"PAIRED COMPARISON" TASTE PANEL PROCEDURES FOR CITRUS JUICE

Transcription

1 258 FLORIDA STATE HORTICULTURAL SOCIETY, 1952 utomticlly in this wy. The University of Mimi hs plnted five cres of Brbdos Cherries 2 yers go which re lredy in pro duction. We will soon hve figures s to the production per cre nd recommendtions s to plnting nd culturl cre of commercil plntings nd indictions re tht they cn be grown very economiclly. Antidesm is nother plnt which is only grown in Florid to limited degree, but could be plnted in creges. The production is very high per plnt nd tons of these berries could be grown should the demnd for such products s the frozen concentrte become populr. All of these frozen fruit concentrte prod ucts which we hve discussed here require lime or lemon juices nd sugr in their mk ing. These re Florid products nd could be grown in greter bundnce. There re mny limes nd lemons grown in the Americn tropics which re wsted ech yer. Even in Florid, we hve thrown wy mny limes especilly mture ones becuse the fresh fruit trde hs been educted up to smll green lime, nd mture lime is just turning yel low when it is t its best yet these re dis crded. These give the best products when processed. In reporting this reserch, it should be point ed out tht the object of the reserch hs been to find uses for wste mteril which is of high nutritionl vlue nd to find more crops for Florid. We need to hve more thn one fruit crop to mke our Stte more economicl ly sound. I don't men tht we should neglect the citrus crop, but we should find other crops which cn be s esily or more esily grown en our soils which would help feed the fst growing popultion of the erth nd t the sme time give work nd better living to the ever incresing popultion of our good Stte of Florid. We predict tht in eight yers time mny of these fruit concentrtes will be on the mrket nd fmilir item to the mny mil lions in North s well s South Americ. We hve the guv concentrte lredy on the mrket nd hope to hve pilot plnt pro duction of the others this next seson. There is gret potentil in mny of our tropicl fruits to be presented to the public in proc essed form. We re presenting smples for you to tste nd hope tht they will receive the sme spontneous reception nd interest tht those first smples of ornge juice con centrte hd just 8 yers go. "PAIRED COMPARISON" TASTE PANEL PROCEDURES FOR CITRUS JUICE A. E. WlLLSON, Minute Mid Corp., Plymouth, Fl., AND W. D. Hnson, Sttistics Consultnt to Minute Mid Corp., College of Agriculture, University of Fl., Ginesville, Fl.* Introduction Tste pnel procedures generlly require the tsting of two or more smples nd decisions re mde by comprison s to difference nd preference. When the product hs strong flvor chrcteristics which tend to linger in The uthors wish to thnk C. W. DuBois nd C. B. Clrk of Minute Mid Reserch nd Development Division for their dvice nd ssistnce in prepring juice smples for this study. the mouth, tste cuity decreses rpidly nd tste response becomes more confused s the number of smples or comprisons is incresed. Binomil designs (4) which include the tringle method (3) hve been developed to increse sensitivity by incresing the number of tste comprisons n individul must mke between two smples. Advntges gined through design in these methods re lost for mny tsters of citrus juices becuse of mrked decrese in tste cuity s successive comprisons re mde. Tste pnel methods now in use (1) (2) (5) hve been developed on vrious food products, but no systemtic studies hve been reported to show how p plicble they re to citrus juices. The method described in this pper hs been developed nd tested on ornge juice. To reduce the confusion of tsters, no more thn two comprisons re required t ny one

