Ability of phenolic acids to protect naturally present alfa-tocopherol during the heating of plant oils

Abstract

Réblová Z., Fišnar J., Tichovská D., Doležal M., Joudalová K. (2012): Effect of temperature and oil composition on the ability of phenolic acids to protect naturally present α-tocopherol during the heating of plant oils. Czech J. Food Sci., 30: 351-357.The ability of phenolic acids (ferulic, gallic, protocatechuic, and sinapic; 600 mg/kg) to protect naturally present a-tocopherol was tested during the heating of sunflower oil on a hot plate set at 120, 150, 180, 210, or 240°C, and during the heating of rapeseed, olive and soybean oils on a hot plate set at 180°C. In all the studied conditions, a-tocopherol was significantly protected only by gallic acid. This phenolic acid prolonged the half-life of a-tocopherol (calculated as the time needed for the a-tocopherol content to decrease to 50% of the original value) typically two-to four-fold. Hence the ability of phenolic acids to protect a-tocopherol in bulk oils does not markedly depend on the experimental conditions as is seen in antioxidant activity, i.e. in the ability of antioxidants to protect fatty acids.

Relationship between tocopherols depletion and polymerised triacylglycerols formation during heating of vegetable oils

“…The observed negative relationship between the rate of tocopherols depletion and the antioxidant capacity of unheated oils indicates the protective effect of some antioxidants naturally present in the studied oils against tocopherols. The ability to protect tocopherols (primarily α-tocopherol) has already been described for numerous antioxidants (Kajimoto et al 1988a;Zhang et al 2001;Raneva et al 2002) under various conditions, including frying or heating of vegetable oils at frying temperatures (Kajimoto et al 1988b(Kajimoto et al , 1991(Kajimoto et al , 1992Tomaino et al 2005;Réblová et al 2012). However, some substances can protect tocopherols but do not protect fatty acids under the given conditions (Psomiadou & Tsimidou 2002;Réblová & Okrouhlá 2010).…”

Extraction of Virgin Coconut (Cocos nucifera) Oil Using Supercritical Fluid Carbon Dioxide

“…As shown in Figure 4, the highest antioxidant activity was obtained when the extraction of virgin coconut oil was performed at the pressure of 18 MPa to 22 MPa and temperature of 40°C to 55°C. Temperature is one of the most significant factors affecting antioxidant activity [8]. When increasing the extraction temperature, the least antioxdant activity was attained because the easily oxidisable antioxidants show a decrease antioxidant activity with increasing temperature at a slower rate than the less oxidisable ones [9].…”