EFFECT OF COOKING OIL TYPE ON FINAL CHOLESTEROL CONTENT AND FATTY ACID COMPOSITION OF GROUND BEEF ABSTRACT

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1 EFFECT OF COOKING OIL TYPE ON FINAL CHOLESTEROL CONTENT AND FATTY ACID COMPOSITION OF GROUND BEEF TIFFANY D. BONSELL, MARK K. ANDERSEN and DANIEL C. RULE Department of Animal Science University of Wyoming Laramie, WY Accepted for Publication May 16, 1993 ABSTRACT The purpose of this study was to compare three oils for extraction of cholesterol when used to cook ground beef and to determine the effect of oil type on fatty acid composition of the ground Ground beef (30% fat) was cooked in 1 L of corn, canola or palm oil at C and then rinsed with 500 ml of boiling water, which significantly decreased ether-extractable fat. Control hamburger was skillet-fried without any added oil. Total lipids were extracted and analyzed for fatty acid composition and cholesterol content. Changes in fatty acid composition of residual fat on the meat afrer cooking reflected those of the oils used for cooking. Cholesterol was significantly lower in all oil-cooked hamburger than in the control. In conclusion, cooking ground beef in any of the three vegetable oils will extract cholesterol, and the lipid remaining after a boiling water rinse will contain fatty acids characteristic of the cooking oil. INTRODUCTION Current recommendations to reduce dietary fat intake in order to lower serum cholesterol have resulted in decreased consumption of red meats (DeBakey et al. 1986). A response to these recommendations has been increased consumption of low fat ( < 20%) ground beef compared with regular (>20% fat) ground beef (Hoelscher et al. 1987). Recently, Small el al. (1991) described a procedure to prepare low-fat, low-cholesterol ground beef whereby the hamburger was cooked in corn oil and then rinsed with boiling water. 'Address all correspondence to: D.C. Rule, Department of Animal Science, University of Wyoming, Laramie. WY Journal of Food Quality 16(1993) All Righrs Reserved. Copyright 1993 by Food & Nutrition Press, Inc.. Trumbull, Connecticut, 383

2 384 T.D. BONSELL, M.K. ANDERSEN and D.C. RULE However, use of other vegetable oils has not been investigated. The objectives of this study were to determine effects of cooking oil type on cholesterol content and fatty acid composition of ground beef cooked in vegetable oil. MATERIALS AND METHODS Ground beef (30% fat), corn oil and canola oil were purchased locally; palm oil was purchased previously. Hamburger was divided into three portions (replicates) at the time of purchase and not frozen prior to cooking. On each of three consecutive days, 1 kg of hamburger was cooked in each oil and 500 g of meat were used for control (skillet-fried without any added oil). Hamburger was cooked in oil as previously described (Small el af. 1991). Briefly, 1 kg of meat was added to 1 L of oil in an electric skillet at room temperature, crumbled and then heated to 80C for 5 min. The temperature was then elevated to 100 C for an additional 5 min to brown the meat. After cooking, the meat and oil were put into a kitchen strainer and the oil collected in a beaker. A sample of the oil was removed for fatty acid analysis. Next, 500 ml of boiling water were slowly poured over the cooked ground beef and collected in the beaker containing the oil; the rinse-water was referred to as "broth." The control ground beef was cooked by frying in its own fat at the same skillet temperatures and cooking times as the oil treatments; samples of drippings from controls were collected for analysis. The water-oil mixture was refrigerated (4C) to allow for complete separation of oil and broth. The oil layer was removed and discarded. One-half of the oil-cooked meat was thoroughly mixed (soaked) with reheated broth and then stored without excess broth in zippered freezer bags at -2OC for 2-3 weeks before lipid analyses. In preparation for extraction, samples of each ground beef were weighed, freeze-dried and then reweighed to account for moisture loss during drying. The freeze-dried samples were then ground with a Krups type 203 household coffee mill. Total lipids were extracted from duplicate 100 mg samples in 1:2:.8 (v/v/v) ch1oroform:methanol:water (Bligh and Dyer 1959) with vortex-mixing for 4 h and were then saponified in 1.0 ml of 33% KOH and 4.0 ml of ethanol at 80C for 30 min (Busboom ef af. 1991). Nonsaponifiable lipids were extracted twice with 3.0 ml of hexane. Free fatty acids were extracted twice with 3.0 ml of hexane after addition of 1 ml of concentrated HCl. Fatty acid methyl esters were prepared by using BF, in methanol (Morrison and Smith 1964) and analyzed by gas chromatography using a 1.83 m X 2 mm (i.d.) column packed with SP 2330 (10%) on 100/120 Chromosorb W/AW (Supelco, Bellefonte, PA). Column temperature was increased from OC at 4C/min. Injector and detector temperatures were both 250C. Fatty acid

