Reading the cultural and historical backgrounds of tea, the layperson is tempted to draw one or more parallels with wine culture. Both grapevines and (Darjeeling) tea plantations are found on steep slopes and their fruit can often only be harvested by hand. For example, pickers need to gather more than 10,000 leaves to obtain one kilogram of Assam tea. For all their differences, both end products are the result of fermentation processes. The vine, like the tea plant, has been cultivated for thousands of years and both types of plant can reach a considerable age. Vineyards and tea gardens require a lot of manual work and care to guarantee the yields. So-called weeds must be constantly eliminated because, as so-called angiosperms, their rate of spread can be significant. Weeds can contain natural toxins known as pyrrolizidine alkaloids, which, like residues of crop protection products, must not be released into the end product at all. And like the taste of good quality wine, a good tea can stir our senses and generate feelings of wellbeing and relaxation.
According to ISO-standard 3720 only the leaves of the Camellia Sinensis can be described as tea. These plants are evergreen upland bushes or small trees. They are considered robust and even frost-resistant for a short time.
Occurrence and consumption
Tea is a high-quality commodity. Around 6.1 million tons of tea was harvested worldwide in the year 2017 with China (40%) and India (22%) being the largest producers followed by Kenya (7%), Sri Lanka (6%) and Turkey and Vietnam (4% each). Pakistan, Russia and the USA are the three biggest tea importers. In Europe, according to Wikipedia, the per capita consumption in East Friesland is the highest, followed by Great Britain, Ireland and Poland. The pleasure of tea drinking, alongside the reviving effect and color of the infusion, is derived from the taste and aroma.
Quality management for good tea should start in the field/ tea garden: Determination of the time of harvest, purity of the harvest and transport. A quality-determining step concerns fermentation. The tea leaves are rolled after harvesting to release moisture containing the plant's unique enzymes. The presence of oxygen then triggers the fermentation. The color of the tea leaves changes, as does the aroma. A feed of hot, dry air or steam halts the fermentation. A short fermentation period results in green tea, a longer fermentation produces black tea. The tea is then dried precisely according to its type and prepared for packaging and safe transport. It must be stored in cool, dry surroundings.
The publications of ISO 3720 2011-04 and directives of the German Tea Association are concerned with the issues of tea production quality from the garden to the consumer.
Tea comes from many countries and is blended and drunk in many more. This places great demands on the industrial mixing and preparation technology.
Blending often takes place in free-fall mixing systems similar to those shown below. Here, different tea varieties can be blended and aromatics can be added in powder form. The mixing of liquid aromatics is possible only to a limited extent.
Similar to spices, tea should retain its flavors even if it has to undergo a sterilization process. In addition to other types of "sterilization /degermination", steam sterilization with amixon® reactors can be used.
Tea houses all over the world generally process and sell not only traditional black and green tea but also fruit teas, which are made of dried fruit, plant and herb derivates and prepared in a similar way to traditional tea.
The mixing process is important from many perspectives. First, harvest batches are gathered from a wide range of different gardens, regions, and harvest times in order to achieve a desired quality standard. Batching is the process of homogenization and often requires the blending of large volumes. The mixing process itself can be very demanding because the form and structure of the tea leaves / dried fruit derivates may not change. Fine particles and dust are undesirable.The amixon® Gyraton mixer is the convenient way to homogenize large volumes gently and precisely.
As a manufacturer of precision mixers, amixon GmbH from Paderborn has dedicated itself particularly intensively to the above-mentioned tasks and established a wide variety of solutions based on vertical helical mixers. To a certain extent, 40 years of experience for the tea, aroma, herb and spice industries have been accumulated here. A well-equipped pilot plant allows practical trials for small and large batches; optionally also beyond 5m³. The trials also provide the user with valuable suggestions for a wide range of processing details. Often, several process steps can be combined.
Producers of food and beverages generally bear a great responsibility. Infused beverages must be tasty and one hundred percent pure. These high quality requirements are met all the better if the raw material components are prepared in process-safe systems. Short mixing times ensure that the particle structure of the raw materials is preserved. Established solutions are available, especially when micro-components such as liquid flavors, vitamin additives or powdery flavors are to be mixed in.
The amixon® twin-shaft mixer is particularly suitable for larger batches of around 2m³ to 25 m³. The mixing tools rotate only after the last powdered formulation ingredient has been added. Liquid additions take place during mixing. Ideal mixing qualities are achieved after 20 to 40 revolutions. Then the closing elements open and the finished mixture flows into containers or big bags. The mixer discharges up to 99.98%. The filled big bags or containers are taken to the packaging plant, where their contents are bagged.
The twin-shaft mixer described here mixes precisely and very gently. The mixing time often takes only 20 to
30 seconds. Delicate components such as herbs, tea leaves or
agglomerated aromatics from fluidized bed granulation or from the spray
remain practically intact.
If required, the vertical twin-shaft mixer can also be manufactured as a
vacuum version. This allows the removal of atmospheric oxygen by the
application of a vacuum.
Saturation to atmospheric pressure is achieved by the addition of inert
In the off-line mixing process, the mixing process is decoupled from the filling process. This saves time, because while the filling machine is filling cans, pouches, sachets, and tea bags, the mixer can already be cleaned and prepared for the next mixing job.
mixer from amixon® has been specially developed for
“end-of-the-line” production concepts for the luxury food industry. In this method, all processing apparatuses are located one
below the other. The finished mixture flows from the mixer
through the mixer outlet bin directly into the packaging machine. Cleaning work is greatly reduced because this mixer empties
Batch sizes are generally from 300 up to 2000 liters. At low rotation speeds the KoneSlid® mixes very precisely and extremely gently. The mixing process is also particularly short. The design of the mixer ensures, for example, that sensitive agglomerates from the spray tower, fluidized bed granulation or from vacuum freeze drying are preserved. This mixer can also be supplied as a vacuum-tight version if required. This allows the atmospheric oxygen to be removed from the porous powder mixture by applying a vacuum during mixing. Saturation is achieved by the addition of appropriate inert gas. Discharging takes place without segregation in just a few seconds. Free-flowing goods usually flow out completely, so that cross-contamination is excluded.
The AMK conical mixer from amixon® can conveniently solve such a mixing task. Tea leaves, chopped pieces of vegetables, fruits and spices, powdery flavors and liquid flavors are continuously fed into the mixer. Mixing takes place in the form of gentle continuous kettle flow and ensures a homogeneous end product. The boiler flow present here can compensate wonderfully for any dosing errors that occur for a short time. Furthermore, with this amixon® continuous mixer there are no product losses during the start or during the termination of a mixing campaign.