Sensory analysis procedure

Discriminant Sensory Analysis. Discriminant sensory analysis, ie, difference testing, is used to determine if a difference can be detected in the flavor of two or more samples by a panel of subjects. These differences may be quantitative, ie, a magnitude can be assigned to the differences but the nature of the difference is not revealed. These procedures yield much less information about the flavor of a food than descriptive analyses, yet are extremely useful eg, a manufacturer might want to substitute one component of a food product with another safer or less expensive one without changing the flavor in any way. Several formulations can be attempted until one is found with flavor characteristics that caimot be discriminated from the original or standard sample. 

Acree, T.E., Barnard, J., and Cunningham, D.G. 1984. A procedure for the sensory analysis of gas chromatographic effluents. Food Chemistry 14 273-286. 

Sample preparation is similar to that of Basic Protocol 1. The sample cleanup procedures should ensure that no extraneous odorants are eluting with chiral odorants of interest. Thus, cleanup procedure 5 is preferred, which should be modified by attaching the polar column to the olfactometer port so that unwanted odorants can be detected. If odorant coelution is found, then a new chiral stationary phase must be chosen for the sensory analysis. Cleanup procedures 2 to 4 will prolong the life of the chiral column. Cleanup procedure 1 is given as Alternate Protocol 2 of this unit. 

Arnold, G.M. and Williams, A.A. (1986) The use of generalised procrusters and techniques in sensory analysis, in Statistical Procedures in Food Research (ed. J.R. Piggott), Elsevier, London, pp. 233-254. 

Oxidative stability of edible oils depends primarily on their fatty acid composition and, to a lesser extent, in the stereospecific distribution of fatty acids in the triacyl-glycerol molecules. The presence of minor components in the oils also affects their oxidative stability. A detailed discussion of oxidative processes in fats and oils is provided elsewhere in this series. Oxidation may occur via different routes and includes autoxidation, photo-oxidation, thermal oxidation, and hydrolytic processes, all of which lead to production of undesirable flavor and products harmful to health. Flavor and odor defects may be detected by sensory analysis or by chemical and instrumental methods. However, chemical and instrumental procedures are often employed in the processing and during usage of edible oils. Indicators of oxidation are those that measure the primary or secondary products of oxidation as well as those from hydrolytic processes or from thermal oxidation, including polymers and polar components (15). 

Hair-cleaning methods may be classihed according to the following categories chemical and physical properties, microscopic methods, and subjective or sensory evaluation procedures. Chemical or physical methods may involve either direct analysis of the hair itself [13, 20] or analysis of hair extracts [17,18]. For direct analysis of hair, chemical methods such as... 

Perfumers were familiar neither with sensory analysis nor with the Flash Profile procedure. They were therefore first given a brief outline of the methodology and procedure. They were then introduced to the 12 samples of perfumes simultaneously. Paper strips were provided for evaluation. 

AU consumers were able to use the Flash Profile methodology. No consumer gave up the study despite the large number of products. They aU fiiUy understood the ranking procedure and managed to complete the task. This was also the case for perfumers even if they were not familiar with sensory analysis protocols, they completed the Flash Profile session even quicker than the consumers, probably because of their ability to smell several perfumes. It is also possible that perfumers recognized some perfumes. 

It is extremely doubtful that there will be any reliable instrumental method in the foreseeable future that will replace the human being for the sensory evaluation of foods. However, there are various instrumental techniques that can be used to supplement sensory analysis (7). These techniques are typically simple rapid screening procedures which reduce the burden on sensory analysis but do not eliminate it. As an example, we see very common usage of headspace gas chromatography to monitor hexanal in vegetable oils. There is a well established correlation between the oxidation of vegetable oils and hexanal. 

Unfortunately, the two basic techniques used to assess flavor/fragrance quality— sensory analysis and conventional GC/MS—are generally too time-consuming, complex, and labor-intensive for routine quality control application. In fact, many of the test procedures and sample preparation methods described in this book are inappropriate for routine quality control testing. In industrial quality control applications, the need for speed and the large number of samples to be tested significantly impact the type of testing procedures and instrumentation that can be used. 

Within Severn Trent a modified version of this procedure is utilised for the analysis of malodorous emissions. The most significant difference in this approach compared to those already discussed is the use of high resolution gas chromatography in combination with olfactory detection. This method also combines physico-chemical and olfactometric or sensory techniques but in an alternative manner. Utilisation of gas chromatography combined with odour detection is not a new concept and has been employed fairly commonly for the analysis of food aromas, essential oils and other fragrances. The technique is equally applicable to environmental problems and is used frequently in this laboratory for the analysis of atmospheric emissions and taste and odours in water. Three important benefits accrue from this approach in the context of odour emission analysis. 

Dupuy and coworkers have reported a direct gas chromatographic procedure for the examination of volatiles in vegetable oils (11). peanuts and peanut butters (12, 13), and rice and com products (14). When the procedure was appTTed to the analysis of flavor-scored samples, the instrumental data correlated well with sensory data (15, 16, 17), showing that food flavor can be measured by instrvmental means. Our present report provides additional evidence that the direct gas chromatographic method, when coupled with mass spectrometry for the identification of the compounds, can supply valid information about the flavor quality of certain food products. Such information can then be used to understand the mechanisms that affect flavor quality. Experimental Procedures... 

The analysis of aroma compounds starts with the isolation of the volatile fraction from the food. Techniques used in the preparation of flavor extracts from foods have recently been reviewed [7-9], The most important task in the choice of the isolation procedure is to test whether the flavor of the extract is identical or at least similar to the flavor of the food itself. This has to be checked by a sensory evaluation of the food extract (e.g., after dilution with an appropriate medium like water or oil) before a time consuming chemical analysis is performed. 

This method is currently being used for routine laboratory analysis of red pepper heat. Results have been consistent and continue to correlate well with HPLC data. A similar procedure has also been used for sensory evaluation of black pepper heat. The American Society for Testing and Materials (ASTM, Committee E-18) has conducted a collaborative study testing the new method in comparison to the Scoville Method. ASTM E-18 is currently preparing to document it as a standardized test method. Also, a modification of the method is being prepared for oleoresin capsicum and for low-heat capsicums. 

---