Aroma studies

Supercritical CO2 is a particularly good choice in aroma studies since it has an extremely low boiling point and leaves no off-odor residue to interfere in either analytical work or sensory evaluation. The fact that the solvent strength of a supercritical fluid depends on density is an additional factor which may be useful. One can vary solvent properties by changing density, thereby obtaining an effective extraction of a broad range of aroma compounds. 

Direct analysis of the eqnilibrium headspace above a food product would appear to be an ideal method for aroma studies. It is very simple, gentle, and easily antomated. In this method, one places a food sample into a vessel, closes the vessel with an inert septum (Teflon-lined), allows equilibration (between the food and the sample headspace — 30 to 60 min) and then draws a few ml of headspace above the food into a gas-tight syringe and makes a direct injection into a gas chromatography (GC). 

The first mass spectrometric investigation of the thiazole ring was done by Clarke et al. (271). Shortly after, Cooks et al., in a study devoted to bicydic aromatic systems, demonstrated the influence of the benzo ring in benzothiazole (272). Since this time, many studies have been devoted to the influence of various types of substitution upon fragmentation schemes and rearrangements, in the case of alkylthiazoles by Buttery (273) arylthiazoles by Aune et al. (276), Rix et al. (277), Khnulnitskii et al. (278) functional derivatives by Salmona el al. (279) and Entenmann (280) and thiazoles isotopically labeled with deuterium and C by Bojesen et al. (113). More recently, Witzhum et al. have detected the presence of simple derivatives of thiazole in food aromas by mass spectrometry (281). 

Initial evaluations of chemicals produced for screening are performed by smelling them from paper blotters. However, more information is necessary given the time and expense required to commercialize a new chemical. No matter how pleasant or desirable a potential odorant appears to be, its performance must be studied and compared with available ingredients in experimental fragrances. A material may fail to Hve up to the promise of its initial odor evaluation for a number of reasons. It is not at all uncommon to have a chemical disappear in a formulation or skew the overall odor in an undesirable way. Some materials are found to be hard to work with in that their odors stick out and caimot be blended weU. Because perfumery is an individuaHstic art, it is important to have more than one perfumer work with a material of interest and to have it tried in several different fragrance types. Aroma chemicals must be stable in use if their desirable odor properties are to reach the consumer. Therefore, testing in functional product appHcations is an important part of the evaluation process. Other properties that can be important for new aroma chemicals are substantivity on skin and cloth, and the abiHty to mask certain malodors. 

Humidity does not affect the permeabihty, diffusion coefficient, or solubihty coefficient of flavor/aroma compounds in vinyhdene chloride copolymer films. Studies based on /n j -2-hexenal and D-limonene from 0 to 100% rh showed no difference in these transport properties (97,98). The permeabihties and diffusion coefficients of /n j -2-hexenal in two barrier polymers are compared in Table 12. Humidity does not affect the vinyhdene chloride copolymer. In contrast, transport in an EVOH film is strongly plasticized by humidity. 

H. O. E. Karlsson, G. Tragadh. Pervaporation of dilute organic waters mixtures A literature review on modeling studies and applications to aroma recovery. J Membr Sci 75 121, 1993. 

Nine-tnetnbered ir-excessive heterocycles with the general formula 1 are commonly referred to as heteronines. They can be regarded as direct analogs of the cyclononatetraenyl anion and have been extensively studied with regard to the question of their potential 1 On-aroma tic character. Heteronines have been the subject of several reviews.1 4... 

GUILLEN M D, MANZANOS M J and IBARGOITIA M L (1996) Smoking of food products. Preparation, use, study methods, and composition of smoke aromas , Alimentaria, 274 45-53. 

Ultrafiltration of heterogenous colloidal suspensions such as citrus juice is complex and many factors other than molecular weight contribute to fouling and permeation. For example, low MW aroma compounds were unevenly distributed in the permeate and retentate in UF in 500 kd MWCO system (10). The authors observed that the 500 kd MWCO UF removed all suspended solids, including pectin and PE. If PE is complexed to pectate in an inactive complex, then it is conceivable that release of PE from pectin with cations will enhance permeation in UF. At optimum salt concentration, less PE activation was observed at lower pH values than at higher pH (15). In juice systems, it is difficult to separate the effect of juice particulates on PE activity. Model studies with PE extracts allows UF in the absence of large or insoluble particulates and control of composition of the ultrafilter. In... 

Aroma compounds are often heat sensitive and their purification by membrane processes, which work at near ambient conditions, can be attractive. Alternatively, when pervaporation is used then temperatures can be kept low. A variety of aroma substances from aqueous solutions have been recovered. Baudot and Marin (1997) and Baudot et al. (1999) have made an extensive study of this subject. Hydrophobic low boilers to very hydrophobic high boilers have been studied. 

The origin of many of the components of black tea aroma has been studied. Aldehydes are produced by catechin quinone oxidation of amino acids. Enzymic oxidation of carotenoids during manufacture generates ionones and their secondary oxidation products such as theaspirone and dihydroactinidolide. Oxidation of linoleic acid is responsible for the formation of trans-2-hexenal.82... 

Herrman, G., Baltes, W., Model studies on aroma formation in coffee, Coll. Sci. Int. Cafe, 9, 77, 1980. (CA96 141420f)... 

Fruits have received extensive study one example is that of the passion fruit volatiles. Another fruit in which sulfur volatiles play an aroma role is musk-melon (Cucumis melo cv. Makdimon). A musky overtone is provided by 3-(methylthio)propanal ( stale ) and 5 -(methylthio)-butanoate ( pine, earthy )... 

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. 

Kompany, E., Rene, F. Optimal conditions for freeze drying of cultured mushrooms (Agari-cus bisporus) - study of aroma retention. Recent Prog. Genie Procedes, 7 (30) Etudes et Conception d Equipements, p. 267-272, 1993... 

Further investigation is needed to confirm these first results, and to substantiate whether milky AG secretions and mainstream milk convey similar or distinct information to infants. Indeed, studies in other species revealed that milk can carry odorant cues of varying origins (e.g., dietary aromas, pheromones) bearing differentiable meanings to newborns (Schaal, Coureaud, Langlois, Ginies, Semon and Perrier 2003 Schaal 2005). 

Solid phase microextraction (SPME) is an ideal approach to monitor volatile flavor components. This approach has been used to identify the volatile compounds in the headspace of fresh fruit during maturation [92], Using SPME fibers and GC/MS, the key flavor components are hexanal, 2-isobutyl-3-methoxypyrazine, 2,3-butanedione, 3-carene, trans-2-hexenal, and linalool (Fig. 8.1). In this study, the principal aroma compounds whose abundance varied during fruit development were specifically identified. 

CS132 Etoh, Hina, K. and M. Iguchi. Studies on the aroma of tea. Part IV. 3S-( + ) 3,7 dimethyl l,5 Octadiene 3,7 diol and ionone derivatives from tea. Agr Biol Chem 1980 44 2999-3000. 

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