LABORATORY CHARACTERISTICS OF GRADED BEEF CARCASSES

Transcription

1 0. LABORATORY CHARACTERSTCS OF GRADED BEEF CARCASSES A M E R C A N MEAT N S T T U T E F O U N D A T O N *.**..**...*..*...*...*...*.*...* Mr. Chairman, Mr. Franklin, bkmbers of the Conference and Guests: t i s a r e a l pleasure t o t a l k before t h i s group about s o w of the studies that we have carried out a t the American *at n s t i t u t e Foundation on graded beef carcasses. As Mr. Pierce has already stated, t h i s work was carried out under contract with the Livestock Branch of the Agricultural Marketing Service, and the d e t a i l e d r e s u l t s w i l l be presented i n a U.S.D.A. technical bull e t i n t h a t is now being prepared. The report that w i l l give t h i s morning i s a s u m r y of t h e r e s u l t s obtained i n t h i s threeyear study which involved some 53 graded beef carcasses.. ntroduction k n y investigators have determined the c h a r a c t e r i s t i c s of beef and attempted t o r e l a t e these c h a r a c t e r i s t i c s t o carcass grade and t o organoleptic properties. No attempt w i l l be made here t o review the l i t e r a t u r e on t h i s subject. This report i s a summary of some of the r e s u l t s obtained from a three year study involving 53 graded beef carcasses. The research was supported by contract with the Livestocks Branch, Agricrzltural h r k e t i n g % m i c e, U.S.D.A., and r e s u l t s w i l l be published i n d e t a i l i n a U.S.D.A. Technical Bulletin. Materials and Methods The carcas8 groups selected f o r study are shown i n Table. Three carcasses from each group were selected each year f o r a three year period making a t o t a l of 27 l i g h t, 27 heavy, 36 l i g h t, 36 heavy, and 27 Commercial Cow carcasses. R i b cuts from a l l carcasses and rounds from /3 of the carcasses were removed approximately 48 hours a f t e r s l a u g h k r and transported t o the laboratory. The Longissimus dorsi of the r i b and Semitendinosus muscle of the round were sampled immediately and a f t e r 2 and 4 weeks aging of the cuts a t 3335OF. The d e t a i l s of sampling and procedures used f o r the various determinations are described i n d e t a i l i n a U.S.D.A. Technical Bulletin which i s i n preparation. Results and Discussion Carcass Composition. Based on the ammat of separable lean, f a t and bone i n t h e 90 r i b section, calculated carccss composition values (Table ) indicate that Grade carcasses contained more f a t and less lean and bone than grade carcasaes, with Commercial Cow carcasses i n t e r mediate between the two groups of younger animals. These findings a r e i n agreement with our expectations and coxxfirm results of other investigatore.

