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Studies on a natural antioxidant for stabilization of edible oil and comparison with synthetic antioxidants
Journal of Food Engineering 74 (2006) 542–545 www.elsevier.com/locate/jfoodeng
Studies on a natural antioxidant for stabilization of edible oil and comparison with synthetic antioxidants D. Bera b, D. Lahiri b, A. Nag
a,*
a
b
Chemistry Department, Indian Institute of Technology, Kharagpur 721302, India Rural Development Center, Indian Institute of Technology, Kharagpur 721302, India
Received 23 August 2002; received in revised form 22 November 2004; accepted 8 March 2005 Available online 14 June 2005
Abstract Flaxseed oil containing essential fatty acids is cheap, plenty and highly used as edible oil in India, Asia and also in the western world but the oil is prone to oxidation. But with the incorporation of a new natural antioxidant (soluble ajowan (Carum copticum) extract), the oxidation of oil could be prevented. The oxidation properties of antioxidant in oil were compared with other synthetic antioxidants (TBHQ, BHT, EQ) at different temperatures. It has been observed that TBHQ showed higher thermal stability than other antioxidants but with comparison to cost with ajowan and for use as a spice in food preparations the above natural antioxidant is more preferred. 2005 Elsevier Ltd. All rights reserved. Keywords: Flaxseed oil; Omega-3; Ajowan powder and synthetic antioxidants
1. Introduction Recently interest has led to produce a great class of foods referred to as nutraceuticals because these type of foods offer either therapeutic or preventive medicinal benefits in addition to nutrition. But lipid peroxidation lowers the nutritive value (Addis & Warner, 1991) of food and deteriorates the flavor and taste of food. It also causes aging, heart diseases, stoke, emphysema, mutagenesis and carcinogensis (Barlow, 1990). It is necessary to suppress lipid oxidation for maintaining the safety and effectiveness of food. Formulation of nutraceuticals with linolenic acid (omega-3) cannot be done without simultaneous incorporation of an acceptable antioxidant as linolenic acid is prone to rapid oxidation both in storage and in the human body (Ito et al., 1986).
*
Corresponding author. Tel.: +95 3222 55221; fax: +95 3222 55303. E-mail address: [email protected] (A. Nag).
0260-8774/$ - see front matter 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.jfoodeng.2005.03.042
Generally oxidation of food can be prevented by synthetic antioxidants including butylated hydroxyanisole (BHA), butylated hydroxy toluene (BHT) and propyl gallate (PG) but their safety has been questioned (Barlow, 1990). Hence, there is a need to identify new natural antioxidants for prevention of lipid peroxidation in the food industry. According to Pokorny (1991) when compared to synthetic antioxidants, natural antioxidants have the following advantages: (i) (ii) (iii) (iv)
They are readily acceptable by the consumers. They are considered to be safe. No safety tests are required by legislation. This natural antioxidant (not as a synthetic chemical antioxidant) is identical to the food which people have taken over a hundred years or have been mixing with food. (v) This antioxidant not only stabilizes the edible oils but also adds to the nutraceutical value of the oil.
D. Bera et al. / Journal of Food Engineering 74 (2006) 542–545 Table 1 Properties of flaxseed oil Properties
Flaxseed oil
Refractive index Saponification value Iodine value Palmitic acid, C16:0 Oleic acid, C18:1 Linoleic acid, C18:2 Linolenic acid, C18:3 Peroxide value Free fatty acid
1.2 220.0 182.0 6.0 22.2 14.2 50.4 5.2 2.0
In this paper, we studied oxidation properties of flaxseed oil, a highly used edible oil in India, Asian countries and also in the western world because it contains high amounts of essential fatty acids (Table 1). We have also compared the thermal stability of different synthetic antioxidants with a natural antioxidant ajowan in oil. Ajowan in powder form is used as a spice in most of the Indian food preparations.
