[Constituents of food aromas]

A comprehensive review is given on the nature of the volatile compounds which participate to the aromas of foods. Its seems that light compounds, which are present in every food stuffs, give the fresh impression, and that more heavy components give the characteristic aromas. Although it is very important to consider that these volatile compounds have very different olfactory detection thresholds. The characteristic components of a food are often those which have very low detection thresholds and which are present at very low concentrations. The new analytical techniques have permitted the identification of more than two thousands compounds often present in minute amounts in foods (less than a gram per ton). But the problem is now to correlate these analytical data with the olfactory impression of tasters. Some correlations have already been obtained when a specific flavor corresponds to a small number of components, as it is often the case for off-flavors. An other problem for the food technologist is the study of the origins of the more interesting components. Some examples are given on raw materials (fruits and vegetables) and on fermented or cooked foods.