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Oxidative Stability to Light and High Temperatures of Butter Product Containing Sunflower Seed Oil
Dxidative Stability to Light and High Temperatures of 8utter Product Containing Sunflower Seed Dil M. A. Amer 1 and A. N. Myhr Department of Food Science University of Guelph Guelph, Ontario
Abstract The peroxide values of a butter product made from modified cream containing milkfat, sunflower seed oil (SSO) (ratio of 70: 30 respectively) and antioxidants (BHA and BHT combined with monoglyceride citrate) were lower than for conventional butter when exposed to fluorescent light for a pcriod of six days. The modified SSO butter product was therefore considered to have relatively ,good oxidative stability under normal merchandising conditions. The rate of oxidation in the surface layers of conventional and modified butters was a great deal more rapid than in the sub-surface portions. After the initial lag period, photochemical oxidation in the surface layer of the modified spread proceeded more rapidly than in normal butter. At 90°C, the modified butter was much more susceptible to oxidation than butter without the vegetable oil additive.
Résumé On peut s'attendre a ce que l'indice de peroxyde du beurre fait de creme de lait et d'huile de toumesol (en proportion respective de 70:30) additionné d'anti-oxydants (B.H.A. et B.H.T. combinés au citrate de monoglyceride), est moins que celui du beurre ordinaire quand il est exposé a la lumiere fluorescente durant six jours. Par conséquent du beurre modifié de toumesol est considéré d'etre relativement plus stable a I'oxidation sous des conditions normales d'entreposage et de mise en marché. Le beurre modifié se montra en effet considérablement plus résistant a la photo-oxydation que le beurre ordinaire. La vitesse d'oxydation des couches superfi,cieHes fut toutefois beaucoup plus rapide que ceHe des couches sous-jacentes pour les deux types de beurre. Apres le retard initial, l'oxydation photochimique se produisant a la surface· du beurre reconstitué se fit plus rapidement que dans le cas du beurre ordinaire. A 90°C, le beurre reconstitué subissait plus d'oxydation que le beurre auquel on n'avait pas ajouté d'huile végétale.
Introduction One of th~ primary problems in the storage of food is the oxidation of its fato There are two recognized factors governing the susceptibility of natural fats to oxidation, namely, the content of unsaturated fatty acids and the presence of antioxidants (Lundberg, 1962, and Amer and Elliot, 1970). In a previous investigation (Amer and Myhl', 1973), it was established that the addition of a minimum of 30% sunflower seed oil (SSO) to milkfat was required to produce low temperature spreadability of the resulting modified butter. In view of the high level of linoleic acid which would be incorporated into the product with addition ,of SSO, it was considered important to assess the oxidative stability of the spread. An increase in the relative proportion of the unsaturated linoleic acid should increase the susceptibility of the product to autoxidation (Lundberg, 1962, and Amer and Elliot, 1970).
Material and Methods Gas Liquid Chromatography The fatty acid composition of tlle oriRinal butter1 Present Address: Gay Lea Foods Ltd., Guelph, Ontario. Can. Inst. Food Sol. Technol. J. Vol. 7, No. 1, 1974
fat, and the fat produced as spread were deterlllined by G.L.O. analysis. Purified fats were prepared by washing melted butter 01' spread with warm water to remove non-lipid constituents and drying the washed fat under vacuum using a Rinco rotary evaporator, followed by filtration using Whatman No. 1 filter papel'. Methyl ester preparation was done by the sealed tube method of deMan, 1968. Stability Toward Oxidation To determine the relative susceptibility to oxidative deterioration of normal and SSO modified butter, samples were placed in white translucent plastic cups (7.5 cm diam.) and exposed to fluorescent light (30 Watts) at a distance of 50.8 cm for 2,4 and 6 days at 4.4°0. To observe the relative rate of oxidation under high temperature conditions, test tubes (3 x 14 cm) were filled with samples, overwrapped with foil and placed in a constant temperature oven at 90°0. Peroxide values (AOOS method, Od-853, 1953) were determined after desired intervals of exposure to light and heat. Results were expressed as milliequivalents of peroxides per 1000 g of fato
Results and Discussion Fatty Acid Composition The addition of 30% sUl1flower seed oil to milkfat resulted in a large increase in the amount of linoleic acid (from an average of 2.8% in milkfat to approximately 19%) after the oil was added (Table 1). There was a cOl1comitant slight decrease of about 1.5% in the oleic acid content and considerable reduction in the saturated fatty acids notably in myristic, palmitic and stearic acids. Stability Tow(trd Oxidation Results contained in Table 2 show the effect of fluorescent light on the development of peroxides in the entire sample, while data in Table 3 show the effect on the 0.6 cm surface layer and in the remainder of samples after removal of the surface layer. None of the samples in Tables 2 and 3 contained detectable peroxides initially. The data in Table 2 indicated that butter containil1g SSO was considerably more resistant to lightinduced oxidation than normal butter for the first 2 days of exposure. Despite the fact that thereafter, the rate of oxidation in the former product generally exceeded that for normal butter, the peroxide values in the SSO cOl1taining product were lower after 6 days exposure to the light. The higher initial resistance to photochemical oxidation with the addition of SSO, may be explail1ed by the presence of the antioxidants in the oil used. 59
Table 1.
