Longevity of the fragrance

Longevity of the fragrance

In the art of flavouring, the persistence of aroma or the ability to retain aroma is closely related to the role of aroma fixation (fragrance preservation). Aroma persistence refers to the limit of aroma retention in a certain medium or matrix under certain environmental conditions (e.g. temperature, humidity, pressure, air circulation, evaporation area, etc.). In other words, it is the ability to retain a fragrance. The longer the duration, the stronger the persistence (longer fragrance retention), the shorter the weakness (shorter fragrance retention). Except for specific reasons or requirements, we always want the stronger the persistence, the longer the fragrance. This is also often the case with consumers' aroma requirements for finished fragrances. However, for the flavourist, it is not enough that the fragrance lasts, but that the fragrance retains its original aroma or aroma characteristics for as long as possible.

The strength of a fragrance aroma persistence, people can use the sense of smell evaluation method, can also use the sense of smell evaluation to draw conclusions. It is much more complicated to assess the strength, weakness or longevity of aroma persistence, especially in the case of finished fragrances. Therefore, as already mentioned, it is not only the duration of the fragrance that is important here, but also the stability or persistence of its aroma or fragrance characteristics. It is difficult to reach a satisfactory conclusion if only instrumental tests are used. At present, the use of the human sense of smell to determine the persistence (including stability) of an aroma (including in fragranced products) is still a relatively simple, fast and effective way. This can be complemented by the results of head space analysis.

The persistence of fragrances is largely related to their molecular weight (or average molecular weight), their vapour pressure, their boiling point (or melting point), their chemical structure or the nature of their functional groups, their chemical activity, etc. Generally speaking, it is believed that fragrances with high persistence are used as body and base fragrance components in flavours, while those with high persistence and a certain diffusion power are suitable for head fragrance components.

As the persistence of the fragrance and the role of fixed fragrance is closely related, here we discuss again about the role of fixed fragrance and the choice of fixed fragrance agent issues.

It is true that the persistence of the fragrance is related to the persistence of the fragrance and the amount of each fragrance, but also with some of the fragrances and the combination of fragrance or fixing performance, of course, also with the performance of the fixing agent used. The categories of fixing agents have already been described in Chapter 4. We will now briefly discuss the issue of fixing. 

In the context of flavouring, the term "fixing" refers to the effect of physical or chemical factors that enable the aroma of certain fragrances that tend to evaporate to be retained for a longer period of time. It can also be said that the fixing effect is the effect of slowing down the evaporation rate of a fragrance or flavour, or the effect of reducing the vapour pressure of a fragrance. The result of this action is to achieve a certain degree of fragrance fixation and purpose.

With regard to the regularity of the fixing effect, flavourists or physical chemists who are interested in the application of basic theory have done experiments or studies. However, due to the complex nature of the components of a flavour, which are inextricably linked to each other, the results obtained by testing and observing the fixing effect of a few flavour varieties or using the same fixing agent on one or several flavourings, cannot yet be generalised into a convincing and practical guiding conclusion. Furthermore, even for the same fragrance or the same combination of fragrances and fixatives, the fixing effect in different media or matrices may vary. The workload of our testing studies is very heavy and requires a fixed number of testers (especially fragrance evaluators), which takes a long time without any interruptions, otherwise the whole test result may become invalid or poorly reproducible. Recently, there have been fewer reports of research in this area.