2. Materials and methods Flaxseed oil was extracted from husk free ground flaxseed with n-hexane (b.pt. 60–65 C) using soxhlet apparatus. Analysis of the fatty acids in the oil was performed in the following way: 100–200 mg of oil was placed in a 100 ml round bottomed flask fitted with a condenser and 10 ml of 0.7% methanolic HCl was added to it. The mixture was refluxed on a water bath for 2 h. The content was cooled, 0.5 ml water was added and the ester was separated using petroleum ether (wash to remove excess acid and drying by anhydrous sodium sulfate). The analysis of methyl esters was done by measuring the peak areas by gas–liquid chromatography (Model—AIMIL-UNCON, series 5700, Hewlett-Packard, Mississauga, Ontario, Canada), FID temp.— 240 C; injection temp.—250 C; silica capillary column (0.025 mm · 60 m; flow rate 40 ml/min; carrier gasnitrogen). The analysis of the fatty acids of oil is shown in Table 1. Oxidation of oil was done in the following way: A 250 ml standard joint round bottomed flask containing 100 g of oil was placed over a thermostatic bath. Air from an air cylinder (pressure of the cylinder 1.7 kg/ cm2) was passed through the oil (2 ml/min). At different time intervals, oil was withdrawn for determination of peroxide value (PV) and thiobarbituric acid (TBA) values (David, 1990). The peroxides formed were measured iodometrically, where the iodine liberated by the peroxide was titrated with a standard solution of sodium thiosulfate (David, 1990). The thiobarbituric acid test was based on the color reaction of TBA with malondialde-
543
hyde (mg/kg) in the sample. The experiment was replicated three times and the average values were taken. The percentage error was within ±0.05. For determination of PV values at different temperatures, the oil was kept in the thermostatic bath at a particular temperature and was withdrawn at different time intervals to determine peroxide values. Antioxidant from ajowan powder was extracted with the addition of ethanol which was 1:15 (wt/volume). Antioxidant was obtained after ethanol evaporation. One gram of antioxidant was taken in a flask and flaxseed oil of known weight was slowly added in it. The minimum weight of flaxseed oil in which the antioxidant was completely soluble was determined. The weight of antioxidant soluble in unit weight of flaxseed oil was 0.035 g/g of oil. Three replicates of the experiment were done and the percentage error was within ±0.3. The inactivation of antioxidant was calculated by using the method of Sanhueza, Nieto, and Valenzuela (2000) Inactivation % ¼ ð1 IPf =IPi Þ 100t Here IPi = initial induction period without antioxidant at t = 0 h and IPf = final induction period with antioxidant at t = different hours. For comparison of thermal stabilities of different antioxidants with ajowan extract we measured the values of IPf and IPi at different times (Fig. 2a–c). The alcoholic extract from ajowan was analyzed in column chromatography. First fraction (about 50%) was eluted from the column by passing the petroleum ether and ethyl acetate solvent mixture (20:1). The structure of the solid compound after evaporating the solvent was characterized by IR and NMR which is as follows. IR (200–400 cm1, KBr); 3338 cm1 (m Phenolic-OH str.), 2961 cm1 (m Aromatic C–H str.), 2872 cm1, 2749 cm1 and 2604 cm1 (m Aliphatic C–H str.), 1154 cm1, 1091 cm1 and 1002 cm1 (m C–C Aliphatic str.), 1246 cm1 (m C–O str.). 1H NMR (200 MHz, CDCl3); d = 7.09 (1H, d, J = 7.88 Hz, Ar-3H.), d = 6.73 (1H, d, J = 3.86 Hz, Ar-4H.), d = 6.58 (1H, s, Ar–6H.), d = 4.64.8 (1H, bs, Ar–OH.), d = 3.133.20 (1H, m,(CH)3CH), d = 2.28 (3H, s, Ar–CH3), d = 1.25 (6H, d, J = 6.86 Hz, (CH3)2 CH–).
