Progress 10/01/01 to 09/30/05

Outputs
Iron accumulation in oil is a potential problem when frying food containing substantial amounts of iron. Selected meat products (skinless chicken breast, beef liver and lean beef) were ground and fried (~2 cm spheres, ~10 g/sphere) in partially hydrogenated soybean oil (PHSBO). Samples (450 g) of ground meat were fried 3 times/hour for 8 hours/day for 3 days. Oil samples were collected for analysis for iron (every 8 hours) and oil degradation (every 4 hours) and replaced with fresh oil. The iron contents of oil samples after 3 days of frying were approximately 0.11, 0.48 and 4.01 mg of iron/kg of PHSBO for the oil used to fry chicken, beef, and liver, respectively. There was a notable darkening in color, and an increased tendency to foam for the beef liver oil sample, compared to the other samples. The thermoxidative stability of partially hydrogenated soybean oil (PHSBO) was examined after addition of ferric stearate and ferrous octanoate, and then heating the samples at 120-200C. In a second experiment, the effect of iron concentration (ferric stearate) on PHSBO stability was examined at 180C, and at concentrations of ~0.5 and ~1.2 mg of added iron/kg PHSBO. Oil samples were heated continuously for 72 hours and sampled every 12 hours. The acid value, p-anisidine value, color, dielectric constant and the triacylglycerol polymer content of oil samples were compared to oil samples containing no added iron. Generally, the value of each oxidative index increased with 1) an increase in temperature, 2) an increase in heating time, and/or 3) an increase in iron. Transition metals, including iron, occur naturally at significant concentrations in meat. The transfer of iron from the food into the oil could decrease the stability of the oil during frying, accelerating thermoxidation. The objective was to examine the thermoxidative stability of partially hydrogenated soybean oil after addition of heme-iron. Heme-iron (2.7 ppm) was added to the oil, and then oil samples were heated at 160, 180 or 200C continuously for 72 hours. Oil samples were removed for analysis every 12 hours. The acid values, color, Food Oil Sensor readings and the TAG polymer content of the heated oil samples were compared to oil samples at the same temperatures containing no added iron. Generally, each oxidative index increased with 1) an increase in temperature, 2) an increase in heating time, and/or 3) with the addition of iron. The extent of oxidation was much greater for samples heated at 200C, than for oil samples heated at 160C or 180C. The oil samples heated at 200C reached the target polymer content of 20% after 27 hours of heating.

Impacts
The research results demonstrate that during frying, iron will transfer from foods, such as meat, into the frying oil. If iron transfer does occur, it will increase the rate of oil degradation and reduce the frying life of the oil. Unless something is done to remove the iron, it will require more frequent replacment of the oil. If the oil is not replaced when needed, there will be an increase in the health risk associated with consuming frying oil that has been excessively degraded.

Publications

• Coscione, A.R. and Artz, W.E. 2005. Vegetable oil stability at elevated temperatures in the presence of ferric stearate and ferrous octanoate. J. Agr. Food Chem. 53(6):2088-2094.
• Artz, W.E., Osidacz, P.C. and Coscione, A.R. 2005. Iron accumulation in the oil during deep-fat frying of meat. J. Amer. Oil Chem. Soc. 82(4):249-254.
• Osidacz, P.C., Coscione, A.R. and Artz, W.E. 2005. Acceleration of the thermoxidation of oil by heme iron. J. Amer. Oil Chem. Soc. 82(8):579-584.

Progress 01/01/04 to 12/31/04

Outputs
Iron from food can accumulate in the oil during frying, which will affect the oil stability and quality. Selected meat products (skinless chicken breast, beef liver and lean beef) were ground and fried (2 cm diameter spheres, 10 grams per sphere) in partially hydrogenated soybean oil. Samples (450 g or approximately one pound) of ground meat were fried 3 times per hour for 8 hours each day for a total of 3 days. Oil samples were collected once a day for iron analysis and twice a day to determine the amount of oil degradation. Oil removed as samples was replaced with fresh oil. The iron content of the oil samples collected after 3 days of frying was approximately 0.11, 0.48 and 4.01 mg of iron per kg of oil for the oil used to fry chicken, beef, and liver, respectively. There was a notable darkening in oil color, and an increased tendency for the oil to foam for the beef liver oil sample, as compared to the other two sample types. After frying, the acid values were 0.9, 1.1 and 1.4 for the oil samples for chicken, beef, and liver, respectively. After frying, the p-anisidine values were 11.5, 12.8 and 32.6 for the oil samples for chicken, beef, and liver, respectively; while the FOS values were 0.96, 0.96 and 0.83 for the oil samples for chicken, beef, and liver, respectively. The acid values and p-anisidine values indicated slightly more oil degradation for the oil used to fry beef liver than for the oil used to fry chicken and ground beef.

