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The Chemistry of F&F: Physiological Coolants

By: Steve Pringle and David Brassington, Oxford Chemicals Ltd.
Posted: January 2, 2007, from the January 2007 issue of P&F magazine.

Similarly, the main aroma may be the first thing one tastes, while a cooling sensation gradually builds up. Finally, there is the coolant that coats the mouth or skin, leaving one with a refreshed feeling.

In the past 30 years, a tremendous amount of research has taken place in the development of compounds that have a “cooling” effect. Wilkinson Sword was probably the most prolific in the early days, evaluating more than 1,200 compounds for a cooling sensation. To this day, three of these compounds are still successful commercial products (F-1). The synthesis of one of these materials, N-ethyl-p-menthane-3-carboxamide, is shown in F- 2.

All of these materials are solids, which potentially can make formulations more difficult due to possible solubility problems. Although flavorists and perfumers have been able to formulate around these potential issues, it is clear that new materials are always welcome in order to avoid such problems. In addition, under Japanese legislation, they cannot be added to foodstuff because amides are not permitted in foodstuffs (see www.jetro.go.jp/en/market/regulations/pdf/flavor2003aug-e.pdf).

More recent developments include menthone glycerol ketal and menthyl lactate, but, again, these are solids and could pose problems, as highlighted previously. In 2005, a number of menthyl ester derivatives were patented, of which N,N-dimethyl menthyl succinamide received GRAS status. At the same time, a range of liquid cooling agents that are blends of 2-2-isopropyl-N,2,3-trimethylbutyramide and N-Ethyl-p-menthane-3-carboxamide also has been released.

An even more recent development in this area is menthyl 3-hydroxyl butyrate. This material has been developed by Oxford Chemicals Ltd. in collaboration with Japan’s San-Ei Gen FFI Inc. (Flavor and Extract Manufacturers Association status pending). The material is a liquid coolant that has almost no detectable odor and a cooling effect that is slightly stronger than that of menthyl lactate (F-3).