Flavor partitioning

Flavor Partitioning The perception of a flavor depends on the precise location of the flavor molecules within an emulsion. The aroma is determined by the presence of volatile molecules in the vapor phase above an emulsion (122, 126). Most flavors are perceived more intensely when they are present in the aqueous phase, rather than in the oil phase (127, 128). Certain flavor molecules may associate with the interfacial region, which alters their concentration in the vapor and aqueous phases (129). It is therefore important to establish the factors that determine the partitioning of flavor molecules within an emulsion. An emulsion system can be conveniently divided into four phases between which the flavor molecules distribute themselves the interior of the droplets, the continuous phase, the oil-water interfacial region, and the vapor phase above the emulsion. The relative concentration of the flavor molecules in each of these regions depends on their molecular structure and the properties of each of the phases (130, 131). 

Flavor partition coefficients. The equilibrium distribution of a particular flavor molecule between two phases (e.g., oil-water, air-water, or air-oil) is characterized by an equilibrium partition function. These partition coefficients determine the distribution of the flavor molecules between the oil, water, and head space phases of an emulsion. 

If an aqueous solution of a compound is shaken with another liquid that is immiscible (mutually insoluble) with water, some of the compound may dissolve in the other solvent. For example, molecular iodine, I>, is very slightly soluble in water but is highly soluble in tetrachloromethane, CC14, which is immiscible with water. When tetrachloromethane is added to water containing iodine, most of the iodine dissolves in the CC14. The solute is said to partition itself between the two solvents. Solvent extraction is used to obtain plant flavors and aromas from aqueous slurries of the plant that have been crushed in a blender. 

Decaffeination of green coffee beans is most usually carried out with a water/solvent partition system. The green coffee beans are first steamed until they are hot, wet, and swollen, to make the caffeine available. Solvent is then used to extract the caffeine out of the aqueous phase of the beans. Finally, the beans are steamed to drive off residual solvent. The coffee beans lose their wax surface covering in the process, as well as some flavor components. For this reason, the Robusta and Brazilian Arabica coffees that are dry-processed and have the most powerful flavors are usually the types that are decaffeinated. They become milder in the process. Mechanical polishing is used to improve the appearance of decaffeinated green coffee beans if they are not to be roasted immediately. Extra care is required, however, to store these decaffeinated beans since the loss of wax covering as well as caffeine renders them much more susceptible to fungal attack. 

In Eq. (37) soft external and a fields, carrying momentum q p l. were assumed. Then, they are present inside of the form-factor F in above mentioned form. If v, a external fields are flavor matrices then form-factor F also becomes matrix Nf x Nf. So, we get the partition function Z[m,V], where W are multi-quark interaction terms in the presence of current quark mass m and external fields V. 

Gunning, Y.M.. Parker. R.. Ring. S.G.. Rigby. N.M.. Wegg, B., and Blake, A. Phase behavior and component partitioning in low water content amorphous carbohydrates and their potential impact on encapsulation of flavors, J. Agric. Food Chem., 48(2) 395-399, 2000. 

Surfactants can act like lipids or emulsifiers in solubilizing flavor materials in surfactant micelles. Headspace analysis techniques were used to follow the release of several common dentifrice flavorants from a solution containing the surfactant sodium lauryl sulfate. Water/micelle partition coefficients were derived to describe the solubilization of the flavorants in tiie surfactant micelle (76). Initially, the flavor is solubilized in the surfactant micelle. As both the micelle and flavor concentration decrease on dilution, flavor compounds, which are highly soluble in the micelle, preferentially increase in the headspace [HGURE11]. 

Uses. Most essential oils are used directly as starting materials in the production of flavor and fragrance compositions. However, some essential oils are fractionated or concentrated by distillation, partitioning, or adsorption. Substances that are important for the desired characteristic odor and taste are thus concentrated, and other components, which possess either an unpleasant or very faint odor or are unsuitable for the application in question, are removed. 

In flavor analysis, the most frequent use of volatile traps is in analyzing the flavor compounds in foods using purge-and-trap or dynamic headspace, followed by GC-MS or GCO. Additionally, the traps can be used to measure static headspace and air-matrix partition coefficients where air is pushed out of an equilibrated cell containing the sample onto a volatile trap (Chaintreau et al., 1995). Volatile traps have been also used for flavor release measurements during eating (Linforth and Taylor, 1993) or simulated eating (Roberts and Acree, 1995). 

Lipids in foods vary from traces as in cereals to 30-50% as in nuts. The physical state and distribution of lipids vary considerably among food items. In each item lipid distributions affect its flavor as it undergoes chemical reactions and act as a flavor components vehicle or partitioning medium. Furthermore, lipids have a pronounced effect upon the structure of food items. Fatty acids of neutral (triglycerides) and polar lipids of beef and pork are tabulated in Table III. 

Dry fractionation involves melting the milk fat, controlled cooling and crystallization of molten milk fat while cooling to or at a desired temperature and separation of the crystals from the liquid phase. The process is attractive because of its simplicity, relatively low costs and ability to select between fractions based on the melting or functional properties of the fats, which is usually the reason for fractionation. It does not involve the use of solvents, detergents or other additives and furthermore, the desirable flavor notes are not lost although they are partitioned differently between the various fractions. 

Quantification of FFAs in dairy products, especially in cheese, is particularly important due to the impact of some FFAs on flavor. However, FFAs act as precursors of a wide range of flavor compounds (e.g., methyl ketones, lactones, esters and aldehydes), (Singh et al, 2003). The extent of lipolysis in cheese varies widely between varieties (Table 19.2). Typically, those cheeses with more than 3000 mg/kg have a characteristic lipolytic aroma/flavor and lipolysis plays an important role in their ripening. A major difficulty in quantifying FFAs in cheese is the distribution of FFAs of different chain length within the cheese matrix. SCFFA (C4 o—C8 0) partition mainly into the aqueous phase, whereas medium (Cio q—C14 0) and longer... 

During mastication, nonvolatile flavor molecules must move from within the food, through the saliva to the taste receptors on the tongue, and the inside of the mouth, whereas volatile flavor molecules must move from the food, through the saliva and into the gas phase, where they are carried to the aroma receptors in the nasal cavity. The two major factors that determine the rate at which these processes occur are the equilibrium partition coefficient (because this determines the initial flavor concentration gradients at the various boundaries) and the mass transfer coefficient (because this determines the speed at which the molecules move from one location to another). A variety of mathematical models have been developed to describe the release of flavor molecules from oil-in-water emulsions. 

Partitioning. A substance may have limited solubility in two mutually immiscible solvents, for instance water and oil. This often happens in foods, for example with many flavoring and bactericidal substances. It then is important to know the concentration (or rather activity) in each phase. For low concentration, the partitioning or distribution law of Nernst usually holds ... 

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