Glycosidically Bound Aroma Compounds

Some aroma compounds are bound as glycosides in fruits and vegetables, and thus make no contribution to food aroma unless released [49-51]. They may be released 

FIGURE 4.14 Pathway proposed for the enzymatic and nonenzymatic formation of lenthion-ine from lentmic acid. (From Yasumoto, K., K. Iwami, H. Mitsuda, Agric. Biolog. Chem., 35 (13 Suppl), p. 2070, 1971. With permission.) 

Research has been driven by two factors, the first being the desire to enhance flavor strength, or yield, in an application. The pool of glycosidicaUy bound aroma compounds in some plants exceeds the free aroma pool by as much as 10 1, thus 

FIGURE 4.15 The conversion of glucosinolate precursors to aroma compounds by myrosi-nase. (From Takeoka, G., Flavor Chemistry 30 Years of Progress, R. Teranishi, E.L. Wick, I. Hornstein, Eds., Kulwer Academ., New York, 1999, p. 287. With permission.) 

Free and Bound Terpene Alcohols in Grapes, Apricot, Mango, and Passion Fruit 

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The release of glycosidically-bound aroma compounds, such as monoterpenes, C13 norisoprenoids, and aliphatic alcohols, can be achieved by the action of glycosi-dase enzymes. 3-Glycosidase activity has not been much studied in wine LAB. McMahon et al. (1999) detected a low p-glycosidase activity in O. oeni OSU and a... 

FIGURE 4.16 Main glycosidically bound aroma compounds found in fruits. (From Crouzet, J., Functionality of Food Phytochemicals, T. Romeo, Ed., Plenum Press, New York, 1997, p. 197. With permission.)... 

Wu O, May C, Ho CT. Glycosidically bound aroma compounds in ginger (Zingiber officinale Roscoe). J. Agr. Food Chem 1990 38(7) 1553-1555. 

H. H. Back and K. R. Cadwallader, Contribution of free and glycosidically bound volatile compounds to the aroma of muscadine grape juice, J. Food Sci. 64 441 (1999). 

Ethyl 2-methylbutanoate, 2-methylbutyl acetate and hexyl acetate contribute most to the characteristic aroma of Fuji apples [49]. In Red Delicious apples, ethyl butanoate, ethyl 2-methylbutanoate, propyl 2-methylbutanoate and hexyl acetate contribute to the characteristic aroma as determined by Charm-Analysis and/or AEDA [50, 51]. In a comparative study of 40 apple cultivars, the highest odour potency or Charm value was found for -damascenone [52]. This compound usually occurs in a glycosidically bound form and is present primarily in processed products owing to hydrolysis of the glycoside bond after crushing fruit cells [53]. -Damascenone has a very low odour threshold with a sweet, fruity, perfumery odour and is not typical of apple aroma in gen-... 

Besides the structural elucidation of glycosides, research is focused on the application of glycosidases to liberate the aroma-active aglycons from their bound forms. The development of a continuous process of enzymatic treatment (simultaneous enzyme catalysis extraction) [50] opened the doors for the industrial large-scale production of aroma compounds from their non-volatile conjugates. 

Vernin G, Parkdnyi C (1982) Mechanisms of formation of heterocyclic compounds in Maillard and pyrolysis reactions. In Vernin G (ed) Chemistry of heterocyclic compounds in flavours and aromas. Ellis Horwood, Chichester, pp 151-207 Versini G, Dalla Serra A, DelPEva M, Scienza A, Rapp A (1988) Evidence of some glycosidically bound new monoterpenes and norisoprenoids in grapes. In Schreier P (eds) Bioflavor 87. de Gruyter, Berlin, pp 161-170... 

The leaves, flowers, and stems of Satureja hortensis (summer savory, Lamiaceae), a common plant widely spread in Turkey, are used as tea or as addition to foods on account of the aroma and the flavor. As a medical plant it is known for its antispasmodic, antidiarrheal, antioxidant, sedative, and antimicrobial properties. Also this EO was investigated for its antioxidative properties. The GC-MS analysis showed that besides 9% p-cymene, carvacrol and thymol are the main compounds of about 22 constituents of the oil. They occur at a ratio of approximately 1 1, which is representative for the genus Satureja, namely 29% of thymol and 27% of carvacrol. In a linoleic acid test system the EO showed an inhibition activity of 95%, this is an indicator for a strong antioxidative activity because the control BHT attained an inhibition of 96% (Giilliice et al., 2003). Thymol is one of the main components of the EO from Satureja montana L ssp. montana (savory) and also one of the glycosidically bound volatile aglycones that were found. The EO with 45% thymol shows a very strong antioxidative capacity that was a bit lower than the standards, BHT, and a-tocopherol. The... 

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