Aroma Formation during Thermal Food Processing: Why do Thermally Treated Foods Smell Differently?

During thermal processing of foods non-volatile precursors undergo various types of reactions leading to the unique aromas of well-accepted product such as cocoa, coffee, cereals or nuts. It is without doubt that the reaction between free amino acids and carbohydrates or their degradation products, known as the Maillard reaction, is among the most important "flavor delivery" systems in such foods. However, studies using approaches of "molecular sensory science" have shown that the majority of the Maillard-type reaction products, identified so far, do not show a contribution to the aroma of processed foods. In addition, many of the key Maillard aroma compounds, such as 4-hydroxy-2,5-dimethyl-3(2H)-furanone, the Strecker aldehydes or various pyrazines were found to be identical in many processed foods. Using several foods as examples, the lecture is intended to show that the quantitative balance of potent Maillard-type flavor compounds is a key to explain the differences in the different aroma perception of thermally processed foods. In addition, the presence of lipid degradation products and/or single "character impact odorants" transferred from the raw materials into the final products have to be considered as "modifiers" of the overall "aroma orchestra".