JOURNAL OF FOOD COMPOSITION AND ANALYSIS 1,26-37 ( 1987) Lipids in Raw and Cooked Beef HALT. SLOVER,' ELAINELANZA,'RAYMOND H. THOMPSON,JR.,~ CAROL S. DAVIS, AND GEORGE V. MEROLA Nutrient Composition Laboratory, Beltsville Human Nutrition Research Center, Agricultural Research Service, United States Department OfAgriculture, Beltsville, Maryland 20705 Received September 8, 1986, and in revised form April 7, 1987 Lipids in the separable lean of raw and cooked beef were determined, as part of an extensive cooperative study to provide current data on the nutrients in retail cuts and quality grades. Paired cuts from right and left sides of 8 carcasseswere analyzed raw and cooked; an additional 172 raw cuts, each from a different carcass of prime, choice, or good grade, were also analyzed raw. In raw separable lean beef, representative values were as follows: total fat minimum, 3.2% in round top round steak, good grade, total fat maximum, 14.6% in rib roast large end, prime grade; cholesterol minimum, 49.9 mg/lOO g in round eye round roast, good grade, cholesterol maximum, 68.1 mg/ 100 g in brisket flat half boneless, good grade; linoleate minimum, 1.6% in brisket flat half boneless, choice grade, linoleate maximum, 5.3% in round top round steak, good grade; saturated fatty acids minimum, 37.9% in brisket point half boneless, prime grade, saturated fatty acids maximum, 48.8% in loin tenderloin steak, choice grade; P/S ratio mini- mum, 0.04 in brisket flat half boneless, choice grade, P/S ratio maximum, 0.16 in round tip roast, left, good grade; trans-monoene minimum, 1.3% in round top round steak, choice grade, trans-monoene maximum, 4.4% in rib roast large end, good grade. Cooking caused a loss of fat from the cuts as a whole, but caused an increase in the fat in the separable lean, ranging from 0.75% in the round eye round roast to 3.26% in the chuck arm pot roast. Estimates of the true retention of fat averaged 125 + 2.0%, of volatiles 59 + 9.0%, and of cholesterol 106 f 10.9%. Cholesterol in the raw separable lean was positively correlated with fat (r = 0.58) and negatively correlated with nonfat solids (r = -0.53). 0 1987 Academic PXSS, Inc. INTRODUCTION Beef, one of the major foods in the United States, contributes significantly to the total caloric intake as well as to the total consumption of fat. Food consumption data (USDA, 1983a) estimate that in 1982 approximately 96.1 g/capita/day of beef was used in some way, or disappeared, in the United States. These “disappearance” data do not represent the amount eaten as beef: actual consumption has been estimated by a survey (USDA, 1983b) in 1978 as 5 1 g/capita/day. The difference between re- ported beef consumption and the disappearance data includes beef eaten in forms not primarily identified as beef, such as canned soups and stews and lunch meats. It was also estimated (USDA, 1985) that beef contributed 10.9%, or 18.1 g/capita/day, of the food fat available in the United States in 1983. Although there is much information on the lipids in various beef samples, most of it was collected for other purposes and can be used as compositional data only with difficulty, since details of sample description, collection, preparation, and analysis are ’ Retired. Present address: Rte. 1, Box 347, Luray, VA 22835. * Present address: Department of Health and Human Services, National Institutes of Health, National Cancer Institute, Bethesda, MD 20205. 3 To whom reprint requests should be addressed at: Nutrient Composition Laboratory, BARC-E, Build- ing 161, Beltsville, MD 20705. 0889-1575187 $3.00 Copyright 0 I987 by Academic Press, Inc. All ri&ts of reproduction in any form reserved. 26
Transcript
JOURNAL OF FOOD COMPOSITION AND ANALYSIS 1,26-37 ( 1987)
Lipids in Raw and Cooked Beef
HALT. SLOVER,' ELAINELANZA,'RAYMOND H. THOMPSON,JR.,~ CAROL S. DAVIS, AND GEORGE V. MEROLA
Nutrient Composition Laboratory, Beltsville Human Nutrition Research Center, Agricultural Research Service, United States Department OfAgriculture, Beltsville, Maryland 20705
Received September 8, 1986, and in revised form April 7, 1987
Lipids in the separable lean of raw and cooked beef were determined, as part of an extensive
