Fruit aroma formation

Cofermentation with two or more strains has recently been exploited to enhance the aromatic profile of Sauvignon Blanc wines, in which a non-volatile 5-cysteinylated precursor (3-(hexan-1 -ol)-L-cysteine) is first hydrolysed by a carbon-sulfur lyase and subsequently esterifled by alcohol acetyltransferase (Sect. 8D.5.2). Strains of Saccharomyces cerevisiae vary in ability to carry out the two reactions (Dubourdieu et al. 2006 Swiegers and Pretorius 2007). Cofermentation with two strains, one having higher hydrolytic function (release of 3-MH) and the other higher esterification activity, substantially enhanced formation of 3-MHA, thereby increasing the passion-fruit aroma when compared to monoculture wines. The authors showed that interaction between the two strains produced more 3-MH and 3-MHA... 

It Is generally recognised that In fruit and vegetable production more attention should be given to the hidden sensory quality parameters, such as flavor and texture. These quality attributes are the result of a number of pre- and post-harvest factors and are closely related with fruit ripening. Palllard distinguishes external and Internal factors Influencing aroma formation In fruits (U. The... 

Flavor formation in fruit products has also extensively been reviewed (10), A distinction can be made between the primary aroma components, which are biosynthesized by the whole fruit and secondary aroma compounds (e.g. hexanal, 2-hexenal), formed after disruption of the cells during processing or chewing (11). The Importance of the peel for aroma formation has also been stressed by several authors (12). An extensive literature on the respiration climacteric (13), the role of ethylene (14) and the enzymes and substrates required for biosynthesis is available (15). 

Lim, M.H., Velasco, P.J., Pangbom, R.M., and Whitaker, J.R. 1989. Enzymes involved in off-aroma formation in broccoli. In Quality Factors in Fruits and Vegetables (MJ. Comstock, ed.), pp. 73-82. ACS Symposium Series 405. American Chemical Society, Washington, DC. 

FIGURE 4.1 The formation of fruit aroma from major food cxrmponents. (From Tressl, R., M. Holzer, M. Apetz, Aroma Research, IT. Maarse, P.J. Groenen, Eds., Wageningen, Netherlands, 1975, p. 41. With permission.)... 

As mentioned earlier, the process leading to aroma formation in vegetables is quite different than that of fruits. Vegetables do not have a ripening period as fruits do. While some vegetables will develop flavor during growth (much of taste and a limited... 

In this chapter, we review the biosynthetic pathways responsible for the formation of floral and fhiit volatiles, the regulation and localization of scent and aroma biosynthesis, and the recent advances in biotechnological manipulation of floral fragrances and fruit aromas. 

Differentiation can be defined as the process of specialisation in terms of shape and function. An example is cell differentiation in plants, animals and humans a young cell, which is initially multifunctional, gradually acquires one specific function and shape. Specialisation is a refinement that is expressed in terms of shape, scent and colour. For example, fruits ripen, leaves change colour in the autumn, the growth of a shoot ends in a terminal bud and seeds become dormant. The primary components are converted into secondary components such as phenols, vitamins, aromas, wax, and so on. Thus differentiation in this context has a broader meaning than only the formation of a new plant organ . 

Microbial spoilage appears to be one of the major causes of quality loss of fresh fruits and vegetables by formation of off-flavors, fermented aromas, and tissue decay. The shelf-life of many food products may be accurately predicted by quantifying the population of microbes present on the food product (Zhuang and others 2003). The... 

Scheme 7.1 Enzymatic degradation of fatty acids by the j -oxidation cycle and formation of various types of aroma compounds in fruits and vegetables...

The berry or the small fruits consist of strawberry, raspberry, blackberry, black currant, blueberry, cranberry and elderberry. The volatiles responsible for the flavour of small fruits are esters, alcohols, ketones, aldehydes, terpenoids, furanones and sulfur compounds (Table 7.3, Figs. 7.1-7.7). As fruit ripen, the concentration of aroma volatiles rapidly increases, closely following pigment formation [43]. 

Figure 10-20 Lipoxygenase Catalyzed Formation of Aroma Compounds in Cucumber. Source Reprinted from Biochim. Biophys. Acta., Vol. 441, T. Galliard, D.R. Phillips, and J. Reynolds, The Formation of cw-3-nonenal, mwu-2-nonenal and Hexanol from Linoleic Acid Hydroperoxide Isomers by a Hydroperoxide Cleavage Enzyme System in Cucumber (Cucumis Sativus) Fruits, p. 184, Copyright 1976, with permission from Elsevier Science.

Methods for the capillary gas chromatographic separation of optical isomers of chiral compounds after formation of diastereoisomeric derivatives were developed. Analytical aspects of the GC-separation of diastereoisomeric esters and urethanes derived from chiral secondary alcohols, 2-, 3-, 4- and 5-hydroxy-acid esters, and the corresponding jf- and -lactones were investigated. The methods were used to follow the formation of optically active compounds during microbiological processes, such as reduction of keto-precursors and asymmetric hydrolysis of racemic acetates on a micro-scale. The enantiomeric composition of chiral aroma constituents in tropical fruits, such as passion fruit, mango and pineapple, was determined and possible pathways for their biosynthesis were formulated. 

Carotenoids are regarded as part of the aroma potential of grape, as they are the biogenetic precursors of C13-norisoprenoids, a chemical family with many powerful odorants, which are mainly found as glycoconjugates in grape (Baumes et al. 2002 Enzell 1985 Mathieu et al. 2005 Winterhalter 1993). Sunshine favors the biosynthesis of carotenoids in the berry, from the first stage of fruit formation... 

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