Observations

Trace components are responsible for most Flavours. Natural Flavours such as essential oils cannot be duplicated easily in spite of the advances in analysis. People are very sensitive to these trace components and can detect minute differences. Off odours at low levels can enhance the flavour and make it appear more natural. (skatole in cheese)

 

Like most things flavours change with time due to chemical reactions. In essences acetals are formed with the solvents. Whiskey matures in oak extracting vanillin from the wood plus numerous other chemical reactions. Oxidation occurs in powdered and other flavours

Low pH will cause Lemon to become Lime like. ( D Limonene to alpha Terpineol. Citral is also destroyed), hence WID Lime oil is so different to cold pressed oil.

Milk releases butyric acid with a drop in pH hence smells sour.

Fishy, tri methyl amine looses its smell with low pH (Vinegar, Lemon)

The flavours in bread and coffee seem to evaporate or change (oxidize) quickly. Leaving stale or old flavours.

Hence the difficulty of making good artificial bread or coffee flavours.

Like perfumes long lasting flavour components need to have very low flavour thresholds and a very low vapour pressure.

The smelling strip was very useful as it allowed the flavourist to detect these low vapour pressure molecules after the more volatile ones had evaporated.

Maturation of Flavours

Volatility

Changing of Flavour with pH

Fresh mown grass has a fresh green odour like cis 3 hexenol, however if conditions are right the grass ferments and the odour becomes “ new mown hay” which is mostly Coumarin.

Coumarin is not allowed in food flavours any more but has a wonderful odour. You can still detect coumarin in some pipe tobacco flavourings.

Most people who work in a flavour laboratory are surrounded with strong odours all day long. Yet they are expected to detect minor differences in other flavours. What I believe happens is that they are able to switch off their odour detectors to this background aroma.

 

While odour thresholds are often sited as the minimum one can detect no one has measured the maximum you can detect. What I believe is that there is a strength beyond which you can not perceive an increase in concentration. Lots of artificial vanilla flavours have ten times the level of vanillin that one can detect when used at the recommended dosage.

 

Natural Vanilla extracts taste great with only 0.2% vanillin.

 

Lots of fruits produce low levels of aroma material during the day. The aroma escapes filling the fruit shop with delicious odours. The level of odour in the fruit remains roughly the same. This cannot be duplicated with artificial flavours.

Insects find their food/mates by the aroma gradient, starting at a few molecules and gradually increasing as they get close to the aroma emitter.

However if the aroma emitter gives off so much aroma that the insect detectors are saturated some distance from the target there is no longer a gradient and the insect get confused and flies away.

 

I have tested this with Raspberry Ketone and the Australian fruit fly