Fruit aroma, analysis

Considerable effort has been made to examine the volatiles and trace components that contribute to food flavors. Sone early techniques for measuring the volatile components in food products by gas chromatography consisted of analyzing headspace vapors to detect vegetable and fruit aromas (5) and volatiles associated with other food materials ( ). AlTo, sample enrichment has been used in the analysis of Tome food products. However, these techniques require steam distillation or extraction and concentration, or both, before the volatile mixture can be introduced into a gas chromatograph (, 9, 10). Besides being... 

Although most consumers appreciate the fieriness of chile, capsaicinoids are not perceived through odor or taste receptors but through the nociceptive pain receptors described earlier. The compounds in chile fruit that create the flavor and aroma are produced in the fruit wall. Buttery et al. [90] generated vacuum steam distilled oil from green bell pepper macerate, with well over 40 peaks on subsequent GC/MS analysis. Of these peaks, the major flavor compound associated with bell pepper aroma was 2-methoxy-3-isobutylpyrazine (Fig. 8.1). They also reported several monoterpenoids in abundance, limonene, trans- 3-ocimene, and linalool as well as other aliphatic aldehydes and ketones. The flavor composition of dried red bell pepper powder (sweet paprika) extracted with ether identified 44 key peaks by GC/MS [91]. In these dried samples the key compounds were P-ionone and several furanones. The post-harvest processing and the different fruit maturities as well as possible varietal differences are all causes for the different aromatic profiles. 

Ethyl 2-methylbutanoate, 2-methylbutyl acetate and hexyl acetate contribute most to the characteristic aroma of Fuji apples [49]. In Red Delicious apples, ethyl butanoate, ethyl 2-methylbutanoate, propyl 2-methylbutanoate and hexyl acetate contribute to the characteristic aroma as determined by Charm-Analysis and/or AEDA [50, 51]. In a comparative study of 40 apple cultivars, the highest odour potency or Charm value was found for -damascenone [52]. This compound usually occurs in a glycosidically bound form and is present primarily in processed products owing to hydrolysis of the glycoside bond after crushing fruit cells [53]. -Damascenone has a very low odour threshold with a sweet, fruity, perfumery odour and is not typical of apple aroma in gen-... 

Later, the chemical characterisation of the volatiles from yellow passion fruit essence and from the juice of the fruit was done by GC-MS and GC-olfactom-etry (GC-O) [27]. Esters were the components found in the largest concentrations in passion fruit juice and essence extracted with methylene chloride. Analysis by GC-O yielded a total of 66 components which appeared to contribute to the aroma of passion fruit juice and its aqueous essence. Forty-eight compounds were identified in the pulp of Brazilian yellow passion fruits (Passiflora edulis f. flavicarpa) [48]. The predominant volatile compounds belonged to the classes of esters (59%), aldehydes (15%), ketones (11%), and alcohols (6%). 

Volatile constituents of fruits contribute to the flavor and aroma of wines, and their detection and levels have received considerable attention from many researchers. This is particularly true in recent years with the development of gas chromatography and mass spectrometry which have permitted accurate volatile analysis of fruits. 

Foods. The determination of antioxidants and food preservatives is a very active part of the gas chromatography field. Adaptations and sample types are almost limitless for example, analysis of fruit juices, wines, beers, syrups, cheeses, beverages, food aromas, oils, dairy products, decomposition products, contaminants, and adulterants. A detailed discussion of this field may be found in Chapter 9. 

In order to evaluate the best temperature and time of baking process, Silva et al. (2008) used an expert panel to analyze seven descriptors, including dried fruit, nutty, baked, oak, mushroom, and brown sugar. The optimal temperature and time of baking process respecting the specificity of Madeira winemaking are considered 45 °C for 4 months. On the basis of aroma extract dilution analysis (AEDA), several Maillard byproducts, such as Sotolon, 2-furfural, 5-methyl-2-furfural, 5-ethoxy-methyl-2-furfural, methional, and phenylacetaldehyde, were identified in both Malvasia and Sercial wines under study which may explain the baked, brown sugar, and nutty odor descriptors. 

