MEASURES OF MUSCLING IN PORK CARCASSES

Transcription

1 139 MEASURES OF MUSCLING IN PORK CARCASSES A We PEARSOW The increased emphasis on production of more lean meat per u n i t of weight, has resulted i n added emphasis being placed on muscling i n pork carcasses This, of course, r a i s e s t h e question a s t o what a r e t h e best measures of muscling and how they a r e r e l a t e d t o cutouts Axthemore, one m i g h t ask what t h e relationship between shape or s i z e of t h e muscle i n crosssection i s a s compared t o t o t a l muscle mass? Thus, f o r the purposes of t h i s paper, I w i l l attempt t o discuss t h e more common methods of measuring muscling along with a f e w other methods, trying t o point out some of t h e advantages and basic weaknesses of each method In measurement of muscling, one of the major problems i s establishing t h e v a l i d i t y of the d i f f e r e n t methods To do t h i s, it is first necessary t h a t standards be set up which accurately r e f l e c t muscling and can be used t o v a l i d a t e new methods Unfortunately, we have l i t t l e information available which will make an accurate comparison possible This is t r u e primarily because of t h e basic concept t h a t methodology is an unproductive f i e l d of endeavor Thus, it i s necessary t o s t a r t with basic information on the composition of s k e l e t a l muscle, since t h i s i s our primary i n t e r e s t Dukes (1943) gives the following composition of mamalism s k e l e t a l tissues: 75s Water 18 ZO$ Protein Carbohydrate (mainly glycogen) 1% Soluble material (nonprotein and noncarbohydra te) 3574 Fatty Acids* (minimum) 051 O$ Way be much higher due t o increased storage f a t It i s obvious from t h e above t a b l e t h a t there i s g r e a t v a r i a b i l i t y i n composition of muscle t i s s u e s T h i s i s especially noticeable in regard t o f a t content, and t o some extent w i t h moisture, which tends t o vary inversely Since muscles d i f f e r i n intramuscular f a t o r marbling, basic information is needed on t h e e f f e c t of marbling on tenderness, juiciness and flavor Work with beef, recently reported by Cover e t a l (1956) indicates t h a t t h e e f f e c t of marbling on tenderness I s not a simple clearcut relationship, but apparently other f a c t o r s besides marbling a r e involved It has been generally accepted that excessive fatness is undesirable i n pork carcasses and though r e s u l t s indicate t h i s t o be t r u e (Birmingham, 1956), we do not have information available indicating how f a r we can go i n t h e opposite direction and s t i l l s a t i s f y t h e

2 140 consumer Furthermore, it is conceivable that we may have considerable muscling present i n combination with excessive fatness, whereas a hog carcass may be lacking i n fatness but s t i l l be d e f i c i e n t i n muscling There would appear t o be two v a l i d measures f o r determining muscling of pork carcasses, first, dissection and separation, and second, chemical analysis In my opinion, these are v a l i d means of measuring t h e r e l i a b i l i t y of other methods f o r determining muscling However, f a i l u r e of other methods t o be i n complete agreement with these two would not preclude their usefulness under c e r t a i n conditions Consequently, I shall discuss each of these methods pointing out sme of the shortcoanings and advantaaes The dissectionseparation technique has been used extensively by Hammond(l921 and 1932) and others of h i s school (McMeekan, 1940; Hirzel, 1939; Palsson, 1939) f o r carcass evaluation In t h i s country it has been used by a number of workers (Eankins and E U l s, 1934; Hankins and Howe, 1946; Loeffel e t,*i a ) This method has t h e advantage of including marbling with t h e l e a n t i s s u e s and i n addition, gives one an opportunity t o observe shape, color and other physical a t t r i b u t e s of t h e muscles However, it is a slow, painstaking t a s k t h a t involves subjective decisions i n dividing the t i s s u e s i n t o the ccmponent l e a n and f a t t y c l a s s i f i c a t i o n s In addition, losses due t o evaporation o r absorption a r e possible added sources of e r r o r However, i n s p i t e of the shortcomings of the dissectionseparation technique, it appears t o be a v a l i d measure of muscling a Next, l e t us consider chemical analysis a s a measure of muscling Numerous workers (Warner et g, 1934; Hankins and E l l i s, 1935; Callow, 1945 and 1948; Brown e t al, 1951; Whiteman e t a 1 195s; Price et g, 1957) have used chemical analysis as a method of measuring leanness or fatness Although chemical analysis i s r a t h e r d i f f i u c l t t o obtain on meat samples due t o problems In sampling, it i s e a s i e r and less tedious than t h e dissectionseparation technique It has t h e disadvantage of not including marbling i n t h e l e a n t i s s u e s, but instead includes intramuscular f a t with other ether soluble meterial f i r t h e m o r e, chemical analysis gives an index of muscling orily from t h e percentage viewpoint and ignores shape or appearance of the muscles However, because of t h e r e l a t i v e l y simpler application and the sound principles on which it is based, chemical analysis would seem t o be a good measure o f muscling The area of t h e "loin eye", or Longissimus d o r s i muscle of t h e l o i n, has been t h e most cammonly accepted measure of muscling i n carcass studies Failure t o standardize t h e point of measurement, t h e muscle t o be traced and t h e plane of c u t t i n g through t h e muscle have resulted i n v a r i a b i l i t y i n result~ Kline and Hazel (1955) have shown t h a t the area of the "loin eye" was l a r g e r a t the last r i b than a t the 10th r i b and concluded t h a t it made l i t t l e difference which was used a s long as it was standardized Consequently, breed c e r t i f i c a t i o n programs have generally adopted t h e area of t h e " l o i n eye" a t the 10th rib However, c e r t i f i c a t i o n data reporting values above 6 square inches of "loin eye" may be viewed with some doubt, and it is l i k e l y such values a r e due t o inclusion of t h e multifidis d o r s i muscle or other small muscles addacent t o the "loin eye" It i s well known t h a t c u t t i n g of the "loin eye" a t an angle greater than 90 w i l l a l s o increase t h e area In addition, it i s possible t o increase o r decrease t h e area of l e a n by pressing

