Aroma lactones

In addition to the 5-lactones of structure (41), other lactonic aroma components with a saturated ring are known, the structure of which, however, is somewhat different from that of the n-series represented by (41). These are 6-hydroxy-5-hexanolide (42), identified in tomato (557), and three cyclic compounds carrying an unsaturated chain in position 5, viz. (Z)-7-decen-5-olide (jasmine lactone) (44) 712), identified in the flavor of black tea (50) together with methyl jasmonate (779). (Z)-9-dodecen-5-olide (45) and (Z)-9-tetradecen-5-olide (46), the latter two lactones having been isolated from butter flavor (50, 725). On the other hand, lactone (43) was isolated from milk where it is present in a quantity of 10 pg/kg (0.001 ppb) (247) this quantity, however, is probably much lower than the threshold value. 

Epoxide hydrolases have been found in such plants as soy bean [40] or in nectarines and strawberries, where they play a crucial role in the enantioselective synthesis of lactone aroma compounds [55]. Furthermore, epoxide hydrolases are involved in the biosynthesis of cutin, a polyester found in the cuticle that forms the first physical barrier against plant infection [56]. It has also been proposed that epoxide hydrolases may be involved in the production of microbial toxins [57]. 

Volatiles or Aroma. The essential oil, or aroma, of tea provides much of the pleasing flavor and scent of green and black tea beverages. Despite this, volatile components comprise only - 1% of the total mass of the tea leaves and tea infusions. Black tea aroma contains over 300 characterizing compounds, the most important of which are terpenes, terpene alcohols, lactones, ketones, esters, and spiro compounds (30). The mechanisms for the formation of these important tea compounds are not fully understood. The respective chemistries of the aroma constituents of tea have been reviewed... 

Lactide polymers, manufacture of, 14 122 Lactisole, 24 246 Lactitol, 12 40 Lactobacillic acid, 5 36t Lactobacillus, 12 478 Lactococcus, 12 478 Lactoferrins, 18 258 Lactones, 10 497 12 663-664 aroma chemicals, 3 256 in beer, 3 582t Lactonitrile, 8 174 Lactonization, 10 499... 

The impact of MOX upon reductive odors was included in the study of McCord (2003) for MOX at 5-10 mL/L/month over 5 months on a Cabernet Sauvignon wine in commercial scale tanks. Lower concentrations of methyl mercaptan and ethyl mercaptan were observed in the oxygenated wines, but no impact was seen upon disulfides, in spite of the suggestion that concentrations of the disulfides could increase due to direct oxidation of sulfides. Dimethyl sulfide concentrations were not affected, except that lower concentrations were seen in wines with added toasted oak staves or segments, with or without MOX. The concentrations of various oak extracted compounds were also measured in this study, with similar levels seen with and without MOX alongside appreciable increases due to the presence of the oak staves or segments in some cases (e.g., lactones and vanillin), oxygenation appeared to enhance aroma extraction. 

Lactones are key components in beef aroma (55). All seven lactones were concentrated in fraction FI compared to the non-extracted control. 8-Tetra-decalactone and a-hexadecalactone were present in the greatest concentration, and were present in the highest concentration of any other constituent in fraction FI. 

The lactones are the intramolecular esters of the corresponding hydroxy fatty acids. They contribute to the aroma of butter and various fruits. 15-Pentadeca-nolide is responsible for the musk-like odor of angelica root oil. Of the naturally occurring bicyclic lactones, phthalides are responsible for the odor of celery root oil, and coumarin for woodruff. 

Additional representatives of six-membered 5-lactones are 5-decalactone 155, constituent of fruits, cheese and dairy products with creamy-coco nut and peachy aroma, jasmolactone 156 as well as 5-2-decenolactone (2-decen-5-olide) 157 (Structure 4.47). 

Peaches and nectarines are members of the same species (Prunus persica). There is controversy over whether nectarine is a separate and distinct fruit or merely a variety of peach [68]. Nectarines lack skin fuzz or pubescence. Approximately 100 volatile compounds have been identified in peaches and nectarines, including alcohols, aldehydes, alkanes, esters, ketones, lactones and terpenes [14, 15, 17, 64, 65, 68-71]. Among them, lactones, particularly y-decalactone and d-decalactone, have been reported as character-impact compounds in peaches and nectarines where they process a strong peach-like aroma [66]. Lactones act in association with Ce aldehydes, aliphatic alcohols and terpenes (Table 7.2,... 

Approximately 75 volatile compounds have been identified in juices prepared from plums Prunus domestica) [35]. Lactones from Ce to C12 are the major class of compound in plums [78]. The distribution of plum lactones differs from that found in peaches in that the C12 y-lactones are found in higher concentrations than the corresponding Cio y-lactones and d-decalactone (Fig. 7.2) [78]. GC sniffing has uncovered benzaldehyde, linalool, ethyl nonanoate, methyl cin-namate, y-decalactone and d-decalactone as volatile compounds contributing to plum juice aroma (Table 7.2, Figs. 7.1, 7.2, 7.4, 7.5) [35]. 

Sugars, acids and aroma compounds contribute to the characteristic strawberry flavour [85]. Over 360 different volatile compounds have been identified in strawberry fruit [35]. Strawberry aroma is composed predominately of esters (25-90% of the total volatile mass in ripe strawberry fruit) with alcohols, ketones, lactones and aldehydes being present in smaller quantities [85]. Esters provide a fruity and floral characteristic to the aroma [35,86], but aldehydes and furanones also contribute to the strawberry aroma [85, 87]. Terpenoids and sulfur compounds may also have a significant impact on the characteristic strawberry fruit aroma although they normally only make up a small portion of the strawberry volatile compounds [88, 89]. Sulfur compounds, e.g. methanethiol. 

