Restaurant Equipment & Supply

Commercial Fryers: The Science of Frying

Feb 5, 2014 7:24:48 AM

Commercial Fryers: The Science of Frying

Frying may seem like a simple process. All you do is put uncooked or frozen food in hot oil and a few minutes later it is cooked. However, there are actually many processes happening in the tank of your fryer. Possibly more than you ever imagined. In a previous blog post, we discussed the types of fryers commonly used in commercial applications. And in this continuation of our frying series, we’ll take a look at the science happening in these fryers and how these processes can impact the flavor and nutrition content of the food you serve.

Essentially, any type of cooking that uses hot fat (oil) is considered frying; the variable is the amount of oil used. When the item is completely submerged in cooking oil it is called “deep-frying”, when the oil only comes partially up the side of the item it is considered “pan frying”, and finally, cooking in a pan with only a little oil is called “sautéing” or “stir frying”. Regardless of the specific frying method you use, you’re always looking for a consistent end result and that delicious golden brown crunch with a moist interior. What’s happening in your frying oil are many Maillard reactions which cause the sugars and proteins to break down, browning the exterior of foods while keeping the inside moist. The surface will dehydrate, creating the crispiness that is a staple of fried foods. The heat from the oil, which is typically between 350ºF-425ºF, rearranges the proteins and simple sugars found in the food item into a series of rings to begin the process. After that is done, the proteins and sugars combine to form hundreds of unique molecules that give the exterior its golden brown color.

Frying is an ideal cooking method for foodservice because it is highly efficient.  The properties of oil allow for this speed in two ways: because the food is submerged, the oil is able to bring heat to all the nooks on the food’s surface, no matter how big or small they may be, and oil transfers and holds heat better than air and water. Oil will also never boil, even when nearly double the boiling temperature of water’s 212ºF which allows you to heat your fry tanks to very high temperatures.  It is this high temperature that causes the steam release from the food.  This release of steam helps to keep oil from penetrating the food’s surface.  The steam also cools the surrounding oil and creates flavor while it lets heat enter the center of the food without burning the exterior.

While frying is often viewed as an unhealthy cooking method, this is not always true. There are a multitude of factors that go into making fried foods high in saturated fats and calories, and they’re all potentially avoidable. The first thing is to know the proper temperature to keep the oil, which will depend on what kind of oil it is. Use the chart below to determine the best temperature range for your specific oil. Letting the oil get too hot will cause it to smoke. When the oil reaches its smoke point, it will emit a burning smell and start releasing a rather large amount of smoke. When the oil gets too hot, the food’s surface will burn before the interior ever cooks through. Conversely, oil that is too cool will cause excess oil absorption during frying. Low oil temperatures mean the crispy crust caused from the steam escape will have a difficult time materializing.  This crust is the main component that blocks excess oil absorption. So without it, or with a delayed formation, oil will penetrate the food, adding grease and fat.

Here are the smoke points of the most common types of oils or fats used in commercial and home settings. Remember that it may slightly vary depending upon the brand of oil or fat used


Smoke Point Temperature





Olive Oil


Corn Oil


Canola Oil


Peanut Oil


Soybean Oil


Another component to proper frying and oil temperature is your fryer’s recovery time. It is important if you have abundant frying needs to invest in a good commercial fryer for your establishment that holds accurate temperatures. Some fryers guarantee accuracy within a couple of degrees, while lower quality fryers may have variations of actual temperature of around 20 degrees. After reading up to this point, you can see the sort of problems inaccuracy would pose for your high volume frying. It is also important to make sure to not overcrowd the pot, regardless of how big or small it may be. That could alter the temperature of the oil or keep each food item from receiving the proper amount of heat, which will result in burnt or undercooked, greasy food. The few minutes extra that it takes to make a separate batch are well worth a proper finished product. It is also far less time consuming and more cost effective than having to throw away inedible food.  

Something else to take into consideration when trying to keep your frying healthy is the cleanliness of the oil. We will go in depth with how to clean certain commercial fryers in future posts but here is a general overview. While the manner in which you clean a gas tube fryer will differ from an open pot, you’re trying to essentially do the same thing. You want to rid the oil and frypot of debris from breading and batters as often as possible. When small and difficult to remove debris builds up, it will burn rather quickly. The burnt debris will alter the nature of the oil with an odd flavor that will taint your food.

Though you can fry items like mozzarella sticks or chicken fingers in a matter of minutes, the process is anything but elementary. Making yourself and your staff aware of the science of frying will keep your food at its optimal taste level while making it as healthy as it can be. As modern developments in the restaurant industry have shown us, people are looking for healthful foods now more than ever. Exposing your customers to the deliciousness of your fried fare without the additional fats and grease could prove to be quite profitable to your establishment.

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