In its Southern California laboratory, the Ventura Foods team has done extensive sensory testing on many different oil types, and what they’ve found may surprise you.

“If the oil is in good shape, most people cannot tell a difference,” Frusteri says. “We’ve worked with soybean, canola, cottonseed, peanut, you name it. When you first use peanut oil, you can sometimes catch a little bit of nutty flavor. At the beginning or at the end of an oil’s life, you may detect a note of flavor. It’s grassy in soybean oil; canola has a fishy note—but this is only when they are starting to break down and you should be changing them anyway. Otherwise, a good fryer oil should be bland.”

Anyone who fries food has heard of the ongoing controversy surrounding trans-fatty acids. These are the unsaturated fats created when vegetable oil is processed to use in cooking. “Trans-fat” may have as much potential for causing clogged arteries and heart disease as saturated fats, and quick-service giant McDonald’s made headlines in September by announcing it has begun frying with a different oil blend that reduces—but does not eliminate—trans-fat and saturated fats.

It’s an interesting trade-off, because the fats in cooking oil make it more stable, and protect it from oxidation. They also provide some of the delectable color and aroma that most of us associate with frying.

“You’ll have customers who are interested in this issue and will want to know about it,” says Jeff Henderson, food chemist and Group Leader for Simplot Foods’ Technical Services Department. “I think people should look at the big picture—that is, look first at the total calories in the product, and then at the type of fat. If you’re going to enjoy fried foods, you do have to accept some modest level of saturated fats. They’ll probably be lowered more in the future, but technology is going to have to catch up with the industry before that happens.”

By that, Henderson means most of the “frying world” is still set up to use hydrogenated soybean oil, which is inexpensive and plentiful. There are other oils in test production that don’t contain trans-fats, including a new process with a formidable name (“interesterification”), but they are experimental and in very short supply.

The ultimate goal is to produce high-quality fried foods while controlling the degradation of the oil. You may have noticed that most manufacturers “rate” their oils with a number that indicates the oil’s potential hours of use. These ratings are strictly guidelines—they represent the hours of use in a tightly controlled laboratory setting. The numbers are not at all indicative of how long the oil will last in a hard-working foodservice kitchen.

Ventura’s Maria Frusteri says no matter where the restaurant is located or what types of food it serves, kitchen employees generally have a few common misconceptions about oil—and they may inadvertently be shortening (no pun intended!) the useful life of their oil.

“First, most people see it as a cooking medium,” she explains. “But it actually becomes part of the food. You’re getting as much as a 30 percent absorption rate on some items. That’s a lot!”

The overall range of oil absorption is 7 to 35 percent, depending on the product. Seen in this light, it is incredibly important to fry in oil that is safe and clean. (More about keeping fryer oil clean in a moment.)

The next misconception is that food fries faster when the oil is hotter. Frusteri says she could make a career of walking into commercial kitchens and turning down the fryer thermostats! Ventura Foods recommends nothing be fried at temperatures higher than 350 degrees Fahrenheit. That is also the recommendation of Simplot Foods.

“When a fry cook is busy, they automatically assume they need to crank up those fryer temperatures,” Frusteri says. “What they often end up doing is burning the outside of the product and undercooking the inside. And the fryer temperature doesn’t recover any quicker than it would have at the proper temperature.”

Heat recovery is a key part of correct fryer use, and it just makes sense. When you throw a bunch of frozen French fries into a fryer basket and put them in oil, the oil can’t help but cool down slightly. Then it cooks the fries, you remove them and throw in another batch. If you keep the batches coming, one after the other, the oil never has time to fully “recover,” or return to its optimum temperature. It stays a bit too cool, which means the fries absorb more oil and taste greasy. Raising the frying temperature doesn’t change this cycle and, in fact, causes the oil to break down more quickly over time.

A cousin to the heat recovery problem is the common notion that fryers must be kept on and ready to use even when they are not needed. Today’s fryer takes all of 15 minutes to heat from room temperature to 350 degrees F. So why do kitchen employees turn them on and let them sit, simmering for hours? Simplot’s Jeff Henderson claims idle fryers cause more damage to oil than anything else he’s seen.

Alternatives could be turning all but one unit off during slow periods—or at least, reducing their temperatures to 200 degrees F. and covering them promptly when not in use. This minimizes exposure to oxygen and, if needed, the other units will take a speedy three minutes to heat to 350 degrees F. Also check the oil temperature daily with a thermometer, and have fryer thermostats calibrated by the manufacturer twice a year.

While temperature is the most important aspect of oil care—keeping it from overheating, and allowing it to recover between uses—there are others that also matter greatly in maintaining oil quality. One is to load food into the fryer correctly. This means not overloading the basket, and not dumping full bags of product into the basket when it is positioned over the fryer. The goal is to minimize food particles floating in the oil, which will quickly burn and compromise its quality.

“But the typical kitchen is pinched for space,” says Henderson. “They do all of their salty and spicy batter applications right next to the fryer, and of course a lot of it ends up in the fryer.”

“Shake off the excess before putting battered or breaded items in the basket,” adds Frusteri. “Skim all the particulates off the surface of the oil, and filter it completely at least once a day.”

Frusteri and Henderson agree that automatic filtration systems are the most effective, with less room for error (or skipping a day), and less danger when employees don’t handle the oil. The other thing they notice in restaurant kitchens is bags of frozen product, thawing as they sit near a fryer waiting to be used.

“Fry frozen foods frozen!” Frusteri cautions. “When you allow them to sit and defrost, all the water particles that were sitting on the surface are now inside the product. They take longer to be released in the cooking process, which means the product takes longer to fry and absorbs more oil. The water doesn’t stay in the oil—it burns off as steam—but the frying process takes longer, and that breaks down the oil a bit faster.”

This type of oil degradation is called hydrolysis—exposure to water—and it’s never a good thing, compromising the quality of the fried food.

To sum it up, the best way to determine whether your fryer oil is performing well and being cared for properly is simple: taste the results.

“Of course, you look for all the obvious signs of deterioration—burning, smoking, foaming,” says Frusteri, “There are different gadgets that test the quality of oil, but it’s really something you can do on your own. If the food starts getting darker, although you’ve fried it the same amount of time; if it smells funny, or starts to taste a little oily...always rely on the quality of the food as your guide, and you’ll be fine.”