3 LIPIDS OF OIL-COOKED HAMBURGER 385 peaks were recorded and integrated. Fatty acids were identified by comparing retention times with those of fatty acid methyl ester standards. Detector response factors for 16:0, 18:0, 18:1, 18:2 and 18:3 were determined by comparing peak areas for 51.6, 52.4, 53.3, 53.7 and 53.1 mg per 75 ml of hexane of respective fatty acid methyl ester standards. Individual peak areas from five repetitions were divided by the pg of each respective methyl ester with the following result: 16:0, 0.98; 18:0, 0.98; 18:1, 0.99; 18:2, 1.00; 18:3, Cholesterol was quantitated by gas chromatography using an SPB-1 fused capillary column (Supelco, Bellefonte, PA): 30 m X 0.53 mm (i.d.) with 0.10 pm film thickness. Column temperature was 250C (isothermal) and injector and detector temperatures were both 300C. Stigmasterol was used as the internal standard. Detector response factors for 0.2 mg each of cholesterol and stigmasterol were 0.99 and 1.OO, respectively. Percent total fat was determined using triplicate, 1 g samples (oven-dried) extracted with petroleum ether as previously described (Helrich 1990). Data were analyzed by analysis of variance for the complete randomized design (n=3) by using the General Linear Model procedure of the Statistical Analysis System (SAS 1985). Duncan s New multiple range test was used to locate differences between means when significant (P <.05) F-values were observed. RESULTS AND DISCUSSION Fatty acid weight percentages of oils before and after being used to cook hamburger are presented in Table 1. Fatty acid compositions of fresh oils were consistent with previously published values for corn, palm and canola (low erucic acid rape seed) oils (Reeves and Weihrauch 1979). Generally, fatty acids of oils after cooking reflected dilution with beef fat (fatty acid composition of raw beef fat and drippings after frying hamburger in its own fat are shown in Table 3). For example, fatty acids that were high in beef fat but low in raw cooking oils (16:O in corn and canola oils, 16:l and l8:o) were greater in oils after being used to cook ground beef. Because only one source of each raw oil was used, no statistical comparison was made between the raw oils and those collected after each batch of hamburger was cooked. Values for percent total fat of raw and cooked ground beef are presented in Table 2. The control-cooked meat contained similar total fat as did the raw hamburger, probably because Loss of fat coincided with moisture loss expected from the meat during cooking. After cooking hamburger in corn oil and then rinsing the meat once with boiling water, about half the total fat was removed. When the corn oil-cooked hamburger was rinsed in boiling water and then soaked in this broth, even more fat was removed. Cooking with canola oil

