Three ways to measure milk homogenization efficiency
The United States Public Health method has been a mainstay since it was introduced in 1947. But it takes 48 hours to carry out. The NIZO centrifugation method is based on the same principle, but it speeds up the natural creaming process and only takes an hour or so.
We recommend a third, more advanced method that measures particle size distribution (PSD) with laser diffraction. All particles scatter light: larger particles in narrow angles and small particles in wide angles. Sensitive detectors and advanced computer models are used to calculate a particle size distribution, which only takes ten minutes. We have shown that measures of PSD correlate extremely well with NIZO values. The resulting measure is homogenization efficiency, measured as percentage between 0 and 100.
So how much pressure is enough?
Let’s start the process at the other end: what kind of product do you want to deliver? Start with what shelf life you want for your milk product (ten days? Three months? Longer?), because this determines how small the fat globules should be. From there we can determine which pressure is optimal for a homogenizer running at a given capacity.
It turns out that if you are only measuring pressure in your homogenization process, you’re missing out a key measurement – the extent to which your milk is actually being homogenized. And to do that, you’ll need to measure the homogenization efficiency.
What affects homogenization efficiency?
Some important variables include:
- Milk composition – including fat content and protein content
- The design of the homogenization device – where the milk is squeezed through under pressure, to break up fat globules.
- Operating temperature and operating capacity.
Top tips for achieving optimal homogenization efficiency
Running the same pressure for all applications is a waste of energy – and money. Don’t be afraid to experiment – just start with small changes. Keep these tips in mind:
- If you are running products with different fat contents, you can lower pressure if you run 0.5% compared with 3.5%
- If you are running different capacities, change the pressure as well to make up for the change in gap height.
- When you are running products with different shelf lives, you’ll need to change the pressure if, for example, you’re changing from normal pasteurized milk to extended shelf life, or moving from locally consumed UHT milk to export milk, where the additional transport time “eats” some of the shelf life.
- Very often the second-stage pressure is set too high, with the optimum setting being 25-30 bar. Too much pressure here steals energy from the first stage and lowers your homogenization efficiency.
- If you are investing in a new machine and want the same milk homogenization efficiency value as your old machine, measure the homogenization index of the milk produced on your current machine and then order your machine based on this – not based on pressure.
- If you are expanding your product lines to achieve longer shelf life, or planning for export transportation, take into account that storage and transportation can have a big impact on creaming.
Contact us to learn what optimized homogenization can mean for your dairy.