Oxidative changes in hazelnut, olive, soybean, and sunflower oils during microwave heating

Figures & data

Table 1. Fatty acid compositions of hazelnut (HO), olive (OO), soybean (SBO), and sunflower (SFO) oils (methyl esters %).

		FAME
Oils	Time	16:0	16:1	18:0	18:1	18:2	18:3
HO	Control	5.11 ± 0.00^a	0.45 ± 0.00^a	2.19 ± 0.01^a	77.20 ± 0.01^b	13.27 ± 0.03^c	0.10 ± 0.00^b
	3 min	5.30 ± 0.05^b	0.47 ± 0.00^b	2.25 ± 0.01^b	77.20 ± 0.01^b	13.21 ± 0.03^a,b	0.09 ± 0.00^a
	6 min	5.35 ± 0.05^b	0.48 ± 0.00^c	2.27 ± 0.01^b	77.20 ± 0.01^b	13.18 ± 0.03^a	0.09 ± 0.00^a
	9 min	5.39 ± 0.05^b	0.48 ± 0.00^c	2.36 ± 0.01^c	77.01 ± 0.10^a	13.18 ± 0.03^a	0.09 ± 0.00^a
OO	Control	13.10 ± 0.11^a	1.20 ± 0.01^a	2.68 ± 0.02^a	71.08 ± 0.01^b	9.69 ± 0.02^b	0.54 ± 0.00^d
	3 min	13.57 ± 0.12^b	1.26 ± 0.01^b	2.76 ± 0.02^b	71.08 ± 0.01^b	9.64 ± 0.02^a,b	0.53 ± 0.00^c
	6 min	13.71 ± 0.12^b	1.29 ± 0.01^c	2.77 ± 0.02^b	71.07 ± 0.01^b	9.62 ± 0.02^a	0.52 ± 0.00^b
	9 min	13.81 ± 0.12^b	1.30 ± 0.01^c	2.89 ± 0.02^c	70.91 ± 0.01^a	9.62 ± 0.02^a	0.51 ± 0.00^a
SBO	Control	11.57 ± 0.10^c	0.50 ± 0.00^b	4.54 ± 0.03^a	22.66 ± 0.00^a	53.86 ± 0.12^c	6.52 ± 0.01^d
	3 min	10.91 ± 0.09^a	0.50 ± 0.01^b	4.56 ± 0.03^a	22.65 ± 0.00^a	53.23 ± 0.12^b	6.46 ± 0.01^c
	6 min	10.55 ± 0.09^b	0.45 ± 0.01^a	4.57 ± 0.03^a	22.64 ± 0.00^a	53.04 ± 0.12^b	6.40 ± 0.01^b
	9 min	11.54 ± 0.10^c	0.46 ± 0.00^a	4.58 ± 0.03^a	23.62 ± 0.00^b	52.65 ± 0.12^a	6.37 ± 0.01^a
SFO	Control	6.77 ± 0.06^a	0.36 ± 0.00^b	3.97 ± 0.02^a	25.05 ± 0.00^b	63.09 ± 0.14^a	0.07 ± 0.00^b
	3 min	6.81 ± 0.06^a	0.38 ± 0.00^c	3.98 ± 0.02^a	24.96 ± 0.03^a	63.03 ± 0.14^a	0.06 ± 0.00^a
	6 min	6.89 ± 0.06^a	0.28 ± 0.00^a	3.99 ± 0.02^a	24.97 ± 0.00^a	63.02 ± 0.14^a	0.06 ± 0.00^a
	9 min	6.89 ± 0.06^a	0.28 ± 0.00^a	3.99 ± 0.02^a	24.97 ± 0.00^a	63.01 ± 0.14^a	0.06 ± 0.00^a

^a–dDifferent superscript letters in the same column for each oil indicate significant difference between values at p < 0.05 level in the same oil, and values are mean of three determinations±standard deviation.

FAME: fatty acid methyl ester (%).

Table 2. Iodine values and free fatty acids % of hazelnut (HO), olive (OO), soybean (SBO), and sunflower (SFO) oils.

		Oils
Parameters	Time	HO	OO	SBO	SFO
IV	Control	90.66 ± 0.03^d	81.35 ± 0.00^d	131.64 ± 0.12^c	132.35 ± 0.21^b
	3 min	90.32 ± 0.04^c	80.93 ± 0.02^c	130.72 ± 0.12^b	132.07 ± 0.17^a,b
	6 min	90.20 ± 0.04^b	80.79 ± 0.02^b	130.56 ± 0.12^b	131.78 ± 0.22^a,b
	9 min	90.04 ± 0.04^a	80.62 ± 0.02^a	129.94 ± 0.12^a	131.75 ± 0.22^a
FFA	Control	0.08 ± 0.00^a	0.23 ± 0.00^a	0.07 ± 0.00^a	0.10 ± 0.00^a
	3 min	0.08 ± 0.00^a	0.24 ± 0.00^b	0.10 ± 0.00^b	0.11 ± 0.00^b
	6 min	0.09 ± 0.00^b	0.25 ± 0.00^c	0.10 ± 0.00^b	0.12 ± 0.00^c
	9 min	0.10 ± 0.00^c	0.25 ± 0.00^c	0.11 ± 0.00^c	0.13 ± 0.00^d

^a–dDifferent superscript letters in the same column for each oil indicate significant difference between values at p < 0.05 level for the same parameter, and values are mean ± standard deviation of duplicate determination.

