J u s t as important i s a study of sampling procedures, which should

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1 78 METHODS OF S A M P L N G V A R O U S MZA.T N G R E D E N T S W T H R E S P E C T TO ACCURACY, P R E C S O N AND L M T A. T O N S OF R A. P 0 MZTHODS TO D E T Z R M N E M O S T U R E, FA.T AND P R O T E N W. A. TEXASA & LANDHANN M UNVERSTY C. O..L.L.E.G. E..S.T.A.T..O. N..,.T.E. X..A.S n t h e processing of meat f o r sausage manufacture one of t h e chief problems has always been obtaining an accurate a n a l y s i s of t h e r a w ingredie n t s so t h a t t h e composition and q u a l i t y of t h e f i n a l product may be assured. Modern packing house p r a c t i c e s include extensive q u a l i t y c o n t r o l which has r e s u l t e d i n uniform, r e l i a b l e products f o r t h e customer, and, hopefully, more economical u t i l i z a t i o n of ingredients. Good q u a l i t y c o n t r o l requires a knowledge of sampling procedures and rapid methods of a n a l y s i s which give accurate r e s u l t s, p a r t i c u l a r l y s i n c e meat i s so heterogeneous i n composition. Poor sampling p r a c t i c e s w i l l give r e s u l t s which are j u s t as u s e l e s s o r u n r e l i a b l e as those obtained by inaccurate methods of a n a l y s i s. A s w i l l be shown l a t e r, t h e methods themselves are o f t e n inaccurate because t h e a n a l y s t confuses precision with accuracy. *ny methods may b e precise, and s t i l l be inaccurate. That is, an a n a l y s t w i l l be a b l e t o repeat h i s r e s u l t s q u i t e closely, b u t these r e s u l t s w i l l not be t h e a c t u a l t r u e value f o r t h e amount of t h e substance being determined. Hence, some of t h e o l d standby methods, when examined by c o l l a b o r a t i v e s t u d i e s show t h e need f o r revision o r replacement. J u s t as important i s a study of sampling procedures, which should b e done before deciding on a p a r t i c u l a r procedure. Perhaps more o f t e n than one would care t o think, t h i s s t e p of t h e q u a l i t y c o n t r o l process i s e n t i r e l y neglected. What i s t h e ideal s i t u a t i o n f o r accurate q u a l i t y c o n t r o l? t would be, think, a simple procedure f o r sampling (preferably from a homogeneous l o t of material), coupled w i t h a rapid method of a n a l y s i s req u i r i n g only a f e w minutes t o complete, thus avoiding shutdown o r delay on t h e processing l i n e. A nondestructive type of a n a l y s i s should perhaps also be included i n t h e s p e c i f i c a t i o n s. A t present, none of t h e procedures commonly used can q u a l i f y i n a l l respects, and it i s doubtful if any ever w i l l meet a l l t h e conditions of i d e a l i t y. L e t u s examine some of t h e sampling procedures used f o r meat trimmings, or meat ingredients. Several standardized sampling procedures Professor, Meats Chemistry, Animal Science Department, Texas A&M Univ e r s i t y. College S t a t i o n, Texas. Paper read by R. L. Hostetler.

2 for meat are published in the Official Methods of the AOAC and in Labora tory Methods of the Meat ndustry. These sampling procedures consist of grinding the entire sample through a plate containing holes l/s in diameter, by means of an electric grinder fitted with a device for halving the sample. One half the sample is then thoroughly mixed and reground, again dividing the sample in half. "he process is repeated until a convenient size sample (46 02.) is obtained, which is placed in closed jars and refrigerated until analyzed. The entire procedure is carried out in the cold to minimize evaporative losses of moisture. While this process is feasible for samples of moderate size, it becomes quite difficult to sample lots of 500 lbs. or more in this manner. How does one then obtain an adequate or "representative" sample? For example, 500 lb. tubs of pork trimmings may be sampled by taking 2"cores at random throughout the tub. The minimum number of such cores should be nine to get a statistically justifiable estimate of the actual mean value of the composition of the contents of the tub. f the process is such that the trimings can be minced before sampling, it would be preferable to remove small samples at random from time to time from the moving stream of minced mixture. Frozen meat, usually packed in CO lb. boxes can be sampled in a similar way by taking 6 drillings at random from each box. n a refrigerated railway car, boxes can be sampled by removing the necessary number at random while they are being unloaded. Each box may then be sampled by drillings. Any procedure such as this should be checked to see if adequate sampling is being obtained. This can be simply done by making several replicate samplings, and comparing the results by means of a hierarchal or nested design, which may be found in any book on statistics. This will give information as to the source of error, and also will indicate whether the number of boxes, the number of samples within boxes, or number of analyses must be increased to achieve maximum accuracy. Once this is done, it is usually not necessary to repeat such a study unless difficulty is again encountered. An interesting approach to the accurate analysis of the percent fat in 500 lbs. of trimmings has been suggested by H. 0. Hartle~.~ The contents of the tub are spread out on a table and separated by eyeestimate into three groups high fat, medium fat, and low fat. Each group is weighed to determine the total bulk weight in each "stratum." Three samples from each group are chosen at random, mixed together, and the fat determined for each group. The total weight of fat in each stratum 79. Official Methods of Analysis A.O.A.C., Ninth Edition, Association of Official Agricultural Chemists, Washington, D. C., 960. Laboratory Methods of the Meat ndustry. Chicago, 957. American Meat nstitute, Hartley, H. 0. Personal Communication.

