Flavour compounds

The chemistry of the flavour of milk fat and butter is very complex, involving a large number of compounds contributing to the overall aroma and taste. Approximately 200 volatile compounds have been identified in milk fat (Schieberle et al., 1993). However, many of the volatile compounds are present at concentrations below their individual flavour threshold level, and the extent to which these compounds contribute to the overall flavour profile is not known fully. The perceived flavour of milk fat can be altered by a change in the concentration of individual volatile compounds. The principal factor that can change the concentration of the volatile compounds is the feeding regime of the cow (Bendall, 2001). 

The main classes of volatile compounds, which are considered to contribute significantly to the overall flavour are lactones, fatty acids, aldehydes and methyl ketones. As noted earlier, there are very small amounts of hydroxy acids, esterified to triacylglycerols, in milk fat. These act as precursors of flavoursome 7-lactones and 8-lactones. It has been reported that three lactones, 8-octalactone, 8-decalactone and y-dodecalactone, are important flavour components in milk fat (Widder et al., 1991 Schieberle et al., 1993). Siek et al. (1969) identified the short-chain fatty acids, 4 0 and 6 0, as key flavour components of milk fat. However, while they may contribute to the overall flavour of milk fat at very low concentrations, 

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Determination of enantiomeric distributionof the lactone flavour compounds of fruits... 

E. Guichard, A. Kustermann and A. Mosandl, Chkal flavour compounds from apricots. Distr ibution of -) lactones enantiomers and stereodifferentiation of dihydroactinidiolide using multi-dimensional gas chromatogr aphy , 7. Chromatogr. 498 396-401 (1990). 

V. Karl, J. Gutser, A. Dietrich, B. Maas and A. Mosandl, Stereoisomeric flavour compounds. EXVIII. 2-, 3- and 4-alkyl-branched acids. Part 2 chirospeciflc analysis and sensoT y evaluation , Chirality 6 427 - 434 (1994). 

H.-G. Schmarx, A. Mosandl and K. Grob, Stereoisomeric flavour compounds. XXXVIII dkect chir ospecific analysis of y-lactones using on-line coupled EC-GC with a chkal separation column , Chromatographia 29 125-130 (1990). 

Flavour compounds and other heat labile constituents will not be lost as extensively in the preparation, thus improving the product and reducing the cost of production. 

Problems Pear ester (43) is an important industrial flavouring compound with a pear-like taste and smell. Consider all possible Wittig disconnections and choose a reaction which should give the right geometrical isomer. 

The application of ever improving analytical methods will continue to reveal new flavouring compounds, be they natural, nature identical or synthetic. Not only are ever more sophisticated analytical techniques available but also improved methods of data analysis. The new science of chemometrics has developed to cope with the situation where chromatograms with hundreds of compounds are obtained. 

Traditionally, butter was made by allowing cream to separate from the milk by standing the milk in shallow pans. The cream is then churned to produce a water in oil emulsion. Typically butter contains 15% of water. Butter is normally made either sweet cream or lactic, also known as cultured, and with or without added salt. Lactic butter is made by adding a culture, usually a mixture of Streptococcus cremoris, S. diacetylactis and Betacoccus cremoris. The culture produces lactic acid as well as various flavouring compounds, e.g. diacetyl, which is commonly present at around 3 ppm. As well as any flavour effect the lactic acid inhibits any undesirable microbiological activity in the aqueous phase of the butter. Sweet cream butter has no such culture added but 1.5 to 3% of salt is normally added. This inhibits microbiological problems by reducing the water activity of the aqueous phase. It is perfectly possible to make salted lactic butter or unsalted sweet cream butter if required. In the UK most butter is sweet cream while in continental Europe most butter is lactic. 

Bicchi C, Manzin V, D Amato A, Rubiolo P, Cyclodextrin derivatives in GC separation of enantiomers of essential oil, aroma and flavour compounds, Flavour... 

Kopke X Schmarr HG, Mosandl A, Stereoisomeric flavour compounds. Part LVII Xhe stereoisomers of 3-oxo-p-menthane-8-thiol acetate, simultaneously stereoanalyzed with their corresponding thiols, FlavourFragr/7 205—211, 1992. 

Fischer N, Nitz S, Drawert F, Original flavour compounds and the essential oil composition ofmarjoram Majorana hortensisN[oenc i), Flavour FragrJ2 55—6, ... 

Nitz S, Fischer N, Drawert F, Flavour compounds in plants I. Commun. Volatile terpenoid compounds from bound precursors in Majorana hortensis Moench, Chem Mikrobiol TechnolLebensm 9 87-94, 1985. 

Mosandl A, Schubert V, Stereoisomeric flavour compounds XXXIX Chiral constituents of essential oils (I), stereo differentiation of linalyl acetate — A new possibility for quality evaluation of lavender oil, Z Lebensm Unters Frosch 190 506-510, 1990. 

Weinreich B, Nitz S, Influences of processing on the enantiomeric distribution of chiral flavour compounds, Part A Linalyl acetate and terpene alcohols, Chem MikrobiolTechnol Lebensm 14 117—124, 1992. 

Certain chloropyrimidines can be metaUated even with BuLi " and the metallation of methoxy- and chloropyrazines is useful in the synthesis of flavouring compounds (Scheme 118) and the antiarrhythmic agent arglecin (Scheme 119) . ... 

Compositional analyses of flavour compounds in fresh and processed fruits are often of limited value because it is clear that compounds with very low aroma thresholds can have dominant effects upon fruit flavour. Moreover after processing, the compounds with the primary influence on flavour may change. Quantification of individual aroma compounds is also problematic requiring high resolution gas chromatographs linked to ion-trap or related detectors (HRGC/MS) although flame-ionisation detection is often more convenient. 

Scheme 7.3 Enzymatic production of sulfur-containing flavour compounds in Allium species from amino acid flavour precursors, a S-Alk(en)yl cysteine sulfoxides and b (+)-S-l-propenyl cysteine sulfoxide (isoalliin) P-5 -Ppyridoxal-5 -phosphate...

Fig. 7.1 Some aliphatic esters that are important flavour compounds in fruits and vegetables that mainly contribute with fruity odours...

Table 7.2 Key flavour compounds in stone fruits (Prunus spp.)... 

Key flavour compounds Peach P. persica) Nectarine P. persica var. nucipersica) Apricot P. armeniaca) Plum P. domestica) Sweet cherry P. avium) Sour cherry (P cerasus)... 

The typical flavour of sour cherries is produced during processing into wine, liqueur, juice, jam or fruit sauce. Benzaldehyde has been determined to be the most important aroma compound in sour cherries [82], but benzyl alcohol, eu-genol and vanillin are also important flavour compounds (Table 7.2, Fig. 7.5) [83]. Growing and storage conditions affect the concentration of benzaldehyde, benzyl alcohol, eugenol and vanillin [83, 84], and cold and rainy weather produces sour cherries with a less delicate sour cherry aroma [83]. 

Key flavour compounds Strawberry Fragaria spp.) Raspberry Blackberry Black currant Blueberry Cranberry Elderberry... 

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