Flavour compounds in tomato fruits: identification of loci and potential pathways affecting volatile composition

The unique flavour of a tomato fruit is the sum of a complex interaction among sugars, acids, and a large set of volatile compounds. While it is generally acknowledged that the flavour of commercially produced tomatoes is inferior, the biochemical and genetic complexity of the trait has made breeding for improved flavour extremely difficult. The volatiles, in particular, present a major challenge for flavour improvement, being generated from a diverse set of lipid, amino acid, and carotenoid precursors. Very few genes controlling their biosynthesis have been identified. New quantitative trait loci (QTLs) that affect the volatile emissions of red-ripe fruits are described here. A population of introgression lines derived from a cross between the cultivated tomato Solanum lycopersicum and its wild relative, S. habrochaites, was characterized over multiple seasons and locations. A total of 30 QTLs affecting the emission of one or more volatiles were mapped. The data from this mapping project, combined with previously collected data on an IL population derived from a cross between S. lycopersicum and S. pennellii populations, were used to construct a correlational database. A metabolite tree derived from these data provides new insights into the pathways for the synthesis of several of these volatiles. One QTL is a novel locus affecting fruit carotenoid content on chromosome 2. Volatile emissions from this and other lines indicate that the linear and cyclic apocarotenoid volatiles are probably derived from separate carotenoid pools

Microwave-assistance provides very rapid and efficient extraction of grape seed polyphenols

A microwave assisted extraction (MAE) method has been developed for the extraction of polyphenols from grape seeds of Vitis vinifera cultivars Cabernet Sauvignon, