The sensory properties are the characteristics of foods perceived by the senses of sight, smell, taste, touch and hearing, such as flavour, texture and appearance. The human sensory organs are a remarkably sensitive means of measuring sensory properties.

Flavour is a complex combination of aromas, smelt through the nose ( i.e. volatile compounds), and taste, experienced by the tongue ( i.e. non-volatile liquids or solids). Aromas are perceived via the olfactory nerve endings in the upper part of the nose, often in very small concentrations (a few milligrams per kilogram of product). The importance of aromas to a flavour can be demonstrated by pinching your nose as you eat: the food will taste blander. The number of volatile compounds responsible for an individual aroma can be very high: there are between 100 and 500 compounds in aromas such as vanilla, strawberry and cocoa. Most adults can detect the difference between about 2000 aromas. Typically taste compounds must be present in concentrations as much as 1000 times higher than aromas. They can only be detected by the taste receptors on the tongue when they are in solution, so dry substances must first be dissolved in saliva. Taste buds are sensitive to five basic stimuli: bitter ( e.g. caffeine and quinine); sour ( e.g. lemon juice); salt; sweet ( e.g. sugar) and umami ( e.g. monosodium glutamate). Interestingly, stereoisomers of chiral molecules can have completely different flavours. For example, one stereoisomer of carvone...