Fabulous Food Plants: Molecular manipulation of milk
At Select Milk, pasteurization and packaging are minor parts of the process.
By standardizing milk in the Pasteurized Milk Ordinance, public health officials helped create a commodity product with little or no differentiation, save perhaps the name on the container.
Select Milk began breaking the commodity mold from its inception. The producer-owned dairy processor began with a simple premise: work with quality-minded dairymen with large herds in isolated regions where residential protests are unheard of and ship the milk to population centers hundreds, even thousands, of miles away. Suppliers deliver raw milk in minimum quantities of a tanker, enabling the plant to monitor cell-count levels to ensure quality standards are met. The plant concentrates the milk through reverse osmosis to remove two-thirds of the water and minimize transportation costs. Initially, the R/O process was done at the farm level, and a network of facilities was established in the Southwest. Enabling technology included the injection of dissolved carbon dioxide to kill bacteria during transport (see pages 151-152 in this issue for further information). Suppliers include Carbonic Systems Inc. in Elmira, NY.
Select's business model began to change in 1998 with construction of Plant #5 in Dexter, NM. The facility now is one of only two Select plants, and a major expansion last year creates the ability to manufacture "nutritionally standardized milk," management's term for fluid milk that has undergone ultrafiltration to produce an enhanced nutritional content. First out of the gate is Mootopia, a dairy beverage produced for Texas grocer HE Butt that contains 75 percent more protein, 35 percent more calcium and 60 percent less sugar than conventional milk.
Producing Mootopia requires twice as much raw milk, and retail prices reflect the higher ingredient costs. Management is betting consumers will pay for a healthier dairy beverage. With bottled water commanding retail prices that challenge or even surpass garden-variety milk, there's reason to believe consumers will pay a premium for milk with a perceived advantage. US per capita milk consumption peaked in the 1940s, points out Select's John Dunker, vice president business development, and has fallen to half the rate of 60 years ago. To reverse the slide, processors need to supply products tailored to consumer demand, and ultrafiltration (UF) is part of the technology matrix that can deliver it.
UF is excellent for concentrating proteins, says Dunker, and some lactose removal is accomplished. However, most of the lactose is removed in a batch process using enzymes from Valley Research that were selected for their purity. The enzymes convert the lactose to glucose and galactose, resulting in milk with balanced sweetness and a relatively low level of carbohydrates. An 8-oz. serving contains 4 grams of carbohydrate, about a third the amount typically found in milk.
Heading product development was Shakeel Ur-Rehman, Select's technical director. Ur-Rehman is a food chemist with an extensive background in applying separation technology, including work with an Irish dairy corporation to isolate beta casein in milk and, more recently, work on protein isolation at California Polytechnic State University's pilot plant. He specified the polymeric spiral wound filters used in Select's UF system.
"Dialing in the flavor profile so you end up with a good-tasting beverage was the most complicated aspect," notes Derek Hibbard, vice president of Membrane System Specialists. He credits Ur-Rehman's development work in producing a healthy, flavorable milk product that is "pretty unique." System engineering issues included cleanability, proper amount of pressure and prevention of foaming that can occur as protein levels are increased.
Physical separation of milk at the molecular level has been a focus in Dexter since the plant opened. The dairy removes lactose and water for some of the milk destined for cheese manufacturing. Lactose contributes to the amount of whey generated in cheese production. By reducing the lactose, Select reduces the amount of whey disposal required of cheese manufacturers. Combined with Select's carbonation process, Select's ultrafiltered milk would enable the dairy to meet the raw material needs of cheesemakers as far away as Wisconsin, where a milk-protein shortage has developed.
The drawback is that USDA standards of identity for most cheese specifies lactose content in raw milk. Lactose-reduced milk can be used for pizza cheese but not mozzarella, for example. Select has joined the lobbying effort to modify the standards, and a petition has been pending for five years. Bioterrorism and other issues have put on hold the drive for component definitions that would allow UF milk for cheese, ice cream and other dairy derivatives, according to Cary Frye, a lobbyist with the International Dairy Foods Association, one of the proponents of regulatory change.
The permeate that forms Dexter's waste stream contains 5 percent dissolved solids. The concentration needs to be elevated to 40 percent solids to make a commercially viable feed for livestock. An evaporation system engineered by Acqua America Inc. came on line last year to accomplish the objective. Select represents Acqua's first US food application, and the two firms have formed a joint venture to bring the technology to other food manufacturers. (See Engineering R&D, Food Engineering, September 2005.)
The evaporator, which processes 37,400 gallons of infeed per hour, required the construction of a 38-ft. high addition to house it. A conventional evaporator would have required an addition twice as high, says Dunker, so the system's compact size limited capital expenditures. "It wasn't half the cost, but the savings were significant," he says. The system also is very energy efficient.
A 550 hp motor powers the evaporator's MVR unit. The energy draw is almost enough to make lights blink in nearby Roswell, NM. A massive variable frequency drive protects the plant's electrical infrastructure at start-up. The electrical room is packed with 64 smaller VFDs for the pumps in the ultrafiltration system. "The more balanced you can make the system, the longer you can run the pumps" between maintenance servicing, points out Tim Gomez, Select's vice president of manufacturing. Six in-house mechanics maintain the facility, with electrical and refrigeration work outsourced.
The facility they keep humming breaks the dairy mold, just as its producer-owners do. Organized a decade ago, Select's 77 members manage herds averaging 2,500 cows, producing 3.3 billion pounds of milk a year, making Select the nation's tenth largest co-operative. Those dairy farmers are committed to a value-added approach at the producer level, and the same aversion to commodity production is reflected in their New Mexico processing facility.
For more information:
Michael Everton, Acqua America LLC,,br> 813-902-9030,
Rick Reynolds, Carbonic Systems Inc.,
Derek Hibbard, Membrane System Specialists Inc.,