneous application of a radially dispersed mixer by rotation, and a combination of axial flow (moving parallel to the mixing rotor) and radial flow (moving perpendicular to the mixing rotor) generate and guide the turbulence needed to extract components from the sides and below and below Pass through the mixing zone without losing precious trace components along the outer edge. However, this turbulence needs to be carefully controlled to avoid applying excessive shear forces, which may damage the delicate trace components.
A mixing concept that applies these opposing forces and minimizes shear uses a biaxial, counter-rotating, horizontal mixing rotor to create a fluidized bed. This allows the mixed product streams to meet in the suspension, which exposes a large amount of the surface area of each particle for mixing and produces a high particle exchange value. At the same time, the mixing tool continuously guides the material flow through the mixing chamber, then separates and returns for a strong mixing action. This type of mixing has been applied to batch mixing systems, and usually produces a uniform mixture within 30 seconds regardless of the number of input ingredients. The same concept that combines dispersion with the optimal combination of radial and axial flow is also applied to continuous mixing. The rotation of the mixing screw tool generates a forward movement, forming a fluidization zone between the screw and the barrel to achieve a strong mixing effect comparable to the batch.
In contrast, a belt mixer applies both radial and axial forces, but lacks the forward and backward movement provided by the radial dispersion required to achieve maximum uniformity. Planetary mixers are usually good at mixing thick materials that require a lot of shear and can withstand tearing forces or the final particle size and shape are not important.
Although not ideal for many micro-ingredient blending applications, these and other blending concepts may be effective, depending on the ingredients, particle size and shape, moisture content, and other factors.
It is tempting to focus on designing the ideal mixer for a new formulation, but if any of the many problems that may arise upstream must be overcome, even a perfect mixer can hardly achieve uniform mixing.
For example, in the process from storage to mixer, many micro-ingredients need to be prevented from contamination. Exposure to the factory environment during the powder transfer process may cause pollution from humidity, environmental dust, pests, and other sources, as well as cross-contamination of any remaining components in the machine. Workers manually handling and emptying sacks into the mixer can also pose a threat to product purity. If traces of waste or other contaminants contaminate the main ingredients in the formula, such as wheat flour, then the typical batch size can solve this problem without any worries. However, if the same, trace amounts of waste or other contaminants contaminate the trace components, then the proportional effects can significantly change the characteristics and destroy the entire batch. In order to ensure the purity of these ingredients, many process engineers specify closed conveyors, such as pneumatic conveying systems, which automatically transfer bulk materials from storage directly to the mixer or first to the sieving machine and/or feeder, and No need for human contact or exposure to the risky plant environment in the air. These closed powder delivery systems can also prevent product degradation and loss to ensure that the entire material volume reaches the mixer safely.
Image courtesy of Gericke USA
Relatively small amounts of micro-ingredients require highly accurate weighing, measurement, and feeding into the mixer, usually using a loss-in-weight feeder. This Gericke gravity feeder is suitable for food, pharmaceutical and other sanitary processes. The addition of micro-ingredients brings some challenges, which need to be solved to make the mixer run at maximum efficiency. When feeding large amounts of main ingredients, considering the relative risk of adverse consequences when mixing, the measurement of volume, weight, and/or feeding rate may allow considerable leeway. However, relatively small amounts of trace components require precise feeding and weighing. Due to the proportional influence of the small volume, even a small error can cause a huge difference between the target quality specification and the actual product discharged from the mixer. The most common culprit is human error. Although workers usually measure the main components in a sufficiently accurate manner to meet the quality specifications, manually measuring the minor components can cause errors and result in the batch being discarded as waste. The number is too small and the consequences are too great, and even more experienced workers cannot risk entrusting this task to them.
In order to ensure that the required amount of micro-ingredients is accurately fed into the mixer, many processors specify an automatic loss-in-weight (LIW) feeder with advanced control technology. These gravity feeders with built-in load cells accurately weigh a preset amount of material and then gently add it to the mixer. Alternatively, the feeder can be set to continuously meter the material entering the mixer at a preset rate for a continuous process. These can be designed to handle 100 g/hr to more than 30 tn/hr. When feeding regulated materials as micro-ingredients, such as APIs used to manufacture drugs or vitamins (in some countries/regions), this computer control provides both feeding accuracy to ensure product quality and meeting record keeping Regulatory required documents. In addition, although the weight gain (GIW) feeder installed on the mixer can be used to measure the feeding amount of the main ingredient, the amount weighed in the mixer is large, so it is difficult to accurately detect the proportionally lighter trace ingredients . Multiple LIW and GIW feeders usually feed multiple ingredients into a single mixer to match each ingredient to the required accuracy.
Image courtesy of Gericke USA Figure 1: This figure illustrates how the mixing quality, expressed in relative standard deviation (RSD), improves as the weight concentration of the material relative to other ingredients increases and the total amount of micro-ingredients increases. This avoids adding more or less material than expected, which wastes valuable material and may make the batch waste. When quantifying the degree of mixing quality in terms of relative standard deviation (RSD), even small changes in the content of micro-ingredients in the formulation are important (Figure 1). The mixing quality increases as the weight concentration of the material relative to other components increases, and as the total amount of trace components increases, the mixing quality improves even more significantly.
Rene Meira Medina is the Executive Vice President of Gericke USA (Somerset, NJ). Founded in 1894, the company designs and manufactures a series of mixers, crushers, pneumatic conveying systems and other powder processing equipment. For more information, please call 855-888-0088, send an email [email protection], or visit www.gerickegroup.com
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