2 . Color of b a n. Lean color of r a w ribeye as determined by comparison with Mmseii Color Plates, was very significcznt.y related t o carcasa grade and extent of aging. The color of Prim grade ribeye uw3 l i g h t e r than t h a t from good o r Commercial grade and aged ribeye was l i g h t e r i n color than unaged ribeye. Marblm. Subjective marbling ratings on raw ribeye indicated t h a t Prim grade ribeye was s i g n i f i c a n t l y better marbled than grade ribeye with Comnercial Cow ribeye intermediate (Table SS). Beavy carcasses i n each grade exhibited aomwhat better ribeye marbling than l i g h t carcasses. Shear Strength. Although the average shear values (/2 inch cylinders) for r a w ribeye f o r the differttnt carca88 groups varied from 4.2 t o 9.4 there was no s i g n i f i c a n t r e l a t i o n s h i p between shear value f o r the r a w ribaye and carcass grade o r weight o r extent of aging. Cooking (broiling) markedly increased t h e shear strength of nngissimus d o r s i but decreased that of Semi.tendinosu6. Aging the raw meat reduced the shear strength of the cooked mat and shear strength of the cooked ribeye was very s i g n f f i c a n t l y d i f f e r e n t f o r the d i f f e r e n t carcass groups. (Table V). Press Fluid. The data (Table V) show that r a w ribeye from carcasses yielded more f l u l d than t h a t from carcasaes with Commercial carcas8e8 intermediate, Aging reduced the y i e l d of press f l u i d. Cooked ribeye yielded more press f l u i d than raw, b u t t h e r e were no consistent carcass grade o r aging e f f e c t s. Similar results were obtained with the Semitendinosus, Other Physical Tests. Specific conductance, pentetrometer readings, and objective firmness values f o r ribeye and Semitendinosus were not related s i g n i f i c a n t l y t o carcass grade o r weight. n t r a m s c u l a r Fat. ntramacular f a t i n the raw ribeye varied from.5 t o 2 6. m ' i n r a w Semitendinosus from 0.6 t o 9.4%. There were d i s t i n c t differences i n i n t r m s c u l a r f a t due t o carcass grade and weight (Table V). Nonprotein N i t r o e, Amino Nitrogen and Soluble Protein Nitrogen The amount of these nitrogenous components of ribeye and Semitendinosus were not r e l a t e d t o carca88 grade o r weight. During aging the &no nitrogen and nonprotein nitrogen content o f raw meat increased s l i g h t l y but significantly. A t the sa= time the soluble protein content decreased and t o a much g r e a t e r extent than could be accounted for by the increase i n nonprotein nitrogen. Creatine and Creatinine. The creatine content of raw ribeye varied from 95 GTOOg t o 43 mg./l%, and the creatinine content varied from 8 t o 44 mg./loog. There were no conslatent dif'ferences related t o carcass grade o r weight. Aging and cooking increaeed the creatinine content of the meat., Muscle Fiber Diamter. The muscle fiber diameter of samples from Phmcle t i s s u e from older animals had s l i g h t l y l a r g e r f i b e r s than corresponding tissue from younger animals. Fiber diameter in the Semitendinosus was g r e a t e r than i n the ribeye from the same carcass. 40 carcaeses varied from 27 t o 74 microns. m e c l e Bundle Size. Primary muscle bundle cross sectional area i n the samples studied varied from 0.07 t o.47 square millimeters but differences

