PHYSICAL AND HISTOLOGICAL PHASES OF MEAT RESEARCH

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1 PHYSICAL AND HISTOLOGICAL PHASES OF MEAT RESEARCH R o b e r t Iv. Bray UNIVERSITY OF WISCONSIN This report is based on the eummrization of 47 questionnaires answered by college meat divisions, related departments, U.S.D.A. and research divisions of several packing companies. Color work is now In progress and has been carried out at a number of inetltutioas. The instruments being used and the degree of satisfaction each has given in meat research a r e s-ized in the following table. Instruments Used f o r Color Work on Meats Instrument Spectrophotometer Color Comparator M U n S e U disc6 Munsell meat scale and c o l o r paddlesphotoelectric cellhunter Color Difference Meter Merz & Paul Color ChartsOstwald Color Chips Fat discs Beall Kodachrome pictures Container Corporation Color Charts No. Inatitutions Using Instrument No, satisfied with perfomnance* *-Partially satisfactory results included. The Spectrophotometer and Munsell meat male and color paddles the more satisfactory of the instruments being used most in color studies. Complete satisfaction was found only where the instrument had been used in one or two institutions. Perhala we should investigate further the use of some of these instruments such as the Hunter Color Difference Meter and such color charts as those by Merz & Paul, and those of the Container Corporation. are In reference to the principal difficulties encauntered in methods of samplirg, it can he clearly stated that the problem of repreeentative sampl i n g is the major one confronting meat researchers. Representative Sampling has many ramifications such a8 variation within the same muscle; changes occurring in samples prior to analysis, such as dehydration, enzymic action, color, etc.; variation in live animals as to grade, weight and age; avoiding aamples obviously abnormal in conten%-of connective tissue and contamination f o r trace element determinations. Grinding several times was a common suggestion for obtaining representative samples. Temperature and hwnldity control, a.nd speed, Elre the only

2 59. aids we have a t preeent In reducing t h e changes occurring between sampling and analysis, Marbling preeents a problem in color determinations, and Mchigan S t a t e has offered the euggeetion t h a t spinniag t h e sample a s well as the d i s c s may be of value. A homogenizer or Waring Alendor have been suggested f o r w e i n homogenizing samples where t h e e x t r a c t is used f o r analysie. Twenty-eix i n s t i t u t i o n s have oarried on research involviiw3 eeparat i o n of fat, lean and bone, Suggeeted methods such as a swine carcase probing technique by Minnesota worker6 may be a desirable. Not enough information wae given i n the questionnaire t o explain haw the technique is used. About t h e o n l y real answer t o date for separation of f a t, l e a n and bone t o be patience and f o r t i t u d e. Several cut8 fram pork were given a6 r e l i a b l e indicators of fat, l e a n and bone compositions of the ewine carcaes. The following is the l i s t of those now i n w e :, Shoulder end of the pork l o i n r o a s t. 2. Entire l o i n, ham, shoulder and sparerib. 3. Loin and f a t back. 4. " I Area percentage over the last r i b a6 meaeured w i t h planimeter give8 a high c o r r e l a t i o n t o carcass cut out. 5. Rib section. 6. Ham 7. Loin and ham, -- as deecrlbed, Jour. Am. Rea. 48, The 9th, loth and l l t h r i b cut of heef as described i n U.S.D,A. Tech. Rull. No, 926, 946, aeerne t o be the moat r e l i a b l e cut i n determining carcae6 coarposition o f b e s f. Very f e w have c m e h t e d percent lean, f a t and bone i n beef cuts w i t h t h e beef carcaes. Likewise, t h e whole r i b cut ae described i n U,S.D,A, Tech. BuU,. No. 944, 947, eeems t o have been the only cut thus far correlated highly w i t h lamb oarcasa compaeltion, It would appear t h a t we need t o carefully evaluate methods and procedures used in hog carcam compoeition ae regard8 f a t, l e a n and bone. It is 8GmeWhat doubtful t h a t a l l the cute and methods used f o r pork carca88 evaluat i o n are of t h e ~amevalue. We need t o know which cut or method l a the beat index of the lean, f a t and bone in t h e C W C ~ B B. Apparently here i s a phase of phyaical metkods of meat research which needs eome attention. Weighing fresh o r f'rozen meat samples i n an ever-changirg atmoephers In reepect to temperature and humidity presents a problem which muat a t least he p a r t i a l l y mercme If our research r e s u l t 8 are t o be comparable. problem seem t o be primarily: Specific