H CH3 C
CH3
CH3 OH 2-isopropyle,5-methyle phenol (First Fraction, Ajowan Extract)
The other volatile oil fractions on passing the solvent mixture of ethyl acetate and petroleum ether (1:40)
544
D. Bera et al. / Journal of Food Engineering 74 (2006) 542–545
found that the mixture contained four compounds (confirmed by TLC), which did not show any antioxidant properties. The first fraction was collected for experiment and used with flaxseed oils as an oxidant to check the antioxidant properties.
3. Result and discussion From the fatty acid values of flaxseed oil (Table 1) it was observed that the oils contained high amount of unsaturated fatty acids (more than 86%). These are more liable to epoxide formation by reaction with oxygen in air. These are experimentally proved by the sharp increase of peroxide values of flaxseed oil (Fig. 1a) at different time without an antioxidant which indicated that flaxseed oil has an extremely high tendency to be oxidized. But peroxide values of flaxseed oil containing antioxidant (ajowan extract antioxidant/oil ratio = 1:40 wt/wt), remained more or less constant during oxidation. Similarly TBA values of oil sample also remained constant with the same antioxidant (Fig. 2). Thus by incorporation of oil soluble ajowan extract, it was possible to inhibit the rate of oxidation to such a degree, almost no rise in PV and TBA values (Fig. 2) occurred. Synthetic antioxidants are used in food industries. Thermal stability of flaxseed oil with synthetic antioxidants (TBHQ, BHT EQ) was studied at different temperatures. Three synthetic commercial antioxidants and the ajowan extract showed good inhibitory effect (IPi value). After application of temperature, IPf values were found for each antioxidants and compared with its respective IPi. Ajowan extract (AE) and TBHQ showed higher thermal stability than the other two synthetic commercial antioxidants (Fig. 2a–c) at different time. From the results it may be explained that the antioxidant properties affect effectively more than the induction period to stabilize flaxseed oil. After reaching a particular temperature inactivation percentage almost remains constant, probably due to the formation of a higher temperature stable structure. Though TBHQ showed higher thermal stability than other antioxidants but with comparison to cost of ajowan (Rs.10/kg in Indian currency and TBHQ—Rs. 50/kg in Indian currency used as a spice in food preparation) the above natural antioxidant is more preferred. It has been found (Adegoke et al., 1998) that phenolic substances (antioxidant) function as free radical acceptors and can terminate free radicals at the initiation stage. Adegoke et al. have concluded that hindered phenolics like BHA, BHT, TBHQ, EQ and tocopherols as well as polyhydroxy phenolics like propyl-gallate are primary antioxidants which either delay or inhibit the initiation step by reacting with a lipid-free radical or inhibit the propagation step by reacting with the peroxy or
Fig. 1. (a) Peroxide value of flaxseed oil at different temperatures in presence of air: s—without antioxidant, m—with antioxidant at 30 C. Peroxide value of flaxseed oil at different times in presence of air: h—without antioxidant, d—with antioxidant. (b) Peroxide value of flaxseed oil at different times in the presence of air: (j) B—without antioxidant, (d) C—with antioxidant.
alkoxy radicals. As the first fraction of ajowan extract contains thymol, active principles with phenolic groups in its structure, it actively prevents further oxidation in the glycerides. The taste of the product was found not to be so strong (tested for salad oil by 50 person) and was found to have no bad effect on the health of any person (Nag, 2000). They recommended that the oil could be used as an edible oil. Still lack of facilities for extensive animal assay details of biological values of the antioxidant with oils are not reported here.
