Lang
Note: This article was AI-translated from Arabic and is currently under manual review. The author is not responsible for any translation errors. Please refer to the original Arabic text for the most accurate and authoritative information.
Professor of Oils and Fats at the National Research Centre; Vice-President of the Egyptian Food Safety Association; WHO National Consultant for the iTFA programme.
From oil composition to golden color and acrylamide: Scientific rules for better crispiness.
French fries emerge from the fryer golden and crispy, their aroma reaching the table first; yet many questions follow: Is all fried food harmful? Is the oil that doesn’t smoke always the best? And does the air fryer give us "healthy crispiness" unconditionally?
The scientific answer is not simplified into the name of an oil or a type of appliance. The outcome of frying is determined by an integrated system that includes the type and quality of the oil, temperature, heating duration, nature of the food, method of operation, portion size, and frequency of consumption. Therefore, we do not look for a "magic oil," nor do we put the fryer in the dock; rather, we understand what happens, then choose and act consciously.
When food is placed in hot oil, it does not absorb the oil immediately like a sponge absorbing water. The heat begins to convert the water near the surface of the food into steam that rushes outward, temporarily restricting the entry of oil. As frying continues, part of the surface dries out, forming a crust, and bringing out the desired color and flavor.
An important part of oil absorption occurs after removing the food and as it begins to cool; the steam inside the pores condenses, pulling some of the surface oil inward. Thus, the amount of absorbed oil is affected by the size of the pieces, surface area, moisture content, type of coating, frying time, and post-frying draining method—it is not determined by temperature alone.
If the heat is too low, frying time is prolonged, leaving the food pale or soggy, and it may absorb more oil. If the heat is excessively high, the surface browns before the inside cooks, accelerating oil degradation and the formation of thermal processing byproducts. Good frying is therefore not a race to the highest temperature, but a balance between crust formation, cooking the inside, and preserving the oil.
One of the most common errors is turning the "smoke point" into a sole pass-or-fail metric. While continuous smoke is a signal that the oil has exceeded its suitable operating temperature, the suitability of an oil for frying is not decided by this indicator alone.
A proper choice is based on five interconnected elements:
Accordingly, refined oil designated for frying or a reliable commercial blend is a practical choice when following usage instructions. High-oleic sunflower oil also features better relative stability than traditional sunflower oil rich in linoleic acid; thus, they should not be treated as a single product regarding thermal performance.
Traditional sunflower and corn oils can be used in controlled household cooking and frying, but their high percentage of polyunsaturated fatty acids makes them less suitable for prolonged and repeated heating compared to higher oleic alternatives or oils specially formulated for frying.
Palm olein deserves a clear place in discussions about frying. It is the liquid fraction derived from the fractionation of palm oil and is not synonymous with "high oleic" oil. It combines a notable proportion of oleic acid with a balanced composition of saturated and unsaturated fatty acids, alongside relatively low polyunsaturates compared to oils like traditional sunflower and corn. This balance contributes to good stability, especially in repeated or extended operations.
In its refined, bleached, and deodorized (RBD) form, it is light in color and relatively neutral in taste and odor, typically not overpowering the characteristics of fried food. It can be used alone or in blends designed to achieve a balance between thermal stability, fluidity at handling temperatures, taste, nutritional value, and cost. "Pure" olein simply means it is unblended with another oil, not that it is virgin or unrefined.
However, the name alone is not an open guarantee; performance is affected by the degree of fractionation, refining quality, antioxidant content, transport, storage, and the final blend composition. More accurately: Palm olein is a suitable frying oil when it complies with specifications and is managed correctly, not an oil that never degrades. Updated Codex specification CXS 210-1999 defines palm olein as the liquid fraction derived from the fractionation of palm oil.
Yes, good olive oil can be used in controlled cooking and frying, and it is incorrect to claim that heating automatically turns it into a harmful substance. Its composition, rich in oleic acid, along with any natural antioxidant compounds it may contain, gives it good stability in many thermal applications.
With heating, it may lose some of its aromatic and phenolic compounds, and its quality is affected by heat, time, and repetition like any other oil. Cost and flavor may be practical reasons for not selecting it for repeated deep-frying, but this is entirely different from claiming it is fundamentally unsuitable for heating.
Similarly, butter and ghee (clarified butter) should not be placed in the same category; butter contains water and milk solids that may brown or burn at high temperatures, whereas clarified fat is more heat-tolerant while remaining rich in saturated fats, which should be consumed in moderation.
Waiting for smoke to know the oil is hot is a delayed method; smoke means operating temperatures have already been exceeded. Therefore, a kitchen thermometer is a small tool with a major impact on frying quality and safety.
For potatoes and many starchy foods, 160–175°C represents a practical range. Temperatures may approach 180°C for certain products depending on size and composition, but there is no benefit in exceeding 180°C unnecessarily.
Oil temperature drops immediately upon adding food; overcrowding the pan prolongs cooking time and weakens crispiness. Alongside the thermometer, color remains an important practical guide: light golden, not dark brown.
Acrylamide is a contaminant that can form naturally in carbohydrate-rich foods when cooked at temperatures above approximately 120°C with low moisture. It arises primarily from the reaction of certain reducing sugars with the amino acid asparagine during the Maillard reaction—the same reaction that imparts desired color and flavor.
The goal is not to eliminate browning, but to control it so we do not cross from acceptable golden color into dark brown or charred territory. The European Food Safety Authority (EFSA) considers dietary exposure to acrylamide a health concern; thus, its formation should be reduced to the lowest reasonably achievable level.
To reduce it in potatoes:
There is no single oil absorption percentage that applies to all foods; practical steps are therefore more useful than attractive numbers:
A common misconception should be corrected here: higher oil temperature does not always lead to lower fat absorption; excessive heat can burn the surface before the interior cooks. What is needed is the correct temperature, not the highest possible temperature.
An air fryer is essentially a small convection oven that circulates hot air rapidly around food, evaporating surface moisture to cause browning and crust formation. It typically uses significantly less added oil compared to deep-frying, helping lower fat content in many foods.
However, it does not turn everything placed inside into healthy food, nor does it automatically prevent acrylamide. If time or temperature is excessive to the point where starchy food turns dark brown, acrylamide can still form.
For better results: Do not overcrowd the basket, shake or turn food when necessary, use the minimum amount of oil needed, stop cooking at a light golden color, and clean out fat and crumbs after the appliance cools down.
It is not a contest between deep fryers and air fryers. If the goal is reducing daily added oil, the air fryer is a practical tool; if traditional frying characteristics are desired, they can be achieved with controlled, infrequent deep frying using suitable oil. Food quality, portion size, degree of browning, and frequency of consumption matter more than the appliance's name alone.
Food must be dried before frying, pans should not be overfilled, pot handles must be turned away from the stove edge, and hot oil should never be left unattended.
When oil catches fire, never use water, as it can violently spread flames. If the fire is small and can be handled safely, turn off the heat source and cover the vessel with a suitable metal lid. If control is lost, priority must be given to evacuating and calling emergency services.
Good crispiness does not begin when food leaves the pan, but from choosing the right oil, controlling temperature, understanding food properties, and stopping at a light golden color. Smoke point alone does not select the oil, the appliance alone does not make food healthy, and dark color is not proof of mastery.
The most important practical question after frying remains: Is the oil safe to reuse? Does filtering or topping off with fresh oil safely extend its life? And when does discarding become mandatory? This will be answered in Part Two, covering everything from home kitchens to restaurants, hotels, and industrial frying lines.