TEXAS AGRICULTURAL EXPERIMENT STATION R. D. LEWIS. Director. College Station. Texas Bullelia 70s The Composition of Meat and Some Other Foods T. Arginine, Histidine, lsoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophcm and Valine DEPARTMENT OF BIOCHEMISTRY AND NUTRITION i L! BRARY Agricultura:Edfechanécal Gellegeafiexas away r949 . i Gsléage Stamn, Texas The TEXAS AGRICULTURAL AND MECHANICAL COLLEGE SYSTEM GIBB GILCHRIST. Chancellor [Blank Page in Original Bulletin] Preface It is well known that the requirement for protein in human and in animal nutrition is essentially a composite requirement for each of a number of different kinds of amino acids. Meat is primarily a protein food and as such it represents one of the most concentrated sources of amino acid we have in the aver- age diet. The 1o amino acids studied in this investigation were chosen on the basis of their established importance in nutrition. They are arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.’ The list includes all of those which have been proved to be essential for humans. The data reported here show the amino acid contents of different kinds of tissues from beef, pork and lamb as well as the variations which occur in samples of ‘the same kind of meat taken from different animals. Tables showing the amino acid contents of a variety of other foods are also given. All amino acid determinations were carried out by microbiological assay procedures developed in the authors’ lab- oratory. This bulletin is number 1 of a series. Studies on other amino acid contents of meat will be reported in number 2. The amino acid composition of cottonseed, peanut and soybean products is given in Texas Station Bulletin 692. CONTENTS Page Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5 Procedures for the Preparation and Analysis of Samples . . . . . . . . . . . . .. 5 Preparation of Meat Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5 Preparation of Other Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7 Determination of Amino Acids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Protein Content of Meat, Table 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Amino Acid Content of Meat, Tables 2-11 . . . . . . . . . . . . . . . . . . . ..1o-19 Amino Acid Content of Other Foods, Tables 12-14 . . . . . . . . . . ..21-23 Literature Values for the Amino Acid Content of Meat, Tables 15-18 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..25-28 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 29 Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 29 Literature Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 30 P21-149-5M-L1B0 BULLETIN 708 JANUARY 1949 The Amino Acid Composition of Meat and Some Other Foods l. Arginine, Histidine, lsoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophon and Valine CARL M. LYMAN and K. A. KUIKEN Department of Biochemistry and Nutrition HE problem of the amino acid content of foods has been one of long standing‘. For example, 4o years ago Osborne and jones published data on the arginine, histidine and lysine content of beef muscle protein, but it was not until a number of years later that we had any information concerning the content of a single other amino acid in meat. Many of the earlier chemical methods were adequate for the determination of some of the amino acids in purified proteins but were much less satisfactory when applied to food materials con- taining carbohydrates and other substances. Again, chemical meth- ods based on isolation procedures were frequently so laborious as to make them impractical for studies dealing with large numbers of samples. Procedures for the Preparation and Analysis of Samples Comprehensive investigations on the amino acid composition of foods as such, instead of on purified, proteins from foods, have been made practical by the development of microbiological assay proce- dures during‘ the last few years. This bulletin gives the results of such a study on meat and a variety of other foods. Preparation of Meat Samples. The different cuts of meat which consisted primarily of muscle tissue were obtained at the College Meats Laboratory at the time the carcasses were cut up. This was usually after 4 to 7 days in cold storage. The various organs were obtained within 2 or '3 hours after the animals were killed. Some kinds of meat, such as liver, tend to lose moisture if kept in cold storage very long. The precau- tions taken served to prevent variations in the samples due to this 6 BULLETIN 708, TEXAS AGRICULTURAL EXPERIMENT STATION cause. Records of the animals were kept t0 be certain that all the different samples of the same kind of meat came from different animals. Superficial fat and large pieces of gristle were discarded in the preparation of the samples for analyses. The meats were ground first with a food chopper and then with a Latapie grinder. Care was taken so that none of the juice was squeezed out and lost. Samples were taken immediately for nitrogen determinations and the bal- ance of the material was dehydrated from the frozen state. The special equipment used for this purpose has been previously described (I). The dried material, which was porous and crisp, was ground in a mortar and then extracted with anhydrous ethyl ether. Samples which did not powder well on the first grinding were reground after the ether extraction. Nitrogen determinations were made on the dried powder and on the extracted fat. In most instances, the equivalence of the dried powder in terms of fresh meat was calcu- lated from the nitrogen content of the fresh material and the dried powder. In a few cases, the nitrogen in the fat amounted to as much as I percent of the total nitrogen. When this was the case, the nitrogen content of the extracted fat was taken into consideration in making the calculations. This is necessary even though the nitrogen lost in the extracted fat does not represent true protein. A typical example is: A sample of beef brain contained 10.75 per- cent crude protein. The dried sample contained 33.76 percent fat and the extracted fat contained 0.98 percent nitrogen. The dry fat- free