"Deaeration" means mechanical removal of dissolved and free gasses from a fluid (by vacuum).
In the Liquid Food Industry removal of dissolved oxygen and air is the most important aspect. Removal of oxygen and air is not only recommended in order to avoid undesired changes in the final product itself, but also to provide a smoother and more efficient downstream process.
GEA’s product deaerator is developed to handle most kinds of liquid foodstuffs, ensuring efficient deaeration along with gentle product handling.
The following description focuses on Juice/Beverage and Milk/Dairy Products, but the considerations also apply to many food products.
Juice/Beverage
Avoidance or minimization of the oxygen content in juice/beverage is the most important single factor in order to maintain a consistent high quality during shelf life.
Air/oxygen in the final juice causes degradation of vitamin C (1 mg oxygen in the final juice corresponds to a theoretical loss of 11 mg vitamin C), and furthermore strong off-flavours and discoloration may occur.
The main sources of air/oxygen in reconstituted Juice and Juice Nectars are:
- Mistreated juice concentrate
- Non-treated process water
- Addition of floating cells
- Insufficient/leaking pumps and pipes
- Wrong design of mixing tanks
- Bad agitator design
Since the oxygen content in the final product originates from several sources, removal of all oxygen from the process water itself does not necessarily remove oxygen from the final product, as it can be “added” again in other production steps. So looking at only one source will lead to misjudgement.
However, the quality of the reconstitution water (process water) significantly influences the final product quality as it is the largest single ingredient (up to 80-85%).
Therefore it will always be an advantage to lower the oxygen content in the process water to the lowest possible value as it is main source of dissolved oxygen in the final juice. Please see the recommended content of process water below.
Normal well water contains 8-12 mg/l dissolved oxygen; by use of a water deaerator (type DIROX, VARIDOX, DA2000 or ON-EX) this value can be reduced to < 0.05 mg/l.
The optimum production process includes water deaeration of the process water along with careful juice reconstitution/blending.
Recommended Content of Process Water for Juice Reconstitution
Smell None
Taste None
Colour None
Dry Matter < 500 mg/l
Hardness < 100 mg CaCO3/l (< 6 °dH)
Chlorine < 0.05 mg/l
Iron < 0.1 mg/l
Manganese < 0.1 mg/l
Trihalomethane None
Oxygen Lowest possible
If the various ingredients for the reconstituted juice add air/oxygen to the product (see also main sources above), the following problems might occur in the production process:
- Floating cells in the blending tank
- Foaming in the product deaerator
- Inconsistent heat treatment in the pasteurizer
- Incorrect filling and product loss (due to foam)
- Oxidation during storage.
For normal fresh juice with a shelf life of 3-4 weeks an oxygen content of 1 to 5 ppm (measured immediately after filling) is recommended to keep its freshness during the expected shelf life.
For fruit drinks and nectars with longer shelf life (6-12 month) the oxygen content is even more critical, however addition of antioxidants is normally permitted which can limit the damage of high oxygen content.
Nevertheless, it is still recommended to keep the oxygen level at 1 to 5 ppm for these types of products.
Our product deaerator is capable of deaerating all free air out of the final product and also to remove dissolved oxygen from the product to a certain extent. The unit’s exact capability of removing dissolved oxygen from the final product will depend on the given product properties and the given amount of air/oxygen prior to deaeration.
We are able to obtain an oxygen content <1ppm with our product deaerator (measured in pure water).
Milk/Dairy Products
Air in the milk may cause cavitation in the homogenizer which problem can be partly eliminated by use of our product deaerator. It is, however, important to locate the air source, ie. whether it is free air or "mechanical" air.
Free air is mainly originating from transportation and tank agitators and such air is easy to remove.
"Mechanical" air appears as "small air bobbles" in a product sample. Mechanical air is mainly due to damaged seals and gaskets or incorrect process design, eg. a centrifugal pump running against a closed valve or a pump with to high NPSH value. In case of very large amounts of mechanical air, it can be very difficult to remove the air from the product; therefore it is recommendable to locate the source.
Our product deaerator is capable of removing all free air and also to remove mechanical air from the product to a certain extent. The capability of removing the dissolved oxygen depends on the given product properties and on the given amount of air/oxygen prior to deaeration.
We are able to obtain an oxygen content <1ppm with our product deaerator (measured in pure water).