Citrus flavor

Acids are added to soft drinks for extra bite. The primary acid used in colas is phosphoric acid, while the one used in citrus-flavored drinks is usually citric acid. Carbonated water (water that has the gas carbon dioxide dissolved in it under pressure) is also mildly acidic (it is chemically carbonic acid, H2C03). 

Uses. Nerol is used in perfumery not only for the same purposes as geraniol, e.g., in rose compositions, to which it lends a particular freshness, but also in other blossom compositions. In flavor work it is used for bouquetting citrus flavors. Technical-grade nerol, often in a mixture with geraniol, is used as an intermediate in the production of citronellol and citral. 

Uses. Because of its strong lemon odor, citral is very important for aroma compositions such as citrus flavors. In perfumery it can be used only in neutral media due to its tendency to undergo discoloration, oxidation, and polymerization. It is used as a starting material in the synthesis of ionones and methylionones, particularly /3-ionone, which is an intermediate in vitamin A synthesis. 

C12H22O2, Mr 198.30, Z PlOl.SkPa 240 °C, d 0.8901, Wp 1.4515, occurs in many essential oils either as one of its optical isomers or as the racemate. The odor of racemic citronellyl acetate differs little from that of the optical isomers. ( )-Citronellyl acetate is a liquid with a fresh-fruity rose odor. It is often used as a fragrance, for example, for rose, lavender, and geranium notes as well as for eau de cologne with citrus nuances. Since it is relatively stable to alkali, it can be used in soaps and detergents. Citrus flavors acquire speciflc character through the addition of citronellyl acetate it is also used to round off other fruit flavors. 

It is used in a large number of blossom fragrances. However, its use in perfumes for soap and cosmetics is limited because it causes discoloration. It is used in aroma compositions (e.g., in grape and citrus flavors). 

The desired citrus flavor is the result of volatile compounds in specific proportions. Citrus oils have unique composition profiles depending on the cultivar, the processing conditions, and the storage conditions. There have been more than 200 different compounds identified in citrus oils. However, the degree of unsaturation in monoterpenes leads to rapid oxidation and unstable compounds. The reactivity and volatility of citrus oils require strict quality control protocols. 

Figure G1.5.6 Chemical structures of compounds important to citrus flavor.

Prolonged storage results in flavor deterioration, drying and fungal growth. A stiff citrus flavored pectin gel applied... 

In this chapter, we present some specific evidence on certain components important to citrus flavor. The interrelationship of certain volatile components to orange flavor is described and the flavor of grapefruit and the importance of specific compounds to the flavor of mandarin and tangerine are related to recent taste panel studies at our laboratory. 

SHAW and Wilson Volatile Components and Citrus Flavor... 

The flavor of most citrus cultivars is complex, and compounding citrus flavors requires the blending of several components in specific proportions to obtain the unique flavor of each citrus cultivar (3). Studies on Sicilian mandarin oil suggest the distinct flavor and aroma of mandarins is mainly due to 2 compounds, thymol and methyl-N-methyl anthranilate (dimethyl anthranilate) but no evidence to support this claim has been presented (42). Thymol has been identified in Dancy tangerine peel oil, and both thymol and dimethyl anthranilate have been identified in Sicilian mandarin oil (3). The reported quantities of thymol in mandarin oil varied from 0.04-0.2% of the oil, whereas only one value (0.9%) was reported for dimethyl anthranilate. 

In addition, a comprehensive sensory evaluation program involving citrus and citrus-based products is being conducted by the author. Many facets of citrus flavor research may be ongoing at any particular time utilizing an assortment of sensory evaluation methods. 

In citrus fruits and products, most flavors and aromas are produced by polyphenolic compounds or essential oils plus a variety of non-volatile organic compounds. For detailed discussions of citrus flavors and chemical composition, the reader is referred to the excellent and comprehensive reviews which have been published (1,.2,.3,A.) ... 

Table II lists 13 of the most commonly-used chemicals in the flavor industry. For example, cinnamic aldehyde is used for the generation of cassia or cinnamon flavors, carvone for spearmint flavors, citral for citrus flavors, and benzaldehyde for cherry flavors. As can be seen, the known s values for these compounds are...

Letinski, J., and Halek, G. W. (1992). Interaction of citrus flavor compounds with polypropylene films of varying crystallinities.. Food Sci. 57, 481M84. 

Various chemical processes of limonene, which lead to the obtainment of useful chemicals and some analytical methods, are based on these reactions. Many flavor chemicals are synthesized from limonene by reaction with water, sulfur and halogens, or hydrolysis, hydrogenation, boration, oxidation and epoxide formation (Thomas and Bessiere, 1989). Hydroperoxides have also been studied and isolated because of their effect on off-flavor development in products containing citrus oil flavoring agents (Clark et al., 1981 Schieberle et al., 1987). Hydration of d-limonene produces alpha-terpineol, a compound that gives off an undesirable aroma in citrus-flavored products. It is also possible to produce alpha-terpineol and other useful value-added compounds... 

Despite the popularity of citric acid as a food additive and preservative, its sharp and overwhelming acidic taste is, however, inclined to overpower the flavor of sweeteners or other flavorants that may be present in a foodstuff. Citric acid also presents a short-lived tartness flavor. Other disadvantages have also been noted when using citric acid as a food additive. For example, due to its hygroscopic nature, it tends to cake when used in dry powders such as soft drink or beverage mixes. It also has an uneven particle size and is not always free-flowing. However, despite these few drawbacks, citric acid is by far the most commonly used food acidulant. The initial sharpness associated with citric acid is preferable in some end products such as citrus-flavored drinks (Fowlds, 2002). 

Malic acid has a smooth lingering taste. Although it also has a tart taste, this is not as sharp as that of citric acid, yet it is longer lasting. It has also been found to mask the bitter aftertaste of synthetic sweeteners, yet when using sweeteners such as aspartame, it was found that the slower increase to peak tartness does not overpower the sweeteners and as such, less sweetener is needed. However, in some end products such as citrus-flavored drinks, the initial sharpness associated with citric acid is preferable (Fowlds, 2002). 

The essence of citrus flavor is a complex mixture of volatile alcohols, aldehydes, esters, hydrocarbons, ketones and oxides. Alcohols are the largest class and ethanol is the main organic constituent of the essence. Esters and aldehydes are considered to contribute most to the characteristic flavor and aroma. In these two classes ethyl butyrate and acetaldehyde were shown to be important components of high quality orange juice (1). 

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