4 386 T.D. BONSELL, M.K. ANDERSEN and D.C. RULE TABLE 1. FATTY ACID WEIGHT PERCENTAGES OF OILS RAW AND AFTER USED TO COOK GROUND BEEF Cookine oil Canola Corn Palm S Eb Fatty after after after acid raw' cooking raw cooking raw cooking 14:O'.1.8'.03.7' '.04 16:O ' ' '.30 16: ''.2 1.2".1 1.2'.06 18:O ' ' ".15 18: ' O '.25 18: ' ' '.31 18: ' 1.0.8'.3.2',14 'For raw oils, data were not compared statistically because only one source per oil was used for this study. bpooled standard error of the mean from oil fatty acids sampled from each of the three cooking replicates (3). 'Number of carbon atoms:number of double bonds. d~c~f~gmea.n~ in the same row with different superscripts are significantly different (P <.05) for oils after cooking only. followed by a single water rinse slightly reduced total fat when compared with the control, but when this hamburger was soaked with its broth, the total fat content decreased by half (P <.05). A similar response was observed for hamburger when cooked in palm oil and then soaked in its broth, but this difference was not significant (P >.05). Apparently, soaking with broth represented a second rinse, which suggests that more than one rinse with boiling water was necessary to significantly reduce total fat in ground beef cooked in canola or palm oils. Moreover, corn oil was more easily rinsed from the meat than were either canola or palm oils, probably because of corn oil's greater proportion of polyunsaturated fatty acids than the latter oils. Fatty acid compositions of hamburger fried in its own drippings or cooked in vegetable oil are presented in Table 3. Raw and fried hamburger had the same weight percentages of fatty acids. Thus, frying hamburger in its own drippings did not affect the composition of fatty acids. No differences in fatty

5 LIPIDS OF OIL-COOKED HAMBURGER 387 TABLE 2. PERCENT TOTAL FAT IN RAW, FRIED AND HAMBURGER COOKED IN OIL Cooking treatment Total fat 96 Raw Fried 3 1.7' 28.4' Corn oil' 14.T Corn oil + brothb 10.3" Canola oil' 23.2'* Canola oil + brothb 11.9" Palm oil' Palm oil + brothb 23. 6'd 16.4' SEf 2.6 'Hamburger cooked in either corn oil, canola oil or palm oil and then rinsed once with boiling water. bhamburger cooked in oil, rinsed and then soaked in its broth (heated rinse water). E~d*cMean~ with different superscripts are different (P<.05). 'Pooled standard error of the mean, n=3. acid composition occurred from soaking the meat in its broth after first rinsing with boiling water for any cooking oil treatment except for 18:3 in canola oil-cooked meat which was decreased 27% (P <.05). All cooking oils decreased the proportions of 14:0, 16:l and 18:O. Hamburger cooked in corn oil had lower 16:0, 18:l and nearly 10-fold greater 18:2 than did the control. Hamburger cooked in canola oil also had lower 16:O and greater 18:2, 18:l and 18:3. With palm oil, residual lipids had greater 16:O and lesser 18:l. Thus, the fatty acid composition of residual lipids of oil-cooked, water-rinsed hamburger reflected the fatty acids of oils used for cooking. Cholesterol contents of hamburger are shown in Table 4. Frying the hamburger in its own drippings concentrated the cholesterol somewhat compared with the raw meat. Compared with the control cooked hamburger, cooking with oils followed by water rinses decreased cholesterol by 32, 37 and 36% for corn, canola and palm oils, respectively. Soaking in broth resulted in the lowest

6 TABLE 3. FATTY ACID WEIGHT PERCENTAGES OF RAW, FRIED AND HAMBURGER COOKED IN OIL Cooking treatment 14:O 16:O 16: 1 18:O 18: 1 18:2 18:3 ~ Fried 3.5' 26. 3d 5.5" 13.0" 49.0' 2.5".2" Corn oila 1.gdc 19.7" 3.4d 7.9' 39.4' 27.2". 5' Corn oil + brothb 2. 0'" 20.3" 3.8' 8. I* 40.2' 25.0".5' Canola oil' 1.7" d 7.0d 55.0' 12.4' 5.9" Canola oil + brothb 2. 1'" 17.2'g 3.8' 7.7d 53.9" 11.Od 4.3d Palm oil' 2.2d 36.4' 2.9' 8.2' 44.3" 5.8".2' Palm oil + brothb 2.3d 35.9' 3.2' 8.3' 44.6" 5.5".2" S Eh W W 00 Raw 3.6' 26. Id 5.2' 13.3' 49. Od 2.5'.2' 'Hamburger cooked in either corn oil, canola oil or palm oil and then rinsed once with boiling water bhamburger cooked in oil, rinsed and then soaked in its broth (heated rinse water). '*d,c,f*gmeans for each fatty acid with different superscripts are significantly different (P <.05). hpooled standard error of the mean, n=3.