sample contained 73.25 percent protein. The figure to be added to the crude protein content of the dry fat free sample for the pur- pose of calculating the equivalence value may be obtained from the following equation: % fat in dry sample 33.76 -——-——————- (% Nin m) (6.2s) : g (0.9s) (0.2s) = 3.12 (100—% fat in dry sample) a 100-3336 The equivalence of the dry fat free sample in terms of fresh tissue is therefore: 73.25 + 3.12 i 10.75 Corrections for the nitrogen lost in the fat were made for the fol- lowing kinds of tissues: beef brain and liver; pork liver, kidney and heart; lamb liver, kidney and heart. Hydrolysis of the samples in preparation for the determination of all of the amino acids except tryptophan was carried out by '» ' *7 "mwww. .. . . THE AMINO ACID COMPOSITION OF MEAT AND SOME OTHER FOODS 7 refluxing o. 5-gm. samples with IOO ml. of 6N hydrochloric acid for 24 hours. Most of the hydrochloric acid was distilled off on the water bath at reduced pressure. Water Was added and the solution neutralized and diluted to a convenient volume. Hydrolysis of the samples for the determination of tryptophan was carried out with sodium hydroxide in the presence of cysteine which protects trpytophan from destruction by oxidative reactions. The procedure was: IOO mg. of L-cysteine were added to I6 ml. of 4Nsodium hydroxide in a Ioo-ml. pyrex beaker. A larger beaker was used as a cover. The solution was autoclaved at I 5 pounds pressure for about 1 hour. While hot, another IOO mg. of cysteine was added along with 0.5 mg. of sample to be hydrolyzed. Auto- claving was continued for I6 hours, then the samples were cooled, neutralized and diluted to a convenient volume. Preparation of Other Samples. Grains and other solid materials of relatively low moisture con- tent were ground to a powder in a small hammer mill, and then hydrolyzed as described for the meat samples. Vegetables and other foods of high moisture content, which were not dehydrated, were blended in a Waring Blendor with a measured volume of water. For example, 4o gm. of Irish potato were blended with 36o ml. of water. One hundred ml. of the blended preparation were then equiv- alent to IO gm. of potato. Aliquots were taken for nitrogen and amino acid determinations. For the preparation of the acid hydroly- sates, equal volumes of the blended mixture and I2N hydrochloric acid were mixed to give a final concentration of 6N hydrochloric acid. The rest of the procedure was the same as that described for the meat samples. Aliquots for the determination of tryptophan were evaporated in 25o ml. beakers so that the solid material (ap- proximately 0.5 gm.) formed a thin layer on the bottom of the beaker. Hydrolysis with sodium hydroxide in the presence of cysteine was carried out as described for the meat samples. In the preparation of the vegetables, 8 or 1o times the amount of material needed for the determinations was cut into small pieces and representative samples taken from this. The fat was extracted from the cheese before preparing the hydrolysates. Determination of Amino Acids. Valine, leucine and isoleucine were determined with Lactobacillus ambinosus 17-5 as ‘described by Kuiken, at al. (2), with the modi- fications that the tomato juice eluate was omitted from the medium 8 BULLETIN 708, TEXAS AGRICULTURAL EXPERIMENT STATION and pyridoxamine wa.s added. L amino acid standards were used for the determination of both leucine and isoleucine. SWPjJfOCOCCZIS faecalis (American Type Culture Collection No. 8043) was used for the determination of histidine a.nd threonine, as described by Lyman, at al. Leuconostoc mesenteroides P-60 was used to determine methionine (Lyman, elf al. (1)), arginine, lysine and phenylalanine. T ryptophan was determined with Streptococcus fae- azlis as the test organism, according to the method of Kuiken, elf wl. Results and Discussion There are several ways in which the amino acid composition of foods ca.n be expressed. The first and simplest of these is to express the results as percentage of the material analyzed. Data in this form do not give us any information concerning the amino acid composition of the protein contained in the sample. For example, the lysine content of the protein in pumpkin is above the average for vegetable foods, yet the percentage of lysine in pumpkin is extremely low simply because there is very little protein in pumpkins. It is then desirable for certain purposes to express amino acid data insome way which indicates the relationship to the total protein of the sample. This is frequently done by calculating the amino acid content to a constant nitrogen basis (usually 16 percent nitrogen). This procedure is equivalent to calculating the amino acid content of the crude protein contained in the samples. Objections have been raised to this way of expressing amino acid data on the theoretical basis that very few proteins contain exactly 16 percent nitrogen. It is, however, impractical when compiling amino acid data to use a different factor for each food studied. The better procedure ap- pears to be to assume that most proteins contain 16 percent nitrogen, and to recognize that this is somewhat of an approximation. The values given in this report are expressed both as percentage of the original sample and as percentage of the crude protein. The average crude protein content of the different kinds of meat studied in this investigation is given in Table 1. The amino acid contents of different kinds of meat from beef, pork and lamb, representing a variety of different types of tissue, are given in Tables 2 to 4. With few exceptions, the amino acid content of samples of the same kind of meat taken from three dif- ferent animals were very nearly alike. It is also of interest that the amino acid content of the same kind of tissue from beef, pork and lamb were for all practical purposes identical. In connection with this finding, attention is called to the fact that in the preparation THE AMINO ACID COMPOSITION OF MEAT AND SOME OTHER FOODS TABLE 1. PROTEIN CONTENT OF FRESH MEAT Average values for samples from three or four dilferent animals 9 Kind of meat Crude protein Kind of meat Crude protein (Nx6.25) (Nx6.25) Percent Percent Beef loin . . . . . . . . . . . . 