The chemical parameters and oxidative resistance to heat treatment of refined and extra virgin Moroccan Picholine olive oil

Peer review under responsibility of Taibah University.

Figures & data

Table 1 Physicochemical parameters of virgin and refined olive oils before and after thermal treatment at 100 °C for 120 h with an air flow air of 10 L/h.

Oil parameters	Extra virgin olive oil (VOO)		Refined olive oil (ROO)
	Before	After	Before	After
Free fatty acids (%)	0.64 ± 0.05	0.82 ± 0.05^a	0.07 ± 0.01	1.24 ± 0.02^b
Peroxide value (meq O2/kg)	2.30 ± 0.5	32.43 ± 2.5^a	0.60 ± 0.2	375.10 ± 5.5^b
E232-value	1.57 ± 0.01	2.59 ± 0.01^a	1.78 ± 0.01	2.79 ± 0.01^b
E270-value	0.13 ± 0.01	0.33 ± 0.01	0.55 ± 0.01	1.99 ± 0.01
Saponification value (mg/g)	188.4 ± 0.5	190.6 ± 0.5	189.2 ± 0.5	205.0 ± 0.50^b
Iodine value (g/100 g)	87.9 ± 0.5	86.8 ± 0.5	88.8 ± 0.5	73.5 ± 0.5^b

Values are least square means ± DS, n = 3. Values are significantly different from each other (p < 0.05) are represented with the letters (a, b).

Table 2 Fatty acid composition (given as % of total fatty acids) of virgin and refined olive oils before and after thermal treatment at 100 °C for 120 h with an air flow of 10 L/h.

Fatty acid composition (%)	Extra virgin olive oil		Refined olive oil
	Before	After	Before	After
Palmitic acid (C16:0)	10.6 ± 0.1	10.9 ± 0.1	9.1 ± 0.1	11.7 ± 0.1^b
Palmitoleic acid (C16:1)	0.2 ± 0.1	0.6 ± 0.1^a	0.5 ± 0.1	0.6 ± 0.1
Heptadecanoic acid (C17:0)	0.1 ± 0.0	0.1 ± 0.1	0 ± 0.0	0.1 ± 0.1
Heptadecenoic acid (C17:1)	0.1 ± 0.1	0.1 ± 0.1	0.1 ± 0.1	0.1 ± 0.1
Stearic acid (C18:0)	2.3 ± 0.1	2.4 ± 0.1	2.5 ± 0.1	2.9 ± 0.1
Oleic acid (C18:1)	73.8 ± 0.1	73.5 ± 0.1	73.5 ± 0.1	77.5 ± 0.1
Linoleic acid (C18:2)	11.0 ± 0.1	10.8 ± 0.1	12.8 ± 0.1	5.7 ± 0.1^b
Linolenic acid (C18:3)	0.9 ± 0.1	0.8 ± 0.1	0.8 ± 0.1	0.2 ± 0.1^b
Arachidic acid (C20:0)	0.2 ± 0.1	0.3 ± 0.1	0.3 ± 0.1	0.3 ± 0.1
Gadolic acid (C20:1)	0.3 ± 0.1	0.3 ± 0.1	0.3 ± 0.1	0.3 ± 0.1
Total saturated fatty acids	13.2 ± 0.1	13.8 ± 0.1	12.1 ± 0.1	15.1 ± 0.1^b
Total unsaturated fatty acids	86.3 ± 0.1	86.1 ± 0.1	87.4 ± 0.1	84.4 ± 0.1^b
Ratio unsaturated/saturated fatty acids	6.5 ± 0.1	6.2 ± 0.1	7.2 ± 0.1	5.5 ± 0.1^b

Values are least square means ± DS, n = 3. Values are significantly different from each other (p < 0.05) are represented with the letters (a, b).

Fig. 1 The relationship between the content of individual fatty acids of extra virgin olive oil before and after thermal treatment (FAb – % of fatty acid before thermal treatment; FAa – % of fatty acid after 120 h at 100 °C with a flow of air of 10 L/h).

Fig. 2 The relationship between the content of individual fatty acids of refined olive oils before and after thermal treatment (FAb – % of fatty acid before thermal treatment; FAa – % of fatty acid after 120 h at 100 °C with a flow of air of 10 L/h).

Table 3 The tocopherol composition (given as % of total tocopherols) of virgin and refined olive oils before and after heat treatment for 120 h at 100 °C with a flow of air of 10 L/h.

Composition of tocopherols	Virgin olive oil		Refined olive oil
	Before	After	Before	After
Alpha-tocopherol (%)	91.3 ± 0.5	n.d.	82.3 ± 0.5	n.d.
Beta-tocopherol (%)	4.7 ± 0.5	n.d.	5.6 ± 0.5	n.d.
Gamma-tocopherol (%)	1 ± 0.5	n.d.	1 ± 0.5	n.d.
Delta-tocopherol (%)	3.1 ± 0.5	n.d.	10.8 ± 0.5	n.d.
Total amount of tocopherols (mg/kg)	210.5 ± 10.5	n.d.	189.7 ± 8.5	n.d.

n.d. = not detectable.