QUAL I T Y C H A R A C T E R i S T l C S I N PORK

Transcription

1 TECHNIQUES OF NfASURlNG SOME QUAL I T Y C H A R A C T E R i S T l C S I N PORK I n previous studies of pork evaluation, t h e term q u a l i t y has received various meanings. Even though some researchers have referred t o muscling, fatback thickness, and lean cut y i e l d as f a c t o r s of pork quality, I prefer t o r e s t r i c t t h e q u a l i t y a t t r i b u t e s of pork muscles t o those which d i r e c t l y a f f e c t t h e p a l a t a b i l i t y and processing c h a r a c t e r i s t i c s of them. The q u a l i t y f a c t o r s of pork, f o r t h e most p a r t, p a r a l l e l those of lamb and beef; namely tenderness, flavor, juiciness and color. It i s t h e purpose of this presentation t o outline a series of procedures which can be used t o measure objectively and subjectively these q u a l i t y a t t r i b u t e s. The data presented today originates f r o m a research study now being conducted by t h e University of Wisconsin i n cooperation with the U.S.D.A. and with t h e assistance of Oscar Mayer and Co., Inc., Madison, Wisconsin. Since the majority of those present a r e familiar with many of the techniques, I will only mention t h e m f o r completeness of the report. If there a r e any questions concerning these, I w i l l attempt t o answer them i n the discussion period which follows. The f i r s t f a c t o r I w i l l discuss i s that of pork tenderness. For many years t h e idea existed that a l l pork was tender. On the contrary, we have observed i n our project that pork chops and f r e s h ham s l i c e s can be very dry and very tough; however, the curing process of t h e hams and b e l l i e s may reduce some of t h i s variation. The techniques used f o r measuring tenderness may e i t h e r be subjective o r objective i n nature. Organoleptic t e s t i n g has received much a t t e n t i o n i n the last several years and a t present it is considered as a very reliable technique i n measuring various q u a l i t y aspects of meat. Certainly a large, well-trained panel may be one of our best methods i n determining t h e degree of tenderness. Panel ratings and number of chews a r e the two general measures considered, The following s l i d e s portray a taste panel t s s t i n g samples f o r our pork q u a l i t y experiment. The remaining techniques a r e objective i n nature and are methods which attempt t o duplicate the tenderness response of t h e human. The dent u r e tenderometer operates on the principle of amount of pressure exerted 011 a s t r a i n gage (which i s i n turn recorded on an oscilloscope) t o force one jaw of a set of dentures t o b i t e a standard s i z e sample of meat. Other modifications of t h i s e x i s t ; however, d i f f i c u l t y has been encountered when more than one d i r e c t i o n of action i s applied t o t h e meat sample. Another method includes the grinder power-recorder technique, similar t o that previously reported by D r. FBlmer last f a l l, One disadvantage of t h i s method i s the large number of meat cores required f o r accurate analysis. A t h i r d measure i s the wedge tenderometer, which was developed by Oscar Mayer and Co., Inc. and the Visking Company of Chicago. The meat sample i s placed on

2 155. a moving table (powered by a small e l e c t r i c motor) and i s elevated toward a wedge, which i s attached t o a recording spring scale. The i n i t i a l purpose of such an instrument was f o r making quick tenderness determinations. The machine could e a s i l y be carried and handled throughout a packing plant. Finally, I should mention the Warner-Bratzler Shear. m c h controversy has been made over t h i s method; however, it remains as one of the most widely used techniques. The next slide shows a camparison of the six methods I have prcesented. The methods we= conducted on a random sample of results which include six pc2k l o i n s i n each of f i v e diffexvnt marbling scores. Each measurement was made on each of the samples included i n t h i s comparison. Table 1 A Comparison of Various Techniques f o r Neasuring Tenderness (6 pork l o i n s per marbling score) Techniques Cooked I Panel score (5 = ve ry tender) (5 ex- tens ive ) Panel Denture Grinder Shear No. Tender- Tender- (J.b5./ Chews ometer ometer in ) (ht. i n (cm2/g) cm) I 'Shear (lbs./ in21 - Wedge Tenderometer (lbs/ in2) OW O e Marbling 1 scores ' Raw.093 i = \I/ J/ It is interesting t o note that a l l techniques follow t h e same trend except the two which were used on raw samples. One may also note the extreme difference i n tenderness as recorded by the shear between the r a w and cooked samples. The above techniques a m only a portion of t h e methods which may be used i n t h e future. Other p o s s i b i l i t i e s are the following: 1. The pmssure technique of measuring tenderness as described by Dr. Hiner of t h e U.S.D.A. 2. The precision penetromter which has received only limited use i n meats. 3. The f i b e r stretching technique as described by Dr. Wag.