The volatiles of fresh leaves, buds, flowers and fruits were isolated by solvent extraction and analysed by capillary gas chromatography-mass spectrometry. Their odour quality was characterized by gas chromatography-olfactometry—mass spectrometry (HRGC-O-MS) and aroma extract dilution analysis (AEDA). In fresh bay leaves, 1,8-cineole was the major component, together with a-terpinyl acetate, sabinene, a-pinene, P-pinene, P-elemene, a-terpineol, linalool and eugenol. Besides 1,8-cineole and the pinenes, the main components in the flowers were a-eudesmol, P-elemene and P-caryophyllene, in the fruits (EJ-P-ocimene and biclyclogermacrene, and... 

By using high resolution capillary gas chromatography, the scope of use of these reagents, which were initially introduced for NMR-analysis (5J and for GC separation of secondary alcohols (6), was enlarged considerably (7,j3). The application of these methods to the analysis of optically active compounds formed during microbiological processes and to the determination of the enantiomeric composition of chiral aroma constituents in some tropical fruits is described in this paper. 

Tropical fruits, such us passion fruits, mangos or pineapples, contain many chiral aroma constituents. So far, their enantiomeric composition is unknown, because the conventional method, measuring optical rotation, can not be applied to these components, which can be isolated from the fruits only in small amounts. The new techniques of capillary GC analysis of diastereoisomeric derivatives made it possible to characterize the enantiomeric composition of several chiral trace constituents. These results may be used to gain insight into the biogenesis of aroma components or to control natural aroma concentrates. 

A peach still attached to the tree was selected for analysis on the basis of its possessing a full, rich, at-the-peak-of-ripeness aroma. Taking care not to bruise the fruit, the peach... 

Ali et al. [146] investigated the passage of aroma constituents of fruit juice during OMD on a pilot plant scale. Using headspace analysis of feed and permeate, they concluded that the loss in aroma could be minimized by operating at low temperature and low feed velocity. 

The aroma of citrus fruit is a speciality. It consists of the so-called water phase and the oil phase. Citrus juices contain small amounts of volatile oils (0.03-0.06%). During processing there is always a small amount of peel oil that gets into the juice. Also the juice contains a small amount of oil, called juice oil. During evaporation these oils get into the aroma where they create the so-called oil phase. This oil has a very special aroma and is different from the peel oil by analysis (gas chromatography) as well as flavour. Oil and water phase are kept separately and added back to the juice according to individual requirements. Properly applied, the oil phase imparts the special fresh note to the juice which cannot be achieved by adding the water phase only. 

Instead by solvent extraction [207], aroma compounds from aqueous media, e.g. fruit juices, can even be separated and enriched by techniques of solid phase micro extraction (SPME), preferably from the headspace [208] , corresponding devices can often be directly connected to GC systems. These techniques provide the complete spec-tmm of the individual compounds of an aroma. As it will normally not be possible and even not necessary to analyse all components of the complex mixture, the separation of its main compounds may demand a multi-dimensional (MD) gas chromatographic system [209[ as displayed in Fig. 6.14 [210[. Examples for the multi-ele-ment/multi-compound isotope analysis by such systems will be given later (6.2.2.4.4, [211[) they can even integrate the identification of the compounds by molecular mass spectrometry and a simultaneous determination of the enantiomer ratios of isomers [210, 211 [. The importance of enantiomer analysis as a tool for authenticity assessment is extensively treated in chapter 6.2.3. 

The most simple sample preparation technique is direct gas chromatographic injection of an aqueous essence on a bonded fused silica column. This technique may be employed when aqueous distillates are available. For example, Moshonas and Shaw ( 31) described a method for the analysis of aroma constituents of natural fruit essences. The essences were collected from the first stage of an evaporator and the essence injected directly into a capillary gas chromatograph. 

Purcell J.M. and Magidam P. (1984) Analysis of the aroma of the intact fruit of Coffea arabica by GC-FTIR. Appl. Spectrosc. 38, 181-4. 

The study of correlation between volatile compounds by instrumental analysis and sensory properties of Albarino wine from NW Spain was performed by Vilanova et al. (2010). The results of the investigation showed the compounds that most contributed to the flavour of Albarino wines in instrumental analysis were those related to fruity (ethyl esters and acetates) and floral aromas (monoterp>enes). Similar results were found in sensory analysis where the descriptors with the highest Geometric Mean were fruity and floral aromas too (citric, flowers, fruit, ripe fruit, ap>ple and tropical). Therefore, this work demonstrates that some relationship between sensory data and volatile compoimds exist to asses sensory properties in Albarino wines. 

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