Without pumps, there’s no peanut butter in your peanut butter and jelly sandwich—there’s also no jelly. In fact, most food processing would not exist. Our eating habits, and diets would be radically different, and our food-and-wine culture would be limited to local distribution. Our collective belly rumbles at the mere thought of it!

If we didn’t have pumps to help process food, we wouldn’t all starve or die of thirst, but a lot more manual labor would be involved in preparing food for consumption. Without pumps, water, juices, beverages, sauces, and other liquids would have to be made in small batches close to their clientele using manual labor. Dairy products would have to be processed near retail outlets because there would be no pumps to transport goods into large vessels for quick transportation.

Solid food would also be affected. Fruits and vegetables are washed during processing, which requires pumps. Many solid foods also require pumps during preparation. Pumps are essential in pickling processes for cucumbers, beets, and other vegetables. Vegetables and fruits packed in jars and cans have liquid pumped in to help keep them fresh and appetizing. After juice is squeezed out of fruits and vegetables, pumps move the liquid through processing steps and eventually into packaging.

But pumps aren’t used just for preparation and packaging. They are also essential for keeping the food products and process equipment clean to prevent bacteria, mold, and other impurities from contaminating food. Food processing plants undergo daily cleaning using high-pressure pumps and other equipment. This is a demanding application itself because the cleaning fluid contains powerful antiseptic chemicals that are often caustic.

Positive Action

Processes involving liquids in food processing make wide use of centrifugal pumps, which provide a reliable and effective way of transferring solutions from one process station to another. But food products in syrup, paste, or other viscous forms usually require a piston, gear, screw, vane, diaphragm, or other type of positive-displacement pump.

Positive-displacement pumps trap a fluid inside a set volume and use mechanical power to move that volume from an inlet to an outlet. The mechanical power usually comes from an electric motor or compressed air. An excellent example illustrating the capabilities of a positive-displacement pump is the making of peanut butter.

Initial processing of peanuts involves shelling, removing the skins, and roasting the raw peanuts. Salt and a little sugar are usually added, then the peanuts are ground and crushed into a thick paste. Moving this paste to the next process could pose quite a challenge because it would adhere to a conveyor, and too viscous for a centrifugal pump.

Centrifugal pumps are kinetic machines in which flow and pressure are generated dynamically through a rotating impeller. When the pumping media has high viscosity, the pump experiences an extreme decrease in flow and head along with an increase in its power consumption.

So instead of centrifugal pumps, positive-displacement pumps move the peanut butter to a filling station. A piston pump or screw pump is usually used. In either case, the pump pushes the thick peanut butter to a filling station where the peanut butter is forced out of one or more nozzles by displacing a set volume to fill each jar or other type of package.

From Farm to Store

As you probably expect, dairies use an awful lot of pumps. An average cow produces six gallons of raw milk per day from two milking sessions which last about 10 minutes each. A typical dairy farm has hundreds of cows and the largest have thousands. Not surprisingly, dozens of cows are usually milked at a time.

The process begins with a specially designed vacuum pump consisting of four teat cups that squeeze and draw milk from a cow’s udder. This vacuum pump that powers the cups also pulls the milk into a clear tank, where another pump then transports the raw milk into a large refrigerated receiving tank that chills the milk to about 36° F. From there, pumps distribute the raw milk into insulated or refrigerated tanker trucks or other vessels to transport the milk for processing.

At the dairy, the raw milk is pumped out of the tanker truck and into the dairy’s stainless steel pipeline for processing. Milk temperature is maintained at 36° F throughout the process until it undergoes pasteurization. The milk is filtered, then goes through a spinning process that separates the raw milk into cream (about 40% milk fat) and skim milk (less than 0.01% milk fat). The cream is pumped through further processing to become butter, ice cream, or just cream. Some of the cream is later pumped back into the skim milk to make 1%, 2%, or whole (3.25% to 3.40%) milk.

Another key step is homogenization. Milk contains inconsistent globules of milk fat that most of us would find unappetizing. Because of their natural random size and distribution, these globules would make it extremely difficult to regulate the percentage of fat in milk. Homogenization uses a positive-displacement pump to force the milk at high pressure through a series of small orifices that break the globules into extremely small masses that remain suspended in milk.

As with most liquids intended for human consumption, milk is pasteurized to kill off bacteria and other organisms that promote spoilage. Pasteurization for milk involves heating it milk to 161° F and holding that temperature for 15 seconds. This is done by pumping the milk at a controlled rate through a heat exchanger that pasteurizes the milk.

After the milk has been pasteurized, it is quickly chilled back down to 36° F and travels to a filling station, where it is pumped into jugs, cartons, bottles, or other packaging. Butter and cream go through similar processes for cleanliness and to give them uniform consistency.

We All Scream for Ice Cream

Raw milk intended to become ice cream undergoes a somewhat different process. It is pumped from the tanker truck into a silo that may hold 5,000 gallons of raw milk. The refrigerated silo maintains the milk at 36° F.

Pumps then transfer the raw milk into large blenders that mix in sugar and other additives. The mixture is then pumped into a pasteurizer, which rapidly heats it to 180° F and holds that temperature long enough to kill any existing bacteria.

Next, the mixture is pumped into a homogenizer, which follows the same process used for milk to break up fat globules. After the mixture ages for several hours at 36° F in another tank, it is then pumped into mixers where flavorings and thickening agents are added.

From there, the mixture is then pumped into freezers, which are essentially refrigerated stainless steel barrels that also inject air into the mixture. This mixture rotates through the barrels which are held at –40°. The partially frozen mixture exiting the opposite end of the barrel is now considered soft-serve ice cream.

At this point, the mixture can be pumped to a station that adds solid ingredients, such as fruit, nut, or candy pieces. The ice cream is then pumped to a packaging station, where it is dispensed into cartons, tubs, or other packaging. The packages are then conveyed to a station that chills the ice cream to sub-zero temperatures.

Made in Your Neighborhood

Soft-serve ice cream and frozen custard may also be made at the outlet where they are sold. In general, a worker pours a specified amount of milk-cream mixture into a tank. A powdered mixture is added, which contains sugar, flavoring, coloring, and stabilizers and emulsifiers that provide thickening and consistency.

The soft-serve machine mixes and adds air to the ingredients and refrigerates and ages the mixture at the optimum temperature. When the product is ready to be dispensed, an operator activates a lever that opens a valve and starts a pump that pushes the product out a nozzle. Screw pumps are often used for dispensing the soft-serve product because they accurately dispense the mixture at a constant uniform flow to distribute just the right amount.

Making it Sweet

It may be surprising that dry products—such as granulated sugar—often make extensive use of pumps in their processing. After sugar cane is cut, water is pumped onto the cane to wash it. The cane is then ground and crushed. Rolling presses then squeeze juice out of the crushed cane.

The juice is then pumped through several refining processes that apply heat to drive off moisture and cause sugar to crystallize. The thickened juice is then pumped into a condenser that transforms it into a paste that is essentially a mixture of molasses and sugar. The sugar is now in a paste-like form, so positive-displacement pumps transfer it into a centrifuge, where centrifugal force drives the molasses away from the sugar crystals.

A final step is to convey the raw sugar into a station that dries and bleaches the sugar into the familiar white sweetener widely used in foods, beverages, candy, and desserts.

With pumps: a balanced meal, a between-meal snack, or junk food and a beverage during leisure time. Without pumps… not so much.

Check out the other World Without Pumps!

Learn more from the Hydraulic Institute.