with empkas is - meat science

375

METHODOLOGY FOR SENSORY TESTING WITH ON LIMITATIONS OF TESTS*

EMPKAS IS

JUNE B . REAUME Amour Food Research Division

Have you ever s t a r t ed t o t a l k about Sensory Evaluation, noticed quizzical expressions on the faces of some of the people t o whom you were speaking and real ized they were mutely asking, "Exactly w h a t i s Sensory Evaluation? I f

It appears t h a t everyone i n the f i e l d has had h i s own explanation because an o f f i c i a l def in i t ion has never been acknowledged or published.

Last week a t t he annual IFT meeting i n Chicago, the Sensory Division adopted--by membership ballot--an o f f i c i a l def in i t ion f o r Sensory Evaluation. def in i t ion input from a l l of the divis ion members both here and abroad. The suggestions were careful ly analyzed and key words were t i e d together and the resul t ing def in i t ion c l ea r ly expressed w h a t sensory evaluation means. This is the def ini t ion:

It was the r e su l t of a two-year e f f o r t col lect ing

Sensory Evaluation is a s c i e n t i f i c d i sc ip l ine used t o evoke, measure, analyze and in te rpre t reactions t o those charac te r i s t ics of foods and materials which a re perceived by the senses of s igh t , smell, t a s t e , touch and hearing.

To accomplish t h i s , we m u s t use psychology, physiology, physics, chemistry, microbiology and s t a t i s t i c s supported by good judgment and p rac t i ca l down-to-earth common sense.

I n Research and Development we need sensory t e s t s t o ensure the quali ty, pa l a t ab i l i t y and s t a b i l i t y of our products when they reach the consumers' table . So far, we have been unable t o measure the t o t a l sensory aspects of foods by mechanical, physical or chemical means. No instrument or combination of instruments has been developed that r e f l e c t s the sensory responses transmitted t o the brain.

The beginning of Sensory Evaluation cannot be spec i f ica l ly dated-- but surely Eve had something t o do with it when she fed Adam the apple.

Improvement i n food f lavor was no doubt generated i n the ea r ly days of c iv i l i za t ion when primitive man accidentally dropped a piece of raw meat i n to h i s campfire. He found a difference i n the meat's aroma, - flavor, juiciness and texture , and a wide nation and food preferences have evolved. preferences have affected h is tory and the

new world of f lavor discrimi- Flavor d is t inc t ions and food

progress of man.

* Presented a t the 28th A n n u a l Reciprocal Meat Science Association, 1975.

Meat Conference of the American

376 Sensory t e s t i n g may appear t o be simple, but it i s not as easy as

it seems t o provide r e l i ab le and val id r e s u l t s . The layman usually knows t h a t f lavor i s nothing more than t a s t e + s m e l l , and t h a t texture i s the way food f e e l s i n the mouth. He might reason tha t bench top t a s t i n g with h i s boss and a few colleagues is suf f ic ien t f o r marketing a new product. s i b i l i t y of estimating consumer acceptance/preference, unassisted by quantitative/ qua l i t a t ive sensory t e s t s .

This procedure burdens the group w i t h the heavy respon-

The complexity of human behavior is a r e a l challenge and it i s a basic consideration i n the scope of sensory analysis . We use people as our instruments and we must be constantly aware that we are dealing with a de l ica te t a s t ing instrument. Special controls a r e required i n the laboratory t o determine the sensory qua l i t i e s of food. Careless, slipshod sensory procedures usually lead t o questionable t e s t r e su l t s .

Many human feelings t h a t have no relat ionship t o the t e s t s i tua t ion must be considered--getting up on the wrong side of the bed, ra in , snow, sunshine, t r a f f i c jams, experience, background, the da i ly grind--any- thing can, i n f a c t , s e t up a psychological chain reaction that can influence the t a s t e pane l i s t s ' sensory perception. The conditions under which we obtain psychological measurements a re important.

For t h i s reason, e f fo r t s a r e made i n our laboratory t o keep the t e s t s i tua t ion as controlled as possible. t e s t i n g areas t h a t a r e quiet , comfortable and designed t o reduce outside pressures. Sample preparation and presentation a re standardized and unif o m .

