The Chemistry Of Scents: Volatile Aroma Compounds Explained

Aroma compounds are volatile molecules that give rise to the smell and flavour of food. They are perceived through the smelling sensory organs of the nasal cavity and can evoke associations and emotions even before the food is tasted.

Aroma compounds are generally classified into organic molecules with a low molecular weight and a lipophilic character. They are present in food in a wide concentration range and their impact on food aroma depends on their concentration and odour threshold.

The main aroma compound classes are:

- Organic acids

- Primary and secondary alcohols

- Amines and other nitrogen compounds

- Carbonyl compounds

- Esters

- Lactones

- Oxygen-containing heterocyclic compounds

- Pyrazines

- Sulfur compounds

- Terpenes

Aroma compounds are volatile molecules that are released from food during eating and reach the olfactory receptors

The main aroma compound classes are:

• Organic acids
• Primary and secondary alcohols
• Amines and other nitrogen compounds
• Carbonyl compounds
• Esters
• Lactones
• Oxygen-containing heterocyclic compounds
• Pyrazines
• Sulfur compounds
• Terpenes

Aroma compounds are perceived through the smelling sensory organs of the nasal cavity, and evoke numerous associations and emotions, even before the food is tasted. The information from these receptors is directed to the hippocampus and amygdala, the key regions of the brain involved in learning and memory.

Aroma compounds are synthesised from amino acids, membrane lipids, and carbohydrates

Amino acids are the monomers that make up proteins. Each amino acid has the same fundamental structure, which consists of a central carbon atom bonded to an amino group, a carboxyl group, and a hydrogen atom. The central carbon's fourth bond varies among the different amino acids, and this is what makes each amino acid distinct.

Carbohydrates are macromolecules with which most consumers are somewhat familiar. They are essential to the very source of life and play an important role in sustaining it. They are classified as monosaccharides, disaccharides, and polysaccharides, depending on the number of monomers in the molecule.

Lipids are a class of macromolecules that are nonpolar and hydrophobic in nature. They serve numerous and diverse purposes in the structure and functions of organisms. They can be a source of nutrients, a storage form for carbon, energy-storage molecules, structural components of membranes, and involved in chemical signalling and communication.

Amino acids, membrane lipids, and carbohydrates are all essential to the synthesis of aroma compounds.

Aroma compounds are classified as primary or secondary compounds, indicating whether they were present in intact fruit tissue or produced as a result of tissue disruption

Primary aroma compounds are those that are naturally present in foods due to physiological and enzymatic processes or generated by microorganisms during fermentation. These compounds contribute to the characteristic smell and flavour of the food product. Examples of primary aroma compounds include organic acids, alcohols, carbonyl compounds, esters, lactones, and terpenes.

On the other hand, secondary aroma compounds are those that are produced or modified during the extraction, processing, and storage of foods. Chemical, biochemical, or microbial changes can lead to the formation or alteration of secondary aroma compounds. For instance, during processing, enzymatic activity, fermentation, lipid oxidation, and thermal reactions (such as the Maillard reaction and caramelization) can result in the generation of secondary aroma compounds.

The distinction between primary and secondary aroma compounds is important as it helps to understand the complex aroma profiles of different food products. It also provides insights into how processing and storage conditions can influence the final aroma and flavour of a product.

Aroma compounds are responsible for the characteristic aroma of the food and are synthesised via a few major biochemical pathways

Aroma compounds are responsible for the characteristic smell of food. They are synthesised via a few major biochemical pathways, including enzymatic activity, fermentation, lipid oxidation, and thermal reactions.

Aroma compounds are volatile molecules, which must be released from the food matrix into the vapour phase to be perceived by the olfactory receptors. They are generally present in food in a wide concentration range, with a molecular weight of under 400 Da.

The main aroma compound classes are organic acids, primary and secondary alcohols, amines and other nitrogen compounds, carbonyl compounds, esters, lactones, oxygen-containing heterocyclic compounds, pyrazines, sulfur compounds, and terpenes.

The production of aroma compounds can be natural or technology-derived. Natural aroma compounds are synthesised as a consequence of physiological and/or enzymatic processes, as well as generated by microorganisms during fermentation processes. Technology-derived aroma compounds are produced via thermal technologies, nonthermal technologies, and nanotechnology.

Aroma compounds are perceived by the olfactory receptors in the nasal cavity

Olfactory receptors are located in the nasal cavity, where they detect volatile aroma compounds. These compounds are detected by the olfactory sensory neurons, which are located in the main olfactory epithelium at the roof of the nasal cavity. Each olfactory sensory neuron expresses a single type of protein receptor on its dendritic extensions, and the binding of an odorant molecule to these receptors triggers a signalling cascade that ultimately results in an action potential. The axons of the olfactory sensory neurons then project through the cribriform plate to form the olfactory nerves, which synapse with the mitral and tufted cells in structures called glomeruli. The glomeruli are found on the surface of the olfactory bulb and are critical for transducing olfaction.

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