Oxidative stability of olive oil during the thermal process: Effect of Pistacia khinjuk fruit oil

Figures & data

Table 1. Chemical composition of Pistacia khinjuk fruit and olive oils.*

Parameter	Pistacia khinjuk fruit oil	Refined olive oil
Fatty acid (%)
C16:0	19.8 ± 0.7^a	13.1 ± 0.5^b
C16:1	4.8 ± 0.3^a	0.7 ± 0.2^b
C18:0	2.1 ± 0.2^b	3.3 ± 0.3^a
C18:1	59.2 ± 1.6^b	71.5 ± 1.5^a
C18:2	13.4 ± 0.5^a	9.4 ± 0.2^b
C18:3	0.7 ± 0.1^a	0.6 ± 0.2^a
C20:0	—–	0.6 ± 0.15
C20:1	—–	0.4 ± 0.1
SFA	21.9 ± 0.6^a	17 ± 0.7^b
MUFA	64 ± 1.3^b	72.6 ± 1.8^a
PUFA	14.1 ± 0.8^a	10 ± 0.5^b
USM content (% of oil)	1.5 ± 0.2^a	1.2 ± 0.3^a
TT content (mg /kg oil)	639.83 ± 14.3^a	350 ± 1.2^b
TP content (mg gallic acid /kg oil)	85.23 ± 2.4^a	26.5 ± 4.5^b
TS content (mg /kg oil)	2167.5 ± 23.2^a	1076.3 ± 17.4^b

*Mean ± SD (standard deviation) within a row with the same lowercase letters are not significantly different at p < 0.05. SFA, saturated fatty acids; MUFA, monounsaturated fatty acids; PUFA, polyunsaturated fatty acids; USM, unsaponifiable matter; TT, total tocopherols; TP, total phenolics; TS, Total sterols.

Table 2. Changes in conjugated diene value (CDV, mmol L^–1) of olive oil as affected by PKFO and TBHQ during heat processing at 170°C.*

Time (hour)	Pure olive oil	Olive oil samples containing
		PKFO					TBHQ
		0.5%	1%	2%	5%	10%	100 ppm
0	11.5 ± 0.04^a	11.5 ± 0.04^a	11.51 ± 0.04^a	11.52 ± 0.04^a	11.55 ± 0.04^a	11.54 ± 0.04^a	11.5 ± 0.03^a
2	19.23 ± 0.06^a	12.84 ± 0.04^f	14.23 ± 0.02^e	16.17 ± 0.02^c	10.47 ± 0.03^g	16.72 ± 0.03^b	14.51 ± 0.02^d
4	20.34 ± 0.08^a	15.32 ± 0.03^b	14.64 ± 0.04^c	20.41 ± 0.04^a	12.39 ± 0.03^f	14.27 ± 0.03^e	14.54 ± 0.04^d
6	31.34 ± 0.07^a	18.00 ± 0.05^c	16.01 ± 0.03^e	27.26 ± 0.03^b	16.01 ± 0.02^e	12.03 ± 0.04^f	16.5 ± 0.04^d
8	29.74 ± 0.05^a	17.86 ± 0.05^d	20.55 ± 0.06^c	26.01 ± 0.03^b	17.49 ± 0.02^e	17.83 ± 0.04^d	16.96 ± 0.02^f

*Mean ± SD (standard deviation) within a row with the same lowercase letters are not significantly different at p < 0.05. PKFO, P. khinjuk fruit oil; TBHQ, tert-butylhydroquinone.

Figure 1. Changes in carbonyl value (CV, µmol/g) of olive oil as affected by PKFO and TBHQ during heat processing at 170°C. A: pure olive oil; B: olive oil containing 0.5% PKFO; C: olive oil containing 1% PKFO; D: olive oil containing 2% PKFO; E: olive oil containing 5% PKFO; F: olive oil containing 10% PKFO; G: olive oil containing 100 ppm TBHQ. PKFO, Pistacia Khinjuk fruit oil; TBHQ, tert-butylhydroquinone.

