Table 1. Retention (%) of tocopherol isomers in soybean oil (SBO) with different antioxidants (200 ppm) during thermal oxidation at 180℃

Sample	Heating time (h)	Retention of tocopherol isomer (%)1)
		α-TO	γ-TO	δ-TO
Initial	0	100	100	100
Blank	4	31.7	47.0	89.8
	8	10.8	18.4	69.9
	16	5.8	7.5	48.9
	24	-	6.1	39.7
	32	-	5.1	-
CA	4	41.0	32.2	83.0
	8	17.7	18.5	60.7
	16	6.3	8.0	52.0
	24	2.5	5.4	29.2
	32	-	5.1	-
CAPE	4	60.4	76.9	95.0
	8	20.4	29.7	88.0
	16	6.9	8.6	54.8
	24	5.4	5.5	35.9
	32	5.2	4.9	-
α-TO	4	43.92) (121.2)	30.8	82.1
	8	21.5 (59.1)	21.1	75.1
	16	4.2 (11.4)	10.7	59.1
	24	3.0 (8.2)	6.1	27.7
	32	2.8 (7.7)	3.3	-
AP	4	52.8	61.8	92.0
	8	19.5	29.5	83.5
	16	2.4	8.9	53.4
	24	-	6.1	39.4
	32	-	4.5	-

CA, caffeic acid; CAPE, caffeic acid phenethyl ester; α-TO, α-tocopherol; AP, ascorbyl palmitate.
¹⁾Tocopherol retention (%) = [(Initial SBO tocopherol content-tocopherol content of each heating time) / initial SBO tocopherol content] × 100.
²⁾α-TO(%) = [(Initial SBO tocopherol content + 200 ppm α-tocopherol)-(tocopherol content of each heating time) / initial SBO tocopherol content] × 100.Initially, SBO contains 114 ppm of α-tocopherol, 191 ppm of γ-tocopherol, and 14 ppm of δ-tocopherol.