Descriptive tests

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In the food industry a range of practical or descriptive tests are used to evaluate product quality and the stability of whippable emulsions. Using such methods a number of reliable and commercially valuable whippable emulsions have been developed over the years. To develop new whippable emulsion systems which are more difficult to stabilize, i.e. primarily low-fat products, more advanced physical methods have been used to elucidate the fundamental mechanisms behind the behaviour of whippable emulsions. 

In this chapter the physical methods for analyzing whippable emulsions are divided into analyses of 1) the emulsified fat phase 2) the fat-water interface and air-water interface, and 3) the continuous water phase. The descriptive tests are mentioned at the end of the chapter as it is easier to explain the meaning of these tests after the fundamental mechanisms have been described. 

As little as 1 % fat in the mix has a very strong effect on the stability of the final ice cream (mentioned later under Descriptive Tests). Due to this strong effect the fat phase is believed not to be in a globular but in a more expanded crystalline state in such systems. This would give better possibilities for covering the air bubbles in the foam. This theory is highly speculative, and requires further studies for clarification. 

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 sensory method chosen for a test is dependent on the type of information required. The appropriate method can only be selected after the objectives of the test are clearly defined. As illustrated in Table 1, there are a substantial number of test methods available and it is important to be familiar with them in order to apply the correct method to achieve the correct results. Familiarity with the test methods also reduces the likelihood of relying on a single method. Difference and descriptive tests are the main tests used to evaluate fat and oil quality. Both tests require the use of trained panelists, but the level of training is considerably more for descriptive testing. In difference testing, panelists only determine if there is a difference between samples. The degree of difference is not determined. In contrast, descriptive tests allow panelists to rate the intensities of several attributes resulting... 

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The brewer and his customer make a subjective assessment of beer flavour each time they taste but for a more objective appraisal it is usually desirable to submit the beer, with suitable controls, to a taste panel. Taste panels may be used to (/) select qualified judges, (//) correlate sensory with chemical and physical measurements, (Hi) study processing effects, maintain quality, evaluate raw material selection, establish storage stability, and reduce costs, (fv) evaluate quality, and (v) determine consumer reaction [Ij. The types of test used include (/) difference tests, (ii) rank order, (Hi) scoring tests, (iv) descriptive tests, (v) hedonic scaling, and (v/) acceptance and preference tests [1]. Difference tests are most commonly used in the brewing industry, the results of which are readily analysed by statistics. Several forms of difference test are used. The A-not-A form of test is perhaps the simplest. Assessors are first familiarized with a standard A and then presented, in a random manner, either with A again or with the comparative sample B. In the paired-comparison test two samples are presented simultaneously (AA, AB, BA, or BB) and assessors report either there is a difference or there is no difference . 

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When subjects provide responses of the perceived intensity for a stimulus on a repeated trial basis, it allows for analyses of individual subjects, attributes, and products. A descriptive test of 10 products, 12 subjects, 3 replicates, and 40 attributes will yield 14 400 values, enabling a wide range of computations including summary statistics, the AOV, correlation of attributes. Factor Analysis, and Principle Components Analysis. In addition, the scaled values can be converted to ranks and additional analyses calculated. All these types of analyses are intended to provide different views of the results to verify that the product differences are consistent, that where interactions occur they have been taken into consideration. When the scaled differences and the ranks are in agreement, this adds to one s confidence with the results. 

Rodrigue, N., GuUlet, M., Fortin, J. and Martin, J.-F. (2000). Comparing information obtained from ranking and descriptive tests of four sweet com products. Food Quality and Preference, 11, 47-54. 

Brussels descriptive tests 25 judges for descriptive testing... 

Belgium Erembodegem Discriminative and descriptive tests 15 judges... 

Brazil Discriminative and descriptive tests Training on-going... 

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