The deep-frying process takes only two minutes; it is very convenient when used in public catering. Deep-fried oil is used many times; it is periodically filtered and poured a second time. To prepare food, it must be completely dipped in the deep fryer using a special spoon. Food with this cooking method has an appetizing even crust, which makes the deep-fried cooking method indispensable for restaurant cuisine. Pan-frying is another common way of cooking that uses considerably fewer fats (just enough to lubricate the frying surface). The oil is used to produce steam which cooks the food material from the downside, while the top side allows steam to escape. Since food is only partially covered in a cooking material, it needs to turn to another side at least once when pan-frying.
All non-animal oils have an index called the oil smoke point. The smoke point is the temperature of active oil oxidation, at which volatile oxidized compounds become visible to the naked eye – such compounds disintegrate in the air, forming soot. There is a relationship between the smoke point and the amount of free fatty acids in vegetable oil: the lower the free fatty acids, the higher the smoke point (Guillaume et al., 2018). The same vegetable oil can have different burning temperatures, depending on whether it is refined or not.
Frying methods differ in terms of appropriate fats and advisable smoke points. For deep-fat frying, oils with a smoke point above 320 – 360 °F are suitable (Lam et al., 2020). These numbers exclude most unrefined oils such as virgin olive (smoke point of 375 °F) or unrefined coconut (340 °F), as well as margarine (660 °F) or lard (370 °F) (Lam et al., 2020). The butter’s smoking point is about 250 °F (Daoud & Mirghani, 2020). It is not recommended to use the same deep-frying oil more than two times because when the oil is periodically heated, free fatty acids are formed in it, and the smoke point decreases. It is also essential to ensure that used fats have no disturbing smell. The most popular in terms of taste and health are sunflower, safflower, and corn oils, with smoke points of 450 °F, 510 °F, and 450 °F, respectively (Lam et al., 2020). In general, for deep frying, almost any high-quality clear, refined vegetable oil is suitable, which will not foam when heated and has no scent.
For the formation of crust, the Maillard reaction temperature is required. Thus, for pan-frying, use oils with a smoke point above 284 – 302 °F. The smoke point, that is, the temperature after which the oil begins to smoke, and its chemical composition changes under the influence of heat. Refined oils have the highest smoke point, while Extra Virgin olive oils have the lowest. It is essential not to forget that usually (not counting deep fat), the product cools the oil to a temperature below the smoke point (Guillaume et al., 2018). Therefore, one can also fry on Extra Virgin, not overheating the oil too much before laying the products (Godswill et al., 2018). Depending on the flavor you want, you can choose from a wide variety of pan-frying oils. They include coconut (365 °F), butter, avocado oil (520 °F), and other fats, including those of animal origin.
It is recommended to use specific oil for different culinary purposes. What is suitable for salad dressing may not be good for stewing, frying, or baking. One can also make a dish unsuitable for eating by heating the oil over high heat and then reducing it, thereby briefly exceeding the smoking point at the beginning of cooking. Rancid odors and tastes are caused by improper storage of the oil and mean that the composition of the fats in it has changed so that it is not suitable for human consumption.
References
Daoud, J. I., & Mirghani, M. E. S. (2020). Statistical analysis investigation on vegetable oils stability during deep frying using selected quality parameters. Journal of Physics: Conference Series, 1489(1). Web.
Godswill, A. C., Amagwula, I. O., Victory, I. S., & Gonzaga, A. I. (2018). Effects of repeated deep frying on refractive index and peroxide value of selected vegetable oils. International Journal of Advanced Academic Research, 4(4).
Guillaume, C., De Alzaa, F., & Ravetti, L. (2018). Evaluation of chemical and physical changes in different commercial oils during heating. Acta Scientific Nutritional Health, 2(6), 2-11.
Lam, H. Y., Roy, P. K., & Chattopadhyay, S. (2020). Thermal degradation in edible oils by surface enhanced Raman spectroscopy calibrated with iodine values. Vibrational Spectroscopy, 106, 103018. Web.