Stability of vitamin E homologs and added retinyl palmitate in frying oils during frying

The stability of natural vitamin E and added retinyl palmitate (12.5 {dollar}mu{dollar}g/g or 250 IU/100 Kcal) in soybean oil, corn oil and palm olein during deep-fat frying was evaluated. Retinyl palmitate was more stable in palm olein compared to soybean or corn oil. Total vitamin E (mg/100g) decreased more rapidly in palm olein than in soybean or corn oil. The relative stabilities of the vitamin E homologs in the oils were {dollar}alpha{dollar}-T {dollar}>{dollar} {dollar}delta{dollar}-T {dollar}>{dollar} {dollar}beta{dollar}-T {dollar}>{dollar} {dollar}gamma{dollar}-T (soybean oil), {dollar}alpha{dollar}-T, {dollar}gamma{dollar}-T {dollar}>{dollar} {dollar}delta{dollar}-T {dollar}>{dollar} {dollar}gamma{dollar}-T3 (corn oil) and {dollar}alpha{dollar}-T {dollar}>{dollar} {dollar}delta{dollar}-T3 {dollar}>{dollar} {dollar}alpha{dollar}-T3 {dollar}>{dollar} {dollar}gamma{dollar}-T3 (palm olein). Addition of retinyl palmitate did not statistically affect thermal stability of the oils (p {dollar}{dollar} corn oil {dollar}>{dollar} palm olein. Loss of individual vitamin E homologs depends on the oils and the foods (p {dollar}<{dollar} 0.01). Stability of the tocopherols and tocotrienols in the oils during their use varied significantly by oil type, food type and the interaction of foods and oil (p {dollar}<{dollar} 0.01). Breaded shrimp that contained low initial fat (0.8%) had higher fat increase compared to the flash-fried chicken nuggets with higher initial fat (9.0%). Total vitamin E in oil extracted from fried chicken nuggets was less than the oil extracted from fried breaded shrimp. The retention of retinyl palmitate in different oils after one frying was 62-86% (soybean oil), 54-60% (corn oil) and 72-74% (palm olein). In corn oil, addition of retinyl palmitate led to increased retention of both the tocopherols and tocotrienols. Accelerated storage of the product at 37{dollar}spcirc{dollar}C led to significant decrease of total vitamin E and retinyl palmitate in each product (p {dollar}<{dollar} 0.01). However, the loss of retinyl palmitate never exceeded 50% during the accelerated storage. Total vitamin E decrease was due to the decrease of {dollar}gamma{dollar}-T in soybean oil and corn oil; whereas, the decrease of total vitamin E in palm olein was due to loss contributed by each vitamin E homolog.