Synergistic Effect of Isopropyl Citrate and Phenolic Antioxidants

Abstract

The synergistic antioxidant effects of tocopherol (Toc), isopropyl citrate (IPC) and certain phenolic antioxidants on lard and palm oil were investigated by the oven and AOM tests. The antioxidant effects of IPC were compared with those of the phenolic antioxidants in the same manner.1) IPC and guaiac resin (GR) had little antioxidant effect on lard or palm oil, but the other antioxidants had considerable efficiency in the order of nordihydroguaiaretic acid (NDGA) > propyl gallate (PG) ≥ tertiary butyl hydroquinine (TBHQ) >dibutyl hydroxy toluene (BHT) on lard, and TBHQ>PG>NDGA>BHT on palm oil.2) TBHQ remarkably enhanced the antioxidant effects of a mixture of Toes (m-Toc) and dl-α-Toc on lard, and particularly hindered any increase in POV in the induction period. Synergistic effects on lard resulted by the addition of PG along with m-Toc, but such effects brought about by the addition of any other combination were either the summation of that for each component or less. Besides, efficiency on palm oil by the addition of any antioxidant along with Toc became lower than that by the addition of antioxidant only.3) As in the case of citric acid previously described [Yukagaku, 32, 695 (1983)], IPC enhanced the antioxidant effects of Toc on lard containing 4.4 ppm of iron. Thus, IPC may act as a metal deactivator in this system.