Triangle test

Let us consider a product developer who is trying to improve the taste of an existing product. The first question one could ask (and should ask before continuing) with the new product is does the new product taste different from the old product If trained panellists cannot establish a significant difference, it is hardly justifiable to do consumer tests, let alone launch the product on the market. A standard overall difference test is the triangle test (Fig. 38.1). In such a test one presents three samples, in no particular order, which should be tasted. Two out of the three samples are identical (e.g. the existing product, as a control) and the task is to identify the odd sample (the new product). If enough panellists correctly 

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Fig. 38.1. Triangle test two similar products and one different product are presented the assessor has to indicate the product that is different.

Table of critical values for the triangle test for differences... 

The most frequently used tests in quality control in the flavour industry are paired-sample comparison tests, and triangle tests, which are often combined with the description of deviation from a reference item. For the selection and training of panellists, further test methods are used, for example ranking tests for colour, taste and odour, threshold detections (taste, off-flavour), colour blindness tests and odour identification tests [6]. 

Number of panellists (out of 15) detecting an odour difference between the reduced and the complete aroma model in a triangle test... 

The sensory evaluation was performed by a panel of 8 trained female and male persons using the triangle test. 

Fig. 11.2. Aqueous molar solubility log(S q) calculated with COSMO-RS diamonds = training set (filled symbols = solids open symbols = liquids) triangles = test data set.

Sensory Analysis. Oat oils and isolates from these oils were sensorially evaluated. Oils from the Magne variety, both crude and heated, were analysed by a panel consisting of 12 to 14 persons who were selected from the laboratory staff. Most of them had previous experience with sensory analysis. Four oat oils, one from crude oats, one heated oil from crude oats and two oils from roasted oats see Figure 1, were subjected to the triangle test followed by descriptive analysis (14, 15). 

Sensory Analysis. Oils from the Magne variety were evaluated by a profile panel. Oil from crude oats (a), two oils from roasted oats (one part milled before roasting (b) and one milled after roasting (c), and heated oil from crude oats (d) were subjected to the triangle test and descriptive analysis. No evaluations were performed of oils from the Chihuauhua variety, due to lack of material and also to similarities with the various Magne oils. 

A triangle test was performed in order to determine whether there was a significant difference between the oil samples studied. Results were as follows ... 

Sample b c roasted (bread, coffee, peanut, walnut, malt), burnt, popcorn, slightly rancid, heated cooking oil Sample ds heated cooking oil, deep-frying fat, solvent, old paint Since the panel found no difference between samples b and c in the triangle test, it was not possible to ask for two distinct "profiles" in the descriptive test. However, it was evident that samples b and c were the most attractive oils from a flavor point of view. There were similarities with sesame oil and Swedish crispbread. 

The triangle test is a measure of odor discrimination. The candidate is presented, in random order, with three blotters, of which two are identical and the third is slightly different. The task is to indicate the odd blotter. This test can be designed to range from easy to very difficult. It is statistically most powerful if the difference between the paired blotters is such that the odd one is correctly identified by about 50% of the candidates. 

Difference testing has not changed greatly over the years. The triangle test and duo-trio test remain popular and well-accepted, although much effort has been extended to prove one better than the other. The best advice is to use the one that fits your test situation. 

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