21.65 Lamb heart . . . . . . . . . 16.35 Beef brisket . . . . . . . . . 20.48 Beef kidney. . . . . . . . 17.76 Beef round . . . . . . . . . . 20.96 Pork kidney . . . . . . . . 15.53 Porkloin........... 20.53 Lambkidney....... 15.44 Lamb chop. . .. . . . . .. 19.67 Beef tongue . . . . . . . .. 17.13 ‘ Beef liver . . . . . . . . . . . 18.40 Pork tongue. . . . . . . . 15.91 Pork liver . . . . . . . . . . . 19.48 Beef brain . . . . . . . . . . 10.65 Lamb liver . . . . . . . . . . 21.24 Beef thymus . . . . . . . . 15.93 Beef heart. . . . . . . . .. 17.74 Beef spleen . . . . . . . .. 18.42 Pork heart . . . . . . . . . . 16.94 of the samples ‘superficial fat was discarded. Although a piece of lean pork is equivalent to a piece of lean beef with respect to amino acid content, a piece of meat which contains a high percentage of fat is certainly lower in the amount of essential amino acids which it contains. The data show one notable exception to the constancy of compo— sition of the same kind of tissue from beef, pork and lamb. This is in the case of the histidine content of muscle tissue. It will be noted that the low for the histidine content of the crude protein in lamb chops was 3.08 percent, while the protein in one sample of beef brisket contained 4.19 percent histidine. This is a difference of about 36 percent. Differences of this order of magnitude were not a. found with any other amino acid. The variations in the histidine content of muscle tissue are due to the presence of substantial amounts of derivatives of histidine which are not part of the true protein of the tissue. These histidine derivatives are carnosine, a peptide of beta alanine and histidine, and anserine, a peptide of beta alanine and methylhistidine. A study of the relationship of these compounds to the histidine content of meat has been reported by Lyman, Kuiken and Hale (3). As much as one-third of the total histidine content of beef loin, or other beef muscle tissue, may be in the form of carnosine. The work of Fuller, at al. (5) indicates that the carnosine content of muscle tissue may vary with the histidine content of the ration. It is of interest to note that the cheaper cuts of meat such as, for example, beef brisket, are equally as rich in essential amino acids as the more expensive loin cuts. 10 BULLETIN 708, TEXAS AGRICULTURAL EXPERIMENT STATION TABLE 2. ARGININE CONTENT OF MEAT Samples of each kind of meat were taken from three 0r four different animals Arginine in Arginine in protein fresh tissue Kind of meat Min. * Max. * Average Average Percent Percent Percent Percent Beef loin . . . . . . . . . . .. 6.09 6.44 6.22 1.35 Beef brisket . . . . . . . . . 6.10 6.87 6.50 1.33 Beef round . . . . . . . . . . 6.00 6.14 6.07 1.27 Pork loin . . . . . . . . . .. 6.28 6. 55 6.41 1.32 Lamb chop . . . . . . . . .. 6.03 6.36 6.19 1.22 Beef liver . . . . . . . . . .. 5.68 6.09 5.85 1.06 Pork liver . . . . . . . . . .. 5.93 6.35 6.11 1.17 Lamb liver . . . . . . . . .. 5.90 6.09 5.96 1.25 Beef heart . . . . . . . . .. 6.26 6.66 6.41 1.15 Pork heart . . . . . . . . . . 6.60 6.88 6.71 1.12 Lamb heart . . . . . . . . . 6.23 6.50 6.38 1.03 Beef kidney . . . . . . . . . 6.06 6.09 6.08 1.08 Porkkidney......... 6.24 6.51 6.38 0.98 Lamb kidney . . . . . . . . 5.94 6.25 6.09 0.92 Beef tongue . . . . . . . .. 6.12 6.93 6. 50 1.11 Pork tongue . . . . . . . . . 6.46 6.68 6. 58 1.05 Beef brain . . . . . . . . . .. 5.84 6.18 6.04 0.62 Beef thymus . . . . . . . . . 6. 50 6.80 6.60 1 . 05 Beef spleen . . . . . . . . .. 5.98 6.37 6.12 1 . 12 *Min. and max. refer to samples from different animals. THE AMINO ACID COMPOSITION OF MEAT AND SOME OTHER FOODS 11 TABLE 3. HISTIDINE CONTENT OF MEAT Histidine in Histidine in N0. of crude protein fresh tissue Kind of meat samplesT Min.* Max.* Ave. Average Percent Percent Percent Percent Beef loin . . . . . . . . . . . . . .. 10 3. 55 3.98 3.74 0.81 Beefbrisket............ 3 3.98 4.19 4.10 0.84 Beef round . . . . . . . . . . . .. 2 3.62 3.73 3.68 0.77 Pork loin . . . . . . . . . . . . . .. 8 3.43 4.36 3.76 0.77 Lamb chop . . . . . .; . . . . .. 7 3.08 3.33 3.14 0.63 Beef liver . . . . . . . . . . . . . .. 4 2.46 2.78 2.64 0.50 Pork liver . . . . . . . . . . . . . . 3 2. 74 2.88 2 . 79 0. 54 Lamb liver . . . . . . . . . . . .. 3 2.70 2.76 2.72 0.58 Beef heart . . . . . . . . . . . . .. 7 2.45 2.73 2.59 0.46 Porkheart.............. 3 2.55 2.74 2.60 0.44 Lamb heart . . . . . . . . . . . . . 3 2.59 2.62 2.61 0.43 Beef kidney . . . . . . . . . . .. 6 2.37 2.76 2.56 0.45 Pork kidney . . . . . . . . . . . . 3 2.56 2.61 2. 58 0.40 Lamb kidney . . . . . . . . . . . 3 2.57 2.66 2.61 0.41 Beeftongue............. 3 2.47 2.69 2.57 0.44 Pork tongue . . . . . . . 3 2.74 2.79 2.76 0.44 Beef brain . . . . . . . . . . . . .. s 2.56 2.70 2.65 0.28 Beef thymus . . . . . . . . . . .. 3 1.71 1.83 1.76 - 0.28 Beef spleen . . . . . . . . . . . . . 2 2.46 2.66 2. 55 0.47 ‘(Each sample from a different animal. *M1n. and max. refer to samples from different animals. 12 BULLETIN 708, TEXAS AGRICULTURAL EXPERIMENT STATION TABLE 4. ISOLEUCINE CONTENT OF MEAT Samples of each kind of meat were taken from three or four different animals Isoleucine in Isoleucine in protein fresh tissue Kind of meat Min.* Max.* Ave. Ave. Percent Percent Percent Percent Beef loin . . . . . . . . . . .. 5.09 5.27 5.20 1.13 Beef brisket . . . . . . . . . 4.85 5.05 4.97 1.02 Beef round . . . . . . . . .. 5.15 5.20 5.18 1.08 Pork10in........... 5.03 5.22 5.11 1.05 Lamb chop . . . . . . . . .. 4.77 4.88 4.81 0.94 Beef liver . . . . . . . . . .. 4.65 4.81 4.73 0.86 Pork liver . . . . . . . . . . . 5.14 5.28 5.22 1.03 Lamb liver . . . . . . . . . . 4.39 4.48 4.45 0.92 Beefheart.......... 4.73 4.95 4.81 0.85 Pork heart . . . . . . . . . . 4.79 4. 98 4.86 0.81 Lamb heart . . . . . . . .. 4.48 4.81 4.68 0.76 Beef kidney . . . . . . . . . 4.33 4. 57 4.47 0.80 ' Pork kidney . . . . . . . .. 4.70 4.76 4.72 0.73 Lamb kidney . . . . . . . . 4.45 4.80 4.63 0.70 Beef tongue . . . . . . . . . 4.72 5.04 4.87 0.83 Pork tongue . . . . . . . . . 