3 minute read
Keeping up the balancing act
between healthier and better tasting products
Natural flavours are more popular now than ever. Even artificial flavours simulate the characteristic of their natural counterpart. The results are sometimes extremely convincing. However, how do flavour companies proceed to create these ‘natural’ artificial flavours? Marí Carmen Inglés, flavourist at Scentium Flavours explains how the magic happens.
The analysis of volatile substances in a natural product is a classic analytical problem, where each phase - such as sample selection and preparation, sampling methods to isolate the volatile fraction - presents particular and peculiar aspects of criticality. Each analytical technique has its advantages and disadvantages and all of them are complementary to each other when studying the aromatic profile of a natural product. Isolation of volatile compounds is a crucial and critical step of food analysis focused on aroma components investigation. Among the techniques used by Scentium, SAFE and SPME stand out.
Once the volatile substances have been isolated, the compounds can be identified and quantified using Gas ChromatographyMass Spectrometry (GC-MS) and Gas Chromatography-FID.
The results of the qualitative and quantitative analysis allow flavourists to define the composition of the volatile fraction, which is generally made up of a large number of compounds, but they do not explain which substances play a role in defining a specific aromatic profile. For this, some techniques have been proposed to find possible relationship between sensory perception and instrumental analysis.
The Odor Units (Uo) concept, theorised and developed by Guadagni et al., is oriented to identify which component is important to define a specific flavour profile. The measure of the smell intensity of a volatile substance is generally expressed by its olfactory-odour threshold that it is defined as its lowest concentration that can be perceived by nose. Uo value is defined by the ratio between the concentration C of a substance, defined via analytical methods, and its odour threshold T, both expressed in mg kg-1. Therefore to be perceived by the sense of smell, a substance will have to have an Uo equal or above 1, because its concentration will have to be equal or greater than its odour threshold. The higher the Uo, the higher the probability that a volatile substance can contribute to the development of the overall aroma.
EXTRACTING THE NATURAL TASTE OF A TOMATO
Let’s take the concrete case of a fresh tomato. In order to identify the compounds responsible for the overall odour of this fruit, its volatile fraction was isolated by solvent extraction of the tomato fruit and subsequent SAFE distillation. A GC-MS system was used for the identification of the compounds and a gas chromatographyflame ionisation detector for its semiquantitation. The odour activity value (OAV) for each of them was also calculated. A total of 49 volatile substances were identified, 21 of which presented an OAV≥1
Aldehydes represented the most abundant chemical class in terms of analytical concentration and their contribution to develop the overall odour is very important. (Z)-3-hexenal, hexanal, 3-methylbutanal and decadienal were the volatiles having the highest OAV. Other compounds such as β-ionone, guaiacol, 3-methylthio propanal and furaneol played an important role in developing the characteristic flavour of this particular tomato. Figure 1 shows the contribution of volatile compounds in terms of their OAVs, expressed in a logarithmic scale. The odourants having OAV≥1 were used to prepare a recombination of the tomato
Figure 1. OAV bar graph in a logarithmic scale of aroma active compounds detected in the SAFE distillate isolated from a tomato.
flavour. This is, in a nutshell, one of the many methods flavour experts use to mimic with such precision a natural aroma. It can be arduous, but the result is highly convincing and satisfying for the consumer. It is a starting point to which flavourists can later add more complexity to the flavour to make it unique. However, this procedure is not universal and is not necessarily compatible with all kinds of natural food. Flavourists must investigate to make sure to use the method that is the most adequate for the food they are working with. •
