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How Does Milk Become Cheese?

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Every morning, 7 days a week, Casper’s milk haulers drove his 6 trucks from farm to farm. Milk is perishable, so it had to be delivered quickly. That way, it wouldn’t go bad before being turned into cheese.

At each farm, the milk haulers picked up 10-gallon cans of fresh milk from the farmer’s cooling tank. A cooling tank was usually a water tank where fresh water flowed freely around the cans. Some farmers had just one or 2 cans. Others might have 8 or as many as 35 cans. The number of cans of milk a farmer had depended on how many cows he or she owned.

Some farmers brought their milk to the factory in their own trucks. One farmer delivered her milk by 6:00 a.m. She was indeed an early bird.

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One of Casper’s workers dumped a 10-gallon can of milk into the scale tank at the left. He then placed the can on the conveyor belt at the right to be sent to a machine where it was washed.

When a milk truck arrived at Casper’s Brodhead Swiss Cheese Factory, a worker dumped the milk from the cans into the scale tank that held 1,000 pounds of milk. From there the milk went to the scale dump. It next went to the holding tank. When the holding tank had 2,000 pounds of milk, there was enough to fill one kettle. That’s when the milk was pumped through pipes running overhead.

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Another worker watched as the separator removed some of the cream from the milk. Do you see the cream flowing into the pail?

Another worker ran the milk through a cream separator that took out some of the cream. Cream contains most of the butterfat in milk. You already learned that milk from different breeds of dairy cows differs in butterfat content. Milk for Swiss cheese making should have about 3.2 percent butterfat to keep the cheese at the right consistency. Too much butterfat would make the cheese greasy or sticky. Casper and his workers usually removed one pail of cream from each batch of milk to get to the perfect 3.2 percent. Casper bottled some of the extra cream and sold it. He also sent some to a nearby creamery to be made into butter.

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This worker uses his left hand to help him measure when enough milk has been pumped into the kettle. He knew it was full when it reached his fingertips.

Once it came out of the cream separator, the milk was pumped through pipes into a round copper kettle. A Swiss cheese kettle was usually 6 feet in diameter and could hold about 2,000 pounds of milk! Some Swiss cheese makers claimed that the round copper kettles helped give Swiss cheese its nutty flavor. These big copper kettles became symbols of Swiss cheese making.

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The pole from the ceiling down into the middle of the kettle is the mechanical stirrer that Casper helped design. This worker is checking the temperature of the milk.

Next, Casper added a special culture called Streptococcus lactis and rennet to the milk in the kettle as it was being heated. For many years, the rennet used in cheese making came from the stomachs of milk-fed calves. Today it is made in laboratories. The rennet caused curd to form in the kettle. Casper then turned on his mechanized stirrer to help the curd separate from the whey.

Good Bacteria

We often think that all bacteria are bad. Some do cause disease. But good bacteria exist, too. For example, the bacteria used in cheese making are good bacteria. One is Streptococcus lactis, a bacteria that changes lactose into lactic acid, which is a key part of the cheese making.

Cheese makers work hard to prevent the growth of harmful, disease-producing bacteria. To do this, they carefully control the temperature of the milk as it cooks. They also control the acidity as the cheese curds form. Remember Casper’s first job as a child? The cheese maker also has to make sure that the cheese factory is kept spotlessly clean. The cheese maker does not want harmful bacteria to form.

When the curd became firm, workers used a curd cutter called a Swiss cheese harp to cut it into small cubes. The tool consisted of a wooden frame with thin wires that did the cutting. First, workers moved the cutter from back to front and side to side in the kettle. Then they stirred the curds for 15 to 30 minutes. Next, Casper and his workers heated the curds to about 120 to 130 degrees. They kept stirring for another 30 to 60 minutes until most of the curd was at the bootom of the kettle and the whey was floating on top. Can you imagine stirring 2,000 pounds of milk for an hour? Plus, the air temperature in the cheese factory often reached 110 degrees. Without air-conditioning, this was very hot and tiring work.

