Identification of aroma

Recent research has Identified numerous aroma chemicals 1n roasted foods, such that hundreds are known. Current work 1s devoted less to Identification of aroma chemicals, but more to Identification of specific flavor notes of significant Importance, and to maximizing the production of these chemicals. 

N. C. D. Costa S. Eri, Identification of Aroma Chemicals. In Chemistry and Technology of Flavors and Fragrances ... 

Techniques for Further Isolation and Identification of Aroma Compounds. 403... 

Historically, modem aroma research began with the isolation and identification of aroma compounds in foods. It was thought that if we could identify all of the aroma compounds in foods, we would be able to reproduce the aroma of that food by formulating a flavor based on the analytical data. This did not prove to be the case. Researchers found that there were very large numbers of aroma compounds present in foods and not all could possibly be contributors to the aroma of a food. Thus, an era began where researchers attempted to determine which aroma compounds were traly needed to recreate the aroma of a food. It was postulated that somewhere between 20 and 30 compounds should be adequate to reproduce the aroma of a food. The question then was, which compounds were needed Several approaches were developed to meet this challenge. These methods will be briefly discussed. 

Qian, M., G.A. Reineccius, Identification of aroma compounds in parmigiano-reggiano cheese by gas chromatography/olfactometry, J. Dairy ScL, 85(6), p. 1362, 2002. 

The aroma substances consist of highly diversified classes of compounds, some of them being highly reactive and are present in food in extremely low concentrations. The difficulties usually encountered in qualitative and quantitative analysis of aroma compounds are based on these features. Other difficulties are associated with identification of aroma compounds, elucidation of their chemical structure and characterization of sensory properties. 

The majority of the early work focused on investigating natural extracts. However, techniques to obtain the true character of flower scents still held high interest for the chemist and the perfumer. The extracts of flowers often lack the delicate aroma of a flower at the peak of its life cycle. Some extractive techniques require heat, which often eliminates key volatile fragrance components and can generate artifacts by hydrolysis, oxidation, or breakdown of the plant metabolites. Flower scents of especially rare species (which cannot be picked) or flowers that are not found in sufficient quantity for extraction are also of interest as a source of new aroma chemicals and scents. This chapter concentrates on the nondestructive headspace techniques that have been developed for the collection of flower scents. The techniques and discussion also have relevance for the collection and identification of aroma chemicals in the headspace of food and beverage samples, as well as many other types of samples. 

Day EA, Anderson DF. 1965. Gas chromatographic and mass spectral identification of natural components of the aroma fraction of blue cheese. J Agric Food Chem 13 2-4. 

Nishimura, O. Identification of the characteristic odorants in fresh rhizomes of ginger (Zingiber officinale Roscoe) using aroma extract dilution analysis and modified multidimensional gas chromatography-mass spectroscopy. J Agr Food Chem 1995 43(11) 2941-2945. 

Silva Ferreira, A. C., Hogg, T., and Guedes de Pinho, P. (2003). Identification of key odorants related to the typical aroma of oxidation-spoiled white wines. /. Agric. Food Chem. 51, 1377-1381. 

Sampling and Analysis. A frozen slice of bread was cut in pieces and stacked in an enlarged sample flask of an aroma isolation apparatus according to MacLeod and Ames (74). Volatile compounds were trapped on Tenax TA and afterwards thermally desorbed and cold trap injected in a Carlo Erba GC 6000 vega equipped with a Supelcowax 10 capillary column (60 m x 0.25 mm i.d.) and a flame ionisation detector. Similar GC conditions were used for GC-MS identification of volatile compounds by dr. M.A. Posthumus (Dept. Organic Chemistry, VG MM7070F mass spectrometer at 70 eV El, 75). 

H. Maarse, R. Belz, Isolation, Separation and Identification of Volatile Compounds in Aroma Research, Akademie-Verlag, Berlin 1981. 

Volatile constituents of cupuacu were isolated by steam distillation-extraction of pulp or juice [2].The identification of volatile constituents was based on mass spectral analysis. The pleasant aroma compounds were mainly esters (Fig. 8.2). Targe amounts of ethyl butanoate and small amounts of ethyl acetate, butyl acetate, and butyl isobutanoate were described. 

Reviews published by Acree and Teranishi [7], Blank [8], Grosch [1, 2, 9], Mistry et al. [10] and Schieberle [11] agree that GC-O was the starting point for the development of a systematic approach for the identification of the compounds causing food aromas. The aim of this chapter is to discuss the potential and the limitations of GC-O. 

G1.3 Identification and Quantitation of Aroma Compounds Basic Protocol Identification (GC-FID GC-MS) and Quantification of Gl.3.1... 

Aroma compounds are present in minute levels in foods, often at the ppb level ( ig/liter). In order to analyze compounds at these levels, isolation and concentration techniques are needed. However, isolation of aroma compounds from a food matrix, which contains proteins, fats, and carbohydrates, is not always simple. For foods without fat, solvent extraction (unit gu) can be used. In foods containing fat, simultaneous distillation extraction (SDE see Basic Protocol 1) provides an excellent option. Concentration of headspace gases onto volatile traps allows sampling of the headspace in order to obtain sufficient material for identification of more volatile compounds. A separate protocol (see Basic Protocol 2) shows how volatile traps can be used and then desorbed thermally directly onto a GC column. For both protocols, the subsequent separation by GC and identification by appropriate detectors is described in unitgu. 

Freitas, V., Ramalho, P., Azevedo, Z., and Macedo, A. (1999). Identification of some volatile descriptors of the rock-rose like aroma of fortified red wines from Douro Demarcated Region. ]. Agric. Food Chem. 47, 4327-4331. 

Miklosy, E., Kalmar, Z., and Kerenyi, Z. (2004). Identification of some characteristic aroma compounds in noble rotted grape berries and aszu wines from Tokaj by GC-MS. Acta Aliment. Hung. 3,215-226. 

Cutzach, I., Chatonnet, P., Henry, R., and Dubourdieu, D. (1997). Identification of volatile compounds with a "toasty" aroma in heated oak used in barrelmaking. J. Agric. Food Chem. 45, 2217-2224. 

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