We accomplish t h i s by using

The type of t e s t used depends upon the par t icu lar objective. development of sensory methodology involves many techniques f o r d i s - crimination tests, preference/acceptance t e s t s and descriptive t e s t s . Sometimes i t ' s necessary t o use more than one type of sensory t e s t t o obtain a complete evaluation of the sensory aspects of a food product. It i s the responsibi l i ty of the sensory s c i e n t i s t t o be thoroughly acquainted w i t h every known sensory method. and asse ts of each t e s t .

The

He must know the l imitat ions

I n order t o c l ea r ly define the objective of a t e s t , it i s of the utmost importance t h a t there i s communication and comprehension between the research s c i e n t i s t and the sensory invest igator . enormous technology, there are times when we communicate no be t t e r t h a n the inhabitants of the Tower of Babel. Committee ( E - B ) of the American Society f o r Testing and Materials and the Internat ional Standards Organization a re working t o provide a glossary of terms and def ini t ions t h a t w i l l be understood and agreed upon. our sensory "Tower of Babel."

Despite our

The Sensory Evaluation

When t h i s e f f o r t i s f u l f i l l e d there may be l e s s pandemonium i n

Many sensory investigators become too secure i n a ro te procedure f o r t e s t ing t o invest igate new methods, modifications and changes t h a t a r e avai lable t o improve sensory s tudies . L iab i l i t i e s occur when t e s t methods a r e used simply because they a re famil iar t o the investigator and the pane l i s t s .

377

Test designs a r e generally planned with a s t a t i s t i c i a n . S t a t i s t i c a l methods a re too numerous t o discuss i n t h i s br ief presentation. However, recommendations f o r the application of s t a t i s t i c a l procedures a re available i n the ASTM-SW 434 manual. Sensory Evaluation, Amerine, Pangborn and Roessler devote Chapter 10 t o s t a t i s t i c a l procedures.

I n the volume Principles of

Basically, there a re three types of Sensory Methodology: Discrimi- A few nation Tests, Descriptive Tests and Preference/Acceptance Tests.

of the t e s t methods a re shown on these s l i des .

Discrimination tests answer the question--1s there a detectable difference or a re these products similar? For these t e s t s , panel members a re screened and t ra ined f o r discriminative a b i l i t i e s . t en judges a re selected and t h e i r performance i s monitored. Occasionally, l i k e our mechanical instruments, they need t o be overhauled and retrained f o r good performance.

Usually

I n the t r iangle test, 1 odd and 2 ident ica l samples a r e presented simultaneously t o the judge. He i s asked t o ident i fy the odd sample. This i s a comfortable t e s t f o r the ro te investigator because it was one of the f i rs t recognized procedures and generally familiar t o a l l . How- ever, because each judge is seeking the odd sample, the samples should obviously d i f f e r only i n the component being studied. For example, it would be f u t i l e t o conduct a t r i ang le t e s t on the f lavor of bacon s l i c e s ( t rea ted versus control) unless a l l samples came from the center o r the shoulder or the f lank of paired b e l l i e s . If the samples are not oriented f o r presentation, the appearance of the s l i c e s i n addition t o the f lavor of the fa t / lean r a t i o would invalidate the t e s t . confined t o homogeneous samples and must be used with discret ion. a r e excellent when applied t o samples with no physical difference.

Triangle t e s t s a r e They

I n the Duo-Trio t e s t , 1 sample is offered first and ident i f ied as the standard. Then, the judge i s given 2 coded samples, i n random order, one of which i s iden t i ca l t o the f i r s t sample. the d i f fe ren t or matching sample. should be used only when samples a r e homogeneous.

H e i s asked t o ident i fy Like the t r iangle t e s t , the duo-trio

Paired Comparison t e s t s a r e used t o determine the differences or similarities of a specified charac te r i s t ic . However, i f differences a re apparent, the Paired Test provides no indication of t he s ize of t he difference.

Rating/Difference scales a r e designed t o measure the in tens i ty of specified components. sca le which i s categorized by descriptive terms. t e s t s , it requires t ra ined panel is ts unless large numbers of panel is ts a r e available.

