Extracting milk proteins
Milk contains many different types of proteins, each with their own unique properties and economic value. Research described here shows that extracting high-value milk proteins on the farm quickly and efficiently could have major economic benefits for farmers.
Valuable milk proteins
Some high-value proteins like lactoferrin are only found at low concentrations in milk, but because of its antimicrobial, antioxidant, and anti-inflammatory properties, lactoferrin is of great value for human health. A lot of money can be made from separating this protein from the rest of the milk proteins and selling it as a concentrate.
Collecting lactoferrin in the factory
Currently, lactoferrin is separated from other milk proteins in the factory. After collection, the milk is chilled (below 5ºC) and stored on the farm for one to two days. The milk is then transported to a processing factory, where it is de-fatted and pasteurised. After all of these steps, the lactoferrin is extracted.
A special ion exchange resin is used to extract the lactoferrin. The resin works by selectively interacting with the lactoferrin protein at a particular pH. In factories, this process is carried out at 4–8ºC.
Get information sheet: Ion exchange chromatography
The extraction of lactoferrin in the factory is not very efficient and gives only low to medium yields.
Collecting lactoferrin on the farm
A protein fractionation robot (PFR) is a machine being developed to recover high-value proteins as the milk is collected on dairy farms. The aim is to optimise protein yield and, at the same time, retain the biological integrity of these proteins. This technology also has the potential to increase a farmer’s earnings.
Students can do anything!
Waikato University student Amita Chand has developed a PFR that can be used on the farm, as part of a PhD project. Her work was supervised by Professor Conan Fee (now at Canterbury University) and supported by Dexcel and Sensortec Limited.
Amita put a PFR between the milking cups and the storage vats on the farm, so that proteins can be extracted from the milk before it is processed. In this system, the PFR extracts proteins from the milk by ion exchange at about 35ºC – the temperature of fresh milk.
In a trial where milk from 16 cows was processed, the average amount of protein extracted was 36 percent higher in the PFR on the farm than in the factory. Exciting news!
Another advantage of having a PFR on the farm is that the extraction process can easily be modified to remove other proteins from raw milk that may otherwise be destroyed by the treatment process.
What makes the PFR so effective?
Proteins are long chains of amino acids arranged in specific shapes. They can only function correctly when their shape is exactly right. However, most proteins are incredibly sensitive to changes in temperature, which can alter their structure.
In the factory process, the milk is cooled to below 5ºC while it is stored. Cooling causes the life processes of microorganisms in the milk to slow down and prevents the milk from going off.
When the milk gets to the factory, it is pasteurised to kill microorganisms. Pasteurisation involves rapidly heating and cooling the milk (from 63ºC to 4–8ºC). The heating and cooling can alter the shape of the proteins (and therefore their charge) and prevent them from binding to the ion exchange resin properly. Therefore, only lactoferrin molecules that retain the right shape through these temperature changes well be extracted.
In contrast, the PFR extracts the proteins immediately after the milk is collected and at much the same temperature at which the milk was collected. Therefore, a greater proportion of the proteins will have the right shape and charge to stick to the surface of the ion exchange resin. This improves the yield of lactoferrin from the milk.
Written by Sara Loughnane – a 2006 New Zealand Science, Mathematics, and Technology Teacher Fellow.
- 16 November 2007