Aroma components

Gc/ftir has both industrial and environmental appHcations. The flavor and aroma components in fragrances, flavorings, and foodstuffs can be identified and quantified via gc/ftir (see Food additives). Volatile contaminants in air, water, and soil can be analy2ed. Those in air are usually trapped in a sorption tube then injected into the chromatograph. Those in water or soil are sparged, extracted, or thermally desorbed, then trapped and injected (63,64). 

Extraction. Traditionally tea leaf is extracted with hot water either in columns or ketdes (88,89), although continuous Hquid soHd-type extractors have also been employed. To maintain a relatively low water-to-leaf ratio and achieve full extraction (35—45%), a countercurrent system is commonly used. The volatile aroma components are vacuum-stripped from the extract (90) or steam-distilled from the leaf before extraction (91). The diluted aroma (volatile constituents) is typically concentrated by distillation and retained for davoring products. Technology has been developed to employ enzymatic treatments prior to extraction to increase the yield of soHds (92) and induce cold water solubiUty (93,94). 

Pervaporation. Vapor arbitrated pervaporation is used to remove ethanol from whiskey by selective passage of the alcohol through a membrane. Whiskey flows on one side of a membrane. A water-vapor stream flows on the other side and sweeps away the ethanol that permeates the membrane. Thus alcohol reduction and selective retention of flavor and aroma components can be achieved usiag membranes with a particular porosity. The ethanol can be recovered by condensing or scmbbiag the vapor stream. Pervaporation systems operate at or slightly above atmospheric pressure (Fig. 

Volatile and semivolatile compounds are present in honeys and are attributed to aroma qualities. Aroma compoimds can indicate floral and geographical origins and processing treatments. Aroma compounds come from nectar or honeydew. Aroma components can be also formed during fhermal processing and sforage (Bonvehi and Coll, 2003 Soria et ah, 2003). More than 400 components have been detected in the volatile flavor fraction of honey... 

It has been suggested that enzymic reaction of leucine during processing could lead to the formation of desirable aroma components and that these reactions would be varied during periods of climatic stress when the... 

Black tea taste is primarily a function of the polyphenols, caffeine, and aroma components. Astringency, an important characteristic of the organoleptic sensation, has been described as consisting of a tangy and a nontangy component.95... 

The organoleptic properties of black tea depend to a considerable extent on the astringency resulting from the interaction of caffeine with the oxidized galloyl ester of the flavanols. The aroma components of black tea also constitute a unique flavor profile that blends well with the taste of the nonvolatile materials. The caffeine provides a moderate level of stimulation, which adds further to the appeal of the beverage, although tea has been shown to provide relaxation as well as revival of character.119... 

Possible differences are also well illustrated by 3-thio- and 3-methyl-thiohex-anols and their esters (Table 1). Among these compounds, there is a tendency for the (R) enantiomers to have a typical, fruity aroma. However, for 3-methylthiohexanol (an aroma component of yellow passion fruit) this situation is reversed the (S) enantiomer had the characteristic fruity aroma ( exotisch, fruchtig ).52 For the separation of enantiomers of odorous compounds, enan-tioselective GLC with chiral stationary phases, and MGDC techniques using a conventional capillary column and an enantioselective column are commonly used.53... 

The sesquiterpene w-famesene, 51, a primary aroma component which occurs in the skin of apples39 and other fruits40, attractant and oviposition stimulant to Laspeyresia pomonella41 42, has been deuteriated at Cq) and at C(4) (equations 19 and 20), for study of the induction of superficial scald of apples43. 

Flavor is one of the major characteristics that restricts the use of legume flours and proteins in foods. Processing of soybeans, peas and other legumes often results in a wide variety of volatile compounds that contribute flavor notes, such as grassy, beany and rancid flavors. Many of the objectionable flavors come from oxidative deterioration of the unsaturated lipids. The lipoxygenase-catalyzed conversion of unsaturated fatty acids to hydroperoxides, followed by their degradation to volatile and non-volatile compounds, has been identified as one of the important sources of flavor and aroma components of fruits and vegetables. An enzyme-active system, such as raw pea flour, may have most of the necessary enzymes to produce short chain carbonyl compounds. 

Optically pure trans- and czs-linalool oxides, constituents of several plants and fruits, are among the main aroma components of oolong and black tea. These compounds were prepared from 2,3-epoxylinalyl acetate (9) (Scheme 17) [102]. The key step consist of a separation of the diastereomeric mixture of 9 by employing an epoxide hydrolase preparation derived from Rhodococcus sp. NCIMB 11216, yielding the product diol and remaining epoxide in excellent diastereomeric excess (de>98%). Further follow-up chemistry gave both linalool... 

Tamogami S, Awano K, Amaike M, Takagi Y, Kitahara T, Analysis of enantiomeric ratios of aroma components in several flowers using a Chiramix column, Flavour Fragr/19 1-5, 2004. 

Koundouras, S. Marinos, V. Gkoulioti, A. Kotseridis, Y. van Leeuwen, C. Influence of Vineyard Location and Vine Water Status on Fruit Maturation of Nonirrigated Cv. Agiorgitiko (Vitis vinijera L.). Effects on Wine Phenolic and Aroma Components. J. Agric. Food Chem. 2006, 54, 5077-5086. 

Harada, N., N. Okazaki, Y. Kizaki, and S. Kobayashi. Identification and distribution of an aroma component in rice. Nippon Jozo Kyokaishi 1990 85(5) 350-352. 

Schottler M, Boland W (1996) Biosynthesis of dodecano-4-lactone in ripening fruits Crmal role of an epoxide-hydrolase in enantioselective generation of aroma components of the nectarine ( Prunus persica var. nucipersica ) and the strawberry (Fragaria ananassa). Helv Chim Acta 79 1488... 

This process has found major application in the wine industry to control the alcohol content of wines (i.e. remove alcohol to the desired level). Wine is initially passed through the equipment at temperatures and pressures that primarily strip aroma components. The dearomatised wine is then passed a second time through the equipment at higher temperatures and vacuum to strip the desired amount of alcohol from the wine. The initially captured aroma fraction can then be added back to the reduced alcohol wine to produce the desired... 

Unspecified isomers of toluidine were found in samples of kale and celery (1.1 mg/kg) and carrots (7.2 mg/kg) (Neurath et al., 1977). ort/ro-Toluidine has been identified in the volatile aroma components of black tea (Vitzthum et al., 1975). 

Certain aroma components from fruits are responsible for the characteristic odor of many wines. An example is the typical aroma of many V. labrusca grapes which often gives their wines a distinctive aroma and flavor. Furthermore, some volatile constituents are characteristic of certain varieties and their wines are recognized by these distinctive aromas. This is significantly important for varietal wines (grape) where their distinct aromas are a prerequisite in rating the quality at the highest level. In addition to the importance of variety in the aroma and flavor of wines, other variables known to influence the volatile components within the fruit variety are maturity, location, climatic conditions, and cultural practices. 

Suomalainen, H., Ronkainen, P., Aroma Components and Their Formation... 

For highly volatile aromas of fruits or wine, the single- or double step separation based on pressure is not sufficient, and needs expensive precipitation at very low temperatures. About minus 50°C are necessary for sufficient recovery of aroma components. For this application an aroma rectification, with multiple withdrawal at different temperatures, is appropriate. 

Coenen et al. [60,61] proposed a two-step extraction for the separation of pungent compounds and carotenoid fractions. Aroma- and pungent components were recovered at 120 bar and 40°C, and the paprika residue was re-extracted at 320 bar and 40°C to recover carotenoids. The solubility of capsaicin in carbon dioxide was relatively low at a pressure of 120 bar, so a great amount of solvent (for example 130 kg of CO2 per kg of paprika) was needed to recover the aroma components totally. The extraction time was 6.5 hour. In the separator the pressure was 56 bar and the temperature was 45°C. The orange, paste-like extract recovered in the first step was extremely pungent in taste. It contained water, and the yield was about 15%. In the second step, a relatively great amount of CO2 (approximately 50 kg/kg) was needed to recover the carotenoids in quantitative yield. The extraction time was 4 hours. The dark red, liquid colour-concentrate is without capsaicinoids. The yield was 2.5%. 

Many undesired substances such as chlorophyll or other polar substances, which are extracted in the alcohol extraction, are only slightly soluble in CO2. In case of necessity, the aroma components can be removed from the extract by a further purification step. 

Esters also constitute a group of important flavour compounds. They are the main aroma components found in fruits (apples, pears,. ..). For example, bananas contain 12-18 ppm acetates. The price of the pure flavour compounds, when isolated from fruit, can range between 10,000 and 100,000 US /kg In the past, research has been carried out by our group about the microbial production of fruity esters by the yeast Hansenula mrakii and the fungus Geotrichum penicillatum [10]. A fermentation was developed whereby fusel oil was continuously converted into a mixture of 3-methylbutyl acetate (isoamyl acetate) and 2-methylbutyl acetate, the character impact compounds of banana flavour. 

Lee, G.-H., Suriyaphan, O., and Cadwallader, K.R. 2001. Aroma components of cooked tail meat of American lobster (Homarus americanus). J. Agric. Food Chem. 49 4324-4332. 

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