cooperative study to provide current data on the nutrients in retail cuts and quality grades. Paired cuts from right and left sides of 8 carcasses were analyzed raw and cooked; an additional 172 raw cuts, each from a different carcass of prime, choice, or good grade, were also analyzed raw. In raw separable lean beef, representative values were as follows: total fat minimum, 3.2% in round top round steak, good grade, total fat maximum, 14.6% in rib roast large end, prime grade; cholesterol minimum, 49.9 mg/lOO g in round eye round roast, good grade, cholesterol maximum, 68.1 mg/ 100 g in brisket flat half boneless, good grade; linoleate minimum, 1.6% in brisket flat half boneless, choice grade, linoleate maximum, 5.3% in round top round steak, good grade; saturated fatty acids minimum, 37.9% in brisket point half boneless, prime grade, saturated fatty acids maximum, 48.8% in loin tenderloin steak, choice grade; P/S ratio mini- mum, 0.04 in brisket flat half boneless, choice grade, P/S ratio maximum, 0.16 in round tip roast, left, good grade; trans-monoene minimum, 1.3% in round top round steak, choice grade, trans-monoene maximum, 4.4% in rib roast large end, good grade. Cooking caused a loss of fat from the cuts as a whole, but caused an increase in the fat in the separable lean, ranging from 0.75% in the round eye round roast to 3.26% in the chuck arm pot roast. Estimates of the true retention of fat averaged 125 + 2.0%, of volatiles 59 + 9.0%, and of cholesterol 106 f 10.9%. Cholesterol in the raw separable lean was positively correlated with fat (r = 0.58) and negatively correlated with nonfat solids (r = -0.53). 0 1987 Academic PXSS, Inc.
INTRODUCTION
Beef, one of the major foods in the United States, contributes significantly to the total caloric intake as well as to the total consumption of fat. Food consumption data (USDA, 1983a) estimate that in 1982 approximately 96.1 g/capita/day of beef was used in some way, or disappeared, in the United States. These “disappearance” data do not represent the amount eaten as beef: actual consumption has been estimated by a survey (USDA, 1983b) in 1978 as 5 1 g/capita/day. The difference between re- ported beef consumption and the disappearance data includes beef eaten in forms not primarily identified as beef, such as canned soups and stews and lunch meats. It was also estimated (USDA, 1985) that beef contributed 10.9%, or 18.1 g/capita/day, of the food fat available in the United States in 1983.
Although there is much information on the lipids in various beef samples, most of it was collected for other purposes and can be used as compositional data only with difficulty, since details of sample description, collection, preparation, and analysis are
’ Retired. Present address: Rte. 1, Box 347, Luray, VA 22835. * Present address: Department of Health and Human Services, National Institutes of Health, National
Cancer Institute, Bethesda, MD 20205. 3 To whom reprint requests should be addressed at: Nutrient Composition Laboratory, BARC-E, Build-
ing 161, Beltsville, MD 20705.
0889-1575187 $3.00 Copyright 0 I987 by Academic Press, Inc. All ri&ts of reproduction in any form reserved.
26
LIPIDS IN BEEF 27
FIG. I. Beef cuts analyzed: Nomenclature as recommended by the National Live Stock and Meat Board (1983). 1, chuck arm pot roast; 2, chuck blade roast; 3, brisket flat half boneless; 4, brisket point half boneless; 5, rib steak small end; 6, rib roast large end; 7, round tip roast, left; 8, round tip roast, right; 9, round top round steak; 10, round bottom round steak; 11, round eye round roast; 12, loin wedge bone sirloin steak; 13, loin tenderloin steak, 14, loin top loin (strip) steak.
often lacking. In fact, no report of the individual lipids in beef, sampled to represent the variables of cut, grade, and preparation, is known despite the importance of this food. A recent review of the fatty acids in beef (Anderson et al., 1975) describes the problems of evaluating data from diverse sources, obtained for a variety of purposes.
In order to provide needed information on lipids and other nutrients in beef, infor- mation collected in a manner designed to optimize its usefulness as compositional data, the United States Department of Agriculture has undertaken an extensive study, in cooperation with the National Live Stock and Meat Board and other organizations. The purpose of the portion of the study reported here was to provide information on the lipid composition of raw and cooked retail beef cuts, by grade, in a form suitable for use by consumers, dietitians, nutritionists, and those investigating the relationship of diet and human health.
