Sensory mapping using Flash profile. Comparison with a conventional descriptive method for the evaluation of the flavour of fruit dairy products

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Abstract

Flash profile is a quick sensory profiling technique designed to meet industrial needs. It is based on the combination of free choice profiling and a comparative evaluation of the whole product set. This study aimed at comparing Flash profile with conventional profiling. This has been done with two product spaces: strawberry blended yoghurts and apricot “fromages frais”, both from the French market. Multidimensional data treatment such as Generalised Procrustes Analysis and Canonical Variate Analysis (CVA) allowed us to assess the correspondence between the sensory maps obtained with both methods. In the case of strawberry yoghurts, very similar results were obtained with the two methods. On the other hand the sensory positioning of the apricot fresh cheeses somewhat differed between the methods. For both product sets, Flash profile was slightly more discriminating than the conventional profile. Advantages and limits of Flash profile are discussed.

Introduction

Sensory profiling methods are used in the industry to draw up the sensory ID of a set of products. This can be done, for example, to investigate the sensory properties of a range of existing products from a given market or to assess the sensory impact of a new formulation, a change of fabrication process or packaging. More generally speaking, sensory profiling is increasingly viewed as a way to explain and possibly anticipate consumer preferences. In this respect, the primary purpose of sensory profiling is implicitly to describe and quantify inter-product sensory differences. Carrying out a sensory profile therefore aims at positioning the products in a multivariate sensory space defined by a relevant combination of sensory attributes.

Contrary to an evaluation performed by a single expert (e.g. an oenologist or a perfumer), the profiling process ideally aims at providing a subject-independent description, free of hedonic judgments. Quantification is performed on descriptive attributes that are clearly identified. Since human subjects are not equally sensitive to sensory stimuli nor equally discriminant regarding the attributes, a panel of judges is used in order to stabilise the generated description.

Since the first developments of sensory profiling methods in the 1950s, sensory scientists from academia and the food and the flavour industry people have developed variations of the original techniques. Recently, Schlich, 2000, Sieffermann, 2002 suggested to combine free choice profiling with a comparative evaluation of the product set in a technique named Flash profile. The goal of our experiment was to compare Flash profile with a well-proven conventional profiling method. Flash profile has been previously run to describe a set of red fruit jams and proved to be satisfactory as compared to conventional profile (Dairou & Sieffermann, 2002) which makes it a potentially useful tool for rapid market analyses. However, in that study the descriptive task was quite easy to achieve due to large differences between the products. The authors therefore pointed out that it would be necessary to compare the two approaches with more similar products. In the present study, we chose to work with two product spaces that would be similar to those encountered in industry, that is to say branded products from the French market that belong strictly to the same family of products (i.e. direct competitors'), and which were thus expected to be very similar. The dairy product sector is amongst the most competitive in the French food industry, providing us with many eligible types of products. We came to the choice of two product spaces: strawberry blended fruit yoghurts on one hand and apricot “fromages frais” (fresh cheeses) on the other hand. In addition, we decided to restrict the evaluation to the description of flavour. We used two distinct panels that were respectively dedicated to the conventional profile and to the Flash profile.

The comparison between the methods will be based on the following criteria:

  • 1.

    Degree of similarity between the sensory spaces. In other words: is the relative product positioning identical from one method to the other? Consequently, the discriminating power of each panel will also be investigated.

  • 2.

    Richness of the semantic information yielded in both cases and correspondence of the descriptive components.

  • 3.

    Practical aspects of the techniques. These aspects directly result from the methodological choices and are therefore discussed in the introduction below.

Traditionally, performing a sensory profile includes the following key steps:

  • 1.

    Development of a common language for the description of the studied products. The constitution of a unique list of attributes is achieved by consensus as a group process.

  • 2.

    Training of the judges for the evaluation of the attributes. This includes flavour identification and quantification (intensity measurement). In order to facilitate this step and to increase the group performances, each attribute comes with a definition and physical references can be provided.

  • 3.

    Evaluation itself is performed individually, usually in a monadic sequential way and it theoretically comprises several repetitions as for any instrumental or sensory measurement.

Various procedures based on this scheme have been proposed. Amongst the most widely used are the QDA® (Stone, Sidel, Oliver, Woosley & Singleton, 1974), the Quantitative Flavor Profiling (Stampanoni, 1993) and the SpectrumTM method (Meilgaard, Civille, & Carr, 1999).

