Heating effects on physicochemical characteristics and antioxidant activity of flaxseed hull oil (<i>Linum usitatissimum L</i>)

HERCHI, Wahid; AMMAR, Kamel BEN; BOUALI, Intidhar; ABDALLAH, Ikram BOU; GUETET, Arbi; BOUKHCHINA, Sadok

doi:10.1590/1678-457X.0109

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Research Paper • Food Sci. Technol (Campinas) 36 (1) • Jan-Mar 2016 • https://doi.org/10.1590/1678-457X.0109 copy

Heating effects on physicochemical characteristics and antioxidant activity of flaxseed hull oil (Linum usitatissimum L)

Authorship SCIMAGO INSTITUTIONS RANKINGS

The aim of this study was to analyze the effects of heating on some quality characteristics and antioxidant activity of flaxseed hull oil. Polyunsaturated fatty acids (PUFA) and Cox value decreased during heating. Heating process led to considerable increase in saponification value (SV), peroxide value (PV), p-anisidine value (p-AnV), oxidative value (OV) and specific extinction at 232 and 270 nm. There was a significant decrease in oil stability during heating process (1.4-1.0 h). Fuel properties of flaxseed hull oil were also changed after heating treatment. Heating process caused loss of total phenolic acids, total flavanoids, carotenoids and chlorophyll pigments. Phospholipids (PL) content were less changed compared to other bioactive compounds. Antioxidant activity of flaxseed hull oil decreased during heating process.

antioxidant activity; flaxseed; heating; hull; oil

Fatty acid content (%)	Control	Heated flaxseed hull oil
Fatty acids
C16:0	7.21 ± 0.02^a	7.98 ± 0.06^a
C18:0	4.16 ± 0.10^a	4.59 ± 0.14^a
C18:1	26.33 ± 0.15^a	30.28 ± 0.21^b
C18:2 n-6	13.72 ± 0.16^a	11.52 ± 0.18^b
C18:3 n-3	47.19 ± 0.41^a	43.94 ± 0.30^b
Fatty acids groups
ΣSFA	11.37 ± 0.12^a	12.57 ± 0.20^a
ΣMUFA	26.33 ± 0.15^a	30.28 ± 0.21^b
ΣPUFA	60.91 ± 0.57^a	55.46 ± 0.48^b
ΣTU	87.24 ± 0.72^a	85.74 ± 0.69^b
ΣTU/ΣSFA	7.67 ± 0.32^a	6.82 ± 0.26^b
Cox value	11.87 ± 0.20^a	10.98 ± 0.16^b

Properties	Control
Average molecular weight^* * Average molecular weight = (356.11000)/saponification value. (g/mol)	935 ± 3.22^a	905 ± 2.84^b
Acid value (mg KOH g^–1 oil)	1.5 ± 0.14^a	2.9 ± 0.25^b
FFA content (% as oleic acid)	0.9 ± 0.06^a	1.7 ± 0.10^a
Peroxide value (mequiv O₂/kg oil)	1.85 ± 0.08^a	5.2 ± 0.15^b
p-Anisidine value	1.10 ± 0.17^a	8.50 ± 0.32^b
Oxidation value	4.8 ± 0.16^a	11.90 ± 0.24^b
Theoretical flavor scores (F)	6.02 ± 0.14^a	3.53 ± 0.10^b
K₂₃₂	1.50 ± 0.10^a	2.35 ± 0.12^b
K₂₇₀	0.24 ± 0.06^a	0.30 ± 0.08^b
Oil Stability (h)	1.4 ± 0.28^a	1.0 ± 0.20^b
Unsaponifiable matter (% of oil)	1.5 ± 0.36^a	1.1 ± 0.17^b
Sterols (mg/100 g oil)	245 ± 6.22^a	220 ± 6.10^b
Aliphatic and triterpenic alcohols (mg/100 g oil)	390 ± 6.15^a	328 ± 6.49^b
Hydrocarbons (mg/100 g oil)	92 ± 3.12^a	150 ± 4.36^b
TH/TS^ TH/TS total hydrocarbons to total sterols ratio.	0.23 ±0 .04^a	0.47 ± 0.04^a
*Fuel properties*
Saponification Value (mg KOH g^–1 oil)	180 ± 3.24^a	186 ± 3.78^b
Iodine value (g of I₂/100 g oil)
Determined IV	168 ± 1.70^a	160 ± 1.39^b
Calculated^* ***** Calculated IV = 0.86 (Oleic acid %) + 1.732 (Linoleic acid %) + 2.616 (Linolenic acid %). IV	170 ± 1.55^a	161 ± 1.14^b
Relative density at 25 ºC/g cm^–3	0.938 ± 0.002^a	0.882 ± 0.001^b
HHV (MJ/ Kg)
2nd Equation	39.53 ± 0.62^a	39.41 ± 0.75^b
3rd Equation	38.56 ± 0.50^a	40.97 ± 0.84^b
4th Equation	38.63 ± 0.66^a	40.66 ± 0.82^b
Cetane number	38.82 ± 1.18^a	39.64 ± 1.72^b

Antioxidant compounds	Control	Heated flaxseed hull oil
Total phenolic acids,
as gallic acid equivalents (mg/100 g oil)	84 ± 9.36^a	60 ± 6.52^b
Total Flavanoids,
as luteolin equivalents (mg/100 g oil)	18 ± 1.40^a	12 ± 0.88^b
Carotenoids (mg/kg oil)	7.82 ± 0.64^a	5.25 ± 0.45^b
Chlorophyll (mg/kg oil)	3.16 ± 0.28^a	1.84 ± 0.16^b
PL (%)	2.27 ± 0.32^a	4.18 ± 0.50^a

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[1] *Corresponding author: wahid1bio@yahoo.fr