2 WILLSON AND HAON: PAIRED COMPARISON 259 time nd the decisions re rted by simple plus nd minus system. Tests for significnce pply for both tste discrimintion nd prefer ence. The pnel rtings for individul sm ples cn be conveniently expressed on rel tive bsis for grphicl presenttion. Sttis ticl rguments for the method hve been supported by experimentl dt nd these, long with dditionl pplictions of the method, re to be presented in publiction by W. D. Hnson. Method Two pirs of smples re presented to pnel members t one time. The code letter identifying ech smple should be on the bot tom of opque cups nd only the pir number (1 or 2) should be visible on the sides of the cups. Tsters should be sked to bse their judg ment on specific qulity fctor or ttribute of the juice, such s cidity, solids, etc. They should be properly instructed how to tste for the fctor in question. A sip of juice should be tken from one cup in ech pir. This is done to obtin similr orienttion for ech test since tste response my be influenced by tste experi ences preceding tests. Tsters should wit for bout one minute before compring the first two smples nd nother minute before com pring the second two smples. FIGURE 1 Lest significnt rtings for individul pired com prisons by pnel of size N.* With ech comprison there re two ques tions to be nswered in the following order: () re the smples the sme or different? (b) if the smples re different: (1) select the smple hving more of the specific qulity fctor (2) select the preferred smple After decision hs been mde, the code letters re obtined from the bottom of the cups nd the results recorded in tbulr form similr to Tble 1. TABLE Nme.. First Pir Second Pir I Method Sme Differ ent Sme Differ ent of Recording Test Tste No. Higher Rted Smple (Code Letter) Higher Rted Smple Responses Dte Preferred Smple (Code Letter) Preferred Smple It is desirble to hve t lest 30 tsters in pnel, prticulrly if the pnel hs not been selected for tste cuity. When more thn two comprisons re to be mde, the pnel should be lrger if possible, nd divided into subpnels or groups. The procedure for testing four smples A, B, C, nd D requires six com prisons; AB, AC, AD, BC, BD, nd CD. This number of smples cn be conveniently stud ied in one dy by dividing the pnel into three groups nd giving ech group two pirs of smples. The test is then repeted three times during dy with ech group receiving different set of smples ech time so tht everyone hs n opportunity to tste ll six combintions. Thus, one-dy study of four smples in six combintions my be orgnized in ltin squre (6) s in Tble II. TABLE II Arrngement of Comprisons With Four Smples in Six Pired Combintions Among Three Pnel Groups Pnel Group Pirs of smples to be presented to Groups Rep. 1 Rep. 2 Rep. 3 AB, BC AC, CD AD, BD AD, BD AB, BC AC, CD AC, CD AD, BC AB, BC I o.i PANEL SIZE N *Thi to bo u«d for testing significnce of figure l mon rting '"» pnol izo N. It cn be used Insted of Tblo k. For ny two smples A nd B, it cn be shown tht the probbility of deciding whether they re the sme or different is 1/2 bsed on pure chnce. If they re different, the probbility is 1/2 tht one will be better or poorer thn the other. Thus, the probbility of hving A the sme s B will be 1/2 nd A better or poorer thn B will be 1/2 x 1/2=

3 260 FLORIDA STATE HORTICULTURAL SOCIETY, /4. The evlution of probbilities nd fre quency distributions for three possible pnel rtings re given in Tble III. TABLE III Evlution of Probbilities nd Frequency Distribu tions for Three Possible Pnel Rtings Evlution. Distributions* Evluted Rtings Prob. Vlues Distributions ' ExpecttObserviExpectObserv A over B A equl B H over A Totls N/4 N/2 N/4 N b c N N/4 0 + N/4 O 0 c- *N = Number of tsters in pnel nd, b, nd c = Number of pnel members mking respective rtings, The verge observed pnel evlution is = N -0 nd the test for significnce is "t"=. Vlues _ V%N of necessry for significnce t.1,.05,.01, nd.001 probbilities hve been clculted for pnels contin ing 15 to 50 members in Tble IV. TABLE IV. Vlues of * necessry for significnce (two tiled) t respective Probbilities. Totl No. of Tsters c When compring smples A nd B (No. plcing A over B) (No. plcing B over A) ~~ Totl number of tsters in the pnel Above tble clculted from 1c =.7071 t. Vl/N with t 1.645, nd t 0.1, 0.05, 0.01 nd.001 levels of probbility respectively. Appliction The ppliction of the method cn be dem onstrted by study which ws conducted on four lots of juice. For the purposes of this pper, the four smples of juice hve been represented s vrying with respect to pr ticulr qulity fctor s follows: SAMPLE B A C % FACTOR LEVEL The six possible pired combintions of these smples were tested by the method de scribed bove on three different dys over period of two weeks. Results of the study hve been summrized in Tble V. Tests for significnce in Tble V were mde both experimentlly nd theoreticlly. The ex perimentl tests were mde by nlyses of vri nce of the dt nd theoreticl tests were bsed on the theoreticl probbilities in Tble III. Dily pnel rtings or one repliction cn be tested theoreticlly by use of Tble IV or Figure I. The tests for the significnce of men pnel rtings hve to be djusted for correltion of errors between replictions nd for different pnel sizes. These djustments hve been mde for 2 nd 3 replictions in the preprtion of Figures 2 nd 3, respec tively. Figure 3 cn be used for testing the verge rtings obtined when pnel hs repeted its evlution of the sme smples three times. Thus, it cn be used for the theoreticl significnce test of the verge pnel rtings t the bottom of Tble V. It cn be seen in Tble V tht there is surprisingly close greement between the ex perimentl nd theoreticl tests for signifi cnce. Pnel rtings for preference were more vrible thn those for qulity nd the two tests for significnt preference did not gree in ll cses. This discrepncy ws not gret nd it would pper tht the theoreticl test cn be pplied to both qulity nd pref erence rtings. The dt in Tble V cn be conveniently orgnized to obtin reltive pnel rtings for individul smples. This hs been done for Dy 1 in Tble VI.

4 WILLSON AND HAON: PAIRED COMPARISON 261 To obtin dt for Tble VI from Tble V,T red the smple letters in the left column11 positive, nd cross the top negtive. If the required order is reversed for dt in Tble V, chnge the sign in front of the number in Tble V, nd enter the dt s indicted. Grphicl procedures for testing the signifi cnce of differences between the men rel tive smple rtings in the lst column of Tble VI hve been prepred nd will be given in Dr. Hnson's pper. These men individul smple rtings, long with similr vlues clculted for Dys 2 nd 3 hve been plotted in Figure 4. pnel rtings should pproch vlue of zero nd with wide differences they should p- FIGURE 2 Lest significnt men rtings for individul com prisons with pnel size N* or Nh for TWO replic tions. Figure 4 should need no explntion. It demonstrtes method of grphicl present tion of the dt bsed on verge reltive rtings clculted from ll possible compri sons. Both the discrimintion nd preference curves were highly reproducible by this tste pnel procedure. Discussion If there is no difference between smples, PASKL SIZE M OR Hjj Al flguro Is to bo usod for tooting tho significnce of noon rting when tho test hs boon replicted twico. Iho pnol slzo will bo N, tho lumber of tsters In tho pnel, if tho sme lzod penl Ms uood both tloo. If tho pnol lso vries for the two replictions, tho hroonie men, Nj,, l usod. Hh = 1/JQ / 1/N2 TABLE tr Tste Pnel Rtings for Culity Fctor nd Preference Summry A~B A-C A-D B-C B-D C-D Informtion Fctor Pref, Fctor Pref, Fctor Pref,. Fctor Prefo Fctor Prefo Fctor Prefo Dy 1 K Theoreticl Experimentl 4,290 «4,226 us us ft-* o s0fl6 -«7 n &# -, U Dy 2 N Theoreticl Experimentl 4,075 MS o0 -,189 US »324 -«* «m f, V225 -o «432 n mt +»8 Dy 3 W Theoreticl 'Experimentl,275 K250 -., * -553 *n. i-132 -,425 H-fc +, o3 4d46 Dys 1, 2 ft 3 Av«r.ce Theoreticl Experimentl IV," n or>3 KS Kit +, IHi ns us o445 ti-k 4d75 N - fhwnber of tsters in pnel. (consider smples A-B, Dy 1) 5 (No, selecting A over B - No8 selecting B over A) 1/N * (15. 6) 1/ «f'290- A negtive sign indictes tht the second smple ws selected over the first. * nd ** significnce t,,05 nd.01 probbility respectively. For exmple, it cn be stted for the comprison A-B, Dy 1; if the smples were the sme, vlue s gret s,29 could oe expected five times in hundred similr tests. Conversely, there re 95 chnces out of hundred tht the smples re differentc