5.00 5.06 5.03 0.80 Beefbrain.......... 4.41 4.59 4.48 0.45 Beefthymus......... 3.35 3.47 3.42 0.56 Beef spleen . . . . . . . . . . 3.69 3.90 3.78 0. 69 *Min. and max. refer to samples from different animals. THE AMINO ACID COMPOSITION OF MEAT AND SOME OTHER FOODS TABLE 5. LEUCINE CONTENT OF MEAT 13 Samples of each kind 0f meat were taken from three or four dilferent animals Leucine in Leucine in protein fresh tissue Kind of meat Min.* Max.* Ave. Ave. Percent Percent Percent Percent Beef loin . . . . . . . . . . .. 8.37 8.94 8.60 1.86 Beef brisket . . . . . . . . . 8.42 8.91 8.61 1.76 Beefround........_.. 8.81 9.10 8.89 1.88 Porkloin........... 8.37 8.77 8.62 1.77 Lamb chop . . . . . . . . . . 8.44 8 56 8.51 1.66 Beef liver . . . . . . . . . .. 9.20 9.70 9.44 1.74 Pork liver . . . . . . . . . .. 9.29 10.13 9. 57 1.87 Lamb liver . . . . . . . . .. 8.72 9.43 9.01 1.91 Beef heart . . . . . . . . .. 9.25 9.38 9.19 1.63 Pork heart . . . . . . . . . . 8.87 9.10 9.07 1.52 Lamb heart . . . . . . . .. 8.78 8.93 8.87 1.45 Beef kidney . . . . . . . . . 8.61 9.06 8.90 1.58 Pork kidney . . . . . . . . . 8.49 8.68 8. 59 1.33 Lamb kidney . . . . . . . . 8.35 8.97 8.65 1.34 Beef tongue . . . . . . . . . 8.04 8.97 8.51 1.50 Pork tongue . . . . . . . .. 8. 53 8.92 8.75 1.39 Beef brain . . . . . . . . . . . 8.45 8.56 8. 51 0.91 Beef.thymus........ 6.56 6.79 6.68 1.06 Beef spleen . . . . . . . . . . 9.14 9.39 9.29 1.71 *Min. and max. refer to samples from diiferent animals. 14 BULLETIN 708, TEXAS AGRICULTURAL EXPERIMENT STATION TABLE 6. LYSINE CONTENT OF MEAT Samples of each kind of meat were taken from three or four different animals _ _ Lysine in Lysine in proteln fresh tissue Kind of meat Min.* Max.* Ave. Ave. Percent Percent Percent Percent Beef loin . . . . . . . . . . .. 8.90 9.24 9.07 1.96 Beef brisket . . . . . . . . . 8.58 8.95 8.79 1.80 Beef round . . . . . . . . .. 9.16 9.28 9.22 1.94 Pork 10in . . . . . . . . . . .. 8.49 9.04 8.69 1.79 Lamb chop.......... 8.45 9.24 8.75 1.75 Beef liver . . . . . . . . . . . 7.22 .68 7.44 1.35 Pork liver . . . . . . . . . .. 7.01 7.22 , 7.13 1.37 Lamb liver . . . . . . . . .. 7.10 7. 51 7.32 1.51 Beef heart . . . . . . . . . . 8.27 8.39 8.32 1.49 Pork heart . . . . . . . . . . 8.08 8.38 8.23 1.38 Lamb heart . . . . . . . .. 7.95 8.22 8.08 1.30 Beef kidney . . . . . . . . . 7.17 7.45 7.32 1.30 Porkkidney......... 6.53 7.02 6.82 1.04 Lamb kidney . . . . . . . . 6.93 7.33 7.19 1.08 Beef tongue . . . . . . . . . 8.43 8.90 8. 65 1.48 Porkt0ngue......... 8.52 8.73 8.59 1.37 Beefibrain . . . . . . . . . . 6 . e4 s. 92 e . 74 o. e9 Beef thymus . . . . . . . . 8.08 8. 62 8.32 1.33 Beef spleen . . . . . . . . . . 7.41 7.78 7. 58 1.39 *Min. and max. refer to samples from different animals. THE AMINO ACID COMPOSITION OF MEAT AND SOME OTHER FOODS 15 TABLE 7. METHIONINE CONTENT OF MEAT Samples 0f each kind of meat were taken from three or four dilferent animals r Methionine in Methionine in protein fresh tissue g Kind of meat Min.* Max.* Ave. Ave. E Percent Percent Percent Percent i 4* Beef loin . . . . . . . . . . .. 2.42 2.57 2.47 0.54 E Beef brisket . . . . . . . . . 2 .42 2. 5s 2 .47 o. 51 E Beef round . . . . . . . . . . 2. 50 2. 50 2. 50 0 . 52 E Porkloin........... 2.42 2.49 2.44 0.50 E Lamb chop....~ . . . . .. 2.36 2.47 2.42 0.48 i Beef liver . . . . . . . . . . . 2.22 2.24 2.23 0.41 . Pork liver . . . . . . . . . .. 2.10 2.22 2.18 0.42 Lamb livr . . . . . . . . .. 1.97 2.16 2.07 0.43 Beefheart.......... 2.32 2.41 2.38 0.42 i Pork heart . . . . . . . . . . 2.32 2.42 2.36 0.40 Lamb heart . . . . . . . .. 2.18 2.20 2.19 0.36 Beef kidney . . . . . . . . . 2.06 2.14 2.09 0.37 Pork kidney . . . . . . . . . 2.10 2.12 2.11 0.32 Lamb kidney . . . . . . . . 1.98 2.02 1.99 0.31 Beef tongue . . . . . . . .. 2.17 2.37 2.26 0.39 Pork tongue . . . . . . . . . 2.33 2. 50 2.41 0.38 Beef brain . . . . . . . . .. ' 2.08 2.11 2.10 0.21 Beefthymus........ 1.38 1.41 1.40 0.22 Beef spleen . . . . . . . . .. 1.91 1.94 1.93 0.36 *Min. and max. refer to samples from different animals. 16 BULLETIN 708, TEXAS AGRICULTURAL EXPERIMENT STATION TABLE 8. PHENYLALANINE CONTENT OF MEAT Samples of each kindi of meat were taken from three or four diiferent animals Phe~ylalanine in Phenylalanine in protein fresh tissue Kind of meat Min.* Max.* Ave. Ave. Percent Percent Percent Percent Beef 10mm“: . . . . . . 4.00 4.43 4 2s 0.91 Beef brisket . . . . . . . . . .. 4.12 4.27 4.19 0.86 Beef round . . . . . . . . . . .. 4.34 4.35 4.34 0.92 Pork loin . . . . . . . . . . . .. 4.09 4.29 4.20 0.86 Lamb chop . . . . . . . . . . . . 4.26 4.39 4.33 0.85 Beef liver . . . . . . . . . . . .. 4.91 5. 65 5.22 0.95 Pork liver . . . . . . . . . . . .. 5.23 5.68 5.43 1.05 Lamb liver . . . . . . . . . . .. 5.47 5.66 5.58 1.15 Beef heart . . . . . . . . . . . . . 4.39 4.73 4.49 0.80 Pork heart . . . . . . . . . . .. 4.24 4.72 4.44 0.75 Lamb heart . . . . . . . . . .. 4.80 4.82 4.81 0.78 Beef kidney . . . . . . . . . . . 4.88 5.07 4.96 0.88 Pork kidney . . . . . . . . . . . 4. 58 4.65 4.62 0.71 Lamb kidney . . . . . . . . .. 4.65 5.02 4.88 0.75 Beef tongue . . . . . . . . . .. 4.08 4.41 4.22 0.72 Pork tongue . . . . . . . . . .. 4.56 4.71 a 4.61 0.73 Beef brain . . . . . . . . . . . . 5.34 5. 53 5.44 0. 55 Beef thymus . . . . . . . . . . 2.71 2.98 2.87 0.46 Beef spleen . . . . . . . . . . .. 4.31 4. 58 4.43 a 0.82 *Min. and max. refer to samples from different animals. 4.1. M. . ..._‘.¢._1m.z..... THE AMINO ACID COMPOSITION OF MEAT AND SOME OTHER FOODS 17 TABLE 9. THREONINE CONTENT OF MEAT Samples of each kind 0f meat were taken from three or four difierent animals Threonine in Threonine in protein fresh tissue Kind of meat Min.* Max.* Ave. Ave. Percent Percent Percent Percent Beef loin . . . . . . . . . . .. 4.41 4.54 4.50 0.97 Beef brisket . . . . . . . . . 4.40 4.55 4.46 0.92 Beef round . . . . . . . . .. 4. 51 4. 58 4. 55 0.95 Pork loin . . . . . . . . . .. 4.38 4. 56 4.48 0.92 Lamb chop . . . . . . . . .. 4.64 4.90 4.75 0.93 Beef liver . . . . . . . . . .. 4.21 4.42 4.32 0.78 Pork liver . . . . . . . . . . . 4.39 4.45 4.42 0.89 Lamb liver . . . . . . . . . . 4. 50 4.65 4. 58 0.96 Beef heart . . . . . . . . .. 4.39 4.74 4. 50 0.80 Pork heart . . . . . . . . .. 4.53 4.71 4.63 0.77 Lamb heart . . . . . . . .. 4.60 4.72 4.66 0.75 Beef kidney . . . . . . . . . 4.48 4. 53 4. 50 0.80 Pork kidney......... 4.37 4.41 4.39 0.67 Lamb kidney . . . . . . .. 4.56 4.67 4.61 0.70 Beef tongue.‘ . . . . . . .. 4.27 4. 69 4.43 0.76 Pork tongue . . . . . . . .. 4.62 4.78 4.68 0.75 Beef brain . . . . . . . . . . 4. 56 4.88 4.68 0.48 Beefthymus........ 3.55 3.71 3.63 0.58 Beef spleen . . . . . . . . .. 4.04 4.22 4.15 0.76 *Min. and max. refer to samples from different animals. 18 BULLETIN 708, TEXAS AGRICULTURAL EXPERIMENT STATION TABLE 10. TRYPTOPHAN CONTENT OF MEAT Samples of each kind of meat were taken from three or four dilferent animals _ Tryptophan in Tryptophan 1n protein fresh tissue Kind of meat Min.* Max.* Ave. Ave. Percent Percent Percent Percent Beef loin . . . . . . . . .. 1.16 1.22 1.19 0.26 Beef brisket . . . . . .. 1.14 1.16 1.15 0.24 Beef round . . . . . . . . 1.20 1.22 1.21 0.26 Pork 10in . . . . . . . .. 1.07 1.21 1.15 0.24 Lambch0p........ 1.14 1.18 1.16 0.23 Beef liver . . . . . . . . . 1.47 1.54 1.50 0.27 Pork liver . . . . . . . . . 1.42 1.54 1.47 0.28 Lamb liver . . . . . . . . 1 . 39 1.46 1.42 0.30 Beefheart........ 1.20 1.31 1.26 0.22 Pork heart . . . . . . .. 1.24 1.28 1.26 0.21 Lamb heart . . . . . .. 1.19 1.24 1.21 0.20 Beef kidney . . . . . . . 1.32 1.43 1.39 0.25 Pork kidney . . . . . . . 1.41 1.42 1.41 0.22 Lamb kidney . . . . . . 1.34 1.51 1.41 0.22 Beef tongue . . . . . .. 1.05 1.16 1.10 0.19 Pork tongue . . . . . .. 1.14 1.17 1 . 16 0.19 Beefbrain........ 1.29 1.42 1.36 0.14 Beef thymus...... 0.72 0.73 0.72 0.11 Beef spleen . . . . . . . 1.12 I 1.21 f 1.17 0.22 *Min. and max. refer to samples from diflerent animals. .1. THE AMINO ACID COMPOSITION OF MEAT AND SOME OTHER FOODS TABLE 11. VALINE CONTENT OF MEAT 19 Samples 0f each kind 0f meat were taken from three 0r four dilferent animals Kind of meat Valine in protein Valine in fresh tissue Min.* Max.* Ave. Ave. Percent Percent Percent Percent Beef loin . . . . . . . . . . .. 5.15 5.44 5.29 1.15 Beef brisket . . . . . . . . . 5.12 5.42 5.27 1.07 Beef round . . . . . . . . .. 5.43 5.54 5.49 1.15 Porkl0in........... 5.44 5.52 5.47 1.12 Lamb chop.......... 5.30 5.54 5.40 1.06 Beef liver . . . . . . . . . .. 6.30 6.63 6.46 1.17 Pork liver . . . . . . . . . .. 6.37 6. 51 6.42 1.29 Lamb liver . . . . . . . . . . 6.42 6.62 6.49 1.36 Beefheart.......... 5.35 5.41 5.38 0.95 Pork heart . . . . . . . . . . 5. 52 5.80 5. 67 0.95 Lamb heart . . . . . . . . . 5.40 5. 50 5.44 0.88 Beef kidney . . . . . . . . . 5.84 6.13 5.96 1.06 Pork kidney . . . . . . . . . 5.92 5.99 5.96 0.91 Lamb kidney . . . . . . . . 5.89 6.12 6.04 0.92 Beef tongue . . . . . . . . . 5.08 5. 51 5.28 0.90 Pork tongue . . . . . . . . . 5. 52 5.81 5.62 0.89 Beefbrain.......... 5.50 5.53 5.52 0.56 Beefthymus...... 4.32 4.35 4.34 0.69 Beef spleen . . . . . . . . . . 5.74 6.33 5.96 1.10 *Min. and max. refer to samples from different animals. 20 BULLETIN 708, TEXAS AGRICULTURAL EXPERIMENT STATION The amino acid composition of a variety of different foods is given in Tables 12 t0 I4. Since the same microbiological assay procedures were used for the studies on meat and the other foods, the results are directly comparable. The data on the other foods are less com- prehensive in that the variations which are to be expected in different samples of the same kind of food were not evaluated. The greatest variations probably occur in the case of some of the vegetables which are likely to fluctuate in their total protein content as a result of the conditions under which they were grown. While this limitation should be recognized, the data given in Tables I2 to 14 do indicate the general level of amino acids to be expected in different kinds of foods and provide a basis for comparison. The accumulated findings of various investigators who have studied the nutritive value of proteins tend to focus attention on the ' importance of lysine, methionine and tryptophan. This is not be- cause the essential nature of these three amino acids is any more real than is the case with several other amino acids, but rather be- cause a deficiency of lysine, methionine or tryptophan is more likely to occur in natural food materials. Among the foods studied in this investigation, the protein of milk, eggs, meat, cheese and corn rank high in their methionine content. In view of the report of Mitchell and Block (6), which indicates that the limiting amino acid in beef muscle and kidney is methionine plus cystine, this statement needs some explanation. It is true that the protein of whole egg contains substantially more methionine than is found in meat proteins. Among all of the 3o foods studied in the present investigation, no other product was found which had as high a percentage of methionine in the protein as that found in eggs. The protein of 25 of the 30 foods studied contained less methionine than that found in beef, pork and lamb muscle tissue. On the basis of pound for pound of fresh food, meat is an outstanding source of methionine. Examination of the data shows that the proteinof many vege- tables contains a higher percentage of tryptophan than that found in meat, but because of its high protein content, on the basis of an equal weight of material, meat ranks among the best sources of trypotophan. Meat is also an excellent source of lysine. It will be noted that the crude protein in about 5o percent of the materials analyzed had less than half of the lysine contained in the crude protein of meat. 21 THE AMINO ACID COMPOSITION OF MEAT AND SOME OTHER FOODS Sim. x zN * NNN NNN NNN SNN NNN NNN NNNNS . . . . . . . . . . . . . . . .323 NNNNB NNN NNN.N NNS NSNN SNN NNNN NNN . . . . . . . . . . . . . . . . . . . . nowwogdaoe NNN NNNN NNS NSNN NNN NNN.N NNN . . . . . . . . . . . . . Iwwofifion NNNEN SN NNNN NNS NSNN S; NNNN NNN . . . . . . . . . .......N_N&&NNN NNNNNN . . . . . . . . . . . . . . . . . . . . . NNN $5 NNN NNN NNN NNN NSS . . . . . . . . . . . . . . . . . ZABQQE Nam NNN NNN NSN 3d Sim $5 NNN . . . . . . . . . . . . :%NNN=NN=NN 8E . . . . . . . . . . . . . . . - . . . - NNN Sod NNN NNNN NNN NNNN NNS . . . . . . . . . . . . . . .225 NNNNSNm . . . . . . . . . . . . - . . . - NNN NNN NSN NNS NNS NNN NNSN . . . . . . . . . . . . . . . . . 