Artisan cheese maker shares secret technology ingredient

Case Study: Gunn’s Hill Cheese uses 15 variable frequency drives (VFDs) to improve consistency and quality. In one application, the installation of a variable speed system resulted in a 50% reduction in horsepower compared to a traditional fixed speed system.

By Patrick Appleby September 17, 2012

Advanced automation helps bring quality and repeatability to recipes for cheese that are thousands of years old, passed down through generations and crossing continents, like the Swiss cheese recipes used by Shep Ysselstein, owner and “grand fromage” of Gunn’s Hill Cheese in Woodstock, Ontario, Canada.

Located in the green-grass dairyland of Oxford County, two hours west of Toronto, Gunn’s Hill Artisan Cheese is known for handcrafted, Swiss-style soft, semi-hard and hard cheeses. They are made from recipes that Ysselstein brought back from a one-year study of cheese making in Switzerland. That Old World recipe is now a New World reality thanks to a secret ingredient, variable frequency drives (VFDs).

Recipe for success

“Cheese making involves processing a lot of fluids,” explained Ysselstein. “We’re pumping thousands of gallons of milk in and out of different vats, stirring in different ingredients, maintaining precise temperatures in a clean environment and lifting and transporting wheels of cheese up to 55 pounds.” These operations depend on VFDs.

Having earned a business degree several years earlier, Ysselstein opened the small, family-owned enterprise in October 2011. He sells cheese in a retail shop attached to the factory and wholesale. A family dairy farm, Friesvale Farms, located next door to the factory, supplies milk.

“Oxford County is famous for being the dairy capital of Canada,” says Ysselstein. “Our family farm has been in business for over 60 years. The quality of the milk comes through in the cheese, especially in the curds. They are immensely rich in flavor and their ‘squeak’ can be enjoyed during a great snack.”

Each of Ysselstein’s three varieties of washed rind cheeses from cow’s milk uses slightly different processes. [Natural rind (as opposed to applied plastic or wax) forms on the outside of some cheese as a natural part of the cheese-making process and is eaten by many.]

The soft cheese is modeled after a little known Swiss recipe called Mutchli. This mild, creamy cheese is excellent for serving or melting, developing a buttery flavor after just four weeks of aging. The semi-hard recipe combines traits from Gouda and another Swiss variety called Appenzeller. Its creamy, rich flavor has sweet overtones with distinctive eyes in the body of the cheese. The mild version is aged 5 months and the semi-hard version, 12 months. Finally, the hard variety is a Swiss mountain-style cheese with rich, dry, nutty overtones aged one year. An extra-aged style will be available in two to three years.

Fluid, motion control

The fluid and motion control required in the process can be seen in the many steps involved in making semi-hard cheeses. Whole Holstein milk is pumped into a cheese vat, where it is pasteurized at 145 F (63 C) for 30 minutes. Then, starter culture is stirred into the milk to turn the lactose into lactic acid. An hour later, rennet (a mix of enzymes) is added to thicken the milk into a mass, like gelatin.

When the milk is at the right thickness, it is cut into small pieces known as “curds.” For semi-hard cheeses, the cut pieces are the size of a kernel. The curds are heated by adding hot water. The hotter the water, the drier will be the cheese as the curds shrink and separate from the liquid whey. The curds are then transferred from the vat to the drain table. Then the whey is removed, while the curds form a mass at the bottom.

Six hours after the milk was first pumped in, the curds are cut into squares and pressed into a round plastic mold, which squeezes out more whey. Pressing can take 20 minutes or overnight, depending on the desired hardness of the cheese. The round wheel of cheese is then immersed into salt brine for two days.

Finally, the cheese is lifted from the brine onto racks where it is aged to develop flavor. The aging room is kept at 54 F (12 C) and 90% relative humidity. The cheese is turned every other day and washed with a salt water solution. The outside surface turns an orange color from natural microbes, forming a natural rind, unlike the dyes used by other cheese makers. After the proper aging time, the cheese is ready to eat, the result of hand craftsmanship and advanced technology.

Throughout the operation, VFDs provide pumping and mixing capabilities.

Using variable frequency drives was recommended by Ysselstein’s heating, ventilation, air conditioning and refrigeration (HVACR) contractor, Ben Kungl, of Oxford Energy Solutions. “The drives operate our ac pump motors, letting us dial the right speed for a given task,” Ysselstein said.

About 15 VFDs are used in the plant for a wide range of jobs, noted Kungl, who grew up on an Oxford County dairy farm. After getting technician’s training at a local technical college and working for the award-winning Performance Dairy Centre, he started his own businesses: Oxford Energy Solutions and Oxford Refrigeration.

“There are a lot of old-school ideas about using fixed-speed pumps and motors in dairy processing equipment,” said Kungl. “But in this day and age, you have to be as efficient as you can be.” Variable speed motors can save up to 50% in energy use, compared to a fixed speed motor.

Energy efficiency ingredients

Kungl improved efficiency and process control with VFDs in three areas: fluid pumps, ventilation system, and cooling compressor.

He applied three VFDs to control the pumps used to off-load milk from the truck into the raw tank, transfer milk into vats, and for washing. “I can set three speeds without damaging the motors,” said Kungl, adding that the drives are easy to program: “Pump control can be done either from the drive pad or a PLC. Plus, they convert single phase household ac current to 3-phase. That means we didn’t need to rewire to supply 3-phase current for the heavy commercial motors.”Kungl applied a drive to control the hoist motor that lifts cheese trays from the brine. Another drive is used for ventilation. Regulations require that a food plant have a positive air pressure inside to keep contaminants outside. A drive was applied to the reverse pressurized air handler that supplies the facility with fresh air.

“It was easy to wire the drive into a pressure transducer,” explained Kungl. “That way, the air handler only needs to supply the make-up air to maintain positive pressure. You can get a small amount of inlet air using 30 hp, compared to an old-school fan system using 60 hp. That takes a lot of energy, considering you can do the same amount of useful work, get better results and use one-half the horsepower compared to a balanced system with fixed supply and exhaust fan systems.”

Finally, Kungl applied a larger VFD in a NEMA 12 enclosure to modulate the compressor in the outdoor chiller. The drive serves a dual purpose: to save cost and give the customer a wide range of adaptability.

The chiller modulates between the process cooling for the building and direct cooling for the product after it has been pasteurized and needs to be cooled. The larger drive controls the scroll compressor speed and capacity, while two smaller VFDs control the Zeihl-Abegg condenser fan motors for a fully modulating system. These types of condensing units/chillers are a very common product made by Oxford Energy Solutions and have become popular in food processing and bio-fuel sectors.

Dependable drives

The industrial drives are reliable, have a large dc bus that gives them a large voltage tolerance, and are built in the U.S. Other sought-after features include dedicated algorithms for flow applications that simplify implementation, a proportional-integral controller, and logic controller that can often double as a programmable logic control for nearby processes. High-temperature rating of 122 F ambient temperatures (50 C) requires no special ventilation.

Efficiency and reliability of the VFDs help Gunn’s Hill Artisan Cheese improve its products.

– Patrick Appleby is vice president sales – industry, Danfoss. Edited by Mark T. Hoske, content manager CFE Media, Control Engineering and Plant Engineering,