Aroma character

Other important North American crosses include the Young- and Boysenberries (7n) 9) and in Scotland crossings between the Oregon blackberry "Aurora" (8n) and tetraploid raspberries (4n) have generated the important Tay- and Tummelberries (hexaploid 6n) (6). In Finland, the arctic raspberry R. arcticus) has been crossed into R. idaeus and the diploid "Heija" has enabled commercial exploitation of the special aroma character of this fruit (70). 

Definition of taste and aroma character in sensory terms, and assigning this to precise variation in fruit composition, allows experiments with sensory panels to be limited to defining compositional componoits correlated with character changes perceived important by observers. Subsequent experimentation can then be effected by automated chromatography. 

The thermal reaction of cystine and 2,3-dimethyl-4-hydroxy-3 (2H)-furanone (DMHF), a modified Maillard reaction is important for the generation of meat flavors. The reaction products, their flavor compounds, aroma character and yield vary, according to the reaction parameters. These parameters include the reaction medium, duration, water content, temperature, pH and presence or absence of oxygen. 

Table 1 Aroma character of each coffee fraction...

In comparison, significant losses of a number of wine components must be expected when in contact with polyolefins because of the large K values for non-polar compounds. Packaging wine in polyolefin-coated containers, which for example is the case for bag-in-box packaging, does not appear to make sense. Quality decreases can occur not only by loss of the aroma but by the alteration of the aroma character due to different K values for different aroma compounds. The uptake (scalping) of non-polar compounds like limonene from fruit juices by polyolefins has been experimentally confirmed (Hirose et al., 1988 Mannheim et al., 1988). 

The most classical artificial substances used in perfumery are as follows (Figure 5). Hydroxycitronellal (99) was found to exhibit the odor of lily of the valley, the essential oil of which is not possible to prepare in the first place. Other classics include ct-amylcinnamaldehyde (100) and musk ketone (101), which were discovered to be good substitutes for jasmine and musk, respectively. Furthermore, perfume No. 5 (Chanel, launched 1921) contained 2-methylundecanal, 1 with so unique an aroma character that it established No. 5 as the pioneer of a new fragrance class — floral aldehydic. 

Both the enantiomers showed the same aroma character at the same concentration near the threshold value of ( ) sotolon moreover, there was no difference in the insect attractancy (house fly and cockroach) among the two enantiomers and the racemate of sotolon. Later, we( ) tried to analyze the aroma compound in fresh sugar cane juice and could not identify sotolon in the same fraction as that separated from cane molasses. These results suggest that sotolon was present in a racemic form prepared by mutual interaction of the constituents in sugar cane juice. 

When Japanese rice wine (sake) is kept under unsuitable conditions, it develops an off-flavor with a burnt or soy-sauce (shoyu)-like odor. Takahashi al.(12) identified the main component as sotolon before our identification, and they claimed that the sotolon concentration was between 140-430 ppb in aged sake. This concentration is much higher than the threshold value of sotolon, and its aroma character would change from sugary to herbal or curry-like. The high sotolon content in aged sake could be a reason for the off-flavor defect. The formation of sotolon in aged... 

Marin and co-workers [44] presented an interesting paper in 1992 on the appHcation of GC-olfactometry to the assessment of the effects of plastic polymers on the aroma character of orange juices. They used data generated from GC-FID, GC-MS and GC-Olfactometry to demonstrate the influence of hmonene contents onto the overall aroma of orange juice. The problems at hand with GC-olfactometry are mainly centred around the fact that the human nose does not have a hnear response. Hence cahbration is somewhat more tedious as the specific sensitivities to aU components are non-related to each other. 

The flavor is weak, chemical (Chemisis, 1963). It has a cracker-popcorn like aroma character according to Buttery (1999) who gave a threshold in water of 37 ppb, ca 4500 times lower than that of 2-acetylpyrrole (K.50). 

Watanabe and Sato (1972) observed that this product adds a slightly caramel-like character to the flavor of cooked beef, but Peterson et al. (1975), on the contrary, considered that it confered to canned beef stew an unpleasant antiseptic-like aroma, reminiscent of plastic. Buttery (1999) compared several 2-acyl nitrogen-containing heterocycles with a cracker, popcorn-like aroma character 2-acetylpyrrole is the less potent with a threshold of 170ppm in water (the 3,4-dihydro-2//-pyrrolyl derivative has a threshold of 0.1 ppb and the pyridyl derivative, N.22, of 19ppb). 

Tressl R., Griinewald K.G., Silwar K.G. and Helak B. (1981 d) Formation of compounds with breadlike aroma character in meat and beer. Proc. Congr. Eur. Brew. Conv. 18, 391-403. 

Some of the data is difficult to explain. For example, m-cresol (peak 26) has a pronounced negative aroma character and was found only in the Valencia oil. Despite these difficulties, much of the observed quality differences between Valencia and Early-Mid season orange essence oils can be explained from the lack of positive aroma components in the Early-Mid season oil and the presence in Early-Mid of aroma components which are not particularly positive. 

Different lots of oleoresin Capsicum obtained at different times varied considerably in aroma character and intensity. 

Numerous minor constituents remain unidentified, especially in the neutral and basic fractions. Sniffing runs have indicated that quantltatively-mlnor components may still provide considerable aroma character, so these minor constituents cannot necessarily be ignored. 