A wide range of volatile compounds from Indian mango were identified by pioneer group research [20,21]. Esters, lactones, monoterpenes, sesquiterpenes, and furanones were among the volatiles. It has been suggested that the ratio of palmitic to palmitoleic acids determines the flavour quality of the ripe fruit, a ratio of less than 1 resulting in strong aroma and flavour [44]. 

Owing to their pleasant odours many y-lactones and d-lactones are known to be Important flavour compounds of fruits and contribute essentially to the characteristic and distinctive notes of strawberries, peaches, apricots and many other fruits [24]. Chiral aroma compounds from fruits and other natural sources are characterised by origin-specific enantiomeric ratios, as their biogenetic pathways normally are catalysed by enzymes. 

Schottler M, Boland W (1996) Biosynthesis of dodecano-4-lactone in ripening fruits Crmal role of an epoxide-hydrolase in enantioselective generation of aroma components of the nectarine ( Prunus persica var. nucipersica ) and the strawberry (Fragaria ananassa). Helv Chim Acta 79 1488... 

The closely related 5-decanolide (5-decalactone), not only found in many fruits but also found in dairy products, exhibits a creamy-coconut, peach-like aroma [49] and can be synthesised from the corresponding a,(3-unsaturated lactone 2-decen-5-olide found in concentrations of up to 80% in Massoi bark oil using basidiomycetes or baker s yeast [229]. After about 16 h of fermentation, 1.2 g 5-decanolide was obtained. At the same time, the minor lactone in... 

Finally, the yeast Yarrowia lipolytica is able to transform ricinoleic acid (12-hydroxy oleic acid) into y-decalactone, a desirable fruity and creamy aroma compound however, the biotransformation pathway involves fi-oxidation and requires the lactonisation at the CIO level. The first step of fi-oxidation in Y. lipolytica is catalysed by five acyl-CoA oxidases (Aox), some of which are long-chain-specific, whereas the short-chain-specific enzymes are also involved in the degradation of the lactone. Genetic constructions have been made to remove these lactone-degrading activities from the yeast strain [49, 50]. A strain displaying only Aox2p activity produced 10 times more lactone than the wild type in 48 h but still showed the same growth behaviour as the wild type. 

The aromas were normally assessed after i, 1, 2, 3, and k min. The maximum yield (0.5%) of the interesting 2-(5-hydroxymethyl-2-formyl-1-pyrrolyl) propionic lactone has been shown to occur from a mixture of glucose and ala in about 3 min under "dry" conditions at 200° ( 3). The full results are available ( ) and a set obtained at 180 2° is given in Table I as an example. 

Higher molecular weight lactones, such as y-decalactone, 6-dodecalactone, y-jasmolactone, occur in fruit (peach and apricot aromas) but have been not found in wine, at least in very small traces by gas chromatography/ mass spectrometry (GC-MS). If they are detected in higher quantities, then these lactones were undoubtedly added illegally, a case for prosecution (10MI3,07MI27). 

From the wine aromas of Pollux, Castor, and Riesling grapes, Rapp et al. and Schreier and Paroschy have isolated an undesirable strawberry aroma by GC-MS (80V13, 81MI112). This lactone was characterized as 2,5-dimethyl-4-hydroxy-2,3-dihydro-3-furanone 8 ("furaneol") having an odor threshold of 50-100 ppb. 

The aroma of botrytized wines has been studied more extensively than that of the grapes. Mashuda et ah (1984) identified the lactone sotolon (4,5-dimethyl-3-hydroxy-2,(5)-furanone) as a principal compound in a botrytized aroma. Sotolon is also a key aroma compound in flor wines, for example, vin jaune, sherry (Dubois et ah, 1976 Martin and Etievant, 1991 Moreno et ah, 2005). However, Sponholz and Hiihn (1993) found no correlation between the degree of Botrytis infection and sotolon... 

The main aroma compounds identified as specific botrytized odorants are indicated in Table 6.6. It seems that while the terpene content decreases, numerous hydroxy-, oxo-, and dicarboxylic acid esters, acetals, and lactones form, all typically in lower concentrations or absent in normal wines (Miklosy and Kerenyi, 2004 Miklosy et al., 2000, 2004 Schreier et al, 1976). 

The nature of the Botrytis aroma compounds has been subjected to extensive research. In addition to the older findings about the importance of hydroxy-, oxo-, and dicarboxylic acid esters, acetals, and some special y- and 8-lactones, the role of volatile thiols has recently been elucidated. Nonetheless, additional research is needed to identify odor active compounds that are specific for botrytized wines. 

The powerful potentialities of SBSE followed by thermal desorption and GC-qMS methodology to characterize Madeira wine was also explored by Perestrelo et al. (2009). This methodology provided higher ability for profiling traces and ultratraces of compounds in Madeira wines, including esters (80.7-89.7%), higher alcohols (3.5-8.2%), Ci3 nor-isoprenoids (1.7-6.5%), carboxylic acids (1.6H-.2%), aldehydes (0.9-3.7%) pyrans (0.2-1.7%), lactones (0.3-2.7%), and mono (0.1-1.4%), and sesqui-terpenoids (0.1-0.8%). The authors reported that the concentration of some of them is above their odor threshold, and therefore can probably play a remarkable impact on the aroma complexity of the corresponding wines. 

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