METHODS
The work was done in two parts: Phase I, to evaluate the effects of cooking by analyzing paired raw and cooked cuts from a limited number of carcasses; and Phase II, to provide further compositional data for individual raw cuts from carcasses graded prime, choice, and good.
Carcass selection. Carcasses were selected from commercial plants by USDA Meat Science Research Laboratory (MSRL) and National Live Stock and Meat Board (NL- SMB) personnel. In Phase I, 8 animals, 3 prime, 1 choice, 3 good, and 1 standard grade carcasses (yield grade 2.4-3.2), were selected at random from packing plants located in the north central, southwestern, and southeastern sections of the United States. Fourteen retail cuts (Fig. 1) (National Live Stock and Meat Board, 1983) were taken from the right and left sides of each carcass by USDA MSRL and NLSMB personnel, using cutting and trimming procedures developed by them for this study (details of these procedures are available from the National Live Stock and Meat Board or the USDA Meat Science Research Laboratory). Subcutaneous fat thickness did not exceed 5.1 cm for the arm and blade pot roasts or 1.3 cm for the other cuts. Steak thicknesses varied from 1.9 to 3.1 cm. One cut from each right and left pair was selected at random to be analyzed raw, and the other was cooked by a commonly used household method (National Live Stock and Meat Board, 1983). In Phase II,
28 SLOVER ET AL.
172 cuts, each from a different beef carcass (yield grade 2.4-3.2) of prime, choice, or good quality grade, were selected from packing plants in either the north central or the southeastern sections of the United States. All these cuts were analyzed raw. All samples for Phase I were analyzed in duplicate; in Phase II each sample was analyzed only once.
Sample preparation. All cuts, raw and cooked, were dissected, following a detailed protocol developed by the USDA MSRL, into fatty tissue, bone plus connective tis- sue, and the lean plus marbling, referred to in this report as the separable lean and intended to approximate the edible portion of the cut freed of as much fat as possible. The separable lean of each cut was analyzed; fatty tissue was composited from several cuts because of the small amounts of fat derived from each cut. In Phase I representa- tive subsamples were prepared by cutting the separable lean into approximately 2- cm cubes, mixing by hand for 2 min, and then randomly distributing the cubes into seven lots. Four of these lots, randomly selected, were ground three times in a Hobart meat grinder with a force plate with 3/16-in. holes. After each grinding, the sample was thoroughly mixed by hand for exactly 2 min. After the last mixing, samples (ap- proximately 10 g) for extraction and determination of lipids were immediately weighed into tared screw-capped glass jars. A separate 2-g sample was taken for the determination of volatiles. Samples were stored at -60°C until analyzed.
The separable lean in Phase II was cut into chunks of 2.5-5.0 cm and homogenized in a 15-qt commercial food processor (Model Ri 5, Robot Coupe, U.S.A. Inc., Jack- son, MS) for 12 s at 1500 t-pm and then for 18 s at 3000 rpm. These times and speeds were selected to produce an acceptably homogeneous sample and a final temperature of not more than 30°C. Otherwise, the subsampling and analysis of the samples from Phase II were the same as those for Phase I. The food processor was also used to homogenize the cornposited samples of fatty tissue from Phase I.
Extraction. The lipid was extracted by the method of Folch et al. (1957) with a few modifications. The sample was transferred to a 200-ml stainless-steel Sorvall Omni-Mixer cup, mixed with 60 ml methanol and 120 ml chloroform4 and homoge- nized for 3 min at maximum speed (approx 16,000 rpm). The entire content of the cup was filtered into a 500-ml separatory funnel through Whatman No. 43 filtered paper with aspirator suction. The residue and the filter paper were returned to the Omni-Mixer and reextracted with 60 ml chloroform/methanol (2/l); this extract was also filtered into the separatory funnel. The cup and blades of the Omni-Mixer were washed with 4 X 15 ml chloroform/methanol, and the washings were also filtered. The combined extract was mixed with 55 ml 0.58% aqueous NaCl and shaken vigor- ously for 1 min. The lower phase was drained into a 200-ml volumetric flask and diluted to volume with methanol. (Small amounts of chloroform were lost by evapo- ration and by entrainment in the aqueous washes. Methanol was used to dilute to volume in order to keep the small amount of dissolved water in solution.) Separate aliquots of this extract were dispensed with a carefully calibrated Hamilton Model 100004 diluter/dispenser (Hamilton Co., Reno, NV) for the determination of total fat, fatty acids, and cholesterol.