Fatty acid composition, as % methyl esters, of milkfat and modified sunflower seed oi!: mi!kfat (ratio 30:70) mixture.
Fatty acid
Mi!kfat
Modified mi!kfat
Fatty acid
Mi!kfat
Modified mi!kfat
4:0 6:0 8:0 10:0 10:1 12:0 14:0
3.2 1.8 0.9 2.0 0.3 2.3 9.2
2.8 1.3 0.7 1.6 0.2 1.8 6.4
A"
2.0 26.8 3.5 13.5 30.9 2.8 0.8
1.5 20.9 2.1 10.7 2904 19.5 0.7
16:0 B" 18:0 18.1 18:2 18:3
A" ineludes aH fatty acids with retention times between 14:0 and 16:0; B" al! those between 16:0 and 18:0.
The rate of oxidation in the surfaee layers of all samples (normal and modified butter) was a great deal more rapid than in the remaining sub-surfaee portions (Table 3). The oxidation retarding effect of the antioxidants in the lllodified SSO butter was ll1ueh less impressive in the exposed surfaee layers after 2 days, and by the fourth day, peroxide values were as high as those in normal butter. After 6 days of expOSUl~e, the extent of surfaee oxidation in modified butter exeeeded that of the control. Coneerning the sub-surfaee portion of the samples, oxidation again progressed mueh more slowly in the samples eontaining SSO during the first 2 days,.after whieh peroxides aeeumulated more rapidly than in the control butter samples. However, because of the apparent extension of the induetion period by the inclusion of antioxidants in the SSO used, peroxide accumulation had still not rpached the level of normal butter after 6 davs exposure .to the fluorescent light. Presumably, the'~l, the proteetlve effect of the antioxidants was diminished with the time of exposure to fluoreseent lightino- as the antioxidants themselves beeame oxidized. However. eonsidering the extent of oxidation in the entire (mixed) sample ('rabIe 2) the antioxidants in the modified butter kept the level of oxidation below that of normal butter during 6 days under fluorescent light. It would seem therefore that by the use of anti-
oxidants, a butter product made from modified cream eontaining milkfat and sunflower seed oil (and probably other vegetable oils) may be expected to have relatively good oxidative stability under normal conditions of merchandising. Table 2.
The effect of exposure to fluorescent light on oxidative changes in normal and modified butter (Temp. =
Table 3.
Trial
Effect of exposure to fluorescent light on oxidation in the top 0.6 cm layer and remaining portion of normal and modified butter (Temp. 4.4 oC).
-----------
Sample
Peroxide value meq/kg fat after: 2 days 4 days 6 days a"
1 2
Normal Butter Modified butter Normal butter Modified butter
2.75 2.34 2.34 2.14
b"" 1.28 0.65 1.09 0.59
a 3.90 3.85 3.50 3.45
b
a
b
1.39 0.98 1.18 0.84
5.06 6.29 5.14 5.95
1.65 1.42 1.72 1.32
" (a) refers to the upper 0.6 cm surface layers and "" (b) the butter remaining after removal of the surface layers.
Oxidative Ohanges During Stora.qe at 90°0 in the Darle vVhen the SSO modified and normal butter were exposed to high temperature conditions (90°C), the rate of oxidation was much more rapid in the SSO butter (Table 4). This was probably due to the destructive effect of elevated temperatures on the antioxidants, which then would permit more rapid oxidation of the linoleie aeid enriched modified butter. The normal butter showed a comparatively remarkable stability under the high temperature conditions. Neither the normal nor the modified butter contained detectable peroxides initially. Table 4.
Relative susceptibility to oxidation in normal amI modified butter heId at 90°C.
