LABORATORY REPORT

SENSORY EVALUATION OF FOOD

DUO-TRIO, TRIANGLE, AND TETRAD TEST

By:

Anthonius Hideyo (03420110017)

Edison Sutiono (03420110021)

Henry William Gomuljo (03420110032)

Nasya Jessica (03420110044)

Livia Cornelia (03420110074)

FOOD TECHNOLOGY DEPARTMENT

FACULTY OF SCIENCE AND TECHNOLOGY

UNIVERSITAS PELITA HARAPAN

KARAWACI

2013

CHAPTER I

MATERIALS AND METHODS

1.1 Materials and Equipment

The materials used for the three tests which were done in this experiment

as samples are soft drink from two different brands, one is as sample A as well as

reference, which is sprite, and the other is as sample B, which is 7up. There is also

pure water for neutralizing the mouth.

The equipment used in this experiment is plastic glasses and labels.

1.2 Procedures

1.2.1 Duo-Trio Test

1. The panelist was first being familiarized with the reference sample.

2. After the reference is returned back, the samples A and B in three-digit

codes in two combination orders, which are A-B and B-A were presented

to the panelist.

3. The panelist was instructed to choose between both samples A and B for

which one is more similar to the reference sample, and also to neutralized

the mouth using pure water every time the panelist want to try another

sample.

1.2.2 Triangle Test

1. The samples A and B were presented in three-digit random number codes

to the panelist by three in six combination orders, which are A-B-B, B-A-

A, A-A-B, B-B-A, A-B-A, and B-A-B.

2. The panelist was instructed to choose between the three samples for

which one is odd or different than the other two, and also to neutralized

the mouth using pure water every time the panelist want to try another

sample.

1.2.3 Tetrad Test

1. The samples A and B were presented in three-digit random number codes

to the panelist by four in six combination orders, which are A-A-B-B, A-

B-A-B, A-B-B-A, B-B-A-A, B-A-B-A, and B-A-A-B.

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2. The panelist was instructed to group the samples by two of which they are

similar to each other, and also to neutralized the mouth using pure water

every time the panelist want to try another sample.

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CHAPTER II

RESULT AND DISCUSSION

2.1 Duo-Trio Test

Lawless and Heymann (2010) stated that duo-trio test is a type of

discrimination test variation. Duo-trio test is good to evaluate sample which have

strong sensory properties, such as taste, odor, and/or kinesthetic effect, because

their impact to the evaluation are able to be reduced to the minimum point in this

method.

Referring to Kemp et al. (2009), duo-trio test is a test which 2 different

samples which are coded are given along with one reference. The panelist will

then being asked to determine which sample is the most similar to the reference

given. The probability chance of this method is 0.5, and one-tailed statistics is

used. Duo-trio test can be divided into two types, constant reference and blanced

reference. As the name implies, the constant reference means the reference taken

by the entire panelists is the same. On the other hand, the balanced reference

means half of the panelists will get sample A as the reference, while the remaining

half will get sample B as the reference (Lawless and Heymann, 2010). Stone and

Sidel (2004) stated that it is suggested for the reference to be removed prior to the

sample testing, so that the panelist unable to refer back to the reference. However,

this might cause the test to become more of test of memory rather that sensory

test.

All the tests in the experiment (duo-trio, triangle, and tetrad test) were

done to analyze whether two different products, sprite and 7up, is having a

significant difference or not. In this test, the reference used is constant reference A

(Sprite), which is the same for all 40 panelists. The result of the experiment is 36

answers out of 40 panelists. The null hypothesis of this test is there is no

significant difference between the two coded samples. Taking the value from

appendix A, it can be seen that the probability of 36 right answers out of 40

panelists is again, far below 0.001 or 0.1%. This value is below the significance

level of 5%, even 1%, so the null hypothesis is rejected. It can be concluded from

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duo-trio test that at the significance level α: 1%, there is a significance difference

between Sprite and 7up.