3 2. were not associated with carcass grade o r weight. Primary muscle bundles were l a r g e r i n the ribeye than i n Semitendinosus from the same carcassr Elastin Content and E l a s t i n Fiber Diaraeter. On the basis of h i s t o chemical es6imatiori f a r e l a s t i n on samples from 84 carcasses the e l a s t i n cont e n t and e l a s t i n ffber diamter were much g r e a t e r i n the Semitendinosus than i n ribeye. Aging and/or cooking had no detectable influence on e l a s t i n. Collagen. Results obtained on all samples studied did not show any consistent differences in the collagen content of raw o r cooked ribeye due t o carca6s grade o r weight, but the amount of collagen was reduced s l i g h t l y by aging and/or cooking (Table V ). The Semitendinosus contained more collagen than Longissimus d o r s i from the same carcass. h s c l e Fiber Autolysis, Fiber autolysis varied from 0 t o 4 or an a r b i t r a r y subjective r a t i n g scale, but was not consistently related t o carcass grade. Autolysis r a t i n g s were increased by aging, especially during t h e f i r s t two weeks period. Autolysis i n t h e Semitendinosus was much less extensive than i n the ribeye and the e f f e c t of aging was not a6 pronounced. Cooking Losses. The t o t a l cooking 068 durfng b r o i l i n g of steaks from r i b and round of c&rcasse8 studied was not associated with carcass grade o r weight. However, d r i p loss was d i r e c t l y correlated with separable fat, E n d evaporation l o s s was inversely correlated with separable fat] of t h e steaks. Aging reduced d r i p loss m d increased evaporation loss during broiling. Lean Flavor of Broiled Steaks. The panel scores f o r lean f l a v o r of broiled ribeye samples ranged from 5. 2 t o 9.9 and those f o r broiled Semitendinosus ranged from 3.5 t o 7.7. There were pronounced differences i n l e a n flavor scores due t o c a r c a ~ sgrade and extent of aging (Table V). Tenderness of Broiled Steaks. The panel scores f o r tenderness of broiled ribeye ranged from 2.2 t o 9.3 and those f o r broiled Semitendinosus ranged from 3.0 t o 8.2. Tenderness of broiled ribeye vas associated with carcass grade and aging (Table X). The aging e f f e c t wa8 more pronounced on and Commercial grade carcasses than on. Juiciness of Broiled.Steaks. Juiciness score6 f o r broiled ribeye varied from 4.3 t o 9.0 and those f o r broiled Semitendinosus varied from 3.7 t o 8.0. Ribeye f r o m l i g h t grade carcasses was s i g n i f i c a n t l y l e s s juicy than that from other carcass grades and weights. Semitendinosus w&s less j u i c y than ribeye. O t h e r than these, differences i n juiciness were not consistently associated with carcass grade o r weight or extent of aging. Biochemical Properties. The a c t i v i t y of proteolytic and c e r t a i n oxidative enzyme systems i n beef muscle t i s s u e was investigated during the course of these studies. The r e s u l t s indicate that variations i n carcass gsde and weight were not r e l a t e d t o the carbohydrate metabolism of the muscle from the time we received the samples (48 hour6 after slaughter) t o the end of a four week6 aging period. ntramuscular Variation and ntermuscular Differences. Data obtained i n the cour6e of t h i s study'indicated some small but d i s t i n c t d i f f e r ences i n c h a r a c t e r i s t i c s of the Longissimus dorei from one end of the r i b cut

4 3. t o the other. The posterior portion contsined less f a t but more collagen and had a higher shear strength than t h e a n t e r i o r portion. n broiled ribeye the posterior end as compared t o the a n t e r i o r had higher s p e c i f i c conductance, more zollagen and lower scores f o r lean f l a v o r and tenderness. The center portion of the Semitendinosus contained more f a t, exhibited a g r e a t e r a u t o l y s i s l e v e l and had a lower shear strength than did e i t h e r end, Wscle fiber diameter n t h e Semitendinosus decreased progressively from top &o bottom. Despite t h e quantitative differences between the muscles and withi n %he same muscle, some of the c h a r a c t e r i s t i c s of the two musclee were f a i r l y weu. correlated (Table X) ReSatlonships of Some Chemical, Physical and E i 6 t o l ~ i C a lproperties t o Organoleptic Characteristics.!tenderness of cooked ribeye was very d e f i n i t e ~ associated w i t h carca88 f a t, intramuscular f a t, and marbling (Table X ) e 6 8 s consistent relationships irere shown between tenderness and Specific conductance, lean color o r a u t o l y s i s rating. Tenderness was not s i g n i f i c a n t l y correlated w i t h the collagen content of raw or cooked meat o r with penetrometer readings. Juiciness ~ c o r e 8of cooked ribeye were very eignificantly correlated w i t h carca88 f a t, intramuscular fat, and marbling rating, but showed no con s i s t e n t relationship t o any other properties of the e a t, Lean f l a v o r scores f o r cooked ribeye t ~ r enot consietently related t o any of the other propertiea of the neat. summary On the b a s i s of r e s u l t s from 53 graded beef carcasses t h e following findings appear most s i g n i f i c a n t. grade carcasees were f a t t e r than grade carcassee. Ribeye from grade c a r c a s e e ~as compared t o t h a t from grade had a lower shear strength (raw and cooked), more press f l u i d (raw), g r e a t e r e l e c t r i c a l conductance (raw), more intrarrmscular fat, b e t t e r marbling and b r i g h t e r lean color, More d r i p 066 but l e s s evaporation l o s s wa6 noted after b r o i l i n g rib steaks from as compared t o grade carcasses. The ribeye of broiled r i b steaks from Prius grade c a r c a 6 3 e ~had b e t t e r lean f l a v o r and was more tender than t h a t from grade carcasse6. Juiciness acores f o r ribeye from l i g h t grade carcasees were less than those f o r ribeye f o r other groups of carcasses. For almost a l l these grade differences ribeye from Commercial carcasses ranked between the mean8 f o r and c a r c a s ~ e s. Aged r a w ribeye as compared t o f r e s h had a higher ph and contained higher percentages of nonprotein nitrogen, free amino nitrogen and creatinine but less soluble protein. Aging increased the autolysis l e v e l and improved the color of raw meat. Aging f o r two weeks improved the tenderness and lean f l a v o r of broiled ribeye. An additional two weeks aging period had l i t t l e tenderizing influence and uas detrimental t o fat and lean flavor.