Trial
Sample
1
Normal butter 30% sunflower Normal butter 30% sunflower Normal butter 30% sunflower Normal butter 30% sunflower Normal butter 30% sunflower Normal butter 30% sunflower
2 3 4 5 6
Peroxide value meq/kg fat after: 20 h 40 h 60 h oH butter oH butter oH butter oi! butter oi! butter oi! butter
0.36 1.71 0.39 2.10 0.32 2.00 0.42 3.10 0.39 2.99 0040 3.00
0.82 5.95 0.85 6.14 0.74 5.75 0.95 6.06 0.89 5.85 0.89 7.15
1.47 9.96 1.95 10.57 1.68 10.10 1.72 11.41 1.84 10.99 1.81 10.95
Acknowledgements This research was supported by funds from the Ontario Cream Producers' Marketing' Board, the Ontario Creamerymen's Association, the Ontario Milk J\-Iarketing Board and the Ontario Ministry of Agrieulture and Food.
404°C).
Trial
Sample
Normal butter 30% sunflower oi! 2 Normal butter 30% sunflower oi! 3 Normal butter 30% sunflower oH 4 Normal butter 30% sunflower oH
Peroxide value meq/kg fat after: 2 days 4 days 6 days
1
60
butter butter butter butter
1.87 0.95 1.95 1.10 1.91 0.90 1.80 0.89
2.44 2.06 2.59 2.08 2.38 2.11 2.65 2.00
3.16 2.71 3.09 2.21 3.07 2.60 3.14 2.18
References Amer, M. A., and Elliot, J. I. 1970. Dietary eopper and stability of pork fato J. Amm. Se!. 31:1014. Amer, M. A., and Myhr, A. N. 1973. Modlflcatlon of butter to lmprove ~~U1~emperature spreadabllity. Can. Inst. Food Se!. Teehnol. J. deMan, J. M. 1968. Preparatlon of methyl esters of fats and oils by the sealed tube method .. Can. Inst. Food Se!. Teehnol. J. 4:126. Lundberg, W. O. 1962. Stabllity and oxidatlve raneidity. Autoxldatlon and antloxldants, Vol. 11. Interscienee Publlsher. A divlslon of John Wlley and Sons, New York, London. Offlelal and Tentatlve Methods of the American Oll Chemlsts' ~~:~icm~953. Tentative Method ed-8-53. Peroxlde Value DeterReeelved February 22, 1973 J. Inst. Can. Se!. Teehnol. Aliment. Vol. 7, No 1, 1974
Abstract The peroxide values of a butter product made from modified cream containing milkfat, sunflower seed oil (SSO) (ratio of 70: 30 respectively) and antioxidants (BHA and BHT combined with monoglyceride citrate) were lower than for conventional butter when exposed to fluorescent light for a pcriod of six days. The modified SSO butter product was therefore considered to have relatively ,good oxidative stability under normal merchandising conditions. The rate of oxidation in the surface layers of conventional and modified butters was a great deal more rapid than in the sub-surface portions. After the initial lag period, photochemical oxidation in the surface layer of the modified spread proceeded more rapidly than in normal butter. At 90°C, the modified butter was much more susceptible to oxidation than butter without the vegetable oil additive.
Résumé On peut s'attendre a ce que l'indice de peroxyde du beurre fait de creme de lait et d'huile de toumesol (en proportion respective de 70:30) additionné d'anti-oxydants (B.H.A. et B.H.T. combinés au citrate de monoglyceride), est moins que celui du beurre ordinaire quand il est exposé a la lumiere fluorescente durant six jours. Par conséquent du beurre modifié de toumesol est considéré d'etre relativement plus stable a I'oxidation sous des conditions normales d'entreposage et de mise en marché. Le beurre modifié se montra en effet considérablement plus résistant a la photo-oxydation que le beurre ordinaire. La vitesse d'oxydation des couches superfi,cieHes fut toutefois beaucoup plus rapide que ceHe des couches sous-jacentes pour les deux types de beurre. Apres le retard initial, l'oxydation photochimique se produisant a la surface· du beurre reconstitué se fit plus rapidement que dans le cas du beurre ordinaire. A 90°C, le beurre reconstitué subissait plus d'oxydation que le beurre auquel on n'avait pas ajouté d'huile végétale.