Volatiles. Volatiles, principally moisture, were removed in a vacuum oven under 80 mm pressure for 3 h followed by 50 mm pressure overnight. Other details were as described by AOAC ( 1980) Method 7.003.
4 The extractant contained 0.0 1% each of BHA and BHT as an antioxidant.
LIPIDS IN BEEF 29
Total extractables. An aliquot (approx 40 ml) of the total extract was dispensed into 50-ml tared beakers, covered with cheesecloth, and allowed to air-dry in a fume hood for 24-36 h. The beakers were then placed in a gravity oven at 100°C for 1 h, cooled, and weighed. This last step was repeated until a constant weight was obtained.
Fatty acids. Fatty acids were determined by gas chromatography, essentially as described by Slover and Lanza ( 1979). Approximately 25 mg of the total lipid extract was mixed with the internal standard, methyl heneicosanoate, and methylated with BF3/CH30H. All Phase I samples were analyzed on 100 m X 25 mm glass capillary columns coated with SP2340. Phase II samples were analyzed on either 10 or 20 m x 0.25 mm glass capillary columns, also coated with SP2340. Reference standards of pure fatty acid triglycerides were mixed with the internal standard and methylated, and the methyl esters were chromatographed to obtain response factors for the fatty acids as the triglycerides. These fatty acid triglyceride response factors were entered into the calculation program of a microprocessor-controlled gas chromatograph (Hewlett-Packard Model 5840) for the automatic calculation of grams of individual fatty acid triglycerides per 100 g of wet tissue. Because the fatty acids in meats occur principally as triglycerides, it seemed appropriate to report the data in units of this most abundant form. The much smaller amounts of fatty acids in phospholipids and free acids are included in the triglyceride total. The data may be converted to other units as needed. For this paper, the data were recalculated as normalized weight per- cent of fatty acid triglycerides; i.e., the amounts of each fatty acid, in grams, were summed and each fatty acid was expressed as a percentage of that sum.
Cholesterol. Cholesterol was determined by gas chromatography as the trimethyl- silyl (TMS) ether, essentially as described for the determination of sterols by Slover et al. ( 1983). Aliquots of the chloroform/methanol total lipid extract, plus cholestane as an internal standard, were saponified, and the unsaponifiables were extracted and reacted with bis(trimethylsilyl)trifluoroacetamide (BSTFA) to form TMS ethers. Samples were chromatographed either on a 4.3 m X 3 mm glass column packed with 0.5% Apiezon L on loo-120 Gaschrom Q or on a 50 m X 0.25 mm glass capillary column wall-coated with Dexsil400 (Quadrex Corp., New Haven, CT). A reference standard containing cholesterol and the internal standard was also derivatized and chromatographed to permit the determination of correction factors for quantitative calculations.
Statistics. Statistical calculations were performed using the SUMMARY and CORR procedures of the SAS Institute, Inc. (Cary, NC).
RESULTS AND DISCUSSION
Throughout this discussion the data refer to the separable lean or the separable fat, as described above. No data were obtained for complete cuts, either raw or cooked. The compositions of the separable lean of all prime, choice, and good cuts, from both Phase I and Phase II studies, are summarized in Tables 1 a and 1 b. Complete data on the dissected cuts will be published elsewhere.
The fat content ranged from 3.2 to 14.6%. Higher amounts of fat were found in the blade roast, the rib steak, the rib roast, and the two brisket cuts, all located in the same area of the carcass (Fig. 1). Cuts of good grade contained the least fat, and in general prime cuts contained the most, although choice cuts of bottom round steak and tenderloin steak were slightly higher in fat. Cholesterol varied from a low of 49.9 to a high of 68.1 mg/ 100 g.
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32 SLOVER ET AL.
TABLE 2
REPRESENTATIVE FAI-IY ACID DATA: FATTY ACIDS OF A SINGLE RIB ROAST, RAW AND GXKED (CALCULATED AS TRIGLYCERIDE)
* The number before the colon gives the number of carbon atoms in the fatty acid molecule; the first number after the colon gives the number of double bonds. The number following the w gives the number of carbons following the double bond farthest from the carboxyl. cis and trans are designated c and t. I=ISO; AI=ANTJ?JSO.
