Many types of industrial mixers and blenders have been produced for food and beverage processors over the years. Some common types include: paddle, ribbon, conical, fluidised bed, impeller, planetary, screw, static and turbine mixers. However, a considerable degree of standardisation in mixing equipment has been reached.
Technologies Influencing Designs
Custom design mixer manufacturers are a good barometer for technical innovation. Here are a dozen technologies that rate high on food processors’ wish lists:
- Mixer process control (programmable controls)
- Network capabilities
- Variable speed drives (agitator speed controllers)
- Safety components
- Bearing and seal design (prevention of product leakage)
- Wear resistance and maintenance
- Sanitary mixing
- Precise temperature control
- Easy cleaning (CIP)
- Wide variety of discharge options
- Measurement capabilities (moisture, temperature, etc.)
- Microwave, vacuum and pressure ratings
Before touching on these new technologies, it is worth mentioning some of the emerging global trends that can be observed in food processing and advanced manufacturing.
Advanced manufacturing processes will likely be more energy and resource efficient in the future, as companies strive to integrate sustainable manufacturing techniques into their business practices, to reduce costs, to decrease supply-chain risks and to enhance product appeal with customers.
Achieving truly flexible manufacturing facilities requires advanced processing machines capable of rapidly changing to new designs and new materials, which not only shorten product-development cycles but also make facilities more robust against supply-chain disruptions. Additionally, this enhances bottom line profitably.
New technology can be separated into two categories: sustaining and disruptive. Sustainable technology relies on incremental improvements to an already established technology, or in other words, the better mousetrap or continuous process improvements.
A new disruptive technology developed by two equipment manufacturers located in the heartland of the US, is an example of a disruptive technology for the food processing industry. Industrial-sized microwave mixers are designed and manufactured to process everything from powdered eggs and growth supplements to elastomers used in the automotive industry.
In recent years, they have conducted research on many different cooking, drying, tempering, sterilisation and pasteurisation applications.
The typical microwave mixing system consists of four components: a customised mixing vessel, a RF transmitter, waveguide and controls.
Microwave mixer systems are custom designed with mixing capacities that range from 10 to 560 cubic feet in size. Smaller lab-size units are also available. High power electromagnetic energy is created in a 75 kW transmitter operating at 915 MHz. Low speed, gentle agitation in a paddle-style, horizontal mixer provides uniform heat distribution with superior product quality.
The combined action of mixing and drying using microwave energy provides faster, more cost effective heating, higher energy efficiencies and better product quality. It is ideal for processing gravies, sauces, chillies, soups, syrups, pet foods, spices, bakery products, jams and jellies, salad dressings, snacks, candy, confectionery items, meat products, and canned fruits & vegetables. These are all accomplished with a high degree of safety and simple maintenance and cleaning requirements.
Mixing In Vacuum
With the right combination of equipment and technique, vacuum can make a process line more productive and the plant environment safer. The following are a few of the processes and benefits mixing in a vacuum can provide:
Vacuum deaeration is achieved when mixing liquid, slurry or paste ingredients within a vacuum. Air bubbles are extracted from the final product as the agitator mixes the ingredients.
Food grade products like syrup, oil and chocolate liquor require deaeration to make the final product visually pleasing to the customer. The visual appeal of an air-free product is often a powerful competitive advantage.
In addition, a batch that has been agitated and deaerated under vacuum winds up more dense than it was initially. This allows a more efficient mix and the product to be shipped more economically. Also, with densification, the physical properties of the end-product are often improved.
Deoxidation is the removal of oxygen. This helps prevent the degradation of sensitive ingredients, and unwanted chemical reactions during the mix cycle. It also minimises microbial growth.
Vacuum blanketing is used when processing ingredients in the absence of air. An inert gas is injected into the vessel which blankets the material. Producers of bakery premixes with high levels of shortening or fat use carbon dioxide to cool the ingredients. This keeps the ingredients flowable until they are evenly mixed.