Table 3. Changes in acid value (AV, mg/ml) of olive oil as affected by PKFO and TBHQ during heat processing at 170°C.*

Time (hour)	Pure olive oil	Olive oil samples containing
		PKFO					TBHQ
		0.5%	1%	2%	5%	10%	100 ppm
0	0.24 ± 0.02^c	0.25 ± 0.02^c	0.26 ± 0.03^bc	0.27 ± 0.03^bc	0.33 ± 0.04^b	0.42 ± 0.03^a	0.24 ± 0.03^c
2	0.26 ± 0.01^d	0.28 ± 0.03^d	0.28 ± 0.01^d	0.35 ± 0.02^c	0.38 ± 0.01^b	0.53 ± 0.02^a	0.27 ± 0.02^d
4	0.31 ± 0.03^c	0.31 ± 0.02^c	0.28 ± 0.02^c	0.38 ± 0.03^b	0.39 ± 0.03^b	0.54 ± 0.01^a	0.31 ± 0.03^c
6	0.37 ± 0.02^d	0.32 ± 0.02^e	0.36 ± 0.02^c	0.41 ± 0.02^b	0.41 ± 0.02^b	0.57 ± 0.04^a	0.31 ± 0.02^e
8	0.41 ± 0.02^c	0.35 ± 0.02^d	0.34 ± 0.03^d	0.46 ± 0.03^b	0.44 ± 0.03^bc	0.6 ± 0.05^a	0.33 ± 0.02^d

*Mean ± SD (standard deviation) within a row with the same lowercase letters are not significantly different at p < 0.05. PKFO, P. khinjuk fruit oil; TBHQ, tert-butylhydroquinone.

Figure 2. Changes in the oil/oxidative stability index (OSI, h) of olive oil as affected by PKFO and TBHQ during heat processing at 170°C. A: pure olive oil; B: olive oil containing 0.5% PKFO; C: olive oil containing 1% PKFO; D: olive oil containing 2% PKFO; E: olive oil containing 5% PKFO; F: olive oil containing 10% PKFO; G: olive oil containing 100 ppm TBHQ.PKFO, Pistacia khinjuk fruit oil; TBHQ, tert-butylhydroquinone.

Table 4. Changes in total tocopherol (TT, mg/kg oil) content of olive oil as affected by PKFO and TBHQ during heat processing at 170°C.*

Time (hour)	Pure olive oil	Olive oil samples containing
		PKFO					TBHQ
		0.5%	1%	2%	5%	10%	100 ppm
0	350 ± 12.1^b	351.5 ± 10.5^b	352.9 ± 9.8^b	355.8 ± 10.8^b	364.5 ± 12.5^ab	379.0 ±11.8^a	350 ± 8.9^b
2	301.2 ± 7.9^a	280.2 ± 9.7^b	270.2 ± 6.3^bc	260.2 ± 9.9^c	300.2 ± 14.3^a	300.9 ± 10.2^a	250.1 ± 7.6^d
4	225.6 ± 8.9^ab	204.5 ± 8.7^c	221.2 ± 5.4^b	180.2 ± 8.7^d	240.1 ± 10.5^a	235.5 ± 8.7^a	124.5 ± 8.8^e
6	97.2 ± 7.6^d	132.5 ± 7.7^ab	104.5 ± 2.8^c	110.4 ± 2.9^c	130.4 ± 4.9^b	142.2 ± 6.7^a	62.5 ± 7.7^e
8	30 ± 3.03^d	66.2 ± 6.1^b	49.5 ± 3.4^dc	52.3 ± 3.6^c	60.1 ± 1.5^b	76.2 ± 3.2^a	16.9 ± 2.3^e

*Mean ± SD (standard deviation) within a row with the same lowercase letters are not significantly different at p < 0.05. PKFO, P. khinjuk fruit oil; TBHQ, tert-butylhydroquinone.

