Aldehydes flavoring from

Bassette and Keeney (1960) ascribed the cereal-type flavor in dry skim milk to a homologous series of saturated aldehydes resulting from lipid oxidation in conjunction with products of the browning reaction. The results of Parks and Patton (1961) suggest that saturated and unsaturated aldehydes at levels near threshold may impart an off-flavor suggestive of staleness in dry whole milk. Wishner and Keeney (1963) concluded from studies on milk exposed to sunlight that C6 to Cn alk-2-enals are important contributors to the oxidized flavor in this product. Parks et al. (1963) concluded, as a result of quantitative carbonyl analysis and flavor studies, that alk-2-4-dienals, especially... 

Natural food flavors such as terpenes, hydrocarbons, alcohols, aldehydes, ketones, esters, acids, lactones, amines, sulfur compounds are enzymatically produced in fruits and vegetables. On the contrary, processed food develops its characteristic acceptable flavors from chemical reactions within its components at temperatures far below those at which its major components, i.e., lipids, proteins and carbohydrates pyrolyze. 

Of the aldehydes generated from the classic Farmer autoxldatlon mechanism, the 2,4,7-decatrlenal Isomers have been Identified as being highly contributory to burnt/flshy or cod liver oll-llke flavors (28, 32). Typically, both Isomers exhibit the burnt/flshy flavor character, but the t,, c-lsomer can also contribute a green-fishy character to oxidizing fish oils at low concentrations (28, 32). 

Chiba, H. N. Takahashi R. Sasaki. Enzymatic improvement of food flavor II. Removal of beany flavor from soybean products by aldehyde dehydrogenase. Agric. Biol Chem. 1979, 43, 1883-1889. 

The most common problem occurring during flavor storage is deterioration due to oxidation. Any flavoring containing citrus oils or oils based on aldehydes is susceptible to oxidative reactions and development of off-flavors. Thus, an important function of an edible film is protection of the flavoring from oxygen. 

We can recognize many organic functional groups in compounds we use every day. Pesticides and Freons often contain chlorinated hydrocarbons. Many fruits get their aromas and flavors from aldehydes, ketones, and esters. The sour taste in foods is because of carboxylic acids, and the many rotting smells are due to amines (6.4-6.13). 

FIGURE 16.6 The formation of acetals in flavorings from aldehyde ethanol reactions. (From Vollaro, R, Physical/Chemical Evaluation Methods of Detection of Changes, Presentation at an IFT sponsored flavor workshop titled, Flavor Interaction with Food, Orlando, FL, March, 2005. With permission.)... 

Other botanical varieties are caUed cassia, but the leaves of these varieties differ in flavor components from those of the bark. Saigon cinnamon, C. loureirii Nees, from Viet Nam, closely resembles Chinese cassia in appearance but is grown on the other side of the mountains and has an entirely different flavor character, containing no orthomethoxy cinnamic aldehyde. C. burmani B/ume, ie, Korintje or Kerintje cinnamon and Padang or Batavia cinnamon, is from Sumatra and Indonesia. C. sintok B/ume is native to Malaysia and of minor commercial importance. 

Diacetyl, acetoin, and diketones form during fermentation. Diacetyl has a pronounced effect on flavor, with a threshold of perception of 0.1—0.2 ppm at 0.45 ppm it produces a cheesy flavor. U.S. lager beer has a very mild flavor and generally has lower concentrations of diacetyl than ale. Diacetyl probably forms from the decarboxylation of a-ethyl acetolactate to acetoin and consequent oxidation of acetoin to diacetyl. The yeast enzyme diacetyl reductase can kreversibly reduce diacetyl to acetoin. Aldehyde concentrations are usually 10—20 ppm. Thek effects on flavor must be minor, since the perception threshold is about 25 ppm. 

There are at least two routes currently being used to produce natural benzaldehyde. Principal flavor houses are reported to market a product which is derived from cassia oil. The chief constituent of cassia oil is cinnamic aldehyde which is hydrolyzed into its benzaldehyde and acetaldehyde constituents. This is a fermentative retroaldol reaction. Whether this hydrolysis allows the final benzaldehyde product to be considered natural is of great concern. The FDA has reportedly issued an opinion letter that benzaldehyde produced from cassia oil is not natural (15). 

Yeast (qv) metabolize maltose and glucose sugars via the Embden-Meyerhof pathway to pymvate, and via acetaldehyde to ethanol. AH distiUers yeast strains can be expected to produce 6% (v/v) ethanol from a mash containing 11% (w/v) starch. Ethanol concentration up to 18% can be tolerated by some yeasts. Secondary products (congeners) arise during fermentation and are retained in the distiUation of whiskey. These include aldehydes, esters, and higher alcohols (fusel oHs). NaturaHy occurring lactic acid bacteria may simultaneously ferment within the mash and contribute to the whiskey flavor profile. 

Much work has been reported and summarized ia the Hterature on the matufing of various whiskeys ia charred or uncharred white-oak barrels (4—7). The early Hterature iadicates that total acids, aldehydes, esters, soHds, and color iacreased with aging time and that their concentrations were iaversely proportional to proof. Thus aging at higher proofs (over 127°) yields less color and flavor. The maximum allowable entry proof for straight whiskeys was iacreased from 110° to 125° by the U.S. Treasury Department ia 1962. 

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. 

None of the analyzed aldehydes exceed their flavor threshold in beer. (Adapted from Vesely et ah, 2003)... 

Robles and Bochet showed that nitrotoluene derivatives 106 (Scheme 50) can be used as a photoremovable protecting group for aldehydes. Irradiation of 106 released aldehydes in good yields, and the authors demonstrated that aldehydes such as phenylacetalaldehyde and citronellal, which are important for flavor and fragrances, are released efficiently from 106. 

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