Top Notes Key Compounds of the Culinary Aroma

One of the most delicate steps in product development is to impart the characteristic flavour note. This concerns both aroma and taste. While the proper taste quality can be achieved by a careful selection of ingredients representing the base note (Fig. 5.50), delivering the typical aroma of a culinary product is in many cases a real challenge. This may be due to losses of odorants caused by high volatility and chemical reactions, thus leading to a misbalanced aroma profile, perceived as weak or even as an off-flavour that is no longer characteristic for the food product. 

Recent research resulted in new and potent impact odorants found in foods or Mail-lard reaction samples [26-28]. Systematic studies revealed common structural elements of sulphur-containing compounds required for developing a basic meat flavour (Fig. 5.53) [29[. The 1,2-oxygen, sulphur grouping has been suggested as a common element of the savoury olfactophore (Fig. 5.54). 

The systematic use of gas chromatography coupled with olfactometry [27, 28] in the last 20 years has resulted in a number of new high-impact aroma chemicals found in natural extracts, food products and reaction flavours. In general, sulphur-containing odorants play a particularly important role in food products and savoury flavours [30]. Some of them are shown in Fig. 5.54. Usually, the odour threshold is one key attribute showing the potential impact of the odorant. This may be as low as 0.00002 pg/L water reported for bis-(2-methyl-3-furyl)disulphide (BMFD) (Fig. 5.55) found in cooked meat with a typical meaty, sulphury note. 

However, not only the odour threshold is an important parameter to consider, but also the specific note that the odorant may impart. 2-Isobutylthiazole is a well-known example that is essential in tomato top notes, but has a relatively high threshold of 3 pg/L water. Another recent example is the identification of 2-heptanethiol (Fig. 5.55) in bell pepper extracts having a sulphury, onion-like and vegetable-like note, reminiscent of bell pepper at lower concentrations [31 ]. This odorant can impart the characteristic bell pepper note to complex top notes despite its moderate threshold value of 10 pg/L water. 

Similarly, 2,3,5-trithiahexane (TTH) was found to contribute to the typical cooked broccoli note when boiled in water (Fig. 5.56A) compared to vapour-cooked broccoli 

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