Formation of cholesterol oxides in lipid medium during microwave heating

Abstract

Microwave (MW) heating of foods may cause the formation of cholesterol oxidation products (COPs). COPs formation depends on the conditions of MW heating and the composition of the food matrix. The aim of this work was to study the formation of major COPs from cholesterol incorporated into palm, extra virgin olive, soybean, or fish oils during MW heating, and to monitor changes in peroxide value and fatty acid (FA) profiles. Model systems composed of mixtures of cholesterol and oil (2.5 mg of cholesterol/g oil), were heated for 20 min in multimode (900 W), unimode MW (≈300 W) ovens, or convection oven at 180°C. Maximum total COPs contents largely varied (46.4–250.4 µg/g lipids), depending on the type of heating system and oil matrix. Multimode MW heating caused greater COPs formation than unimode MW. COPs formation trends in the conventional oven were similar to those of MW heating, except for fish oil. Results indicated that soybean oil, compared with the other oils tested, did not promote cholesterol oxidation during MW heating, while the opposite trend was observed for extra‐virgin olive oil and palm oil. FA profile and natural antioxidants influenced cholesterol and surrounding media oxidation during MW heating. Practical applications: This work explores the formation of oxysterols by microwave heating in model systems. This will help assess the possible risks for formation of these compounds during industrial and home cooking practices. Microwave (MW) heating of foods may cause formation of cholesterol oxidation products (COPs). In this work, a model system consisting of four types of edible oils with added cholesterol was employed and heated with three different forms (unimodal and multimodal MW, and conventional heating) for different time periods. Generation of COPs in all the model systems was monitored.

Impact of Air Frying on Cholesterol and Fatty Acids Oxidation in Sardines: Protective Effects of Aromatic Herbs

“…The air fryer caused an increase of the total saturated fatty acids (SFAs) and monounsaturated fatty acids (MUFAs) contents in the thermal processed samples, between 11.8% and 20.6 %, respectively. Similar results were reported by Leal‐Castañeda and others () in fish oil after microwave heating; Gladyshev and others () in boiled and roasted humpback salmon; and Garcı́a‐Arias and others () in boiled and grilled sardines.…”

“…The temperature used and the time required to prepare fish and fish products are perhaps the main factors that contribute to the degradation of cholesterol, forming cholesterol oxidation products (COPs) (Dantas and others ; Leal‐Castañeda and others ). These substances are structurally similar to cholesterol and are normally present in small quantities formed by endogenous metabolic processes.…”

Quantification of Cooking Method Effect on COP Content in Meat Types Using Triple Quadrupole GC-MS/MS

“…However, this level rose and was recorded to be significantly higher in fried meat samples, suggesting that these COPs require higher temperatures and longer cooking times to be produced. Other studies have demonstrated that 7-keto abundantly forms during microwave heating as compared to frying [14]. Interestingly, a long heating time (>12 min) significantly elevated triol and 7-keto COPs [49,50].…”

“…The degradation of cholesterol due to oxidation produces COPs. Small COP quantities are present in foods due to endogenous metabolic processes [13,14]. However, exogenous COPs can also be produced in foods due to many factors [13].…”

Use of Natural Antioxidants in the Inhibition of Cholesterol Oxidation: A Review

“…During thermal processing, changes such as a loss of antioxidant enzyme activity, disruption of cell membranes, which bring polyunsaturated fatty acids into contact with pro-oxidants, and thermal decomposition of hydroperoxides to pro-oxidant species are responsible for the increase in cholesterol oxidation rate (Hur et al, 2007). Many authors have investigated the instability of the cholesterol molecule during thermal processing (Ansorena et al, 2013;Barriuso et al, 2016;Derewiaka, & Molińska, 2015;Ferreira et al, 2017;Freitas, Amaral, Coutrim, Afonso, & Junqueira, 2015;Leal-Castañeda, Hernández-Becerra, Rodríguez-Estrada, & García, 2017;Saldanha, Benassi, & Bragagnolo, 2008;Tarvainen, Quirin, Kallio, & Yang, 2016;Xu et al, 2016).…”