3 60. Dehydration before sample is weighed and at time of weighing. 2. Condensation of moisture on package8 of Frozen meat prior to weighing. To eliminate dehydration, humidity and temperature control are paramount. The use of a covered weighing jar is very helpful. In weighing frozen samples the most satisfactory results can be obtained by weighing the samples in the same atmosphere as that of storme. In tenderness studies the Warner-Bratzler Shear is being used at 26 institution6 and the majority of opinion is that it is a reliable instrument in measuring tenderness, especially on cooked meat, O n l y 4 imtitutions claimed it uneatisfactory. Many workers are using palatability testing as well as the Shear for tenderness determinations. The penetrometer ha6 not produced satisfactory results in measuring tenderness. A few workers have ueed collagen and elastin content as basis for determining tenderness. The penetrometer has been used by 6 institutions with a moderate degree of satisfaction, primarily for determining firmness of fatty tissues, shortenings and tenderness of sausage items. The general method in use is described in J o u r. Agric. Res, 63, No. 4, 203, 94l. Similar equipment in use in one institution was the micro-penetrometer. The Carver press is the most popular instrument now In use for press fluid studies. The method used by the majority of our workers is the one described in the J o u r. Agric. Res. 66, No., 403, 943. The Minnesota Pressometer was used in 2 institutions. Another worker used the Waring Blendor on samples and filtered the juice. Still another researcher felt that he could highly correlate percent moisture and press fluid. Ten institutions are using some method for measuring humidity. Baslcally, the same general type of instrument is being used for temperatures above and below freezing. The sling psychrometer seems to be the most popular instrument. Other instruments in use axe Foiboro's Dewcel, Taylor recording hydrometer, wet and dry bulb thermometers, fiiez hygrothermograph, Serdex humidity recorder, Bristol humidograph and a dew point apparatus. Only 2 institutions at present are using humidity controls, while several others indicate they will soon have facilities available for thie purpose. A Brown pneumatic and calcium chloride humidity control are in present use by the institutions reporting controlled humidity. Nine institutions are carrying on research involving air flow and the inatruments in use are the differential anemometer and the Alnor Velometer. Temperature recording devices in use are made by many different manufacturers. Recording themometera are ueed in general along with the use of thermocouples and recording potentiometers, In recent years specific gravity has been used by several researchera in mtimating percent moisture and percent fat in carcasse~and cuts. Most of the uork has been done with pork carcasses, while limited work has been carried out with lamb c&~cassesand beef ribs. Researchers indicate that tbie method is fairly reliable and only one worker indicated that he felt the method unaatlsfactory.

4 6. Considerable research i s or has been done involving the study of physical and chemical c h a r a c t e r i s t i c s of f a t and t h e concentration of soluble s o l i d s i n t h e press f l u i d from meat. Eleven i n s t i t u t i o n s report,they have used the refractometer f o r t h i s purpose. The viscometer has been used t o a very limited extent i n meat r e search, but eome researchers have used it i n blood study and developing meat sauces, I n an attempt t o eliminate the tedious task of separating lean, bone and fat and likewise t o g e t a quick estimate of percent l e a n i n c a r c m s e s and cuts, photographe and compensating planimeters have been used i n meat research. O f the two, the planimeter has been used most i n studying area relationships, but researchers indicate t h a t both methods are satisfactory. Marbling has been measured subjectively i n many research projects, but with any evaluation as such it is d i f f i c u l t t o make comparisons between s t a t i o n s. Most workers indicate t h a t the most accurate method we have i n volves determining percent f a t by ether extraction. Most h i s t o l o g i c a l studies have been carried out a s j o i n t projects with the personnel i n f i e l d s r e l a t e d t o meats. No doubt t h i s i s due t o the f a c t t h a t f e w of us f e e l qualified t o carry on independent h i s t o l o g i c a l research work. A t present o n l y a few i n s t i t u t i o n s have histological research projects i n progress. These are concerned f o r the most p a r t with the effect of cookery on various grades of meat. Many p r o j e c t s have been carried on i n t h e past. These projects have been concerned with the e f f e c t of grade, carcaas weight, aging, dehydration and cooking on t h e histological c h a r a c t e r i s t i c s of d i f f e r e n t muscles. I n addition, considerable a t t e n t i o n has been focused upon the s i z e of i c e c r y s t a l s as influenced by rate of freezing and t h e e f f e c t of freezing and thawing of mat, Likewise, Uver and other nonskeletal t i s s u e s have received some a t t e n t i o n. Histological f a c i l i t i e s a r e available i n 27 i n s t i t u t i o n s and t r a i n e d persormel f o r t h i s type of work i s present I n 8. A few of t h e projects t h a t would be studies i n other i n s t i t u t i o n e where f a c i l i t i e s were nat available are:. Study of changea i n connective t i s s u e during ripening, f r e e z ing and storage. 2. Study of changes involved i n heat processing. 3. Texture v a r i a t i o n in ham muscles. 4. Variation i n connective t i s s u e between Brahman and English breeds of c a t t l e. 5. Structure and d i s t r i b u t i o n of connective t i s s u e as r e l a t e d t o tenderness. With the f a c i l i t i e s and personnel available, it behooves some of u s t o c a r r y on some of thin research which i n most instances i s very fundamental.

