Encapsulation of aroma

Abstract

Flavor is one of the most important characteristics of a food product, since people prefer to eat only food products with an attractive flavor (Voilley and Etiévant 2006). Flavor can be defined as a combination of taste, smell and/or trigeminal stimuli. Taste is divided into five basic ones, i.e. sour, salty, sweet, bitter and umami. Components that trigger the so-called gustatory receptors for these tastes are in general not volatile, in contrast to aroma. Aroma molecules are those that interact with the olfactory receptors in the nose cavity (Firestein 2001). Confusingly, aroma is often referred to as flavor. Trigeminal stimuli cause sensations like cold, touch, and prickling. The current chapter only focuses on the encapsulation of the aroma molecules. Aroma consists of many volatile and odorous organic molecules. Most of them are in a gas or liquid state, but also some solid materials may have a distinct smell (e.g. vanillin and menthol). In general, aroma molecules have a low MW (often between 100 and 250) and can be classified as hydrocarbons, alcohols, aldehydes, ketones, esters, acids, sulphides, etc. Typical examples of aroma molecules are shown in Fig. 5.1. Most of the aroma molecules are lipophilic, but some are hydrophilic (their logarithmic values of the octanol-water partition coefficient, log P, ranges from-1 to 7). Aroma molecules can be either added to food products, produced during processing of the food product (the so-called processing or reaction flavor) or are formed during cooking of the food product. Aroma can reach the nose cavity directly when the food is not yet in the mouth (ortho-nasally: direct smell) or via the oral cavity (retro-nasally). Gas and thus aroma is transferred from the oral cavity to the nasal cavity via nasal airflow, which is influenced by mouth action like saliva production, mastication and swallowing. Aroma release from food products before and after eating is controlled by both thermodynamic and kinetic parameters, which depends on the aroma characteristics and on the composition and the physical state of the matrix. These parameters will determine the volatility of the flavor compounds and their resistance to mass transfer between different phases, especially from the product to air (Druaux and Voilley 1997; Van Ruth and Roozen 2002; De Roos 2003). Proper choice of food composition and food microstructures may thus control aroma release during food product preparation and consumption. Encapsulation might be one of the tools in such a design (Porzio 2007a). © 2010 Springer-Verlag New York.