2.2 Triangle Test

Stone and Sidel (2004) stated that one of the most well-known methods in

the sensory test is triangle test. This is a type of discriminative test to differentiate

between two different samples. As the name implies, triangle test involves three

products, which are coded. The panel leader will give the panelists three coded

samples, and two of them are the same, leaving one odd sample among them. The

panelist will then being asked to determine the odd sample among the rest. This

method is claimed to have good sensitivity, due to the chance probability of only

0.33. One of the characteristics of this test is not informing the panelists about the

attribute of the difference, but rather only informing that there is difference

between the samples. It is also important for the samples to have only one

attribute difference, in order to get an accurate result (Watts et al., 1989).

In the experiment, 40 panelists were asked to do the triangle test, with 19

panelists had sample A as the answer, and 21 panelist had sample B as the answer.

The test resulted in 30 right answers out of 40 panelists. The null hypothesis used

in this test is there is no significant difference between the two samples. This test

in having a 1/3 chance, and is one-tailed. Referring to appendix B, it can be seen

that the probability of 30 right answer out of 40 panelist is very low, far below

0.001, or far below 0.1%. Similar to duo-trio test, this value is below the

significance level of 5%, or even 1%. It can be concluded then that at the

significance level α: 1%, there is a significant difference between Sprite and 7up.

2.3 Tetrad Test

Referring to Ennis (2012), in the tetrad sample, 4 coded samples are given

to the panelist. Two of the samples comes from one group (A), and the rest from

another group (B). The panelist is then asked to group the sample into two group,

based on the similarity. This test is often specified into two types, specified and

unspecified, In the unspecified one, the samples are grouped based on the

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similarity of two samples among 4 samples; while in the specified method, the

panelists are asked to paired the sample based on which 2 of the 4 that the panelist

like best, or have the strongest stimulus. Similar with triangle test, the chance

probability of this test is 0.33.

In the experiment, 40 panelists were asked to the tetrad test. The resut of

the experiment is showing 35 right answers out of 40 panelist. The null hypothesis

used in this test is there is no significant difference between the two samples. This

test in having a 1/3 chance, and is one-tailed. Referring to appendix B, it can be

seen that the probability of getting 35 right answers out of 40 panelists is very

low, far below 0.001, or 0.1%. This value is below the significance level α: 5%, or

even 1%. It can be concluded from this test that at the significance level α: 1%,

there is a significance difference between Sprite and 7up.

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CHAPTER III

CONCLUSION

In the experiment, there were three tests being conducted, which are duo-

trio, triangle, and tetrad test. All of three tests conducted were giving a similar

result, which is there is a significant difference between the two samples, sprite

and 7up at the significance level of 1%. It can be concluded then, that the two

brands, sprite and 7up, are different in the flavor aspect, and the difference is

significant enough to be detected by the panelists.

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BIBLIOGRAPHY

Ennis, John M.. “Guiding the Switch from Triangle Testing to Tetrad Testing”. Journal of Sensory Studies 27, no. 4 (2012): 223-231.

Kemp, Sarah E., Tracey Hollowood, Joanne Hort. Sensory Evaluation: A Practical Book. Oxford: Wiley-Blackwell, 2009.

Lawless, Harry T and Hildegrade Heymann. Sensory Evaluation of Food: Principles and Practices. New York: Springer, 2010.

Stone, Harbert, Joel L. Sidel. Sensory Evaluation Practices 3rd edition. Redwood City: Elsevier Academic Press, 2004.

Watts, B.M. et al. Basic Sensory Methods for Food Evaluation. Ottawa: International Development Research Centre, 1989.

APPENDIX

Appendix A : Probability of X or More Correct Judgment in n Trial (one-

tailed, p = (1/2)a

Appendix B : Probability of X or More Correct Judgment in n Trial (one-

tailed, p = (1/3)a