3 156. The next f a c t o r f o r consideration is flavor. Here one i s attempting t o measure the e f f e c t s of meat which w i l l stimulate two senses that -- of smell and taste. These two senses work as a team, and demnstrations have shown t h e extmme d i f f i c u l t i e s encountered when attempting t o separate their responses. The attempts t o reproduce mechanically the action o f several thousand t a s t e buds and b i l l i o n s of olfactory nerve centers have not been completely successful. Therefore, we again t u r n t o t h e taste panel f o r our best 'out not necessarily ultimate technique for evaluating pork flavor. Much work i s now being done t o chemically aaalyze flavors f o r their composit i o n and nature. Several research teams are presently studying f l a v o r s by using p a r t i t i o n ( g a s ) chromatography and mass spectometry. The next s l i d e shows an example of one approach taken i n the analysis of meat flavor. Juiciness is the next f a c t o r. Again, perhaps, the t a s t e panel scoring technique may be our most reliable method a t present. Some panels give only one score while others have attempted t o score the sample a t t h e beginning and again at the completion of mastication. A t t h i s point I w u l d simply l i k e t o make t h i s comment about t h e capacity of a t a s t e panel. It appears that too many evaluations p e r sample may be detrimental t o a t r u e response. When too many d i f f e m n t f a c t o r s ~ incorporated, complications may arise. It is my thinking that t h e number of f a c t o r s should be held t o a minimum. This is in good agreement with judgements made on panel responses by some psychologists. Other techniques which may indicate the degree of juiciness include the f i l t e r press method. Here, expressible juice i s measured by applying pressum t o a standard s i z e sample of meat and then determining the area of j u i c e which i s separated from t h e s o l i d portion. This quantity may be d i r e c t l y o r i n d i r e c t l y associated with panel juiciness scores. S t i l l another method i s that of the centrif'ugation technique as described i n a past conference by Dr. Deatherage. The carver prcss has a l s o been used; however, we have found t h i s method quite d i f f i c u l t i n measuring the ext r a c t e d j u i c e quantitatively. The following table depicts a comparison of panel scores, f i l t e r press determinations, Carver press determinations, '$ t o t a l water, $ cooking l o s s, ph of l o i n after eeven days aging and marbling scores all based on taste panel juiciness scores of the pork l o i n. -- Table 2 Techniques f o r Measuring Juiciness Taste Panel JuiciEess Score No. ples Filter press 5 T o t a l Cook Ekpressi- 2 Camer Press $ Total Juice ph Marbling Score * 24.5** c 2 7. F * 7 samples +w 5 sanples *we 3 samples

4 157. Even though color may not d i r e c t l y influence some of the palatab i l i t y c h a r a c t e r i s t i c s of pork, it does play an important role i n consumer acceptance and as a c r i t i c a l f a c t o r i n d e s i r a b i l i t y of pork f o r processing purposes. It has been demonstrated that color i s highly associated with water binding capacity, expressible juice, and a c i d i t y of pork muscle. Ughter colored pork m a c l e is lower in ph, thus approaching t h e i s o e l e c t r i c point of t h e muscle protein and therefore has less water binding capacity and a higher percentage of expressible moisture as a portion of the t o t a l water content. These f a c t o r s alone are c e r t a i n l y important ones when pork is subjected t o processing techniques which may depend upon good water binding c h a r a c t e r i s t i c s of the nrrscle protein. To masure color, photographic standards f o r subjective evaluation may be used. Since ph i s highly related with color and water binding capacity, t h e ph meter i s used. It has been postulated that the ph of meat may spell out many f a c t o r s o t h e r than color that ma;y be d i r e c t l y responsible f o r the f a c t o r s of pork quality. If m o precise ~ methods for color determinstion are desired, such apparatus as t h e E unter Color Difference Neter, the Munsel color paddles, and spectrophotometors may be used. Firmness of carcass i s another f a c t o r which i s usually considered in t h e discussion of pork quality. Tkis i s insortant f o r good keeping quality of the product and possibly t o allow f o r more uniform curing. The techniques f o r measuring such have been extremely limited except t o relate it t o lean t o fat r a t i o and f i n a l l y t o t o t a l water content of the carcass. Subjective cores are usually established t o indicate whether the carcass o r cut is extremely soft, s o f t, moderately firm, firm, o r extremely firm. This has been the technique used i n our study; however, a more time-consumin@;t e c h i q u e i s a l s o used. The unsaturation of pork fat has been shown t o be related t o firmness. Thus, the Iodine number i s employed f o r our studies. Even though differences prevailed, the magnitude of numbers between carcasses scored as very f i r m and those scomd as very s o f t was not large. Therefore, a chemical investigation was made of twelve fatback samples representing opposite extremes of firmness. Iodine number, saponif i c a t i o n number, t o t a l m o i s t u r e, e t h e r extract and Kjeldahl analysis were included i n this t e s t. The following table gives the r e s u l t s : Table 3 Chemical Analysis of Pork Fatback Iodine No. ( of L I@O g fat) Saponification No. Moisture (mg WH/g f a t ) 9 Fat P Protein % 6 very s o f t carcass es very firm carcasses