Table 5. Changes in total sterol (TS, mg/kg oil) content of olive oil as affected by PKFO and TBHQ during heat processing at 170°C.*

Time (hour)	Pure olive oil	Olive oil samples containing
		PKFO					TBHQ
		0.5%	1%	2%	5%	10%	100ppm
0	1076.3 ± 15.5^d	1081.7 ± 25.6^d	1097.6 ± 18.7^cd	1117.1 ± 8.6^c	1177.7 ± 10.9^b	1260.8 ± 25.5^a	1070.8 ± 15.3^d
2	841 ± 18.3^e	1010 ± 12.2^b	952.4 ± 13.3^d	800.5 ± 16.5^f	1008.4 ± 10.2^b	1050.7 ± 14.9^a	980.6 ± 12.2^c
4	550.4 ± 12.2^f	850.1 ± 9.8^b	721.8 ± 14.5^d	609.1 ± 14.2^e	900 ± 13.6^a	920.2 ± 7.5^a	825.3 ± 13.8^c
6	520.5 ± 11.6^d	705.9 ± 14.8^a	640.4 ± 12.6^b	500 ± 17.1^d	604 ± 17.5^c	712.3 ± 16.5^a	620.5 ± 18.2^bc
8	254.1 ± 13.3^e	585.2 ± 11.1^a	574.3 ± 16.7^a	385.9 ± 10.7^d	498.2 ± 11.4^b	446.3 ± 14.2^c	584.5 ± 14.7^a

*Mean ± SD (standard deviation) within a row with the same lowercase letters are not significantly different at p < 0.05. PKFO, P. khinjuk fruit oil; TBHQ, tert-butylhydroquinone.

Table 6. Resistance of different olive oil samples against changes in oxidation factors during heat processing at 170°C.*

Parameter	Pure olive oil	Olive oil samples containing
		PKFO
		0.5%	1%	2%
Resistance against CDV increase	0.63 ± 0.03^f	1.81 ± 0.04^c	1.27 ± 0.02^d	0.79 ± 0.03^e
Resistance against CV increase	0.73 ± 0.02^d	2.41 ± 0.04^a	2.14 ± 0.03^b	0.72 ± 0.03^d
Resistance against AV increase	1.41 ± 0.03^f	2.42 ± 0.04^d	2.71 ± 0.03^c	1.42 ± 0.05^e
Resistance against OSI reduction	1.26 ± 0.03^d	1.32 ± 0.02^c	1.37 ± 0.04^c	1.14 ± 0.04^e
Mean resistance against oxidation	1.01 ± 0.02^e	1.99 ± 0.04^a	1.87 ± 0.03^b	1.02 ± 0.03^e
	Olive oil samples containing
	PKFO		TBHQ
	5%	10%	100 ppm
Resistance against CDV increase	1.94 ± 0.04^b	1.86 ± 0.03^c	2.11 ± 0.05^a
Resistance against CV increase	0.75 ± 0.04^d	0.53 ± 0.02^e	1.29 ± 0.04^c
Resistance against AV increase	2.95 ± 0.04^a	2.38 ± 0.05^d	2.80 ± 0.04^b
Resistance against OSI reduction	1.57 ± 0.04^b	1.67 ± 0.03^a	1.26 ± 0.02^d
Mean resistance against oxidation	1.80 ± 0.02^c	1.61 ±.03^d	1.87 ± 0.04^b

*Means ± SD (standard deviation) within a row with the same lowercase letters are not significantly different at p < 0.05. PKFO, P. khinjuk fruit oil; CDV, conjugated diene value, CV, carbonyl value, AV, acid value, OSI, oil/oxidative stability Index, TBHQ, tert-butylhydroquinone.

Figure 3. Correlation between remaining TT and TS (TT₈+TS₈) content of olive oil samples after the 8 h thermal process at 170ºC and their final CDV, CV and AV(CDV₈+CV₈+AV₈).AV, acid value; CDV, conjugated diene value; CV, carbonyl value; TS, total sterols; TT, total tocopherols.

Frankel, E.N. Lipid Oxidation. The Oily Press Ltd, 1998, 79–98.

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