The time necessary to carry out such an analysis may vary widely and depends in the first place on the objectives of the study in terms of precision and sensitivity. It also depends on the task difficulty, which is conditioned by the product space (products may be well distinguishable or very confusable) and by the sensory fields under investigation. It is indeed usually easier to describe texture differences than aroma differences for which our concepts are fuzzier. In any cases, the first two steps (language development and training) are the most time consuming. They may last from few weeks to several months.

A weakness inherent in regular descriptive analysis is related to the use of attributes that are common to all the judges. Indeed, the ability of subjects to communicate their sensory perceptions on the same vocabulary bases is sometimes doubtful, even after thorough training. It is well-known for example that a single stimulus can be perceived quantitatively and qualitatively different from one subject to the other, especially when chemical senses are involved (Lawless, 1999). Consequently, the forced use of a common language may in the worst case result in the situation where a given attribute actually stands for differing individual concepts. Alternatively one attribute may represent the lowest common denominator for all the judges, impoverishing greatly the sensory information.

Other limitations come from the use of these techniques in the industrial environment. First, it is not always possible for companies' sensory analysts to set up as many panels as there are kinds of products to analyse. Second, the competitive environment often means that new competitors come out on the market and that recipes are subject to modifications. It is then necessary to adapt the vocabulary to the product space as it changes. Eventually and maybe most important, running a conventional profile is time-consuming and for this only reason, sensory evaluation is often dropped out when results are needed urgently.

Flash profile was initially developed as a flexible method that aims at providing a quick access to the relative sensory positioning of a set of products. In order to save time, the phases of familiarisation with the product space, attribute generation and rating have been integrated into a single step. Several methodological choices made it possible:

  • 1.

    The main specificity of Flash profile is the comparative procedure of evaluation of the whole product set. Judges simply rank the products (with ties allowed) attribute per attribute. This forces them to focus on the perceived differences and to solely use discriminant attributes. There is consequently no longer need for a step of familiarisation with the product set because the panellists have a simultaneous access to all the samples and their differences.

  • 2.

    Second, Flash profile is based on the use of Free Choice Profiling (Williams & Langron, 1984) that allows judges to use their own list of attributes. This frees us from the time-consuming constraints related to the seeking of the consensus and concept alignment (O'Mahony, 1991). This therefore reduces the need for a trained panel.

  • 3.

    Finally, sensory evaluation experts—not necessarily product experts—are selected to participate in the panel. By sensory evaluation experts, we mean subjects who have previously participated in several descriptive evaluation tasks and who are able to understand panel leader's instructions and generate discriminant and non-hedonic attributes. This way, we can benefit from the judges' experience in communicating their perceptions quantitatively. These judges do not need to be trained on a specific product set. In this respect, the selection of judges can be compared to that in the QFP procedure, in which the judges who are trained before participation in the test protocol actually become sensory experts (Stampanoni, 1993).

Section snippets

Samples

This study was split into two experiments respectively conducted with two product spaces: strawberry blended fruit yoghurts on one hand and apricot fresh cheeses on the other hand. This was done to test the two profiling methods with more than one kind of product. Fresh dairy products were chosen because their short shelf-life made them good clients for a rapid descriptive method. Besides, fruit yoghurts and fresh cheeses are amongst the largest sales of fresh food on the French market.

In

Comparison of sensory maps

The PCA plots of the data from the two panels (Fig. 1) show similar structures. In both cases, YOG1a and YOG1b are opposed to other products on the first axis and axis 2 separates YOG3 and YOG4. When limiting the comparison to the first two principal components, products YOG2 and YOG3 that are more centrally located, appear to be slightly differently positioned depending on the profile type. However, not all the sensory information is taken into account on this plot. Another way to assess the

General discussion and conclusion

The use of Flash profile for the evaluation of a set of strawberry yoghurts allowed a rapid access to their sensory positioning. It was found to be identical to that obtained by a conventional method. However, we observed that the match was not perfect for the second product space studied (the apricot fresh cheeses). The reasons for the discrepancy between the results of the two panels are not clear. It is worth noting that the interpretation is inherently limited by such a comparison

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