5 15. This comjywison suggests that unsaturation may be one f a c t o r which i s related t o firmness, but that t o t a l moisture content may a l s o influence firmness. Since the numbers are quite small, final conclusion m u l d not be appropriate a t t h i s t b. Other possible measures f o r firmness include s p e c i f i c gravity on a micro-level of lneasurement, detemination of r e f r a c t i v e index which i s a r a t i o of t h e velocity of l i g h t i n a vacuum t o velocity of l i g h t measured i n the f a t t y t i s s u e, melting point determination, and possibly a measure of v i s c o s i t y a t a temperature i n which a l l fats t e s t e d would be i n the l i q u i d phase. I would finally like t o close t h i s discussion by mentioning a few o t h e r techniques I am presently using with hopes that they will be of sone help i n predicting high-quality pork. An e l e c t r i c a l r e s i s k n c e apparatus is being used on fresh meat samples. It i s postulated that as marbling content increases, t h e resistance against an e l e c t r i c c u r n a t passed will also increase. Also, the water binding capacity and ph may a f f e c t resistance. The next s l i d e i l l u s t r a t e s t h e use of this iizstnunent and the following s l i d e shows a comparison of e l e c t r i c a l resistance t o marbling content of 196 l o i n s and 37 center cut ham s l i c e s. The r e s u l t s indicate that some association may p r e v a i l between these two f a c t o r s.!table 4 E l e c t r i c a l Resistance i n Hams and Loins vs. Marbling Score -- Hams ohms I _ Marbling scores -. Loins Ohms No. NO IC Other measurements f o r consideration t h i s morning include h i s t o l o g i c a l comparisons which are quite time-consuming for preparation, but a technique which may answer questions concerning d i s t r i b u t i o n of marbling and connective t i s s u e. Subjective scores f o r indications of marbling such as overflow and feathering and lumbar marbling way gain importance. Also, e s t i mations of maturity i n carcasses by such indications as t h e redness of bone, pmminance of s o f t cartilaginous buttons and carcass w e i $ h t may be helpful if age does play a r o l e i n quality.

6 . 159 I n summary, I have very b r i e f l y discussed some of t h e techniques which may be masuzxments of pork quality. A t present, no s i n g l e method may stand alone as t h e correct indication of t h e various q u a l i t y f a c t o r s. It remains necessary t o use as many indications as possible t o more nearly i n sure the v a l i d i t y of t h e conclusions d,-awn. Before closing, I want t o emphasize that the data used here a= only preliminary in nature and serve only t o i l l u s t r a t e the values that can be derived from the methods described. - BIBLIOGRAPHY Bluer, T, N. e t. al. Influence of Changing the Kind of Fat i n the D i e t a t Various Weight I n t e r v a l s on Carcass Fat Characteristics of Swine. Journal of Animal Scfence, Vol. 16, No. 1, February, Briskey, E. J., W. G. Hoekstra, R. W. Bray and R. H. Gnunmer. A Comparison of Certain Physical and Chemical C h a r a c e r i s t i c s of Eight Pork Pk.~scles. Journal of Animal Science, Vol. 17, No. 4, November, 195. Doty, D. M. Applications of Physics in the b a t Industry. I n s t i t u t e Foundation, Circular 25, December, American Meat Emerson, J. A. and A. 2. Palmer. A Motorized Food Grinder-Becording Ammeter Technique i n Determining Beef Tenderness. Journal of Animal Science, Vol. 17, No. 4, November, 195. Everson, C. W. e t. al. Rapid Methods f o r Determination of Fat and Moisture Content i n Meat Products. American Meat I n s t i t u t e Foundation, E M. No. 26, Judge, M. D., V. R. Cahill, L. E. Kunkle and F. E. Deatherage. Physical, Chemical and Organoleptic Relationships i n Fresh Pork. Journal of Animal Science, Vol. 1 7, No. 4, November, 195. Pierce, E. A. Bacon Quality, South Eekota Farm and Home Research, Vol. 4, No. 1, Fall, Schweigert, B. S. e t. a l. The Amino Acid Composition of Pork and Lamb Cuts. American Meat I n s t i t u t e Foundation, Publication 10, 1949 and 190, Self, H. L. The Problems of Pork Odor, Proceedings of the Ninth Research Conference, American Meat I n s t i t u t e, University of Chicago, March, Schweigert, B. S. Biochemistry of MyqQobin. Foundation, 1954 and American Meat I n s t i t u t e Wang, H. e t. al. E x t e n s i b i l i t y of Single Beef Muscle Fibers. Animal Science, Vol. 15, Journal of

7 160. MR. AUNAlT: The next discussion is t h e Status of the Application of Ultrasonics i n Meat Animal Evaluation, given by Dr. J. R. Stouffer, Corne 11