Lard contaminated with fish oil (final concentration 40%) was heated at 180°C under the condition of specific surface area 0.132cm2/g, and the effect of tocopherol on its thermal deterioration was studied.
Thermal deterioration of the contaminated lard was retarded by the addition of tocopherol at high concentration. During the course of thermal deterioration, highly unsaturated fatty acids decomposed rapidly, and the thermal decomposition was suppressed to some extent by the addition of tocopherol at high concentration.
When tocopherol was added to fresh lard at the concentration of 0.04%, high stability of the lard in autoxidation was found, but the heated lard (180°C, 16 hours) reached maximum stability by the addition of tocopherol at the concentration of 0.4%. On the other hand, the stability of the contaminated lard did not increase by the addition of tocopherol.
In the course of thermal treatment, tocopherol in the contaminated lard decomposed more slowly than that in fresh lard. The higher the initial concentration of tocopherol became, the larger grew its amount remaining in lard after heating.