Engineers of many types play an integral role in the manufacturing of ice cream. In the transformation of simple ingredients such as milk and cream into one of America’s favorite desserts, mechanical, chemical and industrial are only a few examples of kinds of engineers involved. From the building of the factories and equipment to the production of the ice cream, engineers are a key part in this multi-billion dollar per year industry.
Ice cream most often gets its start in a large manufacturing plant. The plants themselves, as well as the equipment inside of them, are the product of much thought of different kinds of engineers. Even the location of the plant can have an extremely large impact on the quality of the finished product. Engineers have to consider the distances that delivery trucks will have to travel, as well as the altitude of the location of the factory. For instance, if the ice cream is packed in a plastic container, and put on a truck traveling from a lower to a higher altitude, this could cause the ice cream to expand and break the packaging, spoiling the ice cream and losing money for the company.
The manufacturing of ice cream itself begins with ingredients. Chemical engineers alongside biologists put considerable thought into creating just the right mix of ingredients. By legal standards, ice cream is greater than ten percent milk fat, but in some higher quality ice creams it may be as high as sixteen percent milk fat. Ice creams are generally ten to twelve percent milk solids (not fat). These milk solids contain caseins and whey proteins, as well as the lactose found in milk. Eleven to sixteen percent of the recipe is sweeteners, usually a mixture of glucose and sucrose-based corn syrups. Most ice cream formulas contain around a half of a percent of stabilizers and emulsifiers, two extremely crucial components. Stabilizers are a group of polysaccharide compounds that prevent too much lactose crystallization. The smaller the ice crystals are, the smoother the ice cream will be. Stabilizers also lengthen the ice cream's shelf life. The emulsifiers are constituent compounds that help the proper fat structure develop. The final ingredient is water, which is found in the milk and in other ingredients.
All of these ingredients are precisely weighed out prior to being combined. This mix is simply called the ice cream mix. To combine the liquids and dry ingredients, the liquid ingredients are all placed in a large blending vessel, often called the "vat". Attached to the vat by a pipe in the side is a large funnel, as well as an air pump. The dry ingredients are dumped by a human worker into the funnel as the pump forces them into the vat, and the two sets of ingredients are blended together at a high speed. This piece of equipment as a whole is called a hopper. The hopper is crucial to the assembly line style of ice cream making because it quickly and effectively mixes all ingredients together. This task would be much more time consuming if performed solely by a human worker. Engineers, such as mechanical and electrical engineers, are largely to thank for ensuring that this machine does it's job properly and in the allotted time.
The next important step is pasteurization of the ice cream mix. Pasteurization decomposes the pathogenic bacteria, and it also reduces the spoilage organisms. For this step, the mix is transferred to another "vat" type of vessel. There are two methods of pasteurization: batch pasteurization, and continuous pasteurization. Batch pasteurization is believed by some to be more effective, as it leads to more whey protein denaturation. Some would say that this gives better texture to the ice cream. In this particular method, the proper ingredient amounts are blended in the large vats, by some means of heating. Often this heat is provided by steam, occasionally by hot water. The steam or hot water pasteurization units are designed and constructed by engineers. Specifically, mechanical engineers are needed to develop complicated machinery with such a precise task.
The product in the vats must be heated to at least 155 degrees Fahrenheit, and then held at this temperature for a minimum of 30 minutes, to meet legal criteria. The time and temperature combinations may vary. The most important thing is that the heat has enough of an effect to destruct enough of the pathogenic bacteria. Often times in manufacturing plants, they will have two batch tanks/vats operating at once, so that one is pasteurizing, while the next moves on to homogenization and then holding. The mix is homogenized at the pasteurizing temperature, by means of high pressure. This stage breaks down the fat globules, resulting in a smoother, lighter mix. The current mix is passed across some form of heat exchanger, cooling it down to around 39 degrees Fahrenheit.
The next step is referred to as aging. This process takes place over at least four hours, but most often overnight. It gives the fat time to cool down, and then to crystallize. The stabilizers and proteins also become fully hydrated, increasing viscosity. Aging takes place in large refrigerated tanks, at a temperature as low as possible without freezing, which is about 40 degrees Fahrenheit. All of these critical conditions (temperature, amount of mix in each tank, time that the mix will age) are decided with much help of chemical engineers. Now that the mix has finished it's aging phase, this is the time in the process when any colors or flavors will be integrated.
After aging, the mix enters it's freezing process. This freezes some of the water, as well as incorporating air. This is extremely important, since the texture of ice cream is defined by characteristics that are provided by air. Ice cream is essentially a frozen foam, air accounting for up to half of it's volume. The air content, and the speed and amount of whipping needed to achieve such content, can be calculated mathematically. This job is usually done by an engineer. The details of this process are so specific that an engineer is needed to figure out what is required for the task to be successfully completed.
After the air is introduced to the mix, it is frozen. Often times this will be done by means of a spiral wind tunnel freezer, other times it will be done using a nitrogen tunnel freezer. I interviewed Harry Tully, CEO of Uncle Harry's Ice Cream Cakes and Desserts, and he explained to me his company's use of the nitrogen tunnel method. Nitrogen tunnel freezers are complicated pieces of equipment, requiring the expertise of chemical and mechanical engineers. In this technique, the ice cream is already in its mold, and sent on a belt through the tunnel. The liquid nitrogen (or in some cases another cryogen, such as liquid carbon dioxide) is kept in pressurized tanks. It's piped as a liquid into the tunnel freezer and applied directly to the ice cream (H. Tully, personal communication, February 26, 2012).
With this advanced type of technology there are specific hurdles that engineers have had to overcome. For example, in such a cold and wet environment as a tunnel freezer, when you continually pump in the below freezing cryogens, a buildup of ice on the sides of the tunnel will often occur. As a solution to this problem, as well as an improvement to the equipment, engineers designed rotating scraper blades that periodically remove ice from inside the tunnel.
At this point the ice cream is ready to be packaged for sale and shipped to stores accross the country. Mechanical, electrical and systems engineers design the processes and equipment for packaging. It is the responsibility of industrial, computer and electrical engineers to analyze operations and design smart systems for tracking the ice cream they produce and ship.
Often times, large manufacturing plants such as the ones where many popular brands of ice cream are produced, have amazingly intricate systems that are designed with extreme precision for effectively producing large amounts of product at low cost, quickly and with ease. However, often times this means that sacrifices are made when it comes to the environment. It is a fairly recent movement that environmental engineers are striving towards focusing on clean air and water leaving the plants and minimizing air emissions. As an aspiring engineer myself, I hope to be an innovator in the world of engineering, while still putting first values such as taking care of the earth.
It is clear that the production of ice cream would not be possible without the help of engineers. From the designing of the equipment, to the production of the ice cream, and finally to the distribution of the finished product, engineers are involved every single step of the way. Taking a closer look at a single example such as this truly emphasizes what a substantial role engineers play, not only in the manufacturing of products, but in the way that our entire society functions.