Qualitative headspace analysis is used in many applications to determine differences between selected samples and to assess the importance of specific compoimds in defining the aroma character of certain substances. This approach is often termed fingerprinting as in many instances the composition remains chemically unknown. For additional qualitative data, headspace may be used in conjunction with knowledge of GC retention data or with GC-MS techniques for a more definitive chemical identification. 

Aroma is a very complex sensation. While the stimuli available to create taste sensations is limited, more than 7,100 volatile compounds have been identified in foods overall [46-48] each of which may potentially contribute to aroma perception, depending upon their concentrations and sensory thresholds. Some of the more complex food aromas, e.g., a thermally processed food such as coffee, may contain over 800 volatile components. Fortunately, the aroma character of most foods can typically be defined by a smaller subset of the total volatile profile. 

When one considers the effects of chemical interactions (carbohydrate aroma) on sensory perception, one would expect that aroma character and/or intensity will be altered. This is because the various polysaccharides will interact with different aroma compounds to varying degrees, i.e., change the balance of aroma compounds liberated from a food. However, the effect of carbohydrates on limiting mass transfer would be expected to likely affect flavor intensity and not character. This is because mass transfer effects would be more uniform across aroma compounds. 

More than 70 degradation products have been identified. In addition to simple compounds, such as hydrogen sulfide, ammonia, formaldehyde, acetaldehyde, formic acid and acetic acid, dozens of other minor sulfur compounds are formed aliphatic sulfides, aliphatic carbonyl compounds with a thiol group, furans containing sulfur in the molecule (including the previously mentioned meaty aroma character imparting compound 2-methyl-3-furanthiol), thiophenes, thiazoles and alicycHc and heterocycHc bicycHc sulfur... 

Most essential oils contain a significant proportion of terpenes (monoterpenic and sesquiterpenic hydrocarbons). For example, their level in some citrus essential oils is 95% or more. These substances are not usually essential to the smell and aroma character of essential oils, as the most important odoriferous compounds are alcohols, aldehydes, ketones, esters and other compounds. Furthermore, terpenic hydrocarbons are a reason for the limited solubility of essential oils in diluted ethanol and are often the cause of deterioration of essential oils that easily oxidise or polymerise. By removing hydrocarbons from essential oils, concentrates are obtained. Monoterpene-free or sesquiterpene-free essential... 

To determine correctly the influence of random coil polysaccharides on aroma and flavor perception, further investigation of the influence of experimental factors such as those considered is required. In addition, a technique to determine release of tastant, e.g., sucrose, must be developed. Finally, further studies with different thickeners, different tastants, and volatile compounds of different aroma character are needed as the interactions found will most likely be compound- and hydrocolloid-specific. 

Table 9 Static Headspace GC-O of a Commercially Available Food Flavoring with Savory Aroma Character...

The flavor chemistry of sulfur compounds in onion is quite complex (19,20). Early reports of polysulfides and thiosulfinates were later demonstrated to be thermal artifacts from gas chromatographic analysis (20). Character impact sulfur compounds have been proposed for fresh, boiled, and fried onion. In raw, fresh onion, propyl propanethiosulfinate, propenyl propanethiosulfinate thiopro-panal S-oxide, and propyl methanethiosulfinate are impact contributors (18,19). A number of compounds contribute to the aroma character of cooked onion, of which dipropyl disulfide and allyl propyl disulfide provide key impact (18). Fried onion aroma is formed by heating the latter compound, and is characterized by... 

Sulfur-containing heterocyclic compounds are associated with meaty characteristics. Two compounds with the most potent meaty impact include 2-methyl-3-furanthiol (1 ppt) and the corresponding dimer, -(2-methyl-3-furyl) disulflde (0.02 ppt) (18). Both substances have been identified in cooked beef and chicken broth and have a strong meaty quality upon dilution. The disulflde has a recognizable aroma character of rich aged-beef, prime-rib (15). Interestingly, both compounds are produced from the thermal degradation of thiamin (63). A related compound, 2-methyl-3-(methylthio)furan, is the character impact compound for roast beef (18). Other potent modifiers, such as 2-acetyl-2-thiazoline, impart a potent roasty, popcorn note, which enhances the meaty and roast flavor (64). 2-Ethyl-3,5-dimethylpyrazine and 2,3-diethyl-5-methylpyrazine also contribute potent roasty notes to roast beef flavor (65). A summary of character impact compounds for meat and seafood flavors is presented in Table 6. 

Three notable marine character-impact aroma exceptions are 5,8,11-tetradecatrien-2-one, which exhibits a distinct seafood aroma character described as cooked shrimp-like or minnow bucket (73). A second example is an extremely potent odorant in cooked shellfish, including shrimp and clam, identified by Kubota and coworkers (74) as pyrrolidino[l,2-c]-4//-2,4-dimethyl-1,3,5-dithiazine. This dithiazine contributes a roasted character to boiled shellfish and has the lowest odor threshold recorded to date, 10" ppt in water. 2,4,6-Tribromophenol and other bromophenol isomers have been associated with the ocean-, brine-, and iodine-like fiavor character in seafood such as Australian ocean fish and prawns. The source of the bromophenols is thought to be poly-chaete worms, which form an important part of the diet for many fish and prawn species (75). Finally, dimethyl sulfide is the character aroma of stewed clams and oysters (69). Representative structures for meat and seafood flavor impact compounds are shown in Fig. 6. 

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