The panel is t scores on a structured or unstructured Like a l l discrimination

378

Sensory invest igators can relax when the t e s t objective requires pref erence/acceptability judgments . wrong--he does not require "overhaulingtf--because his l ikes and d is l ikes a re in fa l l i b l e . I n a laboratory t e s t , judges a re picked a t random f rom a l l available personnel. Due t o the l imited demographic representation, laboratory r e su l t s from these t e s t s a r e considered t o of fe r d i rec t iona l guidance only. The r e su l t s a re ten ta t ive and subject t o ver i f ica t ion by market tests.

The judges ' responses cannot be

I n preference ranking t e s t s , the questionnaire i s worded so tha t t he panel is t w i l l indicate his order of preference fo r samples. It negates the f a c t that 2 samples m y be l iked equally, and gives no indication of the degrees of difference i n preference.

Hedonic-tests measure the degree of l ike-d is l ike of a product as opposed t o ana ly t ica l sensory assessments regarding product construction. The name of the scale hedonic i s derived f romthe Greek word Hedonist and the scale i s used t o e l i c i t responses re la ted t o pleasant or unpleasant. aspects-- i t cannot a t any time be used t o provide data which could be correlated w i t h an instrument.

Due t o i ts purpose--i.e ., responses based upon the emotional

The Food Action Scale measures acceptabi l i ty i n terms of act ion. For example: "I would e a t t h i s a t every opportunity"--the top of the scale , and a t the bottom of the scale--"I would ea t th i s only when forced t o .'I

Descriptive Sensory analysis uses t ra ined judges who agree upon descr ipt ive terms t o evaluate the aroma, f lavor and tex ture of products. Among descriptive t e s t s i s the Flavor Prof i le Method developed i n the 1940's by A. D . L i t t l e , Inc. The f lavor p ro f i l e method has motivated an evolution i n sensory evaluation leading t o the development of descr ipt ive techniques which w e w i l l touch upon l a t e r in our discussion. It is a prac t ica l , ana ly t ica l method because it can ac tua l ly focus simultaneously on more t h a n one aspect of food flavor. It describes a l l of t he detectable components of aroma and flavor, the in t ens i t i e s of the individual notes, the order of appearance, fee l ing factors , mouthfeel and aftertastes. who a r e t ra ined t o divorce themselves from subjective response, t o describe f lavors objectively. questions--What i s there? --How ample is the flavor? --How appropriate a r e the qua l i t i e s i n this product? o f f e r opinions concerning acceptabi l i ty o r preference. They t e l l ' ' w h a t is there."

It requires 4-6 highly t ra ined panel is ts

The resu l tan t prof i le answers the

A t no time do f lavor p r o f i l i s t s

The pat tern of Good Flavor must be honored by f lavor p r o f i l i s t s . Good i n th i s sense of the word does not mean individual preference. It re fe r s only t o the ana ly t ica l product construction. The pat tern of Good Flavor is--

3 79 1. An ear ly impact of appropriate f lavor ( i f i t ' s bacon, it

must t a s t e l i k e bacon, not f r e sh f a t back).

2 . Rapid development of an impression of highly blended and usually full-bodied f lavor .

3. Pleasant mouth sensations.

4. Absence of isolated unpleasant notes.

5. Anticipation of the next mouthful.

The r e su l t s cannot be analyzed s ta t i s t ica l ly- - they a re pruvided by the consensus of opinion of the highly t ra ined analysts .

The f lavor p ro f i l e method w a s used as a model when General Foods Corporation developed the Texture Prof i le Technique 10 years ago. Texture Profi le , using t ra ined texture analysts, provides an evaluation of the texture complex of a food i n terms of i ts mechanical, geometrical, f a t and moisture charac te r i s t ics , the degree of each present, and the order i n which they appear from f i r s t b i t e through ccgnplete mastication. It can be used i n conjunction with or instead of instrumental t e s t ing . The en t i r e volume of the March 1975 issue of the Journal of Texture Studies is devoted t o papers regarding i ts growth and the modifications t h a t have been recommended i n the past 10 years.