3 80 i s calculated, and t h e values f o r a l l s t r a t a a r e s u m e d. Thus t h e p e r cent f a t i n t h e t o t a l sample (sum of bulk weights of t h e groups) can be determined. The variance of t h e determination i s of t h e order of 2% and t h e accuracy achieved through t h e sum of t h e weighted means i s considerably b e t t e r than with n o n s t r a t i f i e d sampling methods. However, somewhat more eff o r t and time a r e required t o c a r r y o u t such a procedure. n summary, w h i l e many and varied sampling techniques a r e t o be found, any which a r e used should be adequately t e s t e d t o be sure they a r e r e l i a b l e and t h a t they provide r e p r e s e n t a t i v e samples. The r e s u l t s of such a study, properly c a r r i e d o u t, w i l l save time and money i n reducing t o a minimum t h e number of samples t o b e analyzed f o r r o u t i n e q u a l i t y c o n t r o l. Now what about r a p i d methods and t h e i r l i m i t a t i o n s? Meat process o r s a r e i n t e r e s t e d primarily i n t h e moisture, f a t, and p r o t e i n content of t h e i r raw m a t e r i a l s and f i n i s h e d products. Several methods which come t o mind a r e f i n d i n g more o r less general use. Ealances employing i n f r a r e d r a d i a t i o n f o r moisture, Babcocktype o r conductivity analyses f o r f a t, and dyebinding methods f o r p r o t e i n s give s a t i s f a c t o r y r e s u l t s, b u t u s u a l l y must be c o r r e l a t e d with standard methods by means of regression curves. The Cotlove chloride analyzer, o r a r e c e n t potentiometric t i t r a t i o n method4 have been shown t o give e x c e l l e n t r e s u l t s f o r s a l t. A l l of these serve t h e i r purpose i n rapid q u a l i t y c o n t r o l, b u t have not been studied c r i t i c a l l y enough t o e s t a b l i s h them a s standard methods. n making comparisons of r a p i d methods with standard methods, it should be r e a l i z e d t h a t standard o f f i c i a l methods have many shortcomings, and a r e s u b j e c t t o many of t h e same l i m i t a t i o n s a s t h e newer rapid methods. One of t h e d i f f i c u l t i e s i n comparing r e s u l t s of a new method with a standard method is t h a t t h e inherent e r r o r s of t h e standard method a r e not c l e a r l y known. The AOAC has had f o r a number of years a continuing program of c o l l a b o r a t i v e s t u d i e s of methods t o obtain t h i s information and i s continually r e v i s i n g i t s o f f i c i a l methods as r e s u l t s of these s t u d i e s become a v a i l a b l e. The American k a t n s t i t u t e Foundation has a l s o conducted a similar study of meat methods, with s i x t y l a b o r a t o r i e s p a r t i c i pating. Results of these method s t u d i e s have been q u i t e informative, e s p e c i a l l y when examined by a technique described by Youden5, 6, 7. Briefly, t h e r e s u l t s a r e p l o t t e d on a twodimensional s c a t t e r diagram, where t h e Xaxis and Y a x i s have t h e same s c a l e. The values ( s i n g l e determinations) 4Krzeminski, L. F., Bartal, A. and Landmann, W. A., 52 (965). %ouden, W. J., Anal. Chem., 32, 23A (960). Youden, W. J., And. Q u a l i t y Control, 5, 24 (959). 7Youden, W. J., J. O f f. Agr. Chem., 45, 6 9 (962). J. Food Science, 30,

