Vol. 5, Issue 2, Part A (2023)

The objective of the present review is on Chemical Changes In the vegetable oils release harmful carcinogens upon deep fry or reused. Depending on what it is you're cooking, refined oils can be reheated the following number of times: For breaded or battered foods – three to four times. For clean frying, such as making chips or crisps – eight times, although you could reuse it far more than that if you replenish it with fresh oil after the eighth time. Vegetable oils, as used in foods, are comprised of complex mixtures of triacylglycerols (TAGs; usually > 95%) with some minor amounts of diacylglycerols (usually < 5%). Other minor components are tocopherols/tocotrienols (up to 900 mg kg⁻¹) and phytosterol esters/phytosterols (up to 1%). Reusing cooking oil in food preparation, especially during deep-frying, is a common practice to save costs. Repeated heating of the oil accelerates oxidative degradation of lipids, forming hazardous reactive oxygen species and depleting the natural antioxidant contents of the cooking oil. Repeatedly heated cooking oils can generate varieties of compounds, including polycyclic aromatic hydrocarbons, some of which have been reported as carcinogenic. Heating for prolonged periods as well as exposure to air/oxidation are known to decrease the nutritive value of oils. Thermal decomposition of flavanols and poly phenols has been reported after heating of oil at 220 °C for 100 min and on storage at 25 °C for 2 weeks.