Milk is a white liquid produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals before they are able to digest other types of food. Early-lactation milk contains colostrum, which carries the mother's antibodies to the baby and can reduce the risk of many diseases in the baby.
Milk derived from cattle species is an important food with many nutrients. The precise nutrient composition of raw milk vary by species and by a number of other factors, but it contains significant amounts of saturated fat, protein and calcium as well as vitamin C. Cow's milk has a pH ranging from 6.4 to 6.8, making it slightly acidic.
Since the introduction of membrane processing to the dairy industry in the late 1960's, separation of dairy fluids using semi-permeable membranes has been used to clarify, concentrate and fractionate a variety of dairy products. The time honored and tested applications involving whey processing, the by-product of cheese making, have introduced a plethora of refined proteins and commercial uses for a once wasted by-product. The membrane applications for fluid milk have been understood for as long as the whey applications, but have been underutilized in commercial applications. The same concentration method of Reverse Osmosis used in whey processing is often a favorable alternative to evaporation techniques used in milk processing. The fractionating of whey proteins from the lactose in whey processing also has an attractive benefit in the fractionating of the same lactose from the milk proteins in fluid milk using the same Ultrafiltration techniques. Microfiltration fills the separation profile of membranes out by further fractionating the specific milk proteins of casein and serum proteins away from each other.
In a sense, membrane processing of fluid milk is acting like a harvester of specific milk components without imparting a phase change by the addition of heat, as is typical for evaporation, or an enzyme, as done in most cheese making techniques. The milk is modified by separating, clarifying, or fractionating a selected component in milk from other components using differences in their relative molecular weights and pore sizes of the membranes. Here we talk about specific milk membrane filtering applications that are currently in use in the dairy industry and the multifaceted reasons behind their use both in technical as well as market driven, economic terms.
Membrane Solutions’ Milk Filters:
Filtration of milk should not be used as a means of rectifying unsatisfactory milking procedures. Although filtration removes most of the soil and other particles, it does not remove all the bacteria adhering to these particles, nor does it remove any dissolved matter from the milk. Sediment that has been trapped by the filter continues to be washed by the milk flowing through. This dislodges bacteria adhering to the particles and thus contributes to an increased bacterial count in the bulk milk.
Forcing milk through an in-line filter by a pump is the most common method of filtering milk in modern milking plants. The filters may be made of various types of paper, fibre or cloth and they fit over a perforated metal support or cage within a cylindrical tube. In-line filters should be fitted so that the milk is filtered before cooling. This allows the milk to be warm when filtered and facilitates the passage of milk fat through the filter.
Milk filtration is enhanced by low milk pressures and continuous uniform milk flow through the filter. The use of different types of milk pumps, combined with varying milk flow rates, may make low pressure and constant flow difficult to achieve.