Volatile flavor compounds

Hinrichsen, L.L. and Pedersen, S.B. (1995) Relationship among flavor, volatile compounds, chemical changes, and microflora in Italian-type dry-cured ham during processing,/. Agric. Food Chem., 43(11), 2932-2940. 

Van den Ouweland, G. A.M. Components contributing to beef flavor. Volatile compounds produced by the reaction of 4-hydroxy-5-methyl-3(2//)-fiiranone and its thio analog with hydrogen sulfide. J. Agric. Food Chem. 1975, 23, 501-505. 

Analysis of Off-Flavor Compounds in Food 2,4,6-Trichloroanisole (TCA) in Wine Analysis of flavor compounds in food comprises different approaches (1) target compound analysis focused on the detection and quantification of known compounds responsible for specific flavor features, (2) profiling volatile compounds done either to get a knowledge of food flavor/volatile compounds composition or, aided with multivariate analysis (MVA), for the identification of the origin of specific foods or their adulteration, and (3) sensory-oriented identification and quantification of key odorants (also off-odorants) of particular foods. 

OuwELAND, G. A. M. van den, and H. G. Peer Components Contributing to Beef Flavor. Volatile Compounds Produced by the Reaction of 4-Hydroxy-5-methyl-3(2 -furanone and Its Thio Analog with Hydrogen Sulfide. J. Agric. Food Chem. 23, 501 (1975). 

Chemical compounds having odor and taste number in the thousands. In 1969 a description of the odor characteristics of more than three thousand chemical compounds used in the flavor and perfume industries were described (41). The Hst of volatile compounds found in food that may contribute to odor and taste is even larger (42), and the Hst of all possible flavor compounds, including those that have yet to be synthesized, is greater than a thousand. Many different compounds have the same flavor character or quaUty, differing perhaps in their relative intensity but indistinguishable in the type of flavor they ehcit. The exact number of different flavor quaUties is not known, but it appears to be much less than the total number of compounds with flavor. 

Tea oxidation is generally referred to as fermentation because of the erroneous early conception of black tea production as a microbial process.66 Not until 1901 was there recognition of the process as one dependent on an enzymically catalyzed oxidation.67 This step and further reactions result in the conversion of the colorless flavanols to a complex mixture of orange-yellow to red-brown substances and an increase in the amount and variety of volatile compounds. Extract of oxidized leaf is amber-colored and less astringent than the light yellow-green extract of fresh leaf and the flavor profile is considerably more complex. 

In plant tissues, various enzymes convert the hydroperoxides produced by LOX to other products, some of which are important as flavor compounds. These enzymes include hydroperoxide lyase, which catalyzes the formation of aldehydes and oxo acids hydroperoxide-dependent peroxygenase and epoxygenase, which catalyze the formation of epoxy and hydroxy fatty acids, and hydroperoxide isomerase, which catalyzes the formation of epoxyhydroxy fatty acids and trihydroxy fatty acids. LOX produces flavor volatiles similar to those produced during autoxidation, although the relative proportions of the products may vary widely, depending on the specificity of the enzyme and the reaction conditions. 

The types of spoilage caused by bacteria in fruits and vegetables are diverse they include sensory changes, degradation of compounds, and formation of new substances such as acids, volatile compounds, and polymers. For example, the bacteria produce a set of enzymes such as pectinases, cellulases, proteases, and others that causes maceration and softening of tissue. Off-flavor development is common in contaminated tissues, caused by volatile compounds produced by microflora (Jay 1992). 

SPME has also been used in the area of head-space sampling of volatile compounds such as flavors and fragrances [34,35]. In these experiments, the analytes are adsorbed onto the polymer-coated fiber that is in contact with the head space in the vial. The fiber is then inserted into the injection port of a GC and thermally desorbed. 

Selecting an approach Off-flavors are typically due to volatile compounds present at extremely low levels. (Flavor is sensed more by the olfactory system than the tongue, which senses only 5 flavors, sweet, sour, bitter, salty, and umami). GC is ideal for detecting low levels of volatile components. In this case, headspace GC will allow you to treat the plastic directly. Since the off-flavor is suspected to be derived from the polypropylene packaging material, you decide to compare different samples ( good vs. bad ) of the material using headspace GC with both a flame ionization detector (FID) and a sniff port. These chromatograms are shown in Fig. 21.9. 