5 262 FLORIDA STATE HORTICULTURAL SOCIETY, 1952 TABLE VI Clcultion of A B C D A Men Reltive Rtings for Fctor Levels on Dy 1 B C D Totl Men FIGURE 3 Lest significnt men rtings for individul com prisons with pnel size N* or Nh for THREE replic tions. proch vlue of one ccording to the theo reticl ssumption in Tble III. The point where pnel rtings show little or no increse with incresed differences between smples represents the limiting vlue for the fctor being studied. Tste pnel responses were found to vry directly with the differences between smples up to limiting vlue. This vlue depends on the cuity of the tsters. Pnels selected for high tste cuity rech limiting vlues for smple differences sooner thn unselected pnels nd thus hve smll er rnge for comprisons, but their sensitivity Probbility.05.Probbility.10 Probbility PANEL SIZE N OR Nh This figure is to bo used for tooting signiflene of mon rting when the tet hs been replicted three tines. The pnel size will be N, the number of tsters, if the some sized pnel ws uood oil three tines. If the pnel size vries in the three replictions, the hrmonic men, Nh, is used. is greter. I/HI / 1/H2 f 1/H3 FIGURE L RELATIVE PANEL RATINGS FOR QUALITY FACTOR AND PREFERWJCE DISCRIMINATION PRi-JfEtttKCE 2 A 8 PACTOK RANGE IN SAMPLES PACTOH RANGE IN SAMPLES

6 MAGIE AND COWPERTHWAITE: GLADIOLUS RESEARCH 263 Selected pnels of 30 to people re dif ficult to obtin in most processing plnts. It is lso difficult to hve ll these tsters present for three tests in one dy when four different smples re to be compred in six possible pired combintions. The dt re ported in this study were obtined from n unselected group of tsters fter pproximte ly estblishing limiting level for the fctor to be studied. About 75% of the tsters were ble to tste ll three sets of smples in one dy. Thus, with n unselected pnel nd slightly different pnel groups on three dif ferent dys, highly significnt nd reproduci ble results for both the qulity fctor nd preference rtings hve been obtined with this tste pnel procedure. Sensitivity nd high degree of reproducibility re desirble in ny method to be used for qulity control or reserch where rel tive rtings between smples re required. The method described in this pper ws de signed for this purpose nd its ppliction for both qulity nd preference rtings hs been demonstrted. Preference rtings from smll control pnels re not sfe guides for consumer cceptnce. However, the method described in this pper my be used for n indirect check on consumer preference through comprisons with smples of known consumer cceptnce. If the method is unble to de tect significnt qulity differences between smples, it is highly improbble tht con sumer group, hving none of the dvntges of the method, would be ble to detect dif ferences on which to bse preference. REFERENCES 1 Hrrison, S., nd Elder, L. W. Some Applic tion of Sttistics to Lbortory Tste Testing. Food Technology 4, 434- (1950). 2. Hening, J. C. Flvor Evlution Procedures New York Agriculturl Experiment Sttion, Tech nicl Bulletin No. 284 (1948). 3. Helm, Erick nd Trolle, Binger Selection of Tste Pnel Wllerstein Lbortories Commu nictions 9, (1946). 4. Lockhrt, Ernest E. Binomil Systems nd Orgnoleptic Anlysis Food Technology 5, 428- (1951). 5. Roessler, E. B., Wrren, J. nd Guymon, J. F. Significnce in Tringulr Tste Tests Food Reserch 13, (1948). C. Snederor, G. W. Sttisticl Methods Iow Stte College Press, Ed. IV (1946). PROGRESS IN GLADIOLUS RESEARCH Robert O. Pthologist nd Mgie, W. G. COWPERTHWAITE, Formerly Assistnt Horticulturist Gldiolus Investigtions, Gulf Cost Experiment Sttion Brdenton Florid's gldiolus cut flower industry hs grown stedily during the pst 25 yers in spite of succession of production nd mrketing problems, some of which thretened ruin to mny growers. The growers, ided by their Assocition, re solving some of the problems relting to pckging, shipping, nd mrketing of the flowers. The criticl problems of flower production hve been studied for the pst ten yers t the Gulf Cost Experiment Sttion. Since 1950, the stff hs included two men working full time on gldiolus reserch, one on horticulturl problems nd one on disese con trol. Other members of the Sttion's reserch stff help with insect control nd soil prob lems. Reserch work hs been concentrted on disese control primrily becuse the vsculr wilt nd corm rot disese cused by Fusrium oxysporum f. gldioli Snyder nd Hnson is the most importnt production problem. The nnul crop loss due to this fungus disese is estimted to be over one nd one-hlf million dollrs in Florid. The loss of corms hs forced severl growers out of business. Although lrge shre of the reserch ef forts hve been directed towrd the control of Fusrium disese, other diseses hve re quired considerble ttention. Mny cres of