3 141 againet t h e muscle In order t o minimize changes due t o a l t e r e d surface area of the "loin eye'', Bratzler (1957) began taking a l l tracings on the rough l o i n This gives r i g i d i t y t o t h e muscle and reduces errors due t o a l t e r e d surface area The l o i n area t r a c i n g is simple t o make and allows one t o accumulate t h e tracings f o r more l e i s u r e l y measurement Along t h i s l i n e of thought, it should be possible t o develop an electronic device, which would read off the area d i r e c t l y, In addition, t o possible sources of e r r o r i n determining the loinlean area, there is no concrete evidence t h a t loinlean is closely r e l a t e d t o muscling i n t h e remainder of t h e pork carcass Data on cutout and chemical analysis would indicate t h a t "loin eye" is not closely correlated with t o t a l muscling of t h e e n t i r e carcass (Kline and Hazel, 1955; Price et ' a 1, 1957) Specific gravity measurements have been used t o a s c e r t a i n leanness and r e s u l t s indicate t h a t s p e c i f i c gravity more accurately r e f l e c t s the l o i n lean area than backfat thickness (Pearson % 1956a; Price e t a l, 1957) In addition, a higher correlation was obtained between t h e area of t h e "loin eye" and chemical analysis of t h e ham than was t r u e f o r backfat thickness, which tends t o verify t h e relationship between muscling and s p e c i f i c gravity Oklahoma workers (Brown e t al, 1951; Whiteman e t a l e, 195% and 1953b) found chemical analysis t o be more closely r e l a t e d t o leanness than backfat thickness Similarly, Liuzzo e t el, (1956) reported percentage f a t and water s p e c i f i c gravity were closely r e l a t e d with an ltrrfvalue of +99 Thus, r e sults would indicate t h a t muscling is accurately r e f l e c t e d by s p e c i f i c gravity However, s p e c i f i c gravity of t h e e n t i r e carcass or a single ham may not be closely r e l a t e d t o loinlean area Unfortunately, specific gravity has not been a r e a l good measure of cutouts, but it should be mentioned t h a t cutouts a r e not free from v a r i a b i l i t y as shown by e r r o r s i n c u t t i n g opposite sides of t h e same carcass (Lasely and Wine, 1957) e, L The l i v e probe and lean meter have both been used t o p r e d i c t backfat 1954) i n t h e l i v e animal thickness (Hazel and Kline, 1952; Andrews 5 and may possibly be useful i n the carcass Interestingly enough both measures have more accurately indicated cutout on t h e l i v e animal than was t r u e for backfat thickness (Hazel and Kline, 1952; Pearson & &, 195%) However, Price e t,*,a 1 (1957) found l i t t l e difference between the two measures insofar a s t h e i r relationship t o the l o i n lean area is concerned e, Backfat has been used a s an indicator of carcass value, and therefore, it would be assumed t h a t it is r e l a t e d t o muscling Warner e t al, (1934) showed bsckfat thickness was r e l a t e d t o carcass cutouts The North Central Livestock Marketing Research Committee (1952) reported backfat accurately r e f l e c t e d lean cuts on t h e carcass b a s i s w i t h an "r'l value of 84 and t h i s was v e r i f i e d by Hennlrig and Evans (1953) However, other workers have f a i l e d t o obtain such high relationships (Brown e t a l e, 1951; Whiternan e t al, 1953a and 19550; Pearson e t al, 1956a; Price e t, a'1 1957; Whatley e t a ) Although backfat is a simple measurement t o make, it is obvious that even though it r e f l e c t s cutouts, it is not closely r e l a t e d t o muscling e

