Yeast extract concentration

Yeast extract is the common name for various forms of processed yeast products that are used in the food, beverage and pharmaceutical industries. Yeast extracts are often used as flavour enhancers in various foods and are also rich in minerals and various vitamins such as Vitamin B.

Both brewer’s yeast and baker’s yeast can be used for the manufacture of yeast extract. However the physical properties are often quite different between the two sources of yeast that lead to them being used for very different products.

Well known consumer products that are yeast extracts include products such as Vegemite and Marmite. These are thick viscous yeast spreads that are popular in countries such as Australia and the United Kingdom. Many would say that they are an acquired taste. As mentioned previously however, the majority of yeast extract is used as a flavour enhancer additive in the food industry.

The preparation of yeast extracts requires that the yeast cells are lysed. There are a number of different methods used for autolysis of the yeast. The two most common methods for autolysis of yeast cells are addition of a high concentration salt solution (Sodium Chloride) or use of an organic solvent such as ethyl acetate. The dying yeast cells are then heated to complete their breakdown, after which the husks (the thick cell walls) are separated before concentration and/or drying of the liquid extract.

The texture or concentrated yeast extract can range from a light paste to a very thick paste. The colour of yeast extract is generally light brown but may range from grayish to almost blackish. Concentrated yeast extract can also be dried in suitable drying equipment (including belt driers) to produce a powder.

The choice of autolysis technology has a critical impact on the type of concentration equipment selected due to the use of solvents. The autolysis method therefore has to be discussed during the initial inquiry to determine the level of electrical components that may be required in the evaporator to be manufactured.
 
Concentration of yeast extract
The Centritherm® evaporator is an excellent choice for the concentration of yeast extract due to its ability to process highly viscous concentrates. Depending on the source of yeast and the final product (whether it will be a paste or a powder) the equipment can be used to concentrate up to 60-65% DM and even up to 80% DM.

The concentration process used by the Centritherm evaporator is extremely gentle preserving the product’s characteristics and functionality. It is an excellent choice of evaporator as it can concentrate without imparting unwanted cooked or burnt notes. Unlike conventional evaporators that have a long residence time on the heated evaporation surface using high temperatures, the Centritherm evaporator has a residence time of only one second and typically uses temperatures from as low as 40°C.

If an organic solvent is used for autolysis of the yeast, the installation will necessitate an ATEX approved installation.

In dealing with the extremely high viscosities often found in yeast extracts specific attention will be required to determine any unique discharge solutions due to the very high viscosity in the discharge concentrate.

Benefits of the Centritherm evaporator for the concentration of malt extracts include:

• Minimum thermal impact to preserve character and functionality
• Considerably higher viscosities possible than conventional evaporators
• No damage to the natural colour 
• Low hold-up volume means it is ideal for concentrating small batches
• High concentration ratios (up to 80% DM can be possible)
• Easily cleaned with built-in CIP

Click here to find out more about the Centritherm evaporator.