On-Farm Concentration

Since 1996, dairy farmers have successfully used membrane technology to concentrate milk on the farm, near the point of milking. This milk is then transported to manufacturing facilities for further processing.

There are many benefits to concentrating milk on the farm rather than at a separate processing plant. The milk retentate can be concentrated and the permeate separated on site, enabling each product to be shipped to the most profitable location. Customers get a milk ingredient that meets specific requirements such as low lactose or high protein. They also realize a savings in hauling costs since they are no longer paying to ship unneeded water. Concentrated milk also requires smaller storage facilities, thereby reducing refrigeration costs. Once at the destination point, the concentrated product generates additional savings since less fluid must be heated for pasteurization and less wastewater is produced.

The concept of on-farm membrane concentrating dates back to the early 1980s to research conducted by Dr. Robert Zall from Cornell University, Ithaca, NY, and made possible through funding by America's dairy farmers. Zall's work used a conventional UF system which resulted in some problems including fat retention, fat shearing and membrane cleaning.

The current technology, referred to as On-Farm cold concentrating of milk was developed and patented by Membrane System Specialists Inc., Wisconsin Rapids, WI. Since 1996, the company has designed and fabricated several UF and RO systems to operate on large (1,500+ milking cows) Southwest dairies.

The process uses either UF or RO to concentrate milk through multiple vessels without recirculation (single pass). Milk is cooled to about 40°F or lower immediately after milking. At cold temperatures (35-40°F), fat globules are more resilient than at the warmer temperatures experience in conventional UF processing and fat shearing is reduced. The result is a premium milk ingredient with enhanced functionality and greater market potential.

Prior to receiving FDA approval for the process, University of California-Davis researchers showed that there were no increased bacterial concerns with cold UF membrane concentrating of raw milk. They also demonstrated that the processing equipment cleaned in a satisfactory manner and there was no negative impact on pasteurization due to the concentrating process.

Concentration factors range from 3.5X for UF milk to 2.8X for RO milk. However, regardless of the concentration factor, on-farm concentrated milk must meet the same Grade A standards as raw milk. Since this technology not only concentrates the milk, but also concentrates the bacteria, initial raw milk bacterial counts may be very low, approximately one-third of the standard. To further inhibit bacterial growth during the membrane concentration process, FDA requires the milk temperature remain below 45°F During the processing.

This method of cold-filter milk offers yet another technology opportunity which can benefit both the processors and, ultimately, the dairy consumer.