The eight fatty acids listed in Table 1 b accounted for more than 90% of the total, but numerous other acids were present in smaller amounts (Table 2), and trace amounts of others were detectable when larger samples were chromatographed. Ole- ate and cis-vaccenate ( 18: 1 w9c and 18: 1 w7c) were not always separated and are given as the sum; the w7 isomer was typically 1 S-2% of total fatty acids.
The tram unsaturated octadecenoates (TRANS MONOENE in Table la) of the separable lean varied from 1.3 to 4.4%; fatty tissue contained higher amounts. The presence of small amounts of positional and geometric isomers of unsaturated fatty
LIPIDS IN BEEF 33
acids is characteristic of ruminants (Christie, 1981). The isomers of bovine peri- nephric fat were determined by Hay and Morrison (1973) who identified 10 tram 18: 1 isomers and 6 cis 18: 1 isomers.
Linoleic acid (18:206cc), the principal polyunsaturated fatty acid, varied from 1.6 to 5.3%. Small amounts of 18:2A9t, 12t and 18:2A9c, 12t were also found, typically in amounts less than 0.2%. Other octadecadienoic isomers have been reported in beef fat (Christie, 1981), but were not detected in these samples. Very small amounts of other polyunsaturates, including 22:603, were also present.
The fatty acid data in Tables 1 a and 1 b have been expressed as normalized weight percent to permit a comparison of the relative compositions of cuts. For nutritional purposes the absolute weights of the fatty acids are required. To calculate the grams of a specific fatty acid (as the triglyceride) in 100 g of a cut, as sampled, the normalized weight percent must be multiplied by the total grams of fatty acid triglyceride in 100 g, as given in Table lb. If the weight of a free acid is required, this may be obtained by multiplying the weight of triglyceride by the molecular weight of the acid and dividing by one-third the molecular weight of the triglyceride. The total weight of fatty acid triglyceride was found by summing the weights of the individual fatty acid triglycerides, determined by gas chromatography as described above.
Since most fatty acid data are published as normalized weight percent with no information on the total weight of fatty acids, the above calculation of the weight per unit weight of tissue cannot be made from such data. Weihrauch et al. (1977) pub- lished factors for estimating the total weight of fatty acids from the weight of fat pres- ent. From literature data on the amounts of the various lipid classes in beef, they estimated the ratio of fatty acids to fat in beef to be 0.92. In the present study the ratio of fatty acids to fat in the separable lean of raw cuts varied from 0.80 to 0.95, with a mean of 0.85 + 0.06; in the separable lean of cooked cuts the ratio varied from 0.80 to 0.93, with a mean of 0.87 f 0.06. To estimate the total weight of fatty acids, as the free acid, the percentage of fat is multiplied by the appropriate ratio. This estimate is at best a poor substitute for proper analytical data, but may be of use if no data are available.
Raw and Cooked Paired Cuts
The results from the analysis of paired cooked and raw cuts (Phase I) are summa- rized in Table 3. These data permit the estimation of the retentions of these nutrients, and a limited evaluation of their variations from cut to cut.
The percentage of fat in the separable lean of the cooked cuts was invariably higher than that of the paired raw cut, principally because of the loss of volatiles during cooking. However, even on a dry weight basis (calculation not shown), the separable lean of cooked cuts had a higher percentage of fat than the paired raw cuts. This may be explained as the result of the migration of fat from fatty tissue. Some of this migrat- ing fat, rendered fluid by the heat of cooking, went into the drip, and some infiltrated the adjacent lean tissue over which it flowed. The lean tissue, when dissected and analyzed as the separable lean, contained not only the original fat present in the raw cut, but also the fat that infiltrated it during cooking. The cut as a whole lost fat during cooking, but the percentage of fat in the separable lean increased.