The

A technique cal led Quant i ta t ive Descriptive Analysis (@A) has been developed by D r . Herbert Stone and Dr, J o e l S ide l of Tragon Corporation. A schematic representation of the data is achieved. This schematic representation i l l u s t r a t e s how two products can be compared by use of an overlay. perimeter i s the mean value f o r t h a t a t t r i b u t e and t h e angle between each l i ne i s derived from the correlat ion coef f ic ien ts . It combines descr ipt ive analysis and the use of an equal i n t e rva l sca le . of not l e s s than 6 t ra ined judges provides repeated judgments f o r each t e s t product. booths) by marking a v e r t i c a l l i n e across a 6-inch horizontal l i n e . Line scores a re converted t o numbers by the use of a template i n lOths of inches.

The distance from the center of t he

A panel

They record t h e i r impressions ( i n individual t a s t e panel

A spec ia l computer program processes the da ta .

Magnitude estimation, as developed by D r . S . S. Stevens of Harvard University, i s based upon r a t i o scaling. D r . H . Moskowitz, Food Science Laboratory, U.S. Army Natick Laboratories, has qui te recent ly originated a comprehensive sensory package adopting the r a t i o scale procedure (magnitude estimation) f o r use i n the food industry. system quant i f ies the sensory r a t i o between food products or ingredients. It can measure how much more acceptable one component or food product i s than another.

The Moskowitz

Progress i s being made in t h i s r e l a t ive ly new s c i e n t i f i c d i sc ip l ine of sensory evaluation. usefulness. problem do we r i s k obtaining unrel iable and invalid data .

Every recognized sensory t e s t method has i t s Only when a t e s t method i s improperly applied t o a sensory

REFERENCES

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Amer . SOC . Test. Mater. 1968. Manual on Sensory Testing Methods. STP 434.

Amerine, M. A., R . M. Pangborn, E . B. Roessler. 1965. Principles of Sensory Evaluation of Food. Academic Press, New York.

Brandt, M. A., E . Skinner, and J . Coleman. 1963. Texture prof i le method. J. Food Sc i . 284404.

Gaul, Jean F. 1957. The flavor prof i le method of flavor analysis. Advances i n Food Research 7:l.

E l l i s , B. H . 1967. use. Food Prod. Dev. l:l9.

Guide t o sensory methods and t h e i r effect ive

Ins t . Food Tech. Annual Convention. 1975. Sensory Evaluation Division. Definition f o r Sensory Evaluation.

J. Texture Studies. 1975. 6 : i .

Kramer, A. , A. S . Szczesniak (ed .) . 1973. Texture Measurement of Foods. D . Reidel Publishing Company, Dordrecht, Holland.

Larmond, Elizabeth. 1974. Sensory methods--choices and l imitat ions. ASTM Symposium on New Methods fo r Answering Old Problems-- Correlating Sensory Objective Measurements. ( i n press )

Moskaritz, H . R . 1974. Sensory evaluation by magnitude e s t i m a t i o n . J. Food Tech. 28:16.

Peryam, D . R. , Francis J. Pilgrim. 1957. Hedonic Scale Method of Measuring Food Preferences. The Garrard Press, Champaign, Ill.

Schutz, H. G . 1965. Food action rat ing scale fo r measuring food acceptance. J. Food Sci . 30:365.

Stone, H., J. Sidel, e t -- a l . 1974. Sensory evaluation by quanti- t a t i v e descriptive analysis. J. Food Tech. 28:24.

14. Szczesniak, A . S ., G . Civi l le . 1970. Lectures, Center fo r Professional Advancement.

J. H. Ziegler: Are there any questions?

Goldtree, University of Missouri: How does one compare a sensory analysis i n one paper which was done on a preference scale t o another paper which was done in a scaling method?

J. B. Reaume: It would depend on the objective of t he t e s t .

Goldhree: Let's say if they were both the same t e s t . Let's say yau had sausage i n both t e s t s and you were checking fo r juiciness?

J. B. Reaume: Fine. This is the s o r t of procedure we usually recommend f o r t e s t ing . It does sometimes require more than one type of t e s t t o get the complete measurement. Your i n i t i a l t e s t might t e l l you whether or not there was difference i n juiciness and t h i s would be based upon the sca le r technique, extremely juicy, extremely dry, that s o r t of thing. Is that w h a t you mean? The other test, the preference t e s t would indicate whether what spec i f ic degree of juiciness was preferred by a goodly nuniber of people.