4 8. from two different sau.iples of similar materials are plotted for each laboratory, X being the result of the first determination and Y that of the second. The consensus of all values is considered the true value and through this point the diagram is divided into four quadrants. The biasfree estimate of the standard deviation of all points is calculated and two circles are drawn, using the concensus point as the centroid. The smaller circle has a radius of.7s, and the larger, 2.45s. According to probabilities based on circular normal distribution, 95% of the points should lie within the larger circle and cluster around the centroid. f perfect precision existed, but if each laboratory had persistent bias, the points would lie along a 45O line through the centroid, and in the upper right and lower left quadrants. Bratic results (high for one sample, low for another) would place the points in the upper left and lower right quadrants. Examples of the application of these Youden plots to some method studies are shown in the following slides. Slide Moisture Determination. The results show individual laboratory bias, and some serious erratic results. The bias arose here primarily from failure to follow the drying conditions exactly. Oven temperatures and time of heating were often not the same for the two samples, and were the primary causes of the erratic results. Slide 2 Protein Determination. (AOAC) This "old faithful," the Kjeldahl nitrogen method, shows 30% of the laboratories outside the circle which should contain 95% of the points. This distribution was only slightly improved when specific directions were given regarding length of time of digestion, amount and kind of catalyst. Serious deviations from the prescribed method, some of which are not consistent within a laboratory, are indicated here. Slide 3 Fat. This diagram shows results of more than one method, and some of the bias (points close to the 45 line) is due to the method difference. However, all methods appear to give cornparable results, since the methods were not significantly different. The fault again is primarily the individual bias. Slide 4. Salt. The method appears to ce satisfactory, although some results show bias. These laboratories were asked to check their procedures. The clusters of points occur because values were rounded off when reported. Slide 5 Nitrite. The classic example of a thoroughly unsatisfactory method subject to errors due to individual handling and treatment of sample, as well as to individual bias. n closing, these studies show convincingly that the most serious limitation of all rethods is the desire of the analyst to be a nonconforming creative individual. The point wish to make, however, is simply that in using any method rapid or standard one mst be constantly aware of the variations which exist. To keep these differences to a minimum, it

5 82. i s extremely important t o use a r e l i a b l e, t e s t e d sampling procedure and t o follow t h e specified d i r e c t i o n s of t h e a n a l y t i c a l method a s exactly a s possible. Frequent checks on laboratory procedures, using known samples, would seem t o be i n order. Slide Results of moisture determinat i o n on two samples of a l l meat sausage, using AOAC method (a) nner c i r c l e. 7 s t d. dev., o u t e r c i r c l e 2.45 s t d. dev.. ow k b Slide 2 Protein determination on two samples of a l l meat sausage, according t o method AMA4a54, a U e l d a h l procedure specifying HgO as c a t a l y s t, as in AOAC method !

6 Y.2 Slide 3 *! Fat determination on two samples of all meat sausage. Methods indicated in text.! " t i p " Wee a b a.0 dj am b p Y.l z a b S a Salt determination on two samples of all meat sausage, using method AMA6a54. n.*,, 6 f, 2.7 P r C a t U t ia t " Results of determinations of sodium nitrite on two samples of all meat sausage. Range of.7 std. dev. shown by circle is much too large for a reliable method b " Slide 5 Y.2 z. a t *

7 84. n closing, these studies show convincingly that the most serious limitation of all methods is the desire of the analyst to be a nonconforming creative individual. The point wish to make, however, is simply that in using any method rapid or standard one mst be constantly aware of the variations which exist. To keep these differences to a minimum, it is extremely important to use a reliable, tested sampling procedure and to follow the specified directions of the analytical method as exactly as possible. Frequent checks on laboratory procedures, using known sqles, would seem to be in order. DR. ROBERT SAFFLE: Thank you, Bob. We appreciate the presentation of Dr. Landmanns on the methods and some of the limitations which we might expect. t certainly points out an area that needs considerably more research work. Cur third speaker has been with us at least once and believe two times. George Brissey graduated from U.C.L.A. with an A.B. in Fhilosophy and Chemistry in 933; he then joined Swift & Company in their Control Laboratory; hes been with Swift ever since except for a short stint with Uncle Sam. He was transferred to the R & D Center in Chicago in 944 and for several years, he was Associate Director of Research, coordinating the Neat Research activity for Swift & Company. Since 963, he has been Assistant General fanager of the Quality Assurance Department in the General Office of Swift & Coxripany in Chicago. The area which he will cover is the "Specific Needs for Research Related to Statistical Control in Yanufacturing and Nhrketing Processed Neats". By agreement, in setting up the program, he decided to take a specific method concerned with M..D. to shcw how statistic control was used in working out a specific nethod.