Introduction One of th~ primary problems in the storage of food is the oxidation of its fato There are two recognized factors governing the susceptibility of natural fats to oxidation, namely, the content of unsaturated fatty acids and the presence of antioxidants (Lundberg, 1962, and Amer and Elliot, 1970). In a previous investigation (Amer and Myhl', 1973), it was established that the addition of a minimum of 30% sunflower seed oil (SSO) to milkfat was required to produce low temperature spreadability of the resulting modified butter. In view of the high level of linoleic acid which would be incorporated into the product with addition ,of SSO, it was considered important to assess the oxidative stability of the spread. An increase in the relative proportion of the unsaturated linoleic acid should increase the susceptibility of the product to autoxidation (Lundberg, 1962, and Amer and Elliot, 1970).
Material and Methods Gas Liquid Chromatography The fatty acid composition of tlle oriRinal butter1 Present Address: Gay Lea Foods Ltd., Guelph, Ontario. Can. Inst. Food Sol. Technol. J. Vol. 7, No. 1, 1974
fat, and the fat produced as spread were deterlllined by G.L.O. analysis. Purified fats were prepared by washing melted butter 01' spread with warm water to remove non-lipid constituents and drying the washed fat under vacuum using a Rinco rotary evaporator, followed by filtration using Whatman No. 1 filter papel'. Methyl ester preparation was done by the sealed tube method of deMan, 1968. Stability Toward Oxidation To determine the relative susceptibility to oxidative deterioration of normal and SSO modified butter, samples were placed in white translucent plastic cups (7.5 cm diam.) and exposed to fluorescent light (30 Watts) at a distance of 50.8 cm for 2,4 and 6 days at 4.4°0. To observe the relative rate of oxidation under high temperature conditions, test tubes (3 x 14 cm) were filled with samples, overwrapped with foil and placed in a constant temperature oven at 90°0. Peroxide values (AOOS method, Od-853, 1953) were determined after desired intervals of exposure to light and heat. Results were expressed as milliequivalents of peroxides per 1000 g of fato
Results and Discussion Fatty Acid Composition The addition of 30% sUl1flower seed oil to milkfat resulted in a large increase in the amount of linoleic acid (from an average of 2.8% in milkfat to approximately 19%) after the oil was added (Table 1). There was a cOl1comitant slight decrease of about 1.5% in the oleic acid content and considerable reduction in the saturated fatty acids notably in myristic, palmitic and stearic acids. Stability Tow(trd Oxidation Results contained in Table 2 show the effect of fluorescent light on the development of peroxides in the entire sample, while data in Table 3 show the effect on the 0.6 cm surface layer and in the remainder of samples after removal of the surface layer. None of the samples in Tables 2 and 3 contained detectable peroxides initially. The data in Table 2 indicated that butter containil1g SSO was considerably more resistant to lightinduced oxidation than normal butter for the first 2 days of exposure. Despite the fact that thereafter, the rate of oxidation in the former product generally exceeded that for normal butter, the peroxide values in the SSO cOl1taining product were lower after 6 days exposure to the light. The higher initial resistance to photochemical oxidation with the addition of SSO, may be explail1ed by the presence of the antioxidants in the oil used. 59
Table 1.
Fatty acid composition, as % methyl esters, of milkfat and modified sunflower seed oi!: mi!kfat (ratio 30:70) mixture.
Fatty acid
Mi!kfat
Modified mi!kfat
Fatty acid
Mi!kfat
Modified mi!kfat
4:0 6:0 8:0 10:0 10:1 12:0 14:0
3.2 1.8 0.9 2.0 0.3 2.3 9.2
2.8 1.3 0.7 1.6 0.2 1.8 6.4
A"
2.0 26.8 3.5 13.5 30.9 2.8 0.8
1.5 20.9 2.1 10.7 2904 19.5 0.7
16:0 B" 18:0 18.1 18:2 18:3
A" ineludes aH fatty acids with retention times between 14:0 and 16:0; B" al! those between 16:0 and 18:0.
The rate of oxidation in the surfaee layers of all samples (normal and modified butter) was a great deal more rapid than in the remaining sub-surfaee portions (Table 3). The oxidation retarding effect of the antioxidants in the lllodified SSO butter was ll1ueh less impressive in the exposed surfaee layers after 2 days, and by the fourth day, peroxide values were as high as those in normal butter. After 6 days of expOSUl~e, the extent of surfaee oxidation in modified butter exeeeded that of the control. Coneerning the sub-surfaee portion of the samples, oxidation again progressed mueh more slowly in the samples eontaining SSO during the first 2 days,.after whieh peroxides aeeumulated more rapidly than in the control butter samples. However, because of the apparent extension of the induetion period by the inclusion of antioxidants in the SSO used, peroxide accumulation had still not rpached the level of normal butter after 6 davs exposure .to the fluorescent light. Presumably, the'~l, the proteetlve effect of the antioxidants was diminished with the time of exposure to fluoreseent lightino- as the antioxidants themselves beeame oxidized. However. eonsidering the extent of oxidation in the entire (mixed) sample ('rabIe 2) the antioxidants in the modified butter kept the level of oxidation below that of normal butter during 6 days under fluorescent light. It would seem therefore that by the use of anti-
oxidants, a butter product made from modified cream eontaining milkfat and sunflower seed oil (and probably other vegetable oils) may be expected to have relatively good oxidative stability under normal conditions of merchandising. Table 2.
