Proteus Industries found a membrane system that concentrates proteins while preserving the molecular structure of these complex organic compounds. The result? Fat is kept out and moisture is kept in fried foods. Here’s how this technology works…
By Carl R. Hoffman

Dr. Stephen D. Kelleher, founder and chief scientist of Proteus Industries Inc. of Gloucester, MA, has achieved something once thought impossible. He has developed a way to produce tasty low-fat battered and breaded chicken, meat, or fish products. Proteus Industries is the company behind NutriLean and NutraPure fat-impenetrable proteins. By applying NutriLean to chicken or meat products or by applying NutraPure to fish products, it’s possible to reduce the amount of cooking oil that would normally seep into the food during frying. NutriLean is an invisible layer of a fat-impenetrable protein. NutraPure is the NutriLean trademark for fish products.

Kelleher’s technology locks in moisture and enhances taste by enabling the natural flavor of the food to emerge by reducing outside fat absorption. Finished products have between 25 and 75 percent less fat and calories, depending on the cooking method. Since his process locks in moisture and decreases fat absorption, fried coatings stay crispier and avoid the risk of getting soft or soggy after cooking. Also, the protein concentrate has a low pH, which creates an environment hostile to bacteria, increasing the product’s shelf life. Under certain conditions, the protein can actually kill pathogens such as salmonella and E. coli.

Fish Sandwich Success
Figure 1: The tangential flow of the process fluid through hollow fibers mitigates fouling in the Romicon ultrafiltration membranes.
Proteus partners with food processing companies that want to use its technology to retain moisture, minimize oil absorption, and reduce calories. For example, Good Harbor Fillet Co., located in Gloucester, MA, is using NutraPure for fish sandwiches. The company has an agreement with the New York City Board of Education to supply the school system with 200,000 reduced-fat fish sandwiches each month. The school system’s initiative was launched to entice kids to eat healthier. By using NutraPure, Good Harbor is able to retain moisture and minimize oil absorption in its fish sandwiches. The pan-fried product is coated with NutraPure before it goes into the fryer, which reduces calories by using protein instead of oils.

To effectively bond to the substrate, the NutraPure protein solution must be derived from the same animal species. For example, if the solution is to be used on Atlantic pollock, the protein must be derived from Atlantic pollock instead of other types of white fish. Kelleher has been awarded 15 patents for the methods he has developed for extracting protein molecules from various animal muscles. “We have succeeded in making protein functional in the process of extracting it,” he said. “For the coating to perform effectively, we employ special low-temperature extraction and processing techniques to extract intact molecules from muscle tissue and protect the molecular structure of the protein.”

Proteus sought a membrane system that could concentrate the protein at a low temperature to preserve its functional attributes. However, at low temperatures, the highly viscous protein solutions contain large-molecule protein complexes that quickly clog membrane pores. Membrane fouling not only hampers processing performance, but the cleaning process can result in a significant loss of the protein product. “Typically, when you concentrate the protein between 7 and 10 percent, it gets as thick as honey,” explained Kelleher, “and we needed to find a high yield membrane system that could bring us up to 10 or 11 percent concentration.”

Membrane System Solution
Proteus turned to Koch Membrane Systems Inc. (KMS) of Wilmington, MA, to engineer a membrane system that could handle this challenging product stream and provide both high recovery and high yield. “We chose to work with KMS because of their extensive experience with protein concentration applications and their willingness to work closely with us to customize a solution to address the special challenges of our application,” said Kelleher.

Proteus sought a membrane system that could concentrate protein at a low temperature to preserve its functional attributes.
Pilot tests were conducted originally with a reverse osmosis (RO) system, but KMS and Proteus found that ultrafiltration (UF) performed better. While the RO system retained salts in the protein concentrate, the UF membranes allowed a portion of the salts to pass through the membrane into the permeate stream. Thus, by employing UF, salt levels and pH can be balanced and viscosity lowered.

After several months of testing, Proteus purchased a complete pre-engineered protein concentration system from KMS that employed Romicon cartridges containing hollow fiber membranes. These hollow fiber membranes operate with process flow from the inside to the outside during filtration (Figure 1). The process fluid (retentate or concentrate) flows through the center of the hollow fiber, and the permeate passes through the fiber wall to the outside of the membrane fiber. The tangential flow of the process fluid continually acts to limit membrane fouling.

In addition, the construction of the hollow fiber permits backflushing with permeate and the reversal of retentate flow. These cleaning processes are highly effective in restoring flux rates. KMS developed a special low pH cleaning procedure that enhances protein recovery and avoids damaging the molecular structure of the Proteus product.

The Romicon hollow fiber geometry allows for a high membrane surface area contained in a compact cartridge. The cartridge meets USDA sanitary requirements for food processing and is widely used in dairy and pharmaceutical applications.

A Good Match
By applying NutriLean, an invisible layer of fat-impenetrable protein, to chicken, the amount of cooking oil that normally would seep into the meat during frying is dramatically reduced.
“By working closely with KMS, we have been able to find an optimal membrane solution for each type of protein that we process,” said Kelleher. “A KMS engineer has performed test trials on fish proteins in the Aleutian Islands of Alaska and assisted with chicken protein testing at our facility in Alabama.

“Now that we have developed a good way of concentrating our product, tailored for each type of protein, we plan on expanding to three or four new plants during the next 18 months, using the KMS technology. The Proteus business model also calls for drying the protein to powdered form, which the KMS UF technology permits us to do efficiently.

“The systems produce a high yield and require practically no maintenance. The membrane filters just keep going and going,” added Kelleher. “We are able to cost-effectively concentrate the proteins while preserving the molecular structure of these complex organic compounds so that they can perform their function of keeping the fat out of, and the moisture in, our fried foods.”

Carl R. Hoffman is the market manager of food and beverage at Koch Membrane Systems, a leader in separation and filtration products. He has a bachelor’s degree in chemical engineering from Tufts University and an MBA from Boston College. More information is available by contacting him at 978-694-7176 or