FFA: free fatty acids (%); IV: iodine value.

Table 3. Tocopherol contents (ppm) of hazelnut (HO), olive (OO), soybean (SBO), and sunflower (SFO) oils.

		Oils
		HO	OO	SBO	SFO
α-tocopherol	Control	236.16 ± 1.646^d	48.91 ± 0.329^d	34.75 ± 0.115^d	513.01 ± 6.194^c
	3 min	216.14 ± 1.505^c	47.05 ± 0.316^c	31.32 ± 0.205^c	499.13 ± 3.496^b
	6 min	186.69 ± 1.298^b	31.46 ± 0.206^b	29.97 ± 0.195^b	436.54 ± 3.056^a
	9 min	137.40 ± 0.951^a	28.74 ± 0.187^a	23.24 ± 0.148^a	426.57 ± 2.986^a
β-tocopherol	Control	11.19 ± 0.079^c		176.05 ± 1.516^c	6.96 ± 0.071^d
	3 min	10.45 ± 0.074^b		165.82 ± 1.167^b	6.57 ± 0.046^c
	6 min	10.32 ± 0.073^b		163.83 ± 1.153^b	5.54 ± 0.039^b
	9 min	9.29 ± 0.066^a		143.63 ± 1.011^a	5.34 ± 0.038^a
γ-tocopherol	Control	52.93± 0.352^c		240.86 ± 3.449^c	13.84 ± 0.145^d
	3 min	52.01± 0.346^b		221.97 ± 1.542^b	13.29 ± 0.074^c
	6 min	51.16± 0.340^b		212.21 ± 1.473^a	11.34 ± 0.060^b
	9 min	42.47± 0.279^a		210.74 ± 1.463^a	10.18 ± 0.052^a
δ-tocopherol	Control			78.71 ± 0.768^b
	3 min			78.41 ± 0.540^b
	6 min			77.85 ± 0.536^b
	9 min			75.62 ± 0.520^a

^a–dDifferent superscript letters in the same column for each tocopherol indicate significant difference between values at p < 0.05 level for the same compound, and values are mean ± standard deviation of duplicate determination.

Figure 1. Peroxide values of hazelnut (HO), olive (OO), soybean (SBO) and sunflower (SFO) oils.

Table 4. Conjugated diene (K₂₃₂) and triene (K₂₇₀) contents of hazelnut (HO), olive (OO), soybean (SBO), and sunflower (SFO) oils.

		Oils
Parameters	Time	HO	OO	SBO	SFO
Specific extinction at K232	Control	5.38 ± 0.00^b	3.70 ± 0.00^c	14.56 ± 0.01^b	13.38 ± 0.02^b
	3 min	5.58 ± 0.02^d	3.73 ± 0.00^d	15.41 ± 0.03^c	14.17 ± 0.03^c
	6 min	5.48 ± 0.00^c	3.39 ± 0.00^b	18.34 ± 0.05^d	14.31 ± 0.01^d
	9 min	4.41 ± 0.01^a	3.25 ± 0.00^a	12.23 ± 0.04^a	10.89 ± 0.00^a
Specific extinction at K270	Control	1.40 ± 0.00^a	0.93 ± 0.00^a	1.91 ± 0.00^a	1.66 ± 0.01^a
	3 min	1.43 ± 0.01^b	0.94 ± 0.00^b	2.94 ± 0.03^b	2.13 ± 0.03^b
	6 min	1.49 ± 0.00^c	0.93 ± 0.00^a	3.40 ± 0.03^c	2.37 ± 0.04^c
	9 min	2.40 ± 0.00^d	1.17 ± 0.00^c	5.36 ± 0.01^d	4.38 ± 0.00^d

^a–dDifferent superscript letters in the same column for each oil indicate significant difference between values at p < 0.05 level for the same parameter, and values are mean ± standard deviation of duplicate determination.

Figure 2. Hexanal contents of hazelnut (HO), olive (OO), soybean (SBO) and sunflower (SFO) oils.

Table 5. Peroxide and hexanal reaction rate constants (k₁ and k₂) and reaction orders (α and β).

Oils	k1	α	k2	Β
HO	1.74	0.1	0.4344	1
OO	0.91	0.1	0.3643	1
SBO	4.88	0.1	0.5827	1
SFO	4.5	0.1	0.6107	1

HO: hazelnut oil; OO: olive oil; SBO: soybean oil; SFO: sunflower oil.