Influence of natural antioxidants on the formation of trans‐fatty‐acid isomers during heat treatment of sunflower oil

Abstract

The intake of foods containing trans fatty acids (TFAs) can have deleterious effects on human health, mainly on the cardiovascular system. Thus, it is important to consider the processes that form TFAs in foods, and the alternatives to minimise their formation. The influence of two added natural antioxidants on TFA formation during heat treatment (120 h at 1808C) of sunflower vegetable oil were examined: rosemary extract (Rosmarinus officinalis L.) (1 g per kg oil) and lutein (0.1 g per kg oil). Changes in FA composition were determined using Ag-ion SPE and gas-liquid chromatography, with total polar compounds determined using dielectric constant measurements and the index of atherogenicity was calculated. Total TFAs with !1 trans double bond increased from 0.91 to 1.71% in control samples; this increase was significantly less with both rosemary extract (1.55%) and lutein (1.43%) additions. Among the individual TFAs, significant increases were seen for C18:1,t-9, C18:2,t-9,t-12 and C18:2,c-9,t-12/9-t,12-c. Polar compounds also increased, with the highest concentrations in control samples, and significantly less with both rosemary extract and lutein additions. According to results of our study, we can summarize that addition of lutein have greater effect on reduction of TFA formation than rosemary extract.Practical applications: Antioxidants, particularly from plants, are widely used in the food industry. They can provide benefits in food preparation, including improving colour, odour and stability, acting as acid regulators and natural preservatives. They have also become accepted by customers and consumers, and so indirectly they have had effects on consumer perception. Addition of natural antioxidants such as rosemary extract is usually limited by the sensory characteristics of the food, with one study showing that addition of rosemary extract at 1-3 g per kg vegetable oil is recommended. The effects of antioxidants on the formation of TFAs in vegetable oils has not been well studied in the literature. Among the already known benefits, the use of such antioxidants as functional ingredients in lipid technologies might reduce the formation of TFAs during thermal treatment.

The effect of rosemary extract on 3-MCPD and glycidyl esters during frying

“…The content of linolenic acid decreased with frying time. There was not a significant difference between sunflower and rosemary extract containing sunflower oil in terms of fatty acid distribution as was also previously reported by Filip et al, (2011).…”

“…The changes in fatty the acid composition of the frying oil during repeated frying are given in Table 4. Sunflower oil showed a typical fatty acid composition including 56.89% linoleic, 34.03% oleic, 5.97% palmitic and 2.91% stearic acids as is common for most sunflower oils (Sánchez-Gimeno et al, 2008;Filip et al, 2011). There was an obvious reduction in linoleic acid, with a consequent increase in the contents of oleic acid and palmitic acids as reported by Romero et al, (2000) and Casal et al, (2010).…”

“…Therefore, plantderived natural antioxidants are gaining increasing interest. Rosemary (Rosmarinus officinalis L.) extract is the most attractive natural antioxidant due to its high thermal resistance (Man and Jaswir, 2000) and protective effect during frying (Man and Jaswir, 2000;Filip et al, 2011). Oleoresin rosemary has been determined to eliminate thermooxidative changes during frying (Upadhyay et al, 2017a).…”

Rosemary plant (Rosmarinus officinalis L.), solvent extract and essential oil can be used to extend the usage life of hazelnut oil during deep frying

“…Ramolho and Jorge reported that soybean oil supplemented with rosemary extract had 7.99% total polar material content, while non‐supplemented control had 17.35% polar material content at the end of a 10 h heating period at 180 °C. In another study, Filip et al showed that sunflower oil containing rosemary extract and lutein had less polar material than control samples during heat treatment at 180 °C for 120 h.…”

“…In this regard, rosemary is the most commonly used plant for preventing lipid oxidation and has a high antioxidant activity . Carnosol, carnosic acid, and rosmarinic acid are the most important components in rosemary extracts . Essential oil of rosemary also contains components such as 1,8‐cineole, α‐pinene, camphene, and β‐pinene .…”