Concentration of Tea & Coffee Extracts

Today tea and coffee extracts are usually concentrated to higher soluble solids levels for convenience, to reduce transportation and packaging costs and reduce energy consumption in subsequent drying processes. This concentration is normally performed by traditional evaporators, like rising film plate systems, or membrane systems, such as Reverse Osmosis. The Centritherm® evaporator, however, offers a number of unique benefits when processing tea and coffee extracts.

• High concentrations are readily achievable (without product recycle).
  
• Viscous tea and coffee concentrates are easily handled.
  
• Exceptionally short residence times (~1 sec on the heating surface).
  
• Low operating temperatures (around 50°C).
  
• Negligible thermal impact resulting in high quality concentrates.

Benefits of the Centritherm Evaporator when processing Tea

High Quality Concentrates
Both green and black tea extracts are extremely sensitive to heat. Exposure to elevated temperatures for prolonged periods initiates changes to the colour and flavour of the extract as well as degrading health promoting “active ingredients”. In extreme cases, this “thermal impact” can also cause caramelisation of naturally occurring sugars within the tea extract.

In the Centritherm evaporator, the action of the spinning cones reduces the contact time between the heating surface and the tea extract to approximately one second. Centritherm evaporators are usually operated with an evaporation temperature of 50°C and a steam temperature of 120°C. However, due to the heat sensitive nature of tea extracts, these conditions may be reduced to further minimise thermal impact.

No Burnt Characters
A principle of evaporation is that the heating surface must be wetted at all times. Poor coverage of the heating surface or a discontinuity in the product film leads to “burn on” of the product on the heating surface. This degrades the concentrate quality, decreases evaporator performance and can cause cleaning issues.

At high concentrations, tea extract can become extremely viscous making complete coverage of the heating surface difficult. In conventional evaporators, this is overcome by maintaining a high flow rate and  high levels of product recycle. As a result, product residence time is increased, and “stewed”, “cooked” or burnt characters are subsequently observed in the tea concentrate. Unlike these other evaporators the Centritherm evaporator uses centrifugal force to ensure the tea extract is evenly distributed across the heating surface. In fact, the thickness of the product film inside the Centritherm can be reduced to just 0.1 mm without the risk of discontinuity occurring, thus avoiding the need for product recycle.

High Extract Concentrations

Extracts from traditional tea extraction systems are generally within the range of 2.5 to 6.2º Brix (2 to 5% Soluble Solids), although this can vary with tea variety and type of extractor. The Centritherm Evaporator is capable of concentrating such extracts up to 57.8ºBrix (50% Soluble Solids) on a continuing basis with minimal to no damage to the product quality.

Benefits of the Centritherm Evaporator when processing Coffee

High Quality Concentrates
Coffee extracts, like tea, are heat-sensitive. Exposure to high temperatures results in damage to the extract’s colour, flavour and active ingredients. The Centritherm evaporator has been shown to have minimal impact on such factors due to it’s low operating temperatures and short residence times.

No Burnt Characters
Once again, at high concentrations, coffee extracts become extremely viscous. The Centritherm evaporator ensures the extract is evenly distributed across the heating surface, via centrifugal force, thus avoiding development of “cooked” or burnt characters in the resulting concentrates.
 
High Extract Concentrations
Centritherm evaporators are installed around the world for production of both liquid and soluble coffees. Extracts from traditional soluble coffee multi-cell extraction systems are generally within the range of 7.5 to 25°Brix (6.1% to 20.7% Soluble Solids). Extremely high concentrations are then required prior to spray or freeze drying. These concentrations are usually achieved using either:

• Two passes through a Centritherm evaporator;
  
• The Centritherm as a finisher after a traditional evaporator; or
  
• A pre-evaporator coupled to a Centritherm evaporator.

When using such methods, the Centritherm evaporator is capable of concentrating coffee extracts up to 70°Brix (62.0% Soluble Solids) in two passes.

A range of Centritherm evaporator models are available for batch or continuous processing.

Click here to find out more about the Centritherm evaporator.