Goldtree: Well, how can you compare these t w o papers, or can you?

J. B. Reaume: It might be d i f f i c u l t t o compare because you a re r e a l l y ta lk ing about apples and pears. en t i r e ly d i f f e ren t than an hedonic technique, an in tens i ty scale technique. If, f o r instance, it would be impossible t o determine the tenderness of meat on a scale based upon l ikes and d i s l ikes . You might know how people l i k e that par t icu lar tenderness, but you wouldn't know w h a t degree of tenderness i s . You wouldn't knar whether it was tender or tough.

A sca le r technique would be

R . A . Field, Wyoming: I would l i ke t o expand on that j u s t a l i t t l e more. How do you determine tenderness of meat?

J. B. Reaume: I ' m glad you asked. We are a t present using a unstructured scale fo r determining the tenderness of meat. t h i s l i t t l e black folder , please) . We screen people and t r a i n them i n i t i a l l y and i n order t o t r a i n them we have extracted specif ic areas out of the texture p ro f i l e method. During t he t ra in ing procedure we give them a par t icu lar muscle as a frame of reference. t o give us meat that we know i s not tender and meat that we suspect might be. The f i r s t thing we do with our panels is teach them t o evaluate the degrees of fragmentation of a spec i f ic sample across the grain. On the unstructured scale they mark whether t h i s is very d i f f i c u l t or very easy. Then we ask them t o record the amount of connective t i s sue on the unstruc- tured scale . The juiciness , the ease of m s t i c a t i o n that per ta ins t o the adhesion between the f ibe r s . The residual, and then the important thing i t s e l f , the overa l l tenderness. We use t h i s fo r t r a i n h g and repeat our findings u n t i l we know that our panel is ts can repeat themselves. our t e s t begins, using the t ra ined panel is ts , we might use an unstructured scale that can f igure only tenderness and juiciness . For our t ra ining, we go in to the texture parameters that a re involved.

(&y I have

We use an instrument

When

R . A . Field, Wyoming: I ' m not sure I understand an unstructured sca le . Are you ta lking about a 1-5 or 1-7 ra t ing with no l ikes or d i s l ikes preference statement on it?

J. B. Reaume: I ' m t a lk ing about a l i t t l e l ine on a paper. Here is a l i ne with nothing on it. It's not anchored a t e i the r end and one end is extremely tender a id the other end is extremely tough, and boom, boom, boom. The panel is t can put h i s score in a v e r t i c a l slash and i n t h i s way we can determine small distances or large.

R . A . Field, Wyoming: And then for analyses you would t i e t h a t slash t o wherever you put the number of one or whatever?

J. B. Reaume: Yes. We put a template over it, read it o f f , t a l l y it a l l up and submit it f o r analysis. measure the tenderness of meat on a l i k e or d i s l i k e basis. Now my husband doesn't l i ke tenderloin, he would ra ther have something a l i t t l e b i t tougher, so never ever In the world would I get a measurement on the tenderness of meat by conducting a l i ke or d i s l i k e t e s t .

But you cannot a t any time ever

H. R . Cross, USDA: When you a re conducting your t e s t after you have already t ra ined your panel, what parameters do you use t o t e s t the t r a i n - a b i l i t y or performance of the panel through the t e s t ?

J. B. Reaume: Usually we go back and use something a l i t t l e less complicated than a s teak. We use hot dogs f o r t ra in ing a great deal because w e can handle these. I man we can see that we have some -de up with a l i t t l e more fa t and a l i t t l e more of th i s or t h a t s o we can ge t the t ex tu ra l differences. And qui te honestly I give our panel is ts , over a period of time, I don't mke them ea t them a l l a t once, t r iangle t e s t , t r i ang le t e s t , t r i ang le t e s t , u n t i l I am sure they can determine differences. we've got people who have the a b i l i t y t o discriminate and bas ica l ly know w h a t they a r e doing.