D. Bera et al. / Journal of Food Engineering 74 (2006) 542–545
545
75 75 60
Inactivation (%)
Inactivation (%)
60 45
30
45
30
15 BHT TBHQ AE EQ
15
0 100
(a)
120
140
160
180
200
0
220
Temperature (oC)
BHT TBHQ AE EQ 100
120
140
160
180
200
220
Temperature (oC)
(b)
90
75
Inactivation (%)
60
45
30
AE TBHQ
15
BHT EQ
0 100
(c)
120
140
160
180
200
220
Temperature in Degree Centigrade
Fig. 2. (a) Thermal stability of TBHQ, BHT, EQ and AE (azoan extract) at 100 C, 130 C,160 C, 190 C and 220 C, for a 1 h induction period. (b) Thermal stability of TBHQ, BHT, EQ and AE (azoan extract) at different temperatures for 2 h induction period. (c) Thermal stability of TBHQ, BHT, EQ and AE (azoan extract) at different temperatures, for 3 h induction period.
References Addis, P. B., & Warner, G. J. (1991). The potenial aspects of lipid oxidation products in food. In O. I. Aruoma & B. Halliwel (Eds.), Free radicals and food additives. London: Taylor Francis Ltd. Adegoke, G. O., Vijaykumar, M., Gopalkrishna, A. G., Varadraj, M. C., Sambahiah, K., & Lokesh, B. R. (1998). Antioxidants and lipid oxidation in foods. Journal Food Science and Technology, 35(4), 283–293. Barlow, S. N. (1990). Toxicological aspects of antioxidants used as food additives. In B. J. F. Hudson (Ed.), Food antioxidants (pp. 253–307). Amasterdam: Elsevier. David, P. (1990). The chemical analysis of food (3rd ed.). London: J and A. Churchill.
Ito, N., Hirose, M., Fukushima, S., Tsuda, H., Shirai, H. T., & Tatematsu, M. (1986). Studies on auto oxidants their carcinogenic and modifying effects on chemical carcinogenesis. Food and Chemical Toxicology, 24, 1071–1076. Nag, A. (2000). Stabilization and nutraceutical value of flax seed oil by capsicum. Journal of the American Oil Chemists Society, 8, 2041–2042. Pokorny, J. (1991). Natural antioxidants for food use. Trends in Food Science & Technology, 2, 223–227. Sanhueza, J., Nieto, S., & Valenzuela, A. (2000). Thermal stability of some commercial antioxidants. Journal of the American Oil Chemists Society, 77(9), 933–936.
Studies on a natural antioxidant for stabilization of edible oil and comparison with synthetic antioxidants D. Bera b, D. Lahiri b, A. Nag
a,*
a
b
Chemistry Department, Indian Institute of Technology, Kharagpur 721302, India Rural Development Center, Indian Institute of Technology, Kharagpur 721302, India
Received 23 August 2002; received in revised form 22 November 2004; accepted 8 March 2005 Available online 14 June 2005
Abstract Flaxseed oil containing essential fatty acids is cheap, plenty and highly used as edible oil in India, Asia and also in the western world but the oil is prone to oxidation. But with the incorporation of a new natural antioxidant (soluble ajowan (Carum copticum) extract), the oxidation of oil could be prevented. The oxidation properties of antioxidant in oil were compared with other synthetic antioxidants (TBHQ, BHT, EQ) at different temperatures. It has been observed that TBHQ showed higher thermal stability than other antioxidants but with comparison to cost with ajowan and for use as a spice in food preparations the above natural antioxidant is more preferred. 2005 Elsevier Ltd. All rights reserved. Keywords: Flaxseed oil; Omega-3; Ajowan powder and synthetic antioxidants
1. Introduction Recently interest has led to produce a great class of foods referred to as nutraceuticals because these type of foods offer either therapeutic or preventive medicinal benefits in addition to nutrition. But lipid peroxidation lowers the nutritive value (Addis & Warner, 1991) of food and deteriorates the flavor and taste of food. It also causes aging, heart diseases, stoke, emphysema, mutagenesis and carcinogensis (Barlow, 1990). It is necessary to suppress lipid oxidation for maintaining the safety and effectiveness of food. Formulation of nutraceuticals with linolenic acid (omega-3) cannot be done without simultaneous incorporation of an acceptable antioxidant as linolenic acid is prone to rapid oxidation both in storage and in the human body (Ito et al., 1986).