Impacts
Vegetable oils must be purified after extraction to remove a variety of components that would detract from the flavor and stability of the oil if not removed. While the stability of a vegetable oil is primarily dependent upon the unsaturation of the oil, the presence of undesirable minor components, such as iron, can increase the rate of oil degradation during frying. During frying, iron from the meat can be extracted into the oil, reducing the frying life of the oil, so it is important to determine how rapidly iron can be extracted from the meat and into the oil, as well as how much iron can be extracted from the meat. In response to this problem, technologies have been developed to remove the iron to improve oil stability.

Publications

• No publications reported this period

Progress 01/01/03 to 12/31/03

Outputs
The thermoxidative stability of partially hydrogenated soybean oil (PHSBO) was examined after addition of ferric stearate or ferrous octanoate, and then heating the samples at 120, 160, 180 and 200C. In a second experiment, the effect of iron concentration (ferric stearate) on PHSBO stability was examined at 180C, and 0.5 and 1.2 mg of added iron/kg PHSBO. Oil samples were heated continuously for 72 hours and sampled every 12 hours. The acid values, para-anisidine values, color, dielectric constants and the triacylglycerol polymer content of the oil samples were compared to the oil sample containing no added iron. Generally, the value of each oxidative index increased with 1) an increase in temperature, 2) an increase in heating time, and/or 3) an increase in iron. The results demonstrate that low concentrations of iron will increase the rate of oxidation and reduce the frying life of the oil. In a second series of experiments, the relative stability of an expeller expressed and physically refined soybean oil (EE-SBO, iodine value = 126.6) was compared to a low-linolenic acid soybean oil (LL-SBO, iodine value = 120.7) using pan frying. Physicochemical analyses, including free fatty acid analysis, the dielectric constant (Food Oil Sensor), and the Lovibond color were completed. High performance size exclusion chromatography was used to quantify the amount of polymeric triacylglycerol formed in the oil samples during heating. Oil samples were heated as thin films on a teflon-coated frying pan at 180C to a target endpoint of >20% polymer. The endpoint, as determined by high performance size exclusion chromatography, was reached after 10 minutes of heating for the EE-SBO (23.8% polymer) and 12 minutes for the LL-SBO (24.9% polymer) sample. Although the iodine value suggests that LL-SBO should have an oxidative stability comparable to EE-SBO, the results from the physicochemical analyses indicated that the EE-SBO was approximately 20% more stable than the LL-SBO.

Impacts
Vegetable oils are carefully purified after extraction to remove a variety of components that would detract from the flavor and stability of the oil if they were not removed. For example, the crude oil will contain trace amounts of iron that must be removed to insure good storage stability. During frying, iron from meat products can be extracted into the oil, reducing the frying life of the oil. It is important to determine if that effect is sufficient to warrant developing and applying technologies to remove the iron. In a separate experiment, extrusion in combination with an expeller system was used to extract oil from soybeans. The process avoids the environmental and explosion problems associated with solvent extraction. Pan frying was used to determine the stability of the oil, since it causes rapid oil oxidation, and it is the frying technique most commonly used in the home and in non-fast food restaurants. The extracted oil was surprisingly stable, suggesting additional antioxidants, such as certain phenolics, were co-extracted into the oil.

Publications

• Coscione, A.R. and Artz, W.E. 2003. Frying oil stability at elevated temperatures in the presence of ferric stearate and ferrous octanoate. J. Agr. Food Chem. (Accepted).
• Coscione, A.R., Osidacz, P.C., Kiatsrichart, S. and Artz, W.E. 2003. The pan-heating stability of an expeller expressed soybean oil. J. Food Lipids (Accepted).
• Coscione, A.R., Oisdacz, P.C., Kiatsrichart, S. and Artz, W.E. The improved pan heating stability of expeller expressed soybean oil. Presented at the 94th American Oil Chemists' Society Annual Meeting, Kansas City, MO, May 4-7, 2003.
• Coscione, A.R. and Artz, W.E. 2003. Frying oil stability at elevated temperatures in the presence of ferric stearate and ferrous octanoate. Presented at the 94th American Oil Chemists' Society Annual Meeting, Kansas City, MO, May 4-7, 2003.