7 LIPIDS OF OIL-COOKED HAMBURGER 389 TABLE 4. CHOLESTEROL CONTENT OF RAW, CONTROL-COOKED AND OIL-COOKED HAMBURGER Cooking treatment Cholesterol, mg per 100 g of meat Raw Fried Corn oil' Corn oil + brothb Canola oil' Canola oil + brothb Palm oil' Palm oil + brothb SE' 81.7' 88.9' 62.6' 60.8' 69.4' 56.4' 65. 6d 57. I' 4.0 'Hamburger cooked in either corn oil, canola oil or palm oil and then rinsed once with boiling water. bhamburger cooked in oil, rinsed then soaked in its broth (heated rinse water). '*'Means with different superscripts are significantly different (P <.05). 'Pooled standard error of the mean, n=3. cholesterol values for all samples, also indicating that further rinsing would rid cholesterol that was extracted and mixed with the residual oil adhering to the meat. For the most part, results of the present study corroborated previous findings (Small et al. 1991) that losses of about 68% for fat and 39% for cholesterol occurred when hamburger was cooked in corn oil. For example, when broth was mixed with corn oil-cooked meat in the present study, the loss in fat compared with the raw hamburger was 68% (from 31.7 to 10.3 %, Table 2). Additionally, we observed similar ability to extract cholesterol and fat with three types of oil. Thus, the type of oil probably would not influence extraction but would influence the composition and amount of fatty acids remaining. Small et af. (1991) indicated that soaking corn oil-cooked meat in its broth improved flavor of the oil-cooked hamburger, and the utility of this product would be inclusion with sauces or other mixtures rather than alone. Whether

8 390 T.D. BONSELL, M.K. ANDERSEN and D.C. RULE consumed alone or not, this defatted product would likely be consistent with a diet designed to maintain lower serum cholesterol because others (O Dea er al. 1990) have observed decreased cholesterol levels in individuals who consumed a very low fat diet that contained beef as well as about 300 mg/day of cholesterol. Results of a rat feeding study from our laboratory also indicate an interaction between beef fat and cholesterol consumption because rats fed diets with either 0.4% cholesterol and no tallow, or 12% tallow and no cholesterol had significantly lower plasma cholesterol levels than rats fed 12% tallow and 0.4% cholesterol together (Rule et al. 1991). The concern regarding diet and coronary heart disease has led to the development of leaner ground beef products, some of which are used in today s fast food industry. These products include gums to maintain palatability; however, others successfully have used phosphates and water to maintain palatability of ground beef (Andersen ef al. 1989). The remaining fat, however, may not be suitable for many individuals who must modify their diet to lower their serum cholesterol. In the present study, frying hamburger in corn or canola oil resulted in significant increases in mono- and polyunsaturated fatty acids, which are well documented hypocholesterolemic fatty acids in humans. On the other hand, frying hamburger in palm oil resulted in increased 16:0, which may be a hypercholesterolemic fatty acid. In conclusion, hamburger that contains 30% fat can be cooked in several types of oil and then rinsed with boiling water to reduce both total fat and cholesterol contents. Residual fat adhering to the meat after rinsing with boiling water will contain fatty acids characteristic of the oil used for cooking the hamburger and will result in a product consistent with foods recommended for maintaining lower serum cholesterol. REFERENCES ANDERSEN, M.K., MILLER, M.F., LYON, C.E. and REAGAN, J.O The effects of added water and phosphate on the chemical, physical and sensory characteristics of low-fat ground beef patties. J. Anim. Sci. 67, 151 (abstr). BLIGH, E.G. and DYER, W.J A rapid method of total lipid extraction and purification. Can. J. Biochem. Physiol. 37, BUSBOOM, J.R., RULE, D.C., COLLIN, D., MAZHAR, A. and HEALD, T Effects of dietary canola on growth and lipid composition in adipose tissue and muscle of swine. J. Anim. Sci. 69, DEBAKEY, M.E., GOITO, A.M., SCOTT, L.W. and FOREYT, J.P Diet, nutrition and heart disease. J. Amer. Diet. Assoc. 86, 729.

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