Flavor is one of the major characteristics that restricts the use of legume flours and proteins in foods. Processing of soybeans, peas and other legumes often results in a wide variety of volatile compounds that contribute flavor notes, such as grassy, beany and rancid flavors. Many of the objectionable flavors come from oxidative deterioration of the unsaturated lipids. The lipoxygenase-catalyzed conversion of unsaturated fatty acids to hydroperoxides, followed by their degradation to volatile and non-volatile compounds, has been identified as one of the important sources of flavor and aroma components of fruits and vegetables. An enzyme-active system, such as raw pea flour, may have most of the necessary enzymes to produce short chain carbonyl compounds. 

The central question that I want to approach here is the possible relationship between flavor preferences and nutritional value. There are a lot of data to work with. More than 70(X) volatile flavor substances have been identilied in foods and beverages. The situation may not be quite as complex as this would suggest. While it is true that any single fruit or vegetable may synthesize a few hundred volatile compounds, only a modest subset of these will contribute to its flavor profile. So the task is to sort out what these are, identify their sources, and link, where possible, these sources to nutritional value. Studies with the tomato provide a great example. The bottom line is Virtually all of the major tomato volatiles can be linked to compounds providing health benefits to humans. ... 

Finally, carotenoids are the metabolic precursors for three more of the flavor volatiles of the tomato. Although the role of carotenoids, light-harvesting pigments in plants, in human nutrition is the subject of debate, these compounds are antioxidants and P-carotene is the principal source of the visual pigments of the eye. 

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. 

Feeding repellents for pest birds are the most important application of chemical stimuli to manipulate bird behavior. Methyl anthranilate (Fig. 13.1) and dimethyl anthranilate, esters of benzoic acid, are found in concord grapes and are used as artificial flavorings. Starlings, Sturnus vulgaris, have an aversion to methyl anthranilate, which irritates the trigeminal nerve, and they feed less on food flavored with a variety of anthranilates. They avoid the more volatile anthranilates most. The odor is partly responsible for the effect contact is not necessary. In one particular experiment, only volatile compounds were aversive (Mason and Clark, 1987). If only anthranilate-treated food is offered, the birds will accept more of the flavored food than they do if they offered a choice between... 

Nowadays, derivatized cyclodextrins are the most common chiral selector in the direct GC enantiomer separation of flavors, fragrances, essential oils, pheromones and other natural, nature identical and synthetic volatile COmpounds.20.22,23,47,49-57... 

Oxidation, as is well known, leads not only to the formation of heavy compounds but also of volatile compounds that are responsible for off-flavors. Usually they are evaluated by capillary GC, through several sampling techniques are available (purge and trap, head space solid phase microextraction (SPME)). Rovellini et al. [26] recently proposed the application of HPLC for identifying... 

Homstein and Crowe 18) and others (79-27) suggested that, while the fat portion of muscle foods from different species contributes to the unique flavor that characterizes the meat from these species, the lean portion of meat contributes to the basic meaty flavor thought to be identical in beef, pork, and lamb. The major differences in flavor between pork and lamb result from differences in a number of short chain unsaturated fatty acids that are not present in beef. Even though more than 600 volatile compounds have been identified from cooked beef, not one single compound has been identified to date that can be attributed to the aroma of "cooked beef." Therefore, a thorough understanding of the effect of storage on beef flavor and on lipid volatile production would be helpful to maintain or expand that portion of the beef market. 

Lawrence, W. C., Volatile Compounds Affecting Beer Flavor, Wallerstein... 

Wong, N. P. and Patton, S. 1962. Identification of some volatile compounds related to the flavor of milk and cream. J. Dairy Sci. 45, 724-728. 

ODOR. An important property of many substances, manifested by a physiological sensation caused by contact of their molecules with the olfactory nervous system. Odor and flavor are closely related, and both are profoundly affected by submicrogram amounts of volatile compounds. Attempts to correlate odor with chemical structure have produced no definitive results, Objective measurement techniques involving chromatography are under development. Even potent odors must be present in a concentration of 1,7 x I07 molecules/cc to be detected. It has been authentically stated that the nose is 100 times as sensitive in detection of threshold odor values as the best analytical apparatus. 

Spanier, A.M. and Drumm Boylston, T. 1994. Effect of temperature on the analysis of beef flavor volatiles Focus on carbonyl and sulfur-containing compounds. Food Chem. 50 251-259. 

The desired citrus flavor is the result of volatile compounds in specific proportions. Citrus oils have unique composition profiles depending on the cultivar, the processing conditions, and the storage conditions. There have been more than 200 different compounds identified in citrus oils. However, the degree of unsaturation in monoterpenes leads to rapid oxidation and unstable compounds. The reactivity and volatility of citrus oils require strict quality control protocols. 

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