1.5% NNNNNm NNN NSNN NNS NNNN NNNS NSN NNN . . . . . . . . . . . . . . . . . . . . . . 1.3080 NNN SNNN NNN NNNN NNN SN NNN . . . . . . . . . . . . . . . . . . . . . . . . .620 NNN NNN NSN SNN SN NNN NNN; . . . . . . . . . . . . . . . . . . . . QNNE NNo NNN NN.N NNN NNNN NNN NSN NNN . . . . . . . . . . . . . . . . :§NNE fizz NNN NNN SN NNN NNN NNN NNNS . . . . . . . . . . . . . . . . JENNE NNNQ SN NNNN NNN NNNN NNN NNNN NNN . . . . . . . . . . . . . . . . . . . QNNEBNQ NNN NSN NNN NNS NNS SN NNNN . . . . . . . . . . . . . QNNN wwNNmoNboO NNN NNN EN NNN NNN NNN NSN . . . . . . . . . . . .?N=NNN was Eco NNN NSN 3N SNNN NNN NSN NNN . . . . . . . . . . . . . . . . . :2NN.£ =80 NNN RA NNN NNN NNN NNN NNNN . . . . . . . . . . . ..€NNSNN&..N==No NSN NNNN SQ NNNN NNN SNNN NN.N . . . . . . . . . . . . . . . . . . . . . . n-mpoHhNQ . . . . . . . . . . . . . . . . . . . . . NNN NNN SN NNN NNN NNS NNS . . . . . . . . . . . . . . zEoN NNNNaNNNm NNN NNS NNN NNN SN NNS SNNN . . . . . ..€N% NNEN £3 NNNNNNE SNN NNNN NNS NSNN NNS NNNN NNS . . . . . . . . . . . . . . . . . . . . . . . ..BNNm NNN SN E .N NNNN NNN NNNN NNN . . . . . . . . . . . . . . . . ..€2:NN NNNNm NNN SN NSN NNN SN SNN NNS . . . . . . . . . . . . . . . .6155 NwzNm . . . . . . . . - . ~ . . . - - . . . Ncwokmm pcmnfiwm pcwohwm 380.6% pcwuhwm pcmgwm pcmopwm S5305 NSHENN QENEE NEENN 263.5 BQENN 25.8 2H ma» 5 25.6 2H m5 5 $5.6 5 ma» SH 6N6 x Zv cwwuoa cook NESSBNNH Nfiwflfifl @5534 Q36 A 5 ns-x...._»_svi€é ., ( . 22 BULLETIN 708, TEXAS AGRICULTURAL EXPERIMENT STATIQN 3N N»... N». NN... NNN NN... S.» .N... . . . . . . . . . . . . . . . . . . ..........s. .N...? 3N N..... NNN... ..N..... NN... NN..... NN... NN.... . . . . . . . . . . . . . . . . . . . . . . ..N.....Ns..... NN... NN.... N... ..N... NN... NN.... ..N... .N...... . . . . . . . . . . . . . . . . . . .N.....N..... .NN>>N NNN .N..... E. ........ .N.N ..N..... ....... NN.... . . . . . . . . . . . . . . . ......EE=N. NNNNNN ..N.N ..N..... ..N... NN..... .N.... NS... NN... ..... . . . . . . . . . . . . . . . . . . . . . . . . .....N=...N . . . . . . . . . . . ~ . . - . . . . . NN... .N... N..N ...... NN... NN... NNN .N... . . . . . . . . . . . . . . . ..........N......E.. 8... . . . . . . . . . . . . . . . . - . . . - . . N..N NN.... ..N.. NN.... N... ..N..... .N... EN... . . . . . . . . . . . . . . . . . 122.5 N253... . . . . . . . . . . . . . . . . . . . . N...N ....N N.... NN... ..N.N N... ..N... ..... . . . . . . . . . . . . . . . . . . . . ...S......ENNn. .N.N N...... N... N....... NN... .N.... NNN N...... . . . . . . . . . . . . . . . . . . . . . . . . . .26.... NNN ..N..... N... NN.... ..N... N.... N...N N... . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..N..... NNN NN... N... NN... ..N... NN... N... ..... . . . . . . . . . . . . . . . . . . . . . . . ...NNE.N.. SN N.... NNN ...... .N... NN... NNN ..N... . . . . . . . . . . . . . . . . . . . ..........a. 5E. . . - . . ~ . . - - . . - . - . . . - NNN N2... N... ........ ..N... ..N..... N.... NN.... . . . . . . . . . . . . . . . . . . . . . . $2.283. ..N.. .N.N .... NN... N... NNN NN... 5N . . . . . . . . . . . . . . . . . ..N..... Nmwmaofioo NN... N... NNN .N... ....N NN... NN... .... . . . . . . . . . . . . . ...a......... .N.... Eco N..... 2... ..N.N ...... .....N ...... NN... N... . . . . . . . . . . . . . . . . . . . . ..N..... Eoo ..N.N NN. ..N.N NN... NNN NN. ..N... ..N.N . . . . . . . . . . . . . . .....N...NE<. NN...... NNN N.... ..N.. NN.... NN.... .N... NNN .N..... . . . . . . . . . . . . . . . . . . . . . ....Na......=No NNN ..N..... NN.. N....... N». NN.... EN NN.... . . . . . . . . . . . . . . . . . . . . . . . . ..N.....No . - . . . . . - . . . . . . . . . - . . , . . . NN... ..N... ..N.. NN... ..N.N 3.... ..N... .3... . . . . . . . . . . . . . . . . . ..N..... .N....E.2.m NNN ..N.. NN. ..N... NN... S... NNN .... ...:........NNN ..N......NNN.. N..$...N.m ..N.. .N..... ..N... ..N..... NNN 5...... N...N N....... . . . . . . . . . . . . . . . . . . . . . . . . . . ..N...Nm . - . . - . . . . . . . . . . . . - . N... NN... NN. N.... NNN N..... N...» ..N... ...........................a. NNNQN. . - . . . - . . . . . . . ... . . - . ~ . fiEPEm .53.... “$595M 3.095% pfixfiwm 280.8% 3.9.9. Ewfiwm 2.30.... NEENN 530.5 BQENN grape... QEENN 53...... QEENN wws... 2H o... 5 2...... a w... 2H wwP... QH w... 5 awn... 5 w... 5 woom mficmwfizcosm mficofipmg ocmwzd wEoswQ mQOOh miow b0 wHZHHZOO mz.z..4.<..wzmm.. QZ< wC/ZZOZHHHE dzaw. QZKVDHQ .2 mdfié 23 THE AMINO ACID COMPOSITION OF MEAT AND SOME OTHER FOODS . . . - . . . - . - . - . . . . . . . . . - . . . . . . . Hww wmoo moo vooo www owoo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..wmo2mfiom. . . - . . . - . . - - . . . . - . - . . - . . - . - . . . - . - . - . - . - . . . . - - . . - ¢ . - - - . . . . . . - - . - . . . - - - . - . . . . . - . - . . . . . - . . - ~ . . . . - . . . . . . . . . . . . . . . . . . . . . . . . - ix . $ . o . %.. . o - X - C . - . . . . . . . . . . . . . . . . . . . . . . . . . - . - - . - . . . - . . . - . . . . . . . - . . . . - - . - - . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - . . . . . . . . . . - - . - . ~ - . . - - - . - - - - . wwd www wmA w>.o wow woA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Imsow 228mm mow mmoo wwA oHoo wwA omoo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IwnoEO woé mHo wmA wwoo mmiw mooo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1920 wwo ow.o omA wmo mmw wwo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Immmfi pmO . . . - - . . . . - - - - . . - - . - - . - - - - . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . www mwoo wvo mooo wow Zoo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ilhwaasaso vwm mow mo; wwo oww mwA . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5mm wmmmcompoO - . . - . - . . . . . . . - . . . . . - . - - . . . . . . . . . . . - . . . . . . . . . . . . . . ~ - . . . . . . . . . . . . . . . . . . . . . . . . . . . . wmw 5o ow.o owoo “Jim wwmo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ihmkoczsmno wwo wwoo NHA >oo.o wow wmoo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1392.50 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Eh ow.o woA ow.o mom wwo . . . . . . . . . . . . . . . . . . . . . . . . 2.56m ommnBxmsm 3m w: ow.o mmo wmw ow.o . . . . . . . . . . . . . . . . . . . Qmmmm 8x3 mama $22,155 >o.w wwoo ow.o mmoo mww wwoo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Iwpmmm . . . - - - . . . - . . . - . - . - . - . . ~ - . . . . . . . . . - . - - . . . - - - - . . . . - - . - - . - . . . . . . . . . . - . . . . . . . . . . - . . . . . . . . . . - . . . mcmmmmm 283mm 263mm 233mm 2892mm 2822mm E395 mEEmm 2230.5 mmmEmw 22282.2 mmmfimw $22.6 cm ma» cm $5.6 cm m5 cm mosh. cm ma» cm voom mszm> cmsmommzmk mficombrw mmoom 220w HO mezmezoo @255» QZ< 232.202.5522. fizmzommme :3 H.232. 24 BULLETIN 708, TEXAS AGRICULTURAL EXPERIMENT STATION It appears fro-m the report of Mitchell and Block (6) that the limiting amino acid in beef liver and beef heart is isoleucine. For this reason, it is of interest t0 compare the isoleucine content of these kinds of meat with other foods. The protein of all of the vegetables and the grains studied contained less isoleucine than beef heart and kidney with the one exception of blackeye peas. The protein of milk, eggs and cheese had a higher isoleucine content than these two kinds of meat. In making these comparisons, it is to be recognized that not all foods are included in the list. In Tables I5 to I8, a comparison is made of the values obtained in this investigation with the results of previous workers. One of the most noteworthy of the older amino acid studies on meat is that of Beach (II). Fairly satisfactory agreement between the values given by Beach and those reported in the present paper is to be noted for threonine, arginine, lysine, tryptophan and phenylalanine. The agreement of the threonine data is particularly good. Possible causes for the lack of agreement between the values obtained by various investigators may be considered under the following headings: (a) actual differences in the materials ana- lyzed, (b) differences in the preparation of the samples, (c) differ- ences in the purity of the amino acids used as standards, and (d) differences in the specificity and accuracy of the analytical proce- dures. With regard to the first of these, attention is called to the close agreement (except in the case of histidine in muscle proteins) between the values obtained in the present investigation for the three different samples of the same kind of tissue taken from different animals. This finding points to a rather constant amino acid com- position for meat of the same kind. It does not, therefore, appear likely that lack of agreement in the literature values should be attributed to actual differences in the composition of the materials analyzed. ‘ Many of the older values for the amino acid composition of meat proteins were obtained on partially purified samples of protein ob- tained from meat and not on whole meat itself. The mode of prep- aration of the samples then does account for some of the discrepan- cies in the literature values. A few of the amino acids are difficult to purify to the extent that they are entirely satisfactory standards for amino acid determinations. Among these may be mentioned isoleucine. The removal of the la.st 8 or Io percent of allisoleucine from synthetic isoleucine requires at least 8 or 1o recrystallizations after a white crystalline compound is obtained. THE AMINO ACID COMPOSITION OF MEAT AND SOME OTHER FOODS 25 TABLE 15. COMPARISON OF AUTHORS’ DATA WITH VALUES FROM THE LITERATURE FOR ARGININE, HISTIDINE AND LYSINE IN MEAT Amino acid in crude proteinT Kind of meat Reference Arginine Histidine Lysine a Percent Percent Percent Beef muscle 7 .4 1.7 7. 5 Osborne, et al. (7) 5.7 . . . . . . . . . . . . . . . . . . . . Furth, et al. (8) 6.3 .0.6 7.3 Ress,et al. (9) 7.5 1.8 7. 6 Pottinger, et al. (10) 6.9 2.3 8.1 Beach, et al. (11) 7.1 2.2 8.0 Block, et al. (12) 5.9* 3.4* 7.7* Hier, et al. (13) 10.1 4.4 8.1 Edwards, et al. (14) . . . . . . . . .. 2.0* 10.0* Horn, et al. (15) (16) 6.2* 3.7* 9 1* Authors (3) Pork muscle 6.6 2.2 8.7 Beach, et al. (11) 6.4* 3.8* 8.7* Authors (3) Lamb muscle 7.6 2.4 8.7 Beach, et al. (11) 6.2* 2.1* 8.8* Authors (3) Beef liver 6.6 2.0 6.0 Beach, et al. (11) 6.3 2.5 5.1 Block, et al. (12) 3.4* 1.9* 6.1* Stokes, et al. (17) 5.8* 2.6* 7.4* Authors (3) Beef heart 7.4 2.1 7.1 Beach, et al. (11) 6.4 2.7 7.4 Block, et al. (12) 6.4* 2.6* . 8.3* Authors (3) Beef kidney 6.9 2.3 6.2 Beach, et al. (11) 6.3 2.0 5.2 Block, et al. (12) 6.1* 2.6* 7.3* Authors (3) Beef brain 6.4 2. 5 6.0 Beach, et al. (11) 6.5 2.4 5.9 Block, et al. (12) 6.0* 2.6* 6.7* Authors (3) Beef thymus 7.2 2.4 6.1 Block, et al. (12) 6.6* 1.8* 8.3* Authors (3) Beef spleen 6.3 2 . 1 6.1 Block,let al. (12) ‘ 6.1* 2.6* 7.6* Authors (3) TAll values calculated to 16 percent nitrogen. *Values obtained by microbiological assay. 26 BULLETIN 708, TEXAS AGRICULTURAL EXPERIMENT STATION TABLE 16. COMPARISON OF AUTHORS’ DATA WITH VALUES FROM THE LITERATURE FOR TRYPTOPHAN AND PHENYLALANINE IN MEAT Amino acid in crude proteinT Kind of meat Reference Tryptophan Phenylalanine Percent Percent Beef muscle 1.2 . . . . . . . . . . . . Jones, et al. (18) , 0.9 . . . . . . . . . . . . Pottinger, et al. (10) l 1.4 4.9 Beach, et al. (11) 1.4* . . . . . . . . . . . . Greene, et al (19) g 1.3 4 9 Block, et al (12) § 1.2* . . . . . . . . . . . . Wooley, et al. (20) 1.2, 1 3 . . . . . . . . . . . . Horn, et al. (21) 1.5 3 6 Edwards, et al (14) < 1.3* 3 6* Greenhut, et al. (22) 4f . . . . . . . . . . . . 3 8* Hier, et al. (13) i 1.2 . . . . . . . . . . . . Graham, et al (23) l 1.2* 4 2* Authors (24) Pork muscle 1.3 4 0 Beach, et al. (11) ' 1.4* . . . . . . . . . . . . Greene, et al. (19) 1.3* 3.7* Greenhut, et al. (22) (25) 1.2* 4.2* Authors 4) - Lamb muscle 1.4 4 5 Beach, et al (11) 1.4* . . . . . . . . . . . . Greene, et al. (19) 1.3* 4.0* Greenhut, et al. (22) 1.2* 4.3* Authors 4) Beef liver 1.8 6.1 Beach, et a1 (11) 1 . 