Two types of membrane filtration processes, namely ultrafiltration and microfiltration, are used for protein standardization in milk. While ultrafiltration is used to standardize the total protein, microfiltration is used to standardize the casein.
Standardization of the protein using ultrafiltration or microfiltration evens out the seasonal variation of the protein content in milk and results in a more stable cheese making process.
Other advantages include:
- stable ingredient control of the cheese making process
- improved utilization of the cheese vats
- repeatable process parameters day to day
- uniform, high-quality cheese
- same cheese volume from each vat
- reduced rennet consumption
- reduced operational costs
- increased cheese making capacity
- increased yield of cheese per mass of milk
These advantages give more control of production with less quality variation in the final product due to stable process parameters and standardized protein levels.
Incorporated with the membrane system is typically the use of NIR (Near Infrared) technology to optimize the overall membrane filtration process.
Using ultrafiltration, it is possible to concentrate raw or pasteurized whole or skim milk. Ultrafiltration of skim milk can produce different milk protein concentrate (MPC) and milk protein isolate (MPI) products with polymeric spiral membranes. Microfiltration of skim milk can produce casein concentrate with polymeric spiral membranes or ceramic membranes depending on the specific application.
The by-products (permeate stream) from ultrafiltration and microfiltration of milk are also valuable. The permeate stream from the ultrafiltration process is primarily lactose, and this stream is an ideal product for standardization of milk powders.
The permeate stream from the microfiltration process contains native whey proteins that can be further processed into higher value protein products such as whey protein isolate or other whey protein concentrates.