Aroma Molecules as Dynamic Volatile Surfactants: Functionality beyond the Scent

Abstract

Understanding of non-equilibrium processes at dynamic interfaces is indispensable for advancing design and fabrication of solid state and soft materials. The research presented here unveils specific interfacial behavior of aroma molecules and justifies their usage as multifunctional volatile surfactants. As non-conventional volatile amphiphiles we study commercially available poorly water-soluble compounds from the classes of synthetic and essential flavor oils. Their distinctive feature is high dynamic interfacial activity, so that they decrease the surface tension of aqueous solutions on a time scale of milliseconds. Another potentially useful property of such amphiphiles is their volatility, so that they notably evaporate from interfaces on a time scale of seconds. This behavior allows for control of wetting and spreading processes. A revealed synergetic interfacial behavior of mixtures of conventional and volatile surfactants is attributed to a decrease of the adsorption barrier as a result of high statistical availability of new sites at the surface upon evaporation of the volatile component. Our results offer promising advantages in manufacturing technologies which involve newly creating interfaces, such as spraying, coating technologies, ink-jet printing, microfluidics, laundry, stabilization of emulsions in cosmetic and food industry, as well as in geosciences for controlling aerosols formation.

Volatile Aroma Surfactants: The Evaluation of the Adsorption–Evaporation Behavior under Dynamic and Equilibrium Conditions

“…This leads to an increased concentration of the surfactant in the pendant drop. 24 For the solution with a higher concentration than the CMC, the surface tension is constant since the minimum value of the surface tension, and accordingly, maximum adsorption was attained at the time scale of subseconds.…”

“…We note, however, that fast adsorption dynamics of volatile amphiphiles, with a significant decrease in the surface tension happening in the μs range, cannot be satisfactorily fitted with the standard Ward−Tordai model. 24 Also, most of the reported evaluations of the dynamic data covered adsorption kinetics at a 1−100 s time scale, while reliable measurements of adsorption dynamics in the microsecond range remain an experimental challenge. 3,37,38 Evaporation Behavior of Volatile Surfactants.…”

“…In particular, mixtures of nonionic fast-adsorbing aroma molecules and conventional (ionogenic) micellar-forming surfactants are an interesting model system with significant applied potential. 24,25,47 In the following, we describe the interfacial behavior of SDS−benzyl acetate mixtures under dynamic conditions. Figure 6a shows the surface tension, measured with the MBP method, of SDS and benzyl acetate individual solutions, as well as of their mixtures with a constant fraction of benzyl acetate of 0.5 and 0.25 versus the total molar concentration of surfactants in solution.…”

“…However, the use of classical equilibrium methods of colloid chemistry has led to a misapprehension of the effect of aroma molecules on dynamic interfacial processes. It is only recently, that individual interfacial activity − and fast-adsorbing behavior of aroma molecules ,, have been unveiled by measuring dynamic and equilibrium surface tension of individual and of mixed surfactant solutions. These studies indicated the high potential of aroma amphiphilic molecules in dynamic interfacial processes.…”

Gelation characteristics of sodium alginate in presence of flavor molecules

“…The surface activities of flavor molecules have recently received more attention. A study by Soboleva et al (2019) has revealed the surfactant nature of other flavor molecules (e.g., citral, linalool, geraniol) and the volatility of these compounds is considered beneficial in some industrial processes. Coffee oil has also been studied for its surfactant properties (Deotale et al, 2019).…”