The amount of fat that infiltrated the separable lean during cooking may be esti- mated from the fat and volatiles of the paired raw and cooked cuts, if it is assumed
34 SLOVER ET AL.
TABLE 3
BEEF CUTS, RAW AND COOKED (PHASE I)
cut Identity
Cooking N vo1ati1es Fat Cholesterol Total FA Method I 1; mg/1oog glloog tas
trialycecidej
Chuck arm pot-roast
Chuck blade roast
Brisket flat half boneless
Brisket point half boneless
Rib steak small end
Rib roast large end
Round tip roast, left
Round tip roast, right
Round top round steak
Round bottom round steak
Round eye round coast
Loin wedge bone sirloin steak
Lain tenderloin steak
Loin top loin (strip) steak
Fatty composite
raw braise
r*Y braise
raw braise
raw braise
raw broil
raw roast
raw broil
raw braise
raw roallt
raw broil
raw broil
rilv broil
rav braise
72.79f1.84 5.02f1.69 54.58t1.51 10.95r3.06
69.70?3.00 9.31t3.24 50.9.9t3.61 16.70t4.78
69.13f2.50 11.06f2.72 53.3623.44 16.81f4.31
72.4121.23 5.31t1.87 56.52t2.72 9.71t2.79
69.02t2.12 7.96t3.01 57.59f3.35 12.88t3.95
69.3723.81 10.04i3.85 55.87t3.33 15.23t4.33
73.4321.54 4.4321.57 61.91'1.53 8.13C2.35
73.OOt1.46 4.96f1.62 61.82f2.24 8.36f2.77
71.7421.25 4.3521.70 60.23t1.91 6.9622.50
71.51t2.11 5.81i1.73 56.69f4.36 10.94+3.10
71.8521.56 4.89f1.68 62.8Ot1.72 7.01f1.63
71.7421.44 5.09t1.69 57.32t2.87 9.6322.75
71.34f1.76 6.3492.02 59.19f2.40 10.47r2.77
69.17f2.45 6.66i3.21 59.24f3.32 10.28f4.17
20.21+3.32 70.89k4.97 18.5723.66 70.3225.14
58.5f5.2 100.5t4.4
4.3421.74 10.02f2.96
65.5t3.3 105.625.5
8.92f3.42 15.99f4.92
64.0f7.2 90.7t5.5
10.77f2.80 16.47f4.60
58.9f3.1 94.9f6.6
4.72t1.80 0.73t2.75
56.624.2 7.64t3.42 80.423.9 12.21t3.75
58.523.9 80.6?6.8
0.46t4.34 14.68t4.41
58.7k4.0 79.3f8.5
3.85t1.63 7.17t2.34
60.4t2.6 a3.4t7.0
4.26i1.58 7.28t2.45
56.0f5.0 84.224.0
3.62f1.71 5.89f2.11
57.0t4.4 95.7t12.4
5.21f1.62 9.27t3.36
52.3f3.8 69.4t9.2
4.28t1.73 6.3821.56
59.4t3.6 89.1t11.6
4.37?1.78 9.07t2.45
59.9t3.3 84.3t6.3
5.65t2.09 9.5at2.70
55.9t2.4 76.3t3.0
6.25f3.40 9.53t4.33
102.1t8.3 95.2r9.5
69.6825.43 67.53t5.00
that the paired cuts were similar in composition and that the amounts of nonfat solids (NFS), principally protein and ash, lost to the drip were negligible. Although some protein and ash were lost in the drip, the amounts were small. Toepfer et al. (1955) reported amounts of protein and ash in the drippings from roasted and broiled bone- less beef that totaled 0.44% (roasted) and 0.09% (broiled) of the initial weights of the raw cuts. Within the limitations of these assumption, the NFS of the raw meat do not change during cooking and may be used as an internal standard to evaluate changes in other fractions or nutrients.
The change in the amount of fat per gram of NFS as a result of cooking is equal to % Fat (cooked)/% NFS (cooked) - % Fat (raw)/% NFS (raw). If this difference is multiplied by % NFS (cooked), the percentage of fat that has infiltrated 100 g of cooked separable lean is obtained. This calculation has been made for all paired raw and cooked cuts (Table 4). It can be seen that infiltration contributed substantially to the fat present in the cooked separable lean, in amounts ranging from 0.75% in the eye round roast to 3.26% in the arm pot roast. The wide variation among and within cuts could be caused by variations in the amounts of subcutaneous and intermuscular fat, their location in the cut, and the spatial orientation of the cut during cooking.