4 142 Other measurements t h a t have been suggested a s possible measures of muscling include t h e defatted ham (Durham, 1957), t h e depth of lumbar lean (Bray, 1957), t h e area of the outer lumbar muscle (Pearson and Bratzler, 1957), a13 of which a r e not described in the l i t e r a t u r e In addition, blood f a t l e v e l s (Bowland and Hironka) have been reported t o be r e l a t e d t o area of l o b lean and t o backfat This has been p a r t i a l l y v e r i f i e d by Morrow e t a l, (1956), but other varfables have complicated the picture and make further study necessary Other possible measures of muscling in t h e l i v e animal include t h e helium d i l u t i o n technique f o r detemining s p e c i f i c gravity on i n t a c t animals or humans developed by S i r i (1956) and t h e a i r displacement method (Uuzzo et, a I ) To date both methods need f u r t h e r vaiidation and v e r i f i c a t i o n Another suggested method of obtalnlng body volume i s by photogrametry (Pierson and Montoye, 1957), although t h i s method has not been used f o r t h i s purpose, such usege has been suggested Additional carcas8 measurements such as length have been used, but r e s u l t s indicate low relationships with both muscling, of t h e loin and cutouts (Pearson Some simple cut indices have been used for evalu1956b) a t i n g pork carcasses (Pearson e t a l, 1957a), and i n general, the l o i n indices would appear t o be the most promising measure of muscling a t l e a s t as Judged by relationships t o cutouts and " l o i n eye" area s, I n conclusion, it is suggested t b a t chemical analysis and physical separetion a r e valid bases f o r development of sound techniques for measuring muscling i n pork carcasses Although a number of methods a r e available f o r measuring muscling, i t i s b e l i e v e d t b t validation of the available methods is needed List of References Cited Andrews, F N and R M Whaley 1954 A method f o r measurement of subcutaneous f a t and muscular t i s s u e s i n the l i v e animal The authors firdue Univ, Lafayette, Indiana Birmingham, E 1956 Pork quality a s r e l a t e d t o conswner acceptability Proc 9 t h Ann Recip Meat Conf' 9:89 Bowland, J P and R Bironka 1957 Relationship of plasma l i p i d l e v e l s t o carcam quality and r a t e of gain i n swine 16:62 Bratzler, L J 1957 An improved method f o r t r a c i n g t h e "loin eye" sonal Ccmmnication Bray, R W 1957 Depth of lumbar lean a s a index of muscling Comunication Per Personal Brown, C J, J C H i l l i e r and J, A Whatley 1951 Specific gravity as a measure of t h e f a t content of the pork carcass J An Sci 10:97 Callow, E H 1945 Comparative studies of meat Rates of fattening i n rel a t i o n t o t h e deposition of f a t in t h e f a t t y and muscular tissues of meat carcasses J Agr S c i 40:l

