04-04-08-10+analyticalsensory_difftests

04-04-08-10+analyticalsensory_difftests - 3/4/2010 WHICH...

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3/4/2010 VEN125 Spring 2003 1 Analytical Sensory Evaluation Discrimination Tests Ven 125 Hildegarde Heymann WHICH SENSORY TEST TO USE? WHAT IS THE PURPOSE? This wine tastes funny. .. Which vineyard is higher quality. .. What is the threshold for…. SELECT SPECIFIC SENSORY TEST(s) TO ANSWER SPECIFIC QUESTION(s)…. TYPES OF SENSORY TESTS Difference Tests Is there a difference? Duo-trio Triangle Pair Direction of difference…… tical Ranking Tests Sequence or order of the difference? Intensity Rating Tests How large is the difference? Time Intensity Tests How does it change over time? Descriptive Analysis What is different and by how much? Consumer Tests How much is it liked or preferred? Analy Consumer Types of Difference Tests Unspecified difference Specified difference A-not-A Directional Pair (2AFC)* Same/different 3AFC* Duo-Trio Triangle 2 out of 5 (For screening only) *Rare in food/wine Unspecified difference Duo trio Which is same as (most similar to) “Ref”? 314 854 REF Difference tests Triangle Which is sample is odd? Specified difference (Rarely useful….) Directional pair test Which is sweeter? 114 592 673 298 547 Unspecified difference Duo trio p = 1/2 (one tail) Tiang le Probability for each test 314 854 REF Triangle P = 1/3 (one tail) Specified difference (Directional pair test) p = 1/2 (one tail) 114 592 673 298 547
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3/4/2010 VEN125 Spring 2003 2 2 out of 5 test 641 543 128 394 231 5 coded samples ( 3 “clean” and 2 “spiked”) 641 543 128 394 231 Probability of correctly grouping samples is 10% are to be sorted into 2 sets A1 A2 B1 B2 B3 A1 B1 A2 B2 B3 A1 B2 A2 B1 B3 A1 B3 A2 B1 B2 A2 B1 A1 B2 B3 N C = N!/(N – n)!n! 2 out of 5 test A2 B2 A1 B1 B3 A2 B3 A1 B1 B2 B1 B2 A1 A2 B3 B1 B3 A1 A2 B2 B2 B3 A1 A2 B1 C n N!/(N n)!n! 5!/(5 –2)!2! = 10 N C n is the possible number of serving orders 2 out of 5 test (fatiguing) but quick way to test for defects and sensitive judges p = Probability that results could have occurred by chance alone 1-p = Probability that a real difference was perceptible Judges Correct p 61 0 . 4 6 9 N S 62 0 . 1 1 4 N S 63 0 . 0 1 6 * 64 0 . 0 0 1 * If p=0.1 then q=0.9 and binomial expansion for 6 judges would be p 6 + 6 p 5 q 2 +15p 4 q 2 +20p 3 q 3 +15p 2 q 4 +6pq 5 +q 6 , or (0.1) 6 + 6(0.1) 5 (0.9) + …. As an aside: Paired Preference test: Which sample do you prefer? CONSUMERS! Probability: p = ½ ( TWO tailed) Probability: p ½ ( 547 298 Statistical Analysis of Sensory Tests Difference tests: a. Tables based on binomial probabilities ( e.g ., “Roessler” Tables) b. Chi-squared test c. z-value test (most accurate. . .unless exact binomial value calculated by computer) Roessler Tables P<0.05 Number of judges One tail (p=1/2) Two tail (p=1/2) One tail (p=1/3) 10 9 9 7 15 12 12 9 XXXXLawless and Heymann: pp.130-131; 435 (two-tailed) 20 15 15 11 25 18 18 13 50 32 33 23 60 37 39 27 100 59 61 42
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3/4/2010 VEN125 Spring 2003 3 BE CAREFUL N= 10 judges Roessler table: 9 judges to reject H 0 (for p = ½, a = 0.05) But 8 judges correctly matched sample to reference.
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This note was uploaded on 09/29/2010 for the course VEN 91863 taught by Professor Hildergardheymann during the Spring '09 term at UC Davis.

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04-04-08-10+analyticalsensory_difftests - 3/4/2010 WHICH...

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