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A Swiss cheese harp

At this step in the process, one of Casper’s workers had to put his hands into the 120-degree kettle. He needed to place a loosely woven cloth called a “dipping cloth” under the curd. Some workers put their hands in cold water before plunging them into the hot curds and whey mixture.

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Does this look too close for comfort? These workers put their hands and arms into a kettle that was about 120 degrees. For a comparison, hot water coming out of your kitchen faucet is 120 degrees at its hottest. Most of us cannot keep our fingers under such hot water.

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A worker leans over a kettle to tuck a cloth under the newly formed cheese curds. The T-bar holds his feet so he won’t fall into the kettle of hot curds and whey.

To put the cloth in place, a worker leaned far over the edge of the wide copper kettle. Sometimes another worker held the man’s feet so he wouldn’t wind up in the kettle! Others put their feet under a specially made T-bar that kept them from falling in. Workers needed to repeat this step to recover the 4 or 5 pounds of curds they usually missed the first time.

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A team of workers then tied the dipping cloth into a knot to make a bag, so the curds could be removed from the kettle.

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With a special device called a block and tackle, workers lifted the cloth containing the cheese curds out of the kettle.

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A worker had to hold the bag of curds above the kettle for a few minutes to let the excess whey drain back into the kettle. The workers squeezed the bag to help remove this liquid.

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When most of the whey had drained out of the bag, Casper and his workers pulled the bag of curds along the overhead tracks to the press table.

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Casper and one of his workers emptied the curd from the dipping cloth into a round wooden form lined with material called cheesecloth.

Workers covered the cheese with a special lid called a press lid. This lid was made of wood and was 2 inches thick. A machine gently pressed the cheese by pushing on the lid. The pressure forced more whey out of the cheese. That liquid drained out the bottom of the cheese form.

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Casper presses the cheese curds to remove more whey. The liquid runs off the table, where it’s collected in a stainless-steel tub. Casper had other uses for this extra whey.

After about 2 hours, 2 workers turned the cheese and replaced the cheesecloth with burlap. “Turning” the cheese wheel meant turning it upside down so more whey could be pressed out. The machine then pressed the cheese for 2 more hours.

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These workers prepare to turn a wheel of cheese. It could be a 2-person job to lift these 200-pound wheels.

Casper and his crew stopped pressing and turning the cheese when no more whey drained out of it. By this time, they may have turned and pressed the cheese 3 or more times. On the last turn, they placed a special flat cheesecloth underneath so no wrinkles would form in the cheese wheel. Wrinkles could cause splits in the cheese. Mold might grow in those splits as the cheese cured.

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Casper’s workers with wheels of Swiss cheese floating in a brine tank filled with salt and water

The cheese was pressed overnight. The next morning, workers moved the cheese from the making room where temperatures often reached 110 degrees to a room where it was a cooler 55 degrees. They put the cheese wheels into a brine tank. A brine tank was usually about 20 feet long, 3 feet high, and about 10 feet wide. It contained salt and water.

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These workers take a break from washing Swiss cheese wheels. One used the low table and the other stood on the table built on a platform so he could reach the top shelves. Both tables could be rolled down the rows of curing cheese.

To prepare the brine tank, a worker added salt to the water until an egg would float in the solution. When the egg floated, he knew he had added enough salt. The salt helped form a natural cover called a “rind” on the cheese. The longer the cheese floated in the brine tank, the thicker the rind became.

After 2 or 3 days, Casper and his crew removed the cheese wheels from the brine tank. They placed the wheels on shelves in a curing room where the temperature was kept at about 75 degrees. Sometimes they stacked the heavy cheese wheels up on shelves nearly 8 feet high.

The Whole Truth about the Holes in Swiss Cheese

Do you know how the holes get in Swiss cheese?

Somebody once joked that mice ate out the holes. Can you imagine a mouse eating away at a 200-pound wheel of Swiss cheese? We know that mice like cheese, but they could never get inside such a big wheel of cheese.

