Precision mixers for food processing with aroma compounds

Aromas play an indispensable role in modern food production. The word “aroma” comes from the Ancient Greek word meaning spice. Aromas result from chemical compounds such as arenes, esters, terpenes, aldehydes, ketones, and other basic materials. Many of the chemical compounds from which aromas arise are naturally contained in raw foodstuffs, while others develop through the chemical changes induced by baking or cooking. It is possible to synthetically manufacture aromas that are identical to those found nature by replicating their chemical structures.

This same science can also be applied to creating artificial flavors which do not occur naturally. Artificial aromas are prized for their capacity to enhance the flavorful qualities of food products beyond what would be possible with naturally occurring ingredients. But certain natural aromas remain difficult to satisfactorily replicate by synthetic means and therefore must always be sourced from natural ingredients.



Food aromas: How do we taste?

The sensory organs of human beings encompass sight, touch, hearing, smell, and taste. The perception of flavor is the combined result of smell and taste, developing as one inhales through the throat and tastes with the tongue. The aromatic substances are warmed within the throat and reach the receptors in the nose via the passage that connects the throat and nose.

The human tongue can only recognize five types of flavor: sweet, sour, salty, bitter and umami. The flavors “spicy” or “peppery,” on the other hand, are not perceived by taste, but rather predominantly over pain receptors.

The flavor umami was discovered by the Japanese researcher Kikunae Ikeda in 1908. Umami can be roughly translated as “brothy” or “meaty,” and is a dominant flavor in Parmesan cheese, lasagna, pizza, sardines, mackerel, and tuna. The umami taste is carried by glutamic acid, an amino acid found in large quantities in ripe tomatoes, meat, soy sauce, cheese, and human mother’s milk. Its salts are called glutamates.

The receptors in the mucous membranes of the nose can detect over four hundred different odors. Using the combined powers of our senses of smell and taste, we can distinguish between over ten thousand aromas and millions of odors.

Aroma production in the modern food industry

As communities grow increasingly diverse and taste preferences change the world over, aromas play a crucial role in the production of flavored snacks and beverages, including instant drink powders, milk shakes, yogurts, teas, energy drinks, fruit gummies, and candies. These products derive their flavors largely from liquid or powdered aromas.

The challenges of aroma manufacturing companies are not unlike those of the food processors who will ultimately use their products: they prioritize efficient service and consumer preferences above all. But fast, cheap, and tasty is not enough to stay competitive in today’s food industry. Many consumers are increasingly concerned with sustainable production and nutritional health and may avoid purchasing foods containing artificial flavor enhancers or high levels of sugar, salt, and fat.

In light of the rapid population growth and a budding global middle class, it can be assumed that the market for convenience foods will become larger. These include, in particular, dehydrated instant foods, a product in which aroma compounds are pivotal to taste.

The role of mixers in food processing

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Different emerging markets around the world, each with their specific cultural needs, have given rise to a diversity of instant food and drink manufacturers offering their own unique selling points. But before these instant food products end up in consumers’ shopping baskets, they travel through a long supply chain that includes mixing, packaging, and transportation.

The mixing process in particular is decisive to final quality. It is during mixing that the bulk material characteristics of instant foods, such as homogeneity, natural appearance, flowability, texture, and resistance to crumbling, are determined. For instant drinks, proper mixing is crucial if the powders are to sink and dissolve in water. And for food products whose flavor is carried largely by aroma compounds, proper mixing is crucial to creating a product that tastes good.

amixon® precision powder mixers are in food and aroma manufacturing facilities all over the world. These high-performance dry ingredient mixers enjoy a reputation for being especially versatile in their ability to fulfill diverse food processing requirements.

Highlights of amixon® mixers for aromatic food processing

1. A three-dimensional flow produces technically ideal mixing results 

In industrial food processing, powdery substances are typically blended using precision mixing equipment. In the case of the amixon® mixer described here, the aggregate materials are conveyed within the mixing vessel by means of a three-dimensional current.

The mixing vessel consists of a cylinder with a downwards pointing cone as its floor. A helical mixing tool, also known as a ribbon blade, rotates at its center. The helical blades are tilted at approximately 20°. The space between each coil of the helix is such that a fifth of the mixer’s entire contents can be conveyed in a single rotation.

In simple terms, the mixing action can be summarized as follows: the spiral mixing blade forces the powders upwards along the periphery, while gravity carries them back down again along the center. The actual mixing, i.e. particles changing places with one another, happens between these two macro flows.

