As a technique to activate the controlled release of fragrance, one’s first thought would probably not be drawn to Trigger, the favorite horse of the American cowboy star Roy Rogers. Nor would that first thought focus on the finger lever of detective “Dirty Harry” Callahan’s Smith & Wesson .44 Magnum revolver (Figure 1). Yet both of these Hollywood “triggers” have two essential similarities with the triggers used to release fragrances in personal care products: The trigger needs to be “holstered”—i.e., held in reserve—until it is needed and it needs to be uniquely designed for the intended reaction and for the environment in which it is to be used.
This column examines some of the recent patent literature on triggers for controlled release of fragrance and was, itself, triggered by a reading of Andreas Herrmann’s recent review of pro-fragrances in Angewandte Chemie. Herrmann has worked for the past decade at Firmenich SA in Geneva, Switzerland, on the development of new fragrance delivery systems. He writes that current research interest in the flavor and fragrance industry is focused on the design of selective and efficient delivery systems with two goals: to control the slow release of highly volatile odorants in functional perfumery products; and to increase the stability of fragrance raw materials with unstable chemical functional groups such as aldehydes.
Although some of the chemical triggers reviewed by Herrmann have already been commercialized (e.g., in the home care sector), many of them are still discussed mainly in the patent literature. Traditional triggers using an encapsulation approach have been commercialized by companies such as Salvona Technologies and Procter & Gamble and are more broadly discussed in the scientific literature.
This article will consider first some recent developments in fragrance release in encapsulated systems. Then, the controlled release of fragrances through the use of mild chemical reactions will be examined.