Difference testing, sensory evaluation

Sensory Evaluation. Results on the sensory evaluation of the three encapsulated powders showed that all three powders developed oxidized flavor even at first sampling time (3 days). Since an expert trained panel was used, the recognition threshold of members for oxidized flavor was far below the expected value. In addition, since oven stored samples were evaluated against freezer stored samples in the pair comparison test, panelists could not characterize the degree of difference in oxidized flavor between various powders. It is therefore suggested that lower storage... 

A scattering of the threshold levels over an order of magnitude is due to the different sensory sensitivity of individual test persons. This relatively narrow region allows the formation of mediated values for the establishment of simple characteristic numbers. However, for sensory evaluation, the lowest value of the most sensitive tester must be given consideration since complaints often originate because of complaints from such sensitive consumers. 

Sensory Evaluation of the contribution of identified compounds to the aroma In order to identify those compounds mainly contributing to the characteristic flavor of the Black Truffle, the odor of the individual components of the headspace analysis were tested by a panel of eight judges (trained in sensory evaluation of truffles). The compounds tested were diluted in vegetable oil, in a range of concentrations from 30 to 300 ppm. 5 point scales (5 = exceptionally good full truffle aroma, 1 = not different from solvent) were used for flavor imitation and intensity. 

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... 

Figures 1,2, and 3 are provided to illustrate one protocol often used to evaluate sink materials [20,32,42-47] however, other methods are also used. For example, Krebs and Guo [48] reported on a unique method involving two test chambers in series. The first chamber is injected with a known concentration of a pollutant (in this case, ethylbenzene). The outlet from the first chamber provides a simple first-order decay that is injected into the inlet of the second chamber that contains the sink material (gypsum board). Thus, this method exposes the sink test material to a changing concentration typical of many wet VOC sources. The sink adsorption rate and desorption rate results are comparable to one-chamber tests and are achieved in a much shorter experimental time. Kjaer et al. [31] reported on using a CLIMPAC chamber and sensory evaluations coupled with gas chromatography retention times to evaluate desorption rates. Finally, Funaki et al. [49] used AD PAG chambers and exposed sink materials to known concentrations of formaldehyde and toluene and then desorbed the sinks using clean air. They reported adsorption rates as a percentage of concentration differences.

The sensory evaluation of the jams was carried out by 60 potential consumers and the attributes appraised (appearance, aroma, texture, color, flavor and global impression) judged using a structured 9 point hedonic scale (1= disliked extremely to 9= liked extremely). The experiment was applied to a balanced complete block design according to Stone and Sidel (2004), and 20 g of each treatment presented in plastic cups codified with three digit numbers. The tests were carried out in individual booths in the food sensory analysis laboratory. The results were submitted to an analysis of variance (ANOVA) and the differences between the averages compared by the test of Tukey at 5% of probability (Cochram Cox, 1992). 

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 . 

Sensory assessment is a scientific discipline used to evoke, measure, analyze, and interpret responses to those properties of a substance (food or beverage) that are perceived by the five human senses sight, smell, taste, touch, and hearing. Even though individual judgments are subjective, the techniques of sensory evaluation use objective scientific testing methods principally based on working with a panel of assessors. Two types of analytical objective tests can be observed (1) The discriminative tests is there a difference between several products (2) The... 

Challenge the objectives. Focusing on the objectives of the measure is decisive. Although it seems obvious, this point is not always carefully considered and, apart from the basic rules of sensory evaluation (i.e. deciding between hedonic, descriptive and difference testing), many sensory professionals tend to apply a method they are used to, not the method that would best fit their goals. Besides, in the view of rapidity and efficiency, it would seem wise to select the simplest method available. That is to say, a method should be proportionate to... 

To evaluate oxidative stability, different methods are used to measure lipid oxidation after the sample is oxidized under standardized conditions to a suitable end-point. In Table 7.1, different lipid oxidation tests are ranked in decreasing order of usefulness in predicting Ae stability or shelf life of a food product. Methods for sensory evaluations, conjugated diene, gas chromatography of volatiles, peroxide values and thiobarbituric acid-reacting substances were discussed in Chapter 5. 

The sensory evaluation of the potato crisps, appearance, consistency and smell and taste were tested by a trained sensory panel with the results combined to a weighted quality score in the range from 0 to 5. The results showed the sensory quality of potato crisps fried in HOLL canola oil was comparable with potato crisps fried in PO and PHF (HOLT) with no significant difference between the different oils (P = 0.01) when the samples were stored under normal atmosphere (Figure 11.6a). 

One way to standardize the sensory abilities of panelists is to use olfactory tests. Some of them, such as the ETOC, have been designed for sensory evaluation purposes in order to provide sensory and cognitive clues to olfactory capability. The test scores could thus usefully be included in the processing of sensory data. The assessment of panelists for olfactory and for other sensory sensitivity may, in part, account for the difference between flavor perception and flavor release, which remains a major challenge in the characterization of flavor compounds. 

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