5 Table Grade and Weight of Carcassee Studied Dates Sampled Wight Grade c Commercial 650 Jan., June, Aug. t t Jan., June, Aug., Oc,. t t Jan., A u g., Oct. Table Carcass Cornpositdon &nge of Different Grades and Weights Separable Lean Se parable Bone k % F rime Eeavy Eeavy Commercial Cow Table.9% 2.00 Corn. cow 2.3,

6 5 Table V Thf'luence of Carcass Grade, Aging and Cooking on Shear Strength ( l b s. ) ~ ~~~~~ Raw Xlbeye Raw Semitendinosus Cooked Semitendinosus Cooked Ribeye :: 58 0 aging 2GE.J Cooked Ribeye Cooked &mitendinof3lm3 g L9.2 Reavy corn. Ught '~~~~, 2 weeks cow 93.6 ~ L 8*7 9.9 J > p.. Differences between mans not bracketed together is significant. p / Table V Average ~ r e s sfluid i n $ from ~ongissimusdorsi from Carcasses Sampled i n August

7 6. 3.,' 4.6 L,J LJ Corn. cow 6.3 Prim 8.J 8.7.L... L..T. t Table V Average Collagen Content ($ by Volume) of Ribeye and Semiteiidinosus from Carcasses Sampled i n August RAV RBEYE *.. 0 3* COOKED RBEYE

8 7. Table V Average eaa Flavor Scores for Ribeye from Carcasses Sampled i n August and January come Cow eavy 7.7, Difference between means not bracketed together is significant corn. cow ,8 6*2J 0 aging 5.5 PriW L, J 2 weeks 7 2!. (

9 8. Table X Correlation Coefficients f o r Characgeristics of 2 week6 0 aging Tende r e 6s J u i cines s Collagen, raw Fat, raw Sp. Cond., raw r ** , M.375* r No..4 24s W,474* Table X Linear Correlation Coefficients Between Tenderness and Other Properties of Ribeye Second Year's Result6 ~. T. Carcass ktt ntramuscular Fat Marbling Rating Shear, cooked Sp. Cond., r a w Autolysis Rating Lean Color Rating Collagen, Raw Collagen, Cooked Penetrometer, Raw * Significant ** Significant No. r.55w+.598w 33*,03 562** 827w.488*.7**..e2.043 No.? r.2 97*.333*.5* 070.( a t S$ level a t % l e v e l CAlJiMAN PEARSON: Thank you, D r. Doty. 0.m next paper t h i s morning i s e n t i t l e d, "Visual Evidence of Beef Q u a l i t y as Associated with Eating Desirability, ' and t h i s paper w i l l be given by D r. R. L. Hiner of the U.S.D.A.

10 9. DR R, L. XNER, U, S, Dept of Agriculture : M r Chairman, Members of the Reciprocal *at Conference and Guests : The subject that has been aebigned to me is "Viaual Evidence of Beef' Quality a8 Associated with Eating Desirability. " if 8 #. ###.#if i%