5 62 As regards histological techniques, I w i l l attempt to summarize those i n current use. 3br the study of fatty tleeues the Scharlach R etain has been used by some worker's, while other8 studying the location and amount of iatramuscular fat on frozen sample8 used the fat-soluble dye, Sudan IP or osmic acid for study of 2 9fat. In the etudy of connective tissue both collagenic and elastic fibers can be etained with Weigert's or Mallory'e triple stain, This method is quantitative and a recent reference for the method is given In Anat, Rec. 05, 537, 949. Another reference for estimating quantitatively collagenic and, elastic fiber content s given in Food Technology 3: , 949. Reticular fibers are difficult to quantitatively mea~wef r o m collagenic figers. Ensyme studies apparently wen't being carried on t o any appreciable extent with histological techniques. Techniques for study of ice formation arid effect of freezing on tiss u e ~involve weighing and obtain Bamples i n the freezer or using a freezing microtome or the f'reezing-drying method. On frozen muscle sectlone the haemotoxylin stains e r e being used f o r fiber study. References for muscle fiber study can be found i n the Jour. of Animal Science, V o l. 2, No. 3, Aug., 943; Food Research 0, 6-27, 945 and Purdue Agric. Exp. Sta. Bull. 472, 942. General references for techniques i n histological studies are books such as Histopathologic Technique by Lillie; Techniques of Histo and Cyto Chemletry by Gliak; MaClurag's Handbook of Microscopical Technique by Jones and the Microtomistst Vade-Mecum by Gatenby and Painter. In a brief manner I hape listed the physical methods currently in use and i n sr,mmnriziw the needs for reeearch Involving these methods, I w i l l list those most apparent,. In color determinations we need eome rapid method which will minimize the influence of marbling and factors which affect color i n meat. 2. We need W a m e n t a l research in sampling techniques and need further to define what we mean by a representative sample. What can we do to overcome the present difficulties in sampling so that research i e comparable from station to station? 3. We need to standardize, especiallywith pork, the cut o r cuts used a8 reliable indicators of the caxcas8 content of lean, fat and bone. 4, At present dehydration and changes which occur between sampling and analyzing i s a problem which has been attacked in many riifferent ways. Here we need a good standard procedure. 5. In spite of the apparent feud between those using palatability committees and those using the Warner-Bratzler Shear, we apparently have f a i r l y reliable methods for measuring tenderness. Yet a more objective method, easy and simple in design would be desirable.

6 More research i s needed involving s p e c i f i c gxavity since not a l l workers agree on i t 6 merits. 7. We have t h e acceptable technique and t h e f a c i l i t i e s f o r h i s t o l o g i c a l meat research. Obviously, we need t o have more of our meat researchers trained i n hi6tological techniques i f w e are t o have t h e i n t e r e s t needed t o solve t h e many challanging problems involving h i s t o l o g i c a l c h a r a c t e r i s t i c s of meat. CHAIRMAN HANKINS: Thank you very much, Bob. Dr. b a d y is scheduled t o lead t h e discussion on t h i s report, and it is my pleasure t o introduce Dr. Brady. DR. EEUDY: It seems t o me from t h e discussion on t h i s physical and h i s t o l o g i c a l technique t h a t one might almost g e t some other impreseion t h a t these techniques are i n a very general way probably b e t t e r adapted t o q u a l i t y evaluation than they are t o processine: experiments and t o consumer acceptance. That i s a p r e t t y broad generalization. One of t h e big probleme he brings up i s samplilx, and y e t about t h e o n l y one of t h e methods of sampling t h a t he r e f e r r e d t o as being s a t i s f a c t o r y i s grinding, and yet, we r e a l i z e how unsatisfactory t h a t i s f o r q u a l i t y evaluation. The techniques which are involved seem designed mainly t o measure mall, but important differences. One o f t h e things t h a t Bob brought out was with regard t o t h e probing technique, Aunan, I believe t h a t i s some of your work. DO you care t o say anything about it? D r, Aunan: The probing technique w a s developed so we could go i n t o a packing house and c o l l e c t data on a l a r g e number of carcasses i n a hurry and g e t out of t h e i r way as Boon as possible. The reason for using t h e probing technique was t o f i n d out t h e l e a n and f a t content of t h e carcass. The carcasses were probed i n f i v e d i f f e r e n t places t o see whidh place w m the most d e s i r a b l e, The probe taken between t h e f i f t h and s i x t h r i b s, halfway between the sternum and t h e epinal column proved t o be t h e b e s t indication of t h e lean t i e s u e of t h e carcam, o r had the cloeeat r e l a t i o n s h i p between t h e amount of fat and lean i n t h e probe, and t h e f a t and l e a n i n the carcass and ahmed a c o r r e l a t i o n of 0.8. DR BRADY: W e would l i k e t o have t h a t turned i n for t h e report if you have It available 80 it can be included. Are t h e r e any queetione 'that you would l i k e t o d i r e c t t o Bob? MR. MACKINTOSE: Some of us who had t h e good fortune t o be present at some of the Conferences held i n t h e l a t e 2 0 ' s found t h a t a t t h a t t i m e we were confronted with aome of t h e same problems t h a t we a r e today, b u t I t h i n k the r e p o r t we have j u s t heard i s i n d i c a t i v e of an enormous amount of progress t h a t has been made since t h a t t i m e.