Mixing aromas for food production

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Testing and Construction
Each aroma manufacturing and food processing facility has its own operating philosophy. As such, every piece of industrial mixing equipment must be engineered for the customer’s specific needs.

amixon® has more than 30 test mixers in piloting centers located around the globe, including in Paderborn (Germany), Memphis (USA), and Osaka (Japan). Our process engineers have many years of relevant market experience in regions across the world. Our team of 142 employees carefully custom-builds every single one of our mixers according to detailed customer specifications in house at our production site in Paderborn, Germany.

2. Flexible settings: gentle homogenization vs. intensive conditioning

Distributive mixing
Because the mixing action proceeds without any deadspace, technically ideal mixing qualities can be achieved in as few as 70 to 200 revolutions, after which the homogeneity is virtually impossible to improve any further. This gentle and energy efficient mixing process can be described as “distributive mixing”.

The mixer is designed to generate this three-dimensional flow regardless of filling level, ensuring ideal mixing results even at filling levels as low as five percent. amixon GmbH designates the type of each of its mixers on the basis of the effective or working volume. For example, a mixer type AM 3000 can mix 150 liter batches just as well as 1,000 liter batches through distributive mixing. The peripheral speed of the mixing tool (measured in the cylindrical part of the vessel) is typically adjustable between 0.5 m/s to 2.5 m/s.

Dispersive mixing
In other cases, aroma manufacturing and food preparation require supplementary processing steps, such as delumping, dispersion, or agglomeration. An increased energy input is necessary in such cases, which in turn exposes the powders to more shear and friction. amixon® mixers accomplish this by increasing the rotational frequency and using additional dispersive shearing mechanisms.

In this way, a single piece of equipment from amixon® can function as a gentle homogenizer and distributive mixer on the one hand, and an intensive dispersive mixer on the other.

3. Differing filling levels

For dispersive mixing, the filling level should be high enough that the dispersive shearing mechanism is situated approximately 30 to 40 cm below maximum capacity.

The minimum filling level of each mixer depends on the size: the minimum filling level of the AM 3000 is approximately 400 liters, while that of the AM 6000 is approximately 600 liters.

4. Feeding and discharging the powder mixer

The mixer is loaded with individual components from above via one or more feeding connectors; loading can take place batch-by-batch, or continuously.

If the mixer is situated atop loading cells and functions as a hopper scale, it can be stationary. In the case that batches must be mixed in quick succession, it can rotate.

After two to six minutes, the mixing process is complete, and a discharge valve, flush with the floor of the mixer, opens. The mixing goods flow downwards out of the mixer. Discharging proceeds without any segregation and the size of the volumetric flow is determined by the dimensions of the stop fittings.

5. Vacuum- and pressure-tight mixing vessels

The sturdy mixing shaft is sealed and driven only from the top, out of contact with the mixing goods. This particularly hygienic shaft seal guarantees that the operation proceeds free of dust and contamination, even at different system pressures within the mixing chamber.

For example, a vacuum is present in cases when the mixing goods are loaded via pneumatic suction. In other cases, all atmospheric oxygen is eliminated from the mixing vessel before feeding by generating a vacuum of approximately 10 mbar gauge pressure. The mixing chamber is then flooded with nitrogen gas before loading. A gentle positive nitrogen pressure of 50 to 100 mbar is maintained in the mixing chamber during mixing and discharging in order prevent oxidization.

In special cases, loading the mixing vessel takes place via a pneumatic pressure system. Even during operation under extreme pressure, the mixing vessel remains gastight and dustproof. This applies in particular to complex structural elements such as the shaft seal, floor sealing valve, and the inspection door.

6. Inspection and cleaning

amixon® ensures ergonomic access to the mixing chamber by means of generously sized inspection doors. This facilitates quick and reliable manual dry cleaning.

The inspection door is manufactured using the CleverCut® process, during which an O-ring is inserted into the groove, creating a gastight, dustproof, and near-product seal. This door seal is suitable even for automatic wet cleaning, since it seals with virtually no deadspace. Joints and capillaries are largely avoided, accelerating and simplifying the drying process.

7. Hygiene, average degree of roughness Ra selectively 2 µm to 0.2 µm

Every part of the powder mixer that comes into contact with the product is welded flush and polished if desired. Surface polish or roughness is implemented according to customer specifications. Even a mirror-like polish is possible. In special cases, we can electropolish all contact surfaces.

amixon® provides documentation as to the FDA-conformity of all polymer materials, as well as proof of compliance with current EHEDG specifications for both dry and wet operation

8. Complete discharge and automatic wet cleaning

Due to the conical design of the mixing vessel, bulk materials discharge almost entirely and without segregation. This gives end users the flexibility to use the same mixer for different components. Wet cleaning can also be carried out automatically by means of rotary washing heads which spray down all product contact surfaces.

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