Apple flavour compounds

However, in the case of apples and many other fruits the (S)-enantiomer of ethyl 2-methylbutanoate, the impact flavour compound of apples, was identified with high enantiomeric purity, irrespective of the apple variety investigated and was unaffected by processing conditions (e.g. distillation, concentrating) or storage of apple juices. 

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. 

Maillard reactions are responsible for the browning of sugars in the presence of amino acids. They are one of the key routes to flavour compounds in the whole of food science. In practice, any browning in foods is due to the Maillard reaction except where it is enzymic, e.g. the browning of a cut apple is enzymic and hence not a Maillard reaction. 

SPME can also be used to extract target analytes from food and drug samples. Thus, it has been employed for the extraction of caffeine from coffee and tea [225], and for that of volatile impurities in drugs. Headspace SPME has also been tested for flavour analysis in foods. Thus, the SPME/GC/TOF-MS tandem was successfully used for the rapid analysis of volatile flavour compounds in apple fruit. The sample (300-450 g of apple) was subjected to static headspace sampling for 4 6 h in order to allow the volatiles... 

Natural fruit aromas are mixtures of certain organic compounds and esters. Synthetic aromas prepared in laboratories are simple mixtures of these same esters and organic compounds. They are used in perfumes, foods and drinks to give taste and pleasant smells. Ethyl acetate, for example, is a colorless liquid with an apple flavour it is known as apple ester and is used in perfumery as a fruit essence. Propyl acetate has the smell of pears, isopentyl acetate that of bananas and ethyl butyrate smells of pineapples. All are colorless liquids. Higher molar mass esters are odorless. 

AguUar-Rosas, S.R, BaUinas-Casarrubias, M.L., Nevarez-Moorillon, G.V., Martin-BeUoso, O., and Ortega-Rivas, E. 2007. Thermal and pulsed electric fields pasteurization of apple juice Effects on physicochemical properties and flavour compounds. Journal of Food Engineering 83 41 6. 

Twenty-nine odour-active compounds were detected by using aroma extract dilution analysis (AEDA) [60]. The results of AEDA together with GC-MS analysis showed ethyl 2-methylbutanoate (described as fruity flavour), followed by methyl 2-methylbutanoate and 3-methylbutanoate (fruity, apple-like), 4-hydroxy-2,5-dimethyl-3(2H)-furanone (sweet, pineapple-like, caramel-like), d-decalactone (sweet, coconut-like), l-( ,Z)-3,5-undecatriene (fresh, pineapple-like), and a unknown compound (fruity, pineapple-like) as the most odour-active compounds. 

The flavour of distillates from apple and pear is characterised by typical aroma compounds from these fruits formed by enzymatic degradation of fatty acids to C6-fragments like hexanol, trans-2-hexenol, as well as ethyl esters and acetates of hexanoic acid. In distillates of pears, especially of the variety Bartlett pear, the characteristic pear flavour is mainly dominated by the ethyl and methyl esters of frans-2-czs-4-decadienoic acid and trans-2-trans-A-decadienoic acid [27-29], The biogenesis of these monounsaturated, diunsaturated, and triunsaturated esters may be explained by -oxidation of unsaturated linoleic and linolenic acid in the fruits. The sesquiterpene compound a-farnesene, which is formed during postharvest ripening and storage of Bartlett pears [28], shows that quality and intensity of distilled pear spirits is mainly influenced by the quality and degree of ripeness of the fruits. 

During the production of recovery flavours, apple wines or brandies, the interaction with ethanol, acetaldehyde and acetic acid represents the next level of interactions. The reaction products contain compounds which result from esterification and acetal formation reactions, which are summarised in Table 21.4. 

One area of application is the analysis of flavours in foods in order to ascertain, for example, the ripeness of fruit or the maturity of cheeses [42]. For this purpose dendrimers were used which can distinguish certain carbonyl compounds such as ketones, aldehydes, esters, and amides, also in mixtures. For example, measurement of the concentration of 2-heptanal is of importance specifically for determination of the degree of ripeness of apples. The concentration of this compound increases significantly with increasing ripeness [43]. This technique can also serve as an electronic nose for quality control of high-value products such as saffron, which in powder form may contain undesired contaminants (adulterants) such as curcuma, safflower, or marigold. 

As their name implies, compounds containing the carboxylic acid (C02H) group can react with bases, losing a proton to form carboxylate salts. Edible carboxylic acids have sharp flavours and several are found in fruits—citric, malic, and tartaric acids are found in lemons, apples, and grapes, respectively. 

Similarly, such flaws as green apple and earthy aromas were negatively correlated with oak wood components, and this attests to the ability of these oak wood components to mask vegetative aromas and off flavours in wine. However, other authors found that the descriptor wood-vanilla-cinnamon , due to oak extracted compounds in Spanish red wines, was negatively influenced by the presence of 4-ethylphenol, 4-ethylguaiacol and phenylacetaldehyde (Aznar et al. 2003). 

Fats are esters in fact they contain three ester groups. They are formed in the body by condensing glycerol, a compound with three hydroxyl groups, with three fatty acid molecules. Other, more volatile, esters have pleasant, fruity smells and flavours. These three are components of the flavours of bananas, rum, and apples ... 

An IMS for producing apple juice and apple juice aroma concentrates was investigated on laboratory and pilot scale by Alvarez et al. (2000). Ihe integrated process consisted of an enzymatic MR to clarify the raw juice, an RO unit to pre-concentrate the juice up to 25 °Brix, and a PV unit to recover and concentrate aroma compounds and a final evaporation step to concentrate the juice up to 72 °Brix. Rejection of aroma compounds in the PV step exceeded 90% for most compounds considered. Organoleptic evaluation of the clarified and concentrated juice judge it to be excellent in terms of odour and flavour. The final products were clearer and more brilliant than apple juice produced by conventional methods. 

Lindsay RF, Priest FG (1975) Decarboxylation of substituted cinnamic acids by enterobacteria the influence on beer flavour. J Appl Bacteriol 39 181-187 Steinhaus M, Schieberle P (2000) Comparison of the most odor-active compounds in Ifesh and dried hop cones (Humulus lupulus L. variety spalter select) based on GC-olfactometry and odor dilution techniques. J Agric Food Chem 48 1776-1783... 

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