True retentions (Murphy et al., 1975) were estimated on the basis of the assump- tions discussed above, i.e., that paired cuts from opposite sides of a carcass had similar
LIPIDS IN BEEF 35
TABLE 4
ESTIMATES OF FAT INFILTRATED INTO COOKED SEPARABLE LEAN OF BEEF CUTS
cut Identity
Fat infiltrated Cooking per 100 gms. of method edible cooked meat
Chuck arm pot-roast Chuck blade roast Brisket flat half boneless Brisket point half boneless Rib steak small end Rib roast large end Round tip roast, left Round tip roast, right Round top round steak Round bottom round steak Round eye round roast Loin wedge bone sirloin steak Loin tenderloin steak Loin top loin (strip) steak
compositions and that NFS were not lost during cooking. True retentions of fat in the separable lean were greater than 100% (Table 5) and varied from 112 to 144%. Although fat in the cut as a whole decreased with cooking because of drip loss, fat increased in the separable lean because of the infiltration of fat from adjacent fatty tissue that was removed by dissection after cooking. True retentions of cholesterol in the separable lean varied from 99 to 117%, and those of volatiles from 48 to 68%. The loss of volatiles during cooking was the principal cause of the percentage increase of fat and cholesterol in the separable lean of cooked cuts.
The distribution of cholesterol within the beef cut is of interest because of efforts to decrease dietary cholesterol. Cholesterol has sometimes been associated with fat (Sweeney and Weihrauch, 1977) and diets low in meat fats have been recommended. Correlations of cholesterol, fat, NFS, and volatiles in the separable lean of raw and
TABLE 5
TRUE RETENTIONS OF FAT, VOLATILES, AND CHOLESTEROL IN COOKED SEPARABLE LEAN OF BEEF CUTS
cut Identity
Cooking Method Fat
True Retention
Volatiles Cholesterol
Chuck arm pot-roast Chuck blade roast Brisket flat half boneless Brisket point half boneless Rib steak small end Rib roast large end Round tip roast, left Round tip roast, right Round top round steak Round bottom round steak Round eye round roast Loin wedge bone sirloin steak Loin tenderloin steak Loin top loin (strip) steak
cooked beef (Phase I) are given in Table 6. Cholesterol in raw separable lean was positively correlated with fat (r = 0.58) and negatively correlated with NFS (r = -0.53) on a wet weight basis; on a dry weight basis cholesterol was not strongly correlated with either fat or NFS, although the correlation with fat was negative and that with NFS was positive. These correlations suggest that amounts of cholesterol in raw beef were not dependent on fat, but that both fat and cholesterol varied with the amount of volatiles. In the paired wet cooked cuts, cholesterol was positively corre- lated not only with fat (r = 0.34) but also with NFS (r = 0.42); the correlation of cholesterol with volatiles was negative (r = -0.64). In beef as eaten, cholesterol vari- ability was therefore related more to volatiles than to either fat or NFS, as it was in raw beef. On a dry weight basis cholesterol was negatively correlated with fat (-0.32) and positively correlated with NFS (0.32), suggesting that in the absence of the effects of volatiles cholesterol was related to the NFS, or protein, part of the meat. These results are similar to those reported by Rhee et al. (1982a), who found that in beef longissimus muscle steaks the cholesterol was positively correlated with lipid content in wet raw steaks (r = 0.39) and negatively correlated with lipid content in dry raw steaks (r = -0.35). The same authors (Rhee et al., 1982b) found that in beef rib steaks with five different levels of marbling cholesterol was positively correlated (Y = 0.93) with lipid on a wet weight basis, a degree of correlation greater than that re- ported here.
This report has briefly summarized the lipid data derived from the analysis of beef cuts representative of those available to U.S. consumers. Fat in the dissectable tissue varied widely from cut to cut, was generally highest in prime cuts, and decreased with decreasing grade. The relative amounts of fatty acids were similar in all cuts and grades, suggesting the validity of using a median value to describe beef cuts in general. Cholesterol in the dissectable lean varied little, but was considerably higher in the
LIPIDS IN BEEF 37
dissectable fat, although no correlation with nonfat solids (protein) was found. More complete information on the results of this study may be obtained from the United States Department of Agriculture, Nutrient Composition Laboratory, Beltsville, Maryland.
ACKNOWLEDGMENT
This work was partly supported by funds from the National Institutes of Health, National Heart, Lung and Blood Institute, Bethesda, Maryland, under Interagency Cooperative Agreement 2Y0 1 HV6004 109.
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