By Sueli Roel Backes, Mouvex
The production of ice cream is a relatively straightforward process. An ingredient mix is pumped through a pipeline to a double-wall tube or tunnel freezer that is chilled by liquid ammonia to -30 C (-22 F). Inside the freezer, a slow-turning agitator or scraper forces the mix outward, where it briefly touches the frozen outer wall before it is turned back inward. This is when the ice crystals, which eventually become ice cream, are formed.
In order to achieve the required taste and expected creamy mouth feel, the ice cream mix can only spend a highly regulated amount of time in contact with the freezer’s outer wall. This is why the transfer flow and pressure have to be so accurate. 
“If, during the transfer to the ice cream freezer, the flow is pulsating, then the time the mix spends on the wall isn’t under control,” explained Peter Van de Sompel, Manager Bellux for Spin Pompen, an Assen, Netherlands-based distributor of pumps and related equipment.
“When the flow is constant and optimized to the freezer requirement, then the ice cream coming out of there will have ice crystals that are impossible to detect by the eye and impossible to taste. That’s what makes good ice cream. It should be like a cream and solid at the same time,” he said.

More viscous ice cream needs a powerful pump

Achieving proper production within the freezer used to be relatively easy. That has changed over the years, however, as ice cream has evolved from traditional compositions like vanilla, chocolate and Neapolitan to more complicated recipes that can include different ingredients, flavors, nuts and chunks of fruit or candy.
“Ten to 15 years ago, the majority of ice cream mixes were low-viscosity,” said Van de Sompel. “Over the years, what we’ve noticed is that the flowability of ice cream mixes changed because of specific market demands. There are more variants and more components added for taste, etc., that render the mix more viscous.”
The combination of a strict manufacturing process and a change in the makeup and viscosity of the ice cream mixes has brought into question the effectiveness of centrifugal pumps, which have been traditionally used in ice cream manufacture.
“The ice cream freezer is very sensitive. It has to be fed with continuous pressure, which has to be maintained in a very narrow range,” said Van de Sompel. “That’s why the centrifugal pump was a good solution. But with higher viscosity you need a volumetric pump with a very stable flow and that can be regulated in a very linear way. If you look at that, you need a pump with an equal flow and a 1:1 ratio of flow to speed.”

Ysco of Belgium is private-label ice cream processor

One company that has mastered the production of ice cream over the years is Ysco, located in Langemark, Belgium. Since 1949, Ysco has been a major player in the production of private-label ice cream products for retail chains. From its production facilities in Langemark and in Argentan, France, Ysco annually produces 174 million liters (41.2 million gallons) of ice cream in the form of one- to five-liter (0.26 to 1.3-gallon) tubs, cones, molded and extruded sticks, cakes and small cups. That volume resulted in sales of more than 245 million euros ($244 million) in 2015.
Ysco is part of the farming cooperative Milcobel cvba in Kallo, Belgium. It collects, processes and commercializes milk from 2,800 dairy farms. Ysco is one of Belgium’s largest dairy groups. Ysco’s ice cream production accounts for 22% of Milcobel’s annual production volume. Milcobel also processes milk, cheese, butter and cream.
The changes in ice cream recipes were beginning to hamper Ysco’s ability to reliably produce finished products. The higher viscosities of the mixes were incompatible with the operational capabilities of the centrifugal pumps that were being used to transfer the mix from the preparation vessels through the pipelines and into the ice cream freezers.

Looking for a better pump to use in ice cream production

That prompted Krist Levrouw, an engineering assistant who has been employed at the Langemark facility for 26 years, to initiate a search for a better pumping solution.
“The classic centrifugal pump solution does not work properly with mixes in excess of 500 cP, often as high as 2500 cP,” said Levrouw. “Under these circumstances centrifugal pumps are unable to generate the pressure required to transfer the mix and feed the freezer properly. As a result, you can’t empty the vessels completely and you have too much waste.”
Ysco’s Argentan facility uses eccentric disc pumps for its liquid-transfer operations. In talking to his colleagues there, Levrouw learned of the success they had been experiencing with Mouvex pumps. He reached out to Spin Pompen to see if they could suggest a solution for his needs.
“Of course, we knew that eccentric disc pump technology would solve his problem, which was covering the distance between the tanks and the ice cream generator in a controlled way, with constant flow and no pressure peaks, so that the product characteristics were respected,” Van de Sompel said.
The challenge was considerably big because of the layout of the Langemark facility. The supply tanks are located unusually far from the ice cream freezers — 220 meters (720 feet) — which was putting additional strain on the centrifugal pumps.
“If you’re pumping ice cream over 220 meters you don’t want pulsation, which will cause pressure peaks, which is very unbeneficial for the generation of ice cream,” said Van de Sompel.
Addressing these operational challenges, Van de Sompel recommended a seal-less  eccentric disc pump. The design is ideal for hygienic applications because it reduces the risk of product contamination and leaks while avoiding spills, waste and product spoilage. 
“The reality for ice cream manufacturers is that one day they have ice cream mix as milk, then the next day they might have ice cream as thick as 500 cP, up to 2,500 cP,” said Van de Sompel. 
Faced with new recipes that were taxing the efficiency of the centrifugal pumps used in its manufacturing process, Ysco searched for a better solution and found a perfect one in the eccentric disc pump.
“The pump is idiot-proof, which is very important since we are running 24 hours and everyone has to handle it,” said Levrouw. “If the pump is too difficult to clean and maintain, then it’s a problem. It will be destroyed in a short time. It has to be simple to use, simple to clean and simple to maintain. Every step in the process is important. Every step is complicated, but these pumps make life easier. No stress.”

About the Author
Sueli Roel Backes is Market Manager, Food & Beverage for Mouvex and PSG. Based in Auxerre, France, Mouvex is a  manufacturer of positive displacement pumps, screw compressors and hydraulic coolers. Mouvex is a product brand of PSG, a Dover company, headquartered in Oakbrook Terrace, Ill., USA.