The relative rates of destruction of propyl gallate and butylated hydroxyanisole in oxidizing lard

Summary The rate of disappearance of propyl gallate and BHA has been studied in lard stored at 61°C. An antioxidant formulation containing 20% BHA, 6% propyl gallate, and 4% citric acid in 70% propylene glycol was employed. The rate of destruction of propyl gallate was approximately constant with respect to time, irrespective of the concentration, indicating a zero order reaction. The disappearance of BHA occurred in two stages, an initial slow loss which was partially attributed to evaporation of this compound from the surface of the lard, followed by a rapid decrease which was initiated coincident with the disappearance of the propyl gallate. The rapid increase of the fat peroxides in the oxidizing lard containing both BHA and propyl gallate was coincident in all cases with the complete disappearance of the propyl gallate. The results on the disappearance of the 2‐BHA and 3‐BHA isomers indicated that 3‐BHA reacted more readily with the oxidizing fat than 2‐BHA. This factor was considered to be at least partially responsible for the greater effectiveness of 3‐BHA as an antioxidant. The combination of propyl gallate and BHA was much more effective than the BHA alone as judged by peroxide accumulation in lard stored at 61°C.