7 64. I can w e l l remember a report t h a t was offered Conferencee. I believe i t was D r. Black of the U.S.D.A. first e o r t of introduction t o h i s t o l o g i c a l atudiea It differenct, we might eay, t h e 8me a8 a number of other J u s t been mentioned, and f o r which w e now have a method a t one of those He gave the was new. It was items t h a t have of approach. MR. BRATLLER: Bob mentioned several inetrumente f o r meaeuring a i r f l a w. I believe it wae Brady or someboq, who mentioned the a i r meter t h a t waa put out by Haetinge A i r Meter at Hampton, Rhode Island. Crzi. BRADY: Yea, and at a p r e t t y reaeonable coat. ment, he said, cost $65 o r $75. Each i n s t r u - MR. BRA"2LER: Bob a l a o mentioned t h e two Cell Box Burrough Dueale f o r measuring humidity. We were fortunate t h i s year t o obtain the funds t o buy one. It i s euppoeed t o measure humidity, not only abme freezing, but below freezing. We have one ordered and I w i l l b e glad, i f any of you are thinking about g e t t i n g one, w e can give you our experience with I t. I have talked with e l e c t r i c a l engineers and they have r a i s e d t h e i r eyebrows when I t e l l them how i t l a going t o operate. It l e going t o b e accurate, so if any of you a r e interested i n knowing our r e e u l t s, I think I can get it t o you when w e get thinge going. It c o s t s about $540. I would be very much i n t e r e e t e d i n t h e matter of measuring humidit y below freezing. Swift uees t h e carbon dioxide technique. I n t r y i n g t o determine the point where f r o e t c o l l e c t e on a mirror you have t o use your eyes, whereas t h i s inetrument i e supposed t o do it without any pereonal work on the p a r t of t h e operator, and it would be a continuous recording inetrument. Cw BRADY: Ie that the machine that works on the basis of prec i p i t a t i o n on t h e elimination of chloride? MR. BRATZIER: Yes. Mi. B W Y : Bob, you talked about t h e Wwner-Bratzler Shear and said i t was eucceaaful mostly with cooked items. Wae eomething done with raw emplea, and bid you have erne succese, o r do you know of any way of estimating t h e tendernesa of raw aamplee with any degree of accuracy on beef, f o r example? DR. BRAY: Apparently everyone believed t h a t on cooked samples, it does a p r e t t y eood Job. Ae I recall it on the questionnaires, t h e r e wae not a s p e c i f i c mention ae t o t h e r e s u l t a on raw emplea. I underatand t h a t v a r i e e ecinewhat with the muscle you are working with, o r a t least I talked with D r. Doty of the American Meat I n s t i t u t e t h e other day, and he thought that on raw samplee, he g e t s f a i r l y r e l i a b l e r e s u l t a on t h e semi-tendinoeue muscle, whereas on t h e longieeimua dorsi muecle, he did not g e t REI good r e s u l t s DR. BRADY: Are there any other questions? I f not, we w i l l t u r n the meeting back t o our chairman, Mr. Hankina.

8 65 CHAIRMAN HAMaNS: Chemistry I s an lndlspeneible t o o l i n t h e research on meat. There can be no question about t h a t. Perhaps it becomes more and more so, and w 8 have assembled q u i t e an i n t e r e s t i n g report on t h a t phase of our Committee work. Dr. Hall of Kaneaa State College w i l l present t h a t portion D r. Hall, i f you pleaae. of our r e p o r t. ###