Actually, nothing or nobody puts the holes in Swiss cheese. The holes or “eyes” form naturally during the curing process.

Remember the special bacterial culture that Casper added to the cheese while it was being made in the kettle? That bacterial culture causes carbon dioxide to form in the wheel of Swiss cheese after it has cured for about 3 weeks. When these bubbles of carbon dioxide gas break, they leave behind holes. Some holes are as small as a dime. Some are as large as a quarter.

Mystery solved!

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This worker is cutting a wedge of Casper’s Swiss cheese in the shop at his factory.

Two or 3 times a week while the cheese was curing, Casper and his workers turned and washed the wheels of cheese with salt and whey. The washing removed any mold that had developed on the rind. Each time Casper or another worker washed a wheel of cheese, he placed it on a clean cheese lid to help prevent more mold from forming.

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The cheese grader in the white coat inspected a piece of cheese from one of Casper’s Swiss cheese wheels. He visited Casper’s factory about once a week because Casper was making so much cheese! The inspector marked a grade on each wheel. The wheel also was stamped with the word “Wisconsin,” the date, the wheel number, and the number given to Casper’s factory.

The cheese wheels were kept in the heat cellar for 6 to 8 weeks to be cured. Casper and his workers then moved the cheese wheels to the cooler to await grading before the Swiss cheese could be sold.

Trained men called graders inspected each wheel of Swiss cheese. Afterward, they gave it a grade. To get a good grade, a cheese had to develop well.

The cheese grader inserted a metal tube with a sharpened end and T-shaped handle into the wheel of cheese. This tool was called a “trier.” It was about 8 inches long.

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A cheese trier was used to remove a core sample of cheese. It enabled the inspector to grade the wheel without cutting it open.

Once the trier was in the wheel, the grader turned it around so it would cut a core from deep inside the cheese. He removed the piece of cheese to inspect it. He looked at the size of the holes. He smelled and tasted the cheese. If the cheese did not appear to have holes or “eyes,” or had only small ones, he’d say it was “blind.” The grader would repeat the process at different spots. After inspecting the cheese removed from the core, the grader put the plug of cheese back into the wheel. The hole was resealed with paraffin so mold wouldn’t form inside the wheel.

The grader gave each cheese wheel a grade of A, B, C, or D. The grade was based on the cheese’s taste, appearance, and smell. If the eyes of the cheese were similar in size and larger rather than smaller, the cheese got a higher grade.

When the grader finished inspecting the cheese, he placed a mark on the wheel. The more times the grader had to put his trier into the wheel to test the cheese, the more it was marked down. Grade A was one straight mark. This was the highest grade for the best cheese. Two marks forming a T meant a grade B. Three marks forming a capital I meant a C grade. Grade-C cheese holes were too small or too large, and sometimes the cheese was missing holes. Grade-D Swiss cheese had few if any holes. The cheese grader made four marks in a number sign (#) on grade-D cheese.

The lower the grade on one of Casper’s cheese wheels, the less money he could charge when selling it. But Casper had excellent cheese-making skills. He usually received the highest marks for his Swiss cheese.

Casper was truly a master cheese maker, so he had his own way of determining if the eyes were forming properly in the cheese. He tapped the cheese wheel with his fingers in a certain way and listened for the sound. It was an art to know what he was hearing. With his experienced touch, Casper could tell how well the holes in the cheese were developing just by listening.

The longer Swiss cheese was stored or allowed to age, the sharper its flavor became. Some people preferred the taste of aged Swiss cheese. Others liked eating it before it had aged. Casper always wished his customers would wait a while after taking his cheese out of the refrigerator before they ate it. He said you could taste more of its flavor after it had some time to warm up.

“Green County Gold” was the name given to the Swiss cheese made in the area of Wisconsin that Casper called home. The name came partly from the color of the cheese. But it was also called gold because of all the money cheese makers like Casper made by selling it! That money was shared with the farmers in Green County every time a cheese maker bought their milk to make cheese. Swiss cheese was an important part of the local economy in Green County.