*
Corresponding author. Tel.: +95 3222 55221; fax: +95 3222 55303. E-mail address: [email protected] (A. Nag).
0260-8774/$ - see front matter 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.jfoodeng.2005.03.042
Generally oxidation of food can be prevented by synthetic antioxidants including butylated hydroxyanisole (BHA), butylated hydroxy toluene (BHT) and propyl gallate (PG) but their safety has been questioned (Barlow, 1990). Hence, there is a need to identify new natural antioxidants for prevention of lipid peroxidation in the food industry. According to Pokorny (1991) when compared to synthetic antioxidants, natural antioxidants have the following advantages: (i) (ii) (iii) (iv)
They are readily acceptable by the consumers. They are considered to be safe. No safety tests are required by legislation. This natural antioxidant (not as a synthetic chemical antioxidant) is identical to the food which people have taken over a hundred years or have been mixing with food. (v) This antioxidant not only stabilizes the edible oils but also adds to the nutraceutical value of the oil.
D. Bera et al. / Journal of Food Engineering 74 (2006) 542–545 Table 1 Properties of flaxseed oil Properties
Flaxseed oil
Refractive index Saponification value Iodine value Palmitic acid, C16:0 Oleic acid, C18:1 Linoleic acid, C18:2 Linolenic acid, C18:3 Peroxide value Free fatty acid
1.2 220.0 182.0 6.0 22.2 14.2 50.4 5.2 2.0
In this paper, we studied oxidation properties of flaxseed oil, a highly used edible oil in India, Asian countries and also in the western world because it contains high amounts of essential fatty acids (Table 1). We have also compared the thermal stability of different synthetic antioxidants with a natural antioxidant ajowan in oil. Ajowan in powder form is used as a spice in most of the Indian food preparations.
2. Materials and methods Flaxseed oil was extracted from husk free ground flaxseed with n-hexane (b.pt. 60–65 C) using soxhlet apparatus. Analysis of the fatty acids in the oil was performed in the following way: 100–200 mg of oil was placed in a 100 ml round bottomed flask fitted with a condenser and 10 ml of 0.7% methanolic HCl was added to it. The mixture was refluxed on a water bath for 2 h. The content was cooled, 0.5 ml water was added and the ester was separated using petroleum ether (wash to remove excess acid and drying by anhydrous sodium sulfate). The analysis of methyl esters was done by measuring the peak areas by gas–liquid chromatography (Model—AIMIL-UNCON, series 5700, Hewlett-Packard, Mississauga, Ontario, Canada), FID temp.— 240 C; injection temp.—250 C; silica capillary column (0.025 mm · 60 m; flow rate 40 ml/min; carrier gasnitrogen). The analysis of the fatty acids of oil is shown in Table 1. Oxidation of oil was done in the following way: A 250 ml standard joint round bottomed flask containing 100 g of oil was placed over a thermostatic bath. Air from an air cylinder (pressure of the cylinder 1.7 kg/ cm2) was passed through the oil (2 ml/min). At different time intervals, oil was withdrawn for determination of peroxide value (PV) and thiobarbituric acid (TBA) values (David, 1990). The peroxides formed were measured iodometrically, where the iodine liberated by the peroxide was titrated with a standard solution of sodium thiosulfate (David, 1990). The thiobarbituric acid test was based on the color reaction of TBA with malondialde-
543
hyde (mg/kg) in the sample. The experiment was replicated three times and the average values were taken. The percentage error was within ±0.05. For determination of PV values at different temperatures, the oil was kept in the thermostatic bath at a particular temperature and was withdrawn at different time intervals to determine peroxide values. Antioxidant from ajowan powder was extracted with the addition of ethanol which was 1:15 (wt/volume). Antioxidant was obtained after ethanol evaporation. One gram of antioxidant was taken in a flask and flaxseed oil of known weight was slowly added in it. The minimum weight of flaxseed oil in which the antioxidant was completely soluble was determined. The weight of antioxidant soluble in unit weight of flaxseed oil was 0.035 g/g of oil. Three replicates of the experiment were done and the percentage error was within ±0.3. The inactivation of antioxidant was calculated by using the method of Sanhueza, Nieto, and Valenzuela (2000) Inactivation % ¼ ð1 IPf =IPi Þ 100t Here IPi = initial induction period without antioxidant at t = 0 h and IPf = final induction period with antioxidant at t = different hours. For comparison of thermal stabilities of different antioxidants with ajowan extract we measured the values of IPf and IPi at different times (Fig. 2a–c). The alcoholic extract from ajowan was analyzed in column chromatography. First fraction (about 50%) was eluted from the column by passing the petroleum ether and ethyl acetate solvent mixture (20:1). The structure of the solid compound after evaporating the solvent was characterized by IR and NMR which is as follows. IR (200–400 cm1, KBr); 3338 cm1 (m Phenolic-OH str.), 2961 cm1 (m Aromatic C–H str.), 2872 cm1, 2749 cm1 and 2604 cm1 (m Aliphatic C–H str.), 1154 cm1, 1091 cm1 and 1002 cm1 (m C–C Aliphatic str.), 1246 cm1 (m C–O str.). 1H NMR (200 MHz, CDCl3); d = 7.09 (1H, d, J = 7.88 Hz, Ar-3H.), d = 6.73 (1H, d, J = 3.86 Hz, Ar-4H.), d = 6.58 (1H, s, Ar–6H.), d = 4.64.8 (1H, bs, Ar–OH.), d = 3.133.20 (1H, m,(CH)3CH), d = 2.28 (3H, s, Ar–CH3), d = 1.25 (6H, d, J = 6.86 Hz, (CH3)2 CH–).
H CH3 C
CH3
CH3 OH 2-isopropyle,5-methyle phenol (First Fraction, Ajowan Extract)
The other volatile oil fractions on passing the solvent mixture of ethyl acetate and petroleum ether (1:40)
544
D. Bera et al. / Journal of Food Engineering 74 (2006) 542–545
found that the mixture contained four compounds (confirmed by TLC), which did not show any antioxidant properties. The first fraction was collected for experiment and used with flaxseed oils as an oxidant to check the antioxidant properties.
3. Result and discussion From the fatty acid values of flaxseed oil (Table 1) it was observed that the oils contained high amount of unsaturated fatty acids (more than 86%). These are more liable to epoxide formation by reaction with oxygen in air. These are experimentally proved by the sharp increase of peroxide values of flaxseed oil (Fig. 1a) at different time without an antioxidant which indicated that flaxseed oil has an extremely high tendency to be oxidized. But peroxide values of flaxseed oil containing antioxidant (ajowan extract antioxidant/oil ratio = 1:40 wt/wt), remained more or less constant during oxidation. Similarly TBA values of oil sample also remained constant with the same antioxidant (Fig. 2). Thus by incorporation of oil soluble ajowan extract, it was possible to inhibit the rate of oxidation to such a degree, almost no rise in PV and TBA values (Fig. 2) occurred. Synthetic antioxidants are used in food industries. Thermal stability of flaxseed oil with synthetic antioxidants (TBHQ, BHT EQ) was studied at different temperatures. Three synthetic commercial antioxidants and the ajowan extract showed good inhibitory effect (IPi value). After application of temperature, IPf values were found for each antioxidants and compared with its respective IPi. Ajowan extract (AE) and TBHQ showed higher thermal stability than the other two synthetic commercial antioxidants (Fig. 2a–c) at different time. From the results it may be explained that the antioxidant properties affect effectively more than the induction period to stabilize flaxseed oil. After reaching a particular temperature inactivation percentage almost remains constant, probably due to the formation of a higher temperature stable structure. Though TBHQ showed higher thermal stability than other antioxidants but with comparison to cost of ajowan (Rs.10/kg in Indian currency and TBHQ—Rs. 50/kg in Indian currency used as a spice in food preparation) the above natural antioxidant is more preferred. It has been found (Adegoke et al., 1998) that phenolic substances (antioxidant) function as free radical acceptors and can terminate free radicals at the initiation stage. Adegoke et al. have concluded that hindered phenolics like BHA, BHT, TBHQ, EQ and tocopherols as well as polyhydroxy phenolics like propyl-gallate are primary antioxidants which either delay or inhibit the initiation step by reacting with a lipid-free radical or inhibit the propagation step by reacting with the peroxy or
Fig. 1. (a) Peroxide value of flaxseed oil at different temperatures in presence of air: s—without antioxidant, m—with antioxidant at 30 C. Peroxide value of flaxseed oil at different times in presence of air: h—without antioxidant, d—with antioxidant. (b) Peroxide value of flaxseed oil at different times in the presence of air: (j) B—without antioxidant, (d) C—with antioxidant.
