2. Flavour Chemistry
From the point of view of their chemistry, flavours can be classified on the base of their mode of formation, either naturally by biogenetic paths from known precursors or by processing in which biological, chemical or physical conditions are imposed on natural or artificial start materials.
Natural flavours are mostly metabolites so that their formation in living tissues is complex and dependent on genetic factors being highly influenced by the vegetative cycle and the environmental conditions during the natural growth cycle. Coriander leaves and stalks have no linalool before the fruiting, but this constituent increases in percentage as the vegetative cycle is developing, being the majority component in fruits. Plants can develop several chemotypes depending on the place were they are growing. Rosemary with a very high quantity of camphor can be find in Portugal, while in Spain or Maroco the percentage of this component is low.
Flavours produced by processing may be direct breakdown products or complex interaction products depending on the start materials and the processing conditions imposed.
Ohloff (1972) presents the first and simple classification of food flavours based on these concepts.
| Principal flavour type | Subdivision | Examples |
|---|---|---|
| Fruit | Citrus type (terpenic) | Orange, lemon, grapefruit |
| Berry type (non terpenic) | Apple, banana | |
| Vegetable | Celery, beans | |
| Spice | Aromatic | Cinnamon, peppermint |
| Lachymogenic | Onion, garlic | |
| Hot | Pepper, ginger | |
| Beverage | Unfermented | Juices, milk |
| Fermented | Wine, beer, tea | |
| Compounded | Soft drinks | |
| Meat | Mammal | Lean beef |
| Seafood | Fish, clams | |
| Fat | Olive oil, coconut fat, palm oil, pork fat, butter | |
| Cooked | Broth | Beef bouillon |
| Vegetable | Legumes, potatoes | |
| Fruit | Marmalades | |
| Empyreumatic | Smoky | Ham, kippers |
| Broiled, fried | Processed meat | |
| Roasted, toasted, baked | Coffee, snacks, processed cereals, bread | |
| Stench | Cheese | |
| Adapted from Ohloff (1972) | ||
Chemistry of constituents of some types of flavours will be studied.