Olive Oil in Context: TDS uncovers complex interactions

December 2012 - Using the Temporal Dominance of Sensations (TDS) method, the tasting experience that develops over a longer period can be traced. In this way it is possible to comprehend aspects that are not reflected in static sensory profiles. In a recent study on olive oil, Italian researchers demonstrated the advantages of TDS.

Good quality olive oil is a basic foodstuff in many countries encompassing the Mediterranean Sea. In the meantime it has also become a highly desired ingredient in the modern kitchen of other Western countries. A few drops of good olive oil improve and round out the taste of many dishes. However, on closer observation, this effect proves to be extremely complex. Sensory experts need to use more elaborate experimental methods in order to be able to correctly describe the relationships between the oil and the food.

When looking for good quality olive oil in a shop, it is often the case that the customer samples a variety of oils on pieces of white bread. Tasting the oil in this manner invariably gives the taster an indication of the extreme taste differences of the various oils. The olive sort, degree of ripeness, cultivation, harvesting, and pressing methods – all have an effect on the oil’s sensory profile. Despite various attempts, up until now it has not been possible to determine which sensory qualities drive consumer preferences. It seems, at any rate, that they are not the same qualities that many experts praise when, for instance, a particular oil is honored at a food awards competition. Gian Paolo Zoboli from the Adacta Consensory Research Center in Napoli, Italy, conjectures that the reason for this discrepancy is that, “Consumers normally use olive oil in combination with other ingredients, instead of in its pure, unadulterated form. It seemed to us more realistic to investigate how olive oil is perceived in its typical daily use.”

4-step test procedure

Together with Erminio Monteleone and Catarina Dinella from the University of Florence, the team from Napoli developed a research design in which two sorts of extra virgin olive oil were tasted, both in their pure form and as an ingredient in a tomato puree and a bean puree, first by a trained panel from the University of Florence and then by a consumer panel.

The trained panel first developed a vocabulary for describing mouth-feel, taste, and flavor of the olive oil as well as the purees, and the mixture of olive oil and puree.

Secondly the panel did a descriptive analysis based on respectively five to nine taste aspects which were displayed in a balanced sequence by computer. Each aspect had to be rated on a nine-point category scale from “extremely weak” to “extremely strong”.

In a third step, data were collected by the TDS-method. Here the panelists were told to pay special attention to which of the five to nine pre-defined attributes of the taste experiences (defined as “Which sensation in my mouth attracts my attention most?”) were the most pronounced at each particular moment. As soon as they changed their mind as to the particular attribute of the dominant mouth sensation, they would mark the appropriate term on the computer screen. In this way a real-time profile was created concerning the changing perception of the dominant taste over the entire 90 second period of each taste test.

The consumer panel’s experiment was set up as a classic hedonic test. The participants had the task of rating on a nine-point scale a) how good the particular product tasted, and b) how fresh they found the product.

Analysis of the tests displayed the following results:

* While the sample was in the mouth, the TDS evaluation indicated that testers found the vegetable purees with olive oil had a greater variety of taste aspects than the purees without oil.

* Both descriptive analysis (DA) and TDS established that the addition of oil changed the perceived sensory qualities of the tomato and bean puree. Both types of olive oil used in the tests were shown to suppress the watery taste-notes in the tomato puree and the metallic and sweet taste-notes in the bean puree.

* However, each oil showed specific individual effects: The tomato puree with oil A was perceived as sharper and more bitter than the puree with oil B. The bean puree with olive oil A had a markedly more pungent, grassy, artichoke-like, taste than the puree with oil B.

* The influence that the pure olive oil samples had on the taste of the oil and puree combinations could not be traced back to the taste of a particular pure extra virgin oil. Even the special characteristic tasting notes of an oil were not or barely perceivable when used as an ingredient in a recipe. In such cases it was also impossible to predict the consumers’ preference beforehand.

* When the consumer group participants were questioned concerning freshness of taste as well as preference, they rated the pure olive oils differently than the oil-puree mixtures. In the comparison of the two olive oils, they preferred A, finding it fresher. In the oil mixed with tomato puree, the results were reversed – the tomato puree with the olive oil B was perceived as fresher that the puree with A.

* Especially interesting: The TDS methodology revealed that it was clearly not always the most intensive taste aspect that had the most influence. It was found that sometimes less intensive taste-notes that were either unexpected or unusual, or both, were perceived as the dominant ones. One concrete example: the taste aspect “unripe fruit”, an uncommonl flavour for olive oil from Tuscany, clearly attracted the test subjects’ attention more than the more intensive but very well known grassy and bitter notes of Tuscany olive oil.

Gianpaolo Zoboli concludes that, “The TDS method gives us important complementary information with which we can often better explain the consumers’ hedonic reactions than we can with statistic sensory profiles alone. It allows for a clearer description of the more complex interaction between the various components that decisively shape the foodstuffs sensory profile.”

Source:
Dinnella C, Masi C, Zoboli G, Monteleone E:
Sensory functionality of extra-virgin olive oil in vegetable foods assessed by Temporal Dominance of Sensations and Descriptive Analysis
Food Quality and Preference, Volume 26, Issue 2, December 2012, Pages 141–150 (Doi: 10.1016/j.foodqual.2012.04.013)

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