5 143 Callow, E H 1948 Comparative studies of mest The changes i n t h e carcass during growth and fattening, and t h e i r r e l a t i o n t o the chemical canposition of the f a t t y and muscular tissue J Agr Sci 38:174 Cover, S, 0 D Butler and T C Cartmight 1956 The relationship of fatness i n yearling s t e e r s t o juiciness and tenderness of broiled and braised steaks J, An Sci 15:464 Dukes, H H 1943 The physiology of d m e s t i c animals Publishing Co, Ithaca, N Y 5th ed Comstock Durham, R M 1957 The defatted ham as a measure of carca68 cutout sonal Cammunicat ion Per Hamond, J, 1921 On t h e r e l a t i v e growth and development of various breeds and crosses of sheep J Agr, Sci 11:367 &mond, J 1932 Growth and t h e develqpment of mutton q u a l i t i e s i n sheep Oliver and Boyd London Hankins, 0 G and N R E l l i s 1934 Physical c h a r a c t e r i s t i c s of hog carcasses a s measures o f fatness Res 48:257 Hankins, 0 G and P, E Howe 1946, Estimation of t h e composition of beef carcasses and cuts USDA Tech Bul 926 Hazel, L, N and E A Kline 1952, Mechanical measurement of fatness and carcass value on l i v e hogs J An Sci 11:313, Hewing, G F and M B Evans 1953 Market hogs can be accurately graded Ohio Agr Escp Sta Res Bul 728 Hirzel, R 1939, F'aators a f f e c t i n g quality in mutton and beef with s p e c i a l reference t o t h e proportion of muscle, f a t and bone Ouderstepoort J V e t Sci and An M u s 12:379 Kline, E A and L, N Hazel 1955, Loin area a t t h e 10th and l a s t r i b as r e l a t e d t o leanness of posk carcasses J An Sei 14:659 Lasely, E L and E A Kline 1957 S p l i t t i n g and cutting e r r o r s i n swine carcass evaluation J An S e i, 16:685 Liuzzo, J A, E P Reineke and A M I Pearson 1956 An a i r displacement method f o r determining s p e c i f i c gravity J An Sci 15:1270 Loeffel, W J, W, 61, Derrick and M Peters 1943 Weight of pigs a s it a f f e c t s gains and carcass q u a l i t i e s Neb Agr E x p Sta B u l 351 McI&ekan, C P 1940 Growth and development in t h e pig with p a r t i c u l a r reference t o carcass quality J Agr Sci 30:276 Morrow, R E, A M Pearson, E P, Reineke and J A Hoefer 1956 Factors influencing blood l i p i d l e v e l s and t h e i r relationships t o carcass charact e r i s t i c s of swine J An Sci 15:1288

6 144 North Central Livestock Marketing Research Committee 1952 Objective carcass grade standards f o r slaughter hogs M i n n Agr Expt Sta Bul 414 Palsson, H 1939 Meat q u a l i t i e s in t h e sheep with special reference t o Scottich breeds and crosses J Agr Sci 29:544 Pearson, A M and L J Bratzler 1957, Area of lumbar lean a s an indicat o r of muscling Unpublished data Pearson, A M, L J Bratzler, R J Deans, J F Price, J, A, Hoefer, E P Reineke and R W, Luecke 1956a The use of s p e c i f i c gravity o f cer"5ain untrimmed pork cuts a s a measure of carcass value J An Sci 15:86 Pearson, A M, L J Bratzler, J A, Hoefer, J, F Price, W T Magee and R J, Deans The f a t l e a n r a t i o i n t h e rough l o i n a s a t o o l i n evaluation of pork carcasses J An Sci 15:896 Pearson, A M, L J, Bratzler and W, T Magee 1957a Some simple c u t indices f o r predicting carcass t r a i t s of s w i n e I Cutouts and loinl e a n area J An Sci (submitted for publication) Pearson, A PI, L J, Bratzler and W T Magee 195% Some simple cut indices for predicting carcass t r a i t s of swine 11 Supplementary measures of leanness J An Sci (submitted for publication) Pierson, W R and E, J Montoye 1957 Determining volume by photogrammetric methods Personal Comunications Price, 3 F, A, M, Pearson and E, J Benne 1957 Specific gravity and chemical composition of the untrimmed ham a s r e l a t e d t o leanness of pork carcasses J An Sci 1 6 : s S i r i, W E 1956, Apparatus for measuring human body volume S c i e n t i f i c Instruments 27:729 Warner, K F, N R Ellis and P, E Howe 1934 an index of fatness J A p Res 48:24l Whatley, J A 1957 Communication Review of Cutting y i e l d s of hogs a s Specific gravity as a measure of muscling Personal Whiteman, J V, J A Whatley and J C, H i l l i e r 1953a Evaluation of some swine carcass measurements J An Sci, 12:591 Whiteman, J V, J A Whatley and J C Hillier , A further i n v e s t i gation of s p e c i f i c gravity as a measure of pork carcass value J An Sci 12:859

7 DR STRONG: Thank you, AI, for bringing us up t o date and tabiag a look a t one of t h e rising s t a r s t h a t has come i n t o prominence f o r use i n pork carcass evalxation and w h e t has been done a t various points with regard t o measuring of muscling AnQtber aspect t h a t we are interested i n when evaluating pork carcasses, of course, is quality You a l l r e a l i z e t h a t t h i s i s absoe have talked about it for t h e l a s t three or l u t e l y noncontroversial W four years a t times, and we a r e all i n complete agreement on it However, s o t h a t you will know what we a r e i n agreement on, since you may be confused from same of t h e discussions since George Wilson covered t h i s subject back i n 195?, we have asked Ernie Briskey, from Wisconsin, t a give us a l i t t l e reevaluation of t h i s quality f a c t o r Ernie ##I######