Case Studies & Field Reports

Screening for dollars

Reducing protein loss in skim milk cold filtration system prevents waste.

The membrane filtering system at California Dairies uses HFK-131 UF spiral element filters from Koch Membrane Systems. Source: KMS.

With increasing capacity of about 4% annually, California Dairies Inc. is the state’s largest dairy cooperative with 650 members. To lower shipping costs to cheese producers, the milk handling process at the cooperative’s Tipton, CA, plant uses an ultra-filtration (UF) process to remove water and selected non-protein components from milk, allowing just the concentrated milk solids to be transported.

But the process provides other benefits besides reduced freight and storage costs. During UF, a single-pass cold milk process enables production of a non-pasteurized, non-denatured raw product providing high functionality with significantly less whey disposal. Also, UF concentrated skim milk allows cheese to be made at 15% total solids instead of 9%, which increases cheese production efficiency.

“The UF concentration system has been a good way for us to rapidly and economically supplement our butter and milk powder production, with low capital costs and relatively short build time,” explains Steven Cooper, vice president of operations for the Tipton and Artesia, CA, facilities. “The ongoing operating costs of the UF concentration system are also significantly lower than other types of milk processing operations.”

The UF plant has been expanded three times during the past seven years, bringing total capacity to 3.8 million pounds per day. Installed in 2006, a skim milk system accounts for 1.9 million pounds of total production.

“Unfortunately, the expansion into skim milk concentration did not go as planned,” reports Cooper. “Our cold process results in a high-quality product that improves the yield for our cheese-producer customers. But this cold process presents a serious challenge for UF, especially for skim milk. Our existing UF membrane could process whole milk, but simply could not handle skim milk.”

“In the whole milk system, we get about two to three years of membrane life, but within three weeks of running skim milk through the membranes, we started seeing a great deal of protein loss,” says Cooper. “The permeate stream should have been a clear liquid with a slight yellow tint, but we were seeing an almost milky stream. We were not recovering proteins or solids, which are very costly to lose.”

After being unable to resolve these issues with the existing membrane supplier, Cooper decided to run side-by-side comparison tests of filter products from several other manufacturers. Based on these tests, California Dairies installed the dairy series HFK-131 UF spiral element from Koch Membrane Systems Inc. (KMS), of Wilmington, MA. The HFK elements use a proprietary polyethersulfone membrane to achieve 99.8% instantaneous true protein rejection, which reduces protein losses by as much as 33% compared to other membranes.

“We chose the KMS membranes because of their superior performance, but an added benefit of working with them is their quick turnaround time,” Cooper says. “They delivered their membranes in three weeks, about half the time required by other vendors.”

The new membranes continue to perform extremely well after more than nine months of operation. “With protein levels in the permeate at less than 0.01%, we are saving money every day,” says Cooper. “We usually run the system for 24 hours or longer between cleanings, and the membranes clean-up well.” 

For more information: Carl Hoffman, 978-694-7176,

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