The effect of exposure to fluorescent light on oxidative changes in normal and modified butter (Temp. =
Table 3.
Trial
Effect of exposure to fluorescent light on oxidation in the top 0.6 cm layer and remaining portion of normal and modified butter (Temp. 4.4 oC).
-----------
Sample
Peroxide value meq/kg fat after: 2 days 4 days 6 days a"
1 2
Normal Butter Modified butter Normal butter Modified butter
2.75 2.34 2.34 2.14
b"" 1.28 0.65 1.09 0.59
a 3.90 3.85 3.50 3.45
b
a
b
1.39 0.98 1.18 0.84
5.06 6.29 5.14 5.95
1.65 1.42 1.72 1.32
" (a) refers to the upper 0.6 cm surface layers and "" (b) the butter remaining after removal of the surface layers.
Oxidative Ohanges During Stora.qe at 90°0 in the Darle vVhen the SSO modified and normal butter were exposed to high temperature conditions (90°C), the rate of oxidation was much more rapid in the SSO butter (Table 4). This was probably due to the destructive effect of elevated temperatures on the antioxidants, which then would permit more rapid oxidation of the linoleie aeid enriched modified butter. The normal butter showed a comparatively remarkable stability under the high temperature conditions. Neither the normal nor the modified butter contained detectable peroxides initially. Table 4.
Relative susceptibility to oxidation in normal amI modified butter heId at 90°C.
Trial
Sample
1
Normal butter 30% sunflower Normal butter 30% sunflower Normal butter 30% sunflower Normal butter 30% sunflower Normal butter 30% sunflower Normal butter 30% sunflower
2 3 4 5 6
Peroxide value meq/kg fat after: 20 h 40 h 60 h oH butter oH butter oH butter oi! butter oi! butter oi! butter
0.36 1.71 0.39 2.10 0.32 2.00 0.42 3.10 0.39 2.99 0040 3.00
0.82 5.95 0.85 6.14 0.74 5.75 0.95 6.06 0.89 5.85 0.89 7.15
1.47 9.96 1.95 10.57 1.68 10.10 1.72 11.41 1.84 10.99 1.81 10.95
Acknowledgements This research was supported by funds from the Ontario Cream Producers' Marketing' Board, the Ontario Creamerymen's Association, the Ontario Milk J\-Iarketing Board and the Ontario Ministry of Agrieulture and Food.
404°C).
Trial
Sample
Normal butter 30% sunflower oi! 2 Normal butter 30% sunflower oi! 3 Normal butter 30% sunflower oH 4 Normal butter 30% sunflower oH
Peroxide value meq/kg fat after: 2 days 4 days 6 days
1
60
butter butter butter butter
1.87 0.95 1.95 1.10 1.91 0.90 1.80 0.89
2.44 2.06 2.59 2.08 2.38 2.11 2.65 2.00
3.16 2.71 3.09 2.21 3.07 2.60 3.14 2.18
References Amer, M. A., and Elliot, J. I. 1970. Dietary eopper and stability of pork fato J. Amm. Se!. 31:1014. Amer, M. A., and Myhr, A. N. 1973. Modlflcatlon of butter to lmprove ~~U1~emperature spreadabllity. Can. Inst. Food Se!. Teehnol. J. deMan, J. M. 1968. Preparatlon of methyl esters of fats and oils by the sealed tube method .. Can. Inst. Food Se!. Teehnol. J. 4:126. Lundberg, W. O. 1962. Stabllity and oxidatlve raneidity. Autoxldatlon and antloxldants, Vol. 11. Interscienee Publlsher. A divlslon of John Wlley and Sons, New York, London. Offlelal and Tentatlve Methods of the American Oll Chemlsts' ~~:~icm~953. Tentative Method ed-8-53. Peroxlde Value DeterReeelved February 22, 1973 J. Inst. Can. Se!. Teehnol. Aliment. Vol. 7, No 1, 1974