alkoxy radicals. As the first fraction of ajowan extract contains thymol, active principles with phenolic groups in its structure, it actively prevents further oxidation in the glycerides. The taste of the product was found not to be so strong (tested for salad oil by 50 person) and was found to have no bad effect on the health of any person (Nag, 2000). They recommended that the oil could be used as an edible oil. Still lack of facilities for extensive animal assay details of biological values of the antioxidant with oils are not reported here.
D. Bera et al. / Journal of Food Engineering 74 (2006) 542–545
545
75 75 60
Inactivation (%)
Inactivation (%)
60 45
30
45
30
15 BHT TBHQ AE EQ
15
0 100
(a)
120
140
160
180
200
0
220
Temperature (oC)
BHT TBHQ AE EQ 100
120
140
160
180
200
220
Temperature (oC)
(b)
90
75
Inactivation (%)
60
45
30
AE TBHQ
15
BHT EQ
0 100
(c)
120
140
160
180
200
220
Temperature in Degree Centigrade
Fig. 2. (a) Thermal stability of TBHQ, BHT, EQ and AE (azoan extract) at 100 C, 130 C,160 C, 190 C and 220 C, for a 1 h induction period. (b) Thermal stability of TBHQ, BHT, EQ and AE (azoan extract) at different temperatures for 2 h induction period. (c) Thermal stability of TBHQ, BHT, EQ and AE (azoan extract) at different temperatures, for 3 h induction period.
References Addis, P. B., & Warner, G. J. (1991). The potenial aspects of lipid oxidation products in food. In O. I. Aruoma & B. Halliwel (Eds.), Free radicals and food additives. London: Taylor Francis Ltd. Adegoke, G. O., Vijaykumar, M., Gopalkrishna, A. G., Varadraj, M. C., Sambahiah, K., & Lokesh, B. R. (1998). Antioxidants and lipid oxidation in foods. Journal Food Science and Technology, 35(4), 283–293. Barlow, S. N. (1990). Toxicological aspects of antioxidants used as food additives. In B. J. F. Hudson (Ed.), Food antioxidants (pp. 253–307). Amasterdam: Elsevier. David, P. (1990). The chemical analysis of food (3rd ed.). London: J and A. Churchill.
Ito, N., Hirose, M., Fukushima, S., Tsuda, H., Shirai, H. T., & Tatematsu, M. (1986). Studies on auto oxidants their carcinogenic and modifying effects on chemical carcinogenesis. Food and Chemical Toxicology, 24, 1071–1076. Nag, A. (2000). Stabilization and nutraceutical value of flax seed oil by capsicum. Journal of the American Oil Chemists Society, 8, 2041–2042. Pokorny, J. (1991). Natural antioxidants for food use. Trends in Food Science & Technology, 2, 223–227. Sanhueza, J., Nieto, S., & Valenzuela, A. (2000). Thermal stability of some commercial antioxidants. Journal of the American Oil Chemists Society, 77(9), 933–936.