Progress 01/01/02 to 12/31/02

Outputs
Pan-frying is a popular frying method at home and in many restaurants. Pan-frying stability of two frying oils with similar iodine values (IV); mid-oleic sunflower oil (NuSun oil; IV = 103.9) and a commercial canola oil (IV = 103.4) were compared. Each oil sample was heated as a thin film on a teflon-coated frying pan at 180C to a target endpoint of >20% polymer. HPSEC analysis of the mid-oleic sunflower and canola oil samples indicated the heated samples contained 20% polymer after approximately 18 minutes and 22 minutes of heating, respectively. The FOS values increased from zero to 19.9 for the canola sample and 19.8 for the mid-oleic sunflower sample after 24 minutes of heating. The apparent first order degradation rate for the mid-oleic sunflower sample was 0.102+/-0.008 per minute, while the rate for the canola sample was 0.092+/-0.010 per minute. The acid value increased from approximately zero prior to heating, to 1.3 for the canola sample and 1.0 for the mid-oleic sunflower sample after 24 min of heating. In addition, sensory and volatile analyses on the fried hash browns obtained from both oils indicated there were no significant differences between the two fried potato samples. Excessive amounts of iron in the frying oil can reduce the oxidative stability of the oil, particularly at frying temperatures. Transition metals, such as iron, catalyze the degradation of fatty acid hydroperoxides and thereby accelerate oil oxidation and deterioration. Iron is particularly problematic for fried meat products, since meat contains relatively large amounts of iron in the form of myoglobin and hemoglobin. Selected meat products (skinless chicken, beef liver and ground beef meatballs) were deep fat fried (1 lb of meat per hour, 9 hours per day for a total of 54 hours). The iron content was analyzed each day, as well as selected oil quality parameters. Aliquots of oil were removed each day after frying and analyzed for iron content, changes in the acid value, the p-anisidine value, triacylglycerol polymer content, and the dielectric constant (food oil sensor, FOS). The acid value for the oil used for frying beef increased faster than in the oil used for frying chicken or liver oil, reaching 6.5 in 54 hours, while it reached 4.1 in the same time while frying chicken and only 3.6 while frying liver for the same period of time. The p-anisidine value was greatest after frying the liver (47.6), as compared to 16.0 for the chicken and beef fried for the same length of time. At the end of the heating period, the dielectric constant, as measured by the Food Oil Sensor, ranged from 2 for the liver to 2.75 for the chicken. The oil used for the beef had a final polymer content of 1.8%, as compared to 2.8% for the chicken and 3.5% for the liver. The iron content was greatest after frying the liver (3.35 ppm). The oil in which the beef had been fried had 0.36 ppm of iron and the amount of iron in chicken oil was less than 0.03 ppm.

Impacts
Pan frying results in a rate of oxidation approximately 50 to 100 times faster than deep fat frying. The oil remaining in pan can be very highly oxidized and should not be reused. As the iron from meat and other sources accumulates in the oil during deep-fat frying, the rate of oxidation increases. If this iron is regularly removed, the frying "life" of the oil can be extended, reducing the cost to restaurants and reducing the amount of degraded oil that must be discarded.

Publications

• Kiatsrichart, S., Brewer, M.S., Cadwallader, K.R. and Artz, W.E. 2003. Pan frying stability of NuSun oil, a mid-oleic sunflower oil. J. Amer. Oil Chem. Soc. (Accepted).
• Coscione, A.R. and Artz, W.E. 2002. Iron and oil stability during frying. Presented at the 93rd American Oil Chemists' Society Annual Meeting, Montreal, Canada, May 5-8, 2002.

Progress 01/01/01 to 12/31/01

Outputs
Experiments on this project were begun in mid-October of 2001. The effect of iron on oil stability during frying was examined. These experiments were done to obtain the appropriate parameters (kinetics and thermodynamics) to quantitate the effect of iron and temperature on frying oil degradation. The procedure adopted involved heating oil samples (350 grams of a partially hydrogenated soybean oil) containing the added iron compounds (iron stearate and iron octanoate) for 72 hours at three different temperatures (160, 180 and 200 degrees C). Aliquots were taken every 12 hours and analyzed for color, acid value, p-anisidine value, the percentage of triacylglycerol polymer, and an estimate of the polar material content using the food oil sensor (FOS). A sample of oil without the addition of any iron was heated under the same conditions. The production of polar compounds in the oil containing iron octanoate and iron stearate, as determinated with FOS, was very similar. The reaction followed a second order polynomial behavior quite distinct from that observed for the linear trend observed in the oil sample without added iron heated during the same time interval. The same trend was observed for the acid value and the percent polymer. The aldehyde formation, as determined by the p-anisidine value, presented a different trend, increasing rapidly from zero to 36 hours, followed by a much slower rate of increase from 48 to 72 hours of heating. The color also changed significantly, with a large increase in the yellow and red color intensity. The samples containing iron increased in color intensity faster than the sample without added iron.

Impacts
As the iron from meat and other sources accumulates in the oil during deep-fat frying, the rate of oxidation increases. If this iron is regularly removed, the frying "life" of the oil can be extended, reducing the cost to restaurants and reducing the amount of degraded oil that must be discarded.

Publications

• No publications reported this period