Microwave Vacuum Processing
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Many of the advantages of mixing, blending and drying under vacuum have been recognised for years in the food industry. However, microwave vacuum drying is relatively new.
Microwave vacuum drying is an excellent method for removing moisture or vapour from heat-sensitive materials without fear of thermal degradation. Pulling a vacuum inside the mixer lowers the boiling point of liquids. This creates a pressure gradient that changes the drying rate, and facilitates drying at a faster pace due to lower operating temperatures.
This efficient dehydration method can yield unique characteristics which may improve product quality compared to conventionally dried products. The microwave energy penetrates the interior of the food, where it is converted to thermal energy. This provides a rapid heating mechanism and shorter batch times.
Drying can typically occur in minutes rather than hours or days compared to other conventional drying methods. Another advantage is superior product quality. The vaporisation of water provides an expansive force to maintain an open cellular structure in the dried product, which translates into excellent rehydration rates. For products consumed in the dry state, a unique crisp texture can be achieved.
Microwave vacuum processing, with its unique characteristics, has also been utilised for tempering, thawing and the inactivation or preservation of enzymes and microorganisms. The uniform heat distribution is achieved with a gentle, mixing agitation.
There is probably nothing more important in the food industry than maintaining a high standard of aseptic and hygienic processing. Consider the many adverse effects of a product recall. In the US, mixer manufacturers elect to maintain their own sanitary equipment standards.
Some manufacturers write their own mixing and blending equipment standards that comply with the principles of 3A-Sanitary and global standards. These standards cover the sanitary aspects of blending equipment used for combining and/or mixing either wet or dry products.
Main Shaft Seal Design
To repair main-shaft seals in a shaft-driven mixer is time consuming and costly. For example, certain flour, sugar or spice blends may get less than one month wear life out of expensive mechanical seals.
New innovative sanitory shaft seal products are now available that help prevent leakage and have longer wear life. Some of these benefits and features include:
- Clean in place (CIP) designs
- Positive installations (no cutting required to fit)
- New shaft–friendly materials
- Non-intrusive material (unlike packing that can be porous and hold media)
- Won’t degrade like packing
- Easy disassemble (can be washed and reused)
- Proven, longer run times compared to other seals
- Sanitary-compliant materials
These new lip seals will outperform stuffing box seals, are less expensive than mechanical designs and can be disassembled, cleaned and re-installed in less than five minutes. For liquids, slurries and many other 3A-sanitary applications a single lip, non split-design is available.
Advanced Process Control
Creating an efficient mixing or blending system is a balancing act. Throughput must be balanced against batch size, agitator sizes, motor sizes, shear and tip speeds, viscosity, thermal capacity, moisture, temperature and pressure ratings, energy costs, labour costs, amongst many other variables.
Jayesh Tekchandaney, founder of the popular online site Mixer Expert states, “Today’s competitive production systems necessitate robust equipment that are capable of faster blend times, lower power consumption and adaptability of equipment for use with multiple products.”
“Many modern mixers are designed to combine different processing steps in a single equipment, eg: coating, granulation, heat transfer, drying, and so on,” he added. “A mixer is no longer a generic production tool, but a critical and decisive business tool. This is because profitability and competitive advantage are dependent upon subtle improvements in product quality through gains in mixing performance and efficiency.”
With a wide range of equipment choices and competitive pressure to optimise performance, the specification of process control equipment is extremely important. This requires solid custom-design engineering capabilities. The control system must balance the need for precision, consistency and adjustability, against the need to manage resources.
Testing plays an important role in selecting and optimising mixing and drying equipment. Fully equipped test centres use some of the latest technologies in processing. When a new material is used or if the knowledge of the material is limited, then the special material has to be tested.
Some of the test data that will be required includes:
- Moisture percentage
- Bulk density
- Energy consumption
- Decibel level
- Airflow in cubic feet
- per minute
- Rf energy absorption
- Mass balance
Those who are unsure about mixing, blending or drying applications should seek assistance from application and design engineers. Test facilities can be utilised to test specific ingredients and have a first-hand observation of the the production time and energy savings that can be achieved.