2 7.3 Block, et al (12) 1.4* 5.3* Stokes, et al. (17) 1.6* 4.3* Greenhut, et al. (22) (25) 1.5* 5.2* Authors (24) Beef heart 1.4 5.1 Beach, et al. (11) 1.1 5.7 Block, et al. (12) 1.3* 4.2* Greenhut, et al. (22) (25) 1.3* 4. 5* Authors 4) Beef kidney 1.8 5. 5 Beach, et al. (11) 1.2 5. 5 Block, et al. (12) 1.5* 4.3* Greenhut, et al. (22) (25) 1.4* 5.0* Authors (24) Beef tongue 1.1* 4.0* Greenhut, et al. (22) (25) 1.1* 4.2* Authors (24) Beef brain 1.6 4.1 Kaplansky (26) 1.6 5.8 Beach, et al. (11) 1.2 5.4 Block, et al. (12) 1 . 1* 4.0* Greenhut, et al. (22) 1.4* 5.4* Authors (24) Beef thymus 0.6 3.3 Block, et al. (12) 0.7 * 2.9* Authors (24) Beef spleen 0.8 4.6 Block, et al. (12) 1.2* 4.4* Authors (24) TAll values calculated to 16 percent nitrogen. *Values obtained by microbiological assay. THE AMINO ACID COMPOSITION OF MEAT AND SOME OTHER FOODS 27 TABLE 17. COMPARISON OF AUTHORS’ DATA WITH VALUES FROM THE LITERATURE FOR THREONINE AND METHIONINE IN MEAT _ Amino acid 1n crude proteinf Kind of meat Reference Threonine Methionine Percent Percent “TI -- muscle . . . . . . . . . . . . 3. 5 Beach, et al. (27) 4.6 3.2 Beach, et al. (11) 3. 5 3.3 Block, et al. (12) 5.3* . . . . . . . . . . . . Hier, et al. (13) 5.1 4.1 Edwards, et al. (14) 4.5* 2. 5* Authors (1) rk muscle 4.6 3.4 Beach, et al. (11) 4.8* . . . . . . . . . . . . Greenhut, et al. (28) . . . . . . . . . . . . 3.0* Riesen, et al. (29) _ 4.5* 2.4* Authors (1) _ mb muscle 5.3 3.1 Beach, et al. (11) 1 4.3* . . . . . . . . . . . . Greenhut, et al. (28) 4.8* 2.4* Authors (1) -- liver 4.8 2.4 Beach, et al. (11) 3.8* 2.0* Stokes, et al. (17) 4. 5* . . . . . . . . . . . . Greenhut, et al. (28) . . . . . . . . . . . . 3.4 Block, et al. (12) A 4.3* 2.2* Authors (1) ' ork liver . . . . . . . . . . . . 3 . 9* Riesen, et al. (29) . . . . . . . . . . . . 2.2* Authors (1) l-- heart 4.7 3.0 Beach, et al. (11) f“ 4.0 . . . . . . . . . . . . Block, et al. (12) . . . . . . . . . . . . 3 . 1* Riesen, et al. 9) a 4.5* 2.4* Authors (1) kidney 4.6 2.7 Beach, et al. (11) ’ - 4.6* . . . . . . . . . . . . Greenhut, et al. (28) . . . . . . . . . . . . 1.9* Riesen, et al. (29) . . . . . . . . . . . . 2.8 Block, et al. (12) u 4. 5* 2.1* Authors (1) ’ i tongue 4.7* . . . . . . . . . . .. Greenhut, et al. (28) ’ 4.4* . . . . . . . . . . . . Authors (1) . brain 5.3 2.7 Beach, et al. (11) -* 4.6* . . . . . . . . . . . . Greenhut, et al. (28) . . . . . . . . . . . . 2.6* Riesen, et al. (29) _ 4.7* 2.1* Authors (1) thymus 4.1 . . . . . . . . . . .. Block, et al. (12) I 3.6* . . . . . . . . . . . . Authors (1) spleen 3.8 . . . . . . . . . . . . Block, et al. (12) 4.2* . . . . . . . . . . . . Authors (1) i 1A1] values calculated to 16 percent nitrogen. j.-Values obtained by microbiological assay. 28 BULLETIN 708, TEXAS AGRICULTURAL EXPERIMENT STATION TABLE 18. COMPARISON OF AUTHORS’ DATA WITH VALUES FROM l THE LITERATURE FOR VALINE, LEUCINE ‘ AND ISOLEUCINE IN MEAT* Amino acid in crude proteinT Kind of meat . Reference Valine Leucine Isoleucine I Percent Percent Percent _ Beef musclei,‘ 5.1 7.8 5.9 Schweigert, et al. (30) (31) 3 5.1 7. 5 5.2 Hier, et al. (13) t 5.2 7.7 5.7 Edwards, et al. (14) 5.3 8.6 5.2 Authors Pork muscleT 5.3 7 .3 5. 9 Schweigert, et al. (30) 5.4 8.6 5.1 Authors Lamb musclei 4.8 8. 1 6.0 Schweigert, et al. (30) (31) A 5.4 8.5 4.8 Authors Y Beef liver 6.2 8.4 5.6 Schweigert, et al. (30) (31) 5.7 8.3 4.0 Stokes, et al. (17) 6.5 9.4 4.7 Authors Beef kidney 5.4 7. 8 5. 5 Schweigert, et al. (30) (31) 6.0 8.9 4. 5 Authors ' Beef brain 4.8 7.4 . . . . . . . . .. Schweigert, et al. (so) (s1) ' 5. 5 8. 5 4. 5 Authors ’ Beef heart 6.3 8.4 . . . . . . . . . . Schweigert, et al. (30) (31) 5.4 9.2 4.8 Authors TAll values calculated to 16 percent nitrogen. *A1l data obtained by microbiological assay. » IValues reported for different cuts of meat consisting of muscle tissue have been averaged. Of all the possible causes for lack of agreement between the l literature values for the amino acid composition of meat, probably the most important is the question of specificity and reliability of the analytical procedures employed. This is particularly true with some of the older methods. > a. W, k r THE AMINO ACID COMPOSITION OF MEAT AND SOME OTHER FOODS 29 Summary The arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and Yaline contents of I9 dif- ferent kinds 0f meat were determined. These included various types 0f tissue from beef, pork and lamb. Thirty other foods were also analyzed for the same 1o amino acids. Variations in the amino acid content of samples of the same kind of meat taken from different animals were in almost all cases very small. Furthermore, the amino acid composition of a given type of tissue was very nearly the same whether it came from’ beef, pork or lamb. One outstanding exception was found in the case of the histidine content of muscle tissues, where wide variations occurred. Meat was found to be a good source of all of the zunino acids studied. As compared with the grains and vegetables. it xvas found to be an outstanding source of lysine. ' Acknowledgment This investigation was supported by a grant from the American Meat Institute. To Betty Butler, Olive Moseley’. Suzanne Wood. Shirley Dieter- ich, Nlarjory Golden, Mary Trant and Lila Corley, the authors wish to express their appreciation for technical assistance. The cooperation of the Meats Laboratory at A. and M. College of Texas and the assistance of its manager, Roy \\7. Snyder, are gratefully acknowledged. 3.0 IO. II. I2. 13. 14. 15. 16. 17. BULLETIN 708, TEXAS AGRICULTURAL EXPERIMENT STATION Literature Cited Lyman, C. M., B. Butler, O. Moseley, S. Wood and F. Hale, 1946. The Methionine Content of Meat. J. Biol. Chem. Vol. 166, p. 173. Kuiken, K. A., W. H. Norman, C. M. Lyman, F. Hale and L. Blotter, 1943. The Microbiological Determination of Amino Acids, I. Valine, Leucine and Isoleucine. J. Biol. Chem. Vol. 151, p. 615. Lyman, C. M., K. A. Kuiken and F. Hale, 1947. The Histidine Content of Meat. J. Biol. Chem. Vol. 171, p. 233. Kuiken, K. A., C. M. Lyman and F. 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