And when they can repeat the performnces, then we know

R. A . Field: How important do you f e e l it is t o judge tenderness You indicated you used

-- with the panel and w i t h the mechanical device? a mechanical device as your final estimation of huw tender or tough that sample w a s and then t ra ined the panel t o agree w i t h it. Do we need both tests?

J. B. Reaume: We don't t r a i n t h e panel t o agree w i t h it under any s i tua t ion . I think the ult imate goal i n our science is t o be able t o use instruments so the more our e f fo r t s a re directed i n that direct ion, the b e t t e r off w e might be. Sensory people don't l i k e t o think that they w i l l n w e r be needed, but it is a marvelous thing t o think the day may come when instruments can quickly, e f f i c i en t ly , and economically provide us with t h e information we need regarding sensory aspects.

R . A . Field: Let's tu rn the question around then. Does your panel agree with the instrument?

383

J. B. Reaume: Yes, on occasion. There are many fac tors involved. I w a s very interested today i n the discussion regarding the temperature of meat and the instruments. Warner-Bratzler Shear, Instrom, and our Tenderometer. We use our Tender- ometer t o provide us with meat we can use f o r t ra in ing . t he supermrket and say, Here, give me a piece of tough meat, I want t o t r a i n some people, be sure you give a tender piece. same muscle and I want a tender muscle and I want a tough muscle. When w e s tar t t h i s t ra ining, our s c i e n t i s t s go out and put the l i t t l e Tender- ometer t o work and bring me back some tough meat and bring me back some tender meat, and then we can start our t ra in ing .

We have found good correlat ion with the

I can' t go t o

I want t o use the

M. C . Brockman, Natick Labs: There seems t o be among people who a r e guided by panels i n formulated foods, a growing recdgnition t h a t panels seem t o l i ke sal t and l i ke sugar Now i f you were guided by panels, you a re going t o end up get t ing salt ier and s a l t i e r foods or sweeter and sweeter products.

J. B. Reaume: Actually, our panel's guidance is ana ly t ica l . We don't care whether they l i k e salt or sugar, we want them t o t e l l us h3w much is there from the sensory aspect. Is it barely detectable, is it s l igh t , i s it moderate, is it strong. We want t o how w h a t we got and i n order t o determine whether people l i ke salt or sugar we go t o the consumer. Our laboratory work tells us w h a t is there . We get a l i t t l e indication from our lab panel. t o run a preference test ju s t t o see how they correlate . Nine times out of ten, we have found that when we have sa t i s f i ed our panel is ts with what they consider with a market leader, consumers w i l l l i ke it a lso . But everybody has h i s personal l ikes with salt and sugar. We mske no determinations of w h a t people l i ke i n the laboratory, we tu rn that over t o the market experts and t o the consumers. Thank you.

It k i l l s me not t o have an opportunity

J. H e Ziegler: Thirdly, we come t o the piece de resis tance that G a r y Smith promised you during the introduction f o r t h i s conference. We come t o a revival-of the par t ic ipatory event during R E . you can remember from past conferences when such a c t i v i t i e s occurred. Once f o r P. T Ziegler you compared pork chops. about h i s evaluation of t he s i tua t ion . featur ing ProTen Beef, and yesterday you par t ic ipated in an a c t i v i t y planned and carr ied out by our own Dr . Darrell Cornish. Most of you know Darrell , he is with the Oscar &yer Company i n Madison. he has been there since 1972 when he received h i s Ph.D. degree from the University of Nebraska. and mnufacturing processes. Darre l l teamed up with a loca l spec ia l i s t i n the area of sensory evaluation and t h i s person is D r . Ruth Baldwin. D r . Baldwin is Professor of Food Science here a t t he University of Missouri. d i e t e t i c s , UCLA in home economics and public heal th and the University of Wisconsin where she received her doctorate. i n our program is much appreciated. gracious hosts we have encountered during the 1975 R E . t u rn t h i s program over t o Darre l l and Dr . Baldwin. I understand Darre l l i s going t o cwry the b a l l i n the vernacular one.

Elany of

We won't say anything Another time you a t e lunch

I guess

H e is i n R&D with new and exis t ing products

She has received degrees from Kansas S ta t e University i n

Her in t e re s t and a c t i v i t y She is just another one of t he

I am going t o