The Behaviour of Phenolic Antioxidants, Synergists and their Mixtures in Two Vegetable Oils

Abstract Tertiary butylhydroquinone (TBHQ), hydroquinone (HQ), propyl gallate (PG), butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA) had much higher antioxidant activity in crude safflower oil than in a commercial brand vegetable oil (Bint oil). The following active oxygen (AOM, hours at 97.8° C) and storage stability (days at 45° C) values for each antioxidant in safflower oil were; (27.9, 105.0), (21.2, 44.8), (15.3, 45.5), (9.8, 36.8) and (7.9, 33.5) respectively compared with (6.8, 31.5) for the control. Ascorbyl palmitate (AP), ascorbic acid (AA) and citric acid (CA) were found to improve the AOM stability of both oils. The same values in Bint oil were: (9.0, 34.3), (9.0, 28.3), (9.4, 41.0), (7.3, 28.5) and (6.2, 2.5) respectively compared with (5.3, 23.3) for the control. Ascorbyl palmitate (AP), ascorbic acid (AA) and citric acid (CA) were found to improve the AOM stability of both oils. AP was more effective and CA least effective in safflower oil, whereas the reverse was true in Bint oil. The five antioxidants were individually blended with the three synergists (0.01 % of each) and the 15 combinations added to each oil and compared with the antioxidant controls at 0.02 %. Safflower oil stability was greater with pure TBHQ, HQ and PG than with any of the synergist mixtures whereas the BHA, BHT‐synergist mixtures were found equal or superior to that treated with BHA or BHT alone. Bint oil treated with CATBHQ or CA‐HQ mixtures showed improved stability compared to oils treated with these antioxidants alone. However, the AOM method alone suggested CA‐PG, CA‐BHA and CA‐BHT mixtures improved the stability compared to the oil‐antioxidant controls. Chelation of metals by CA was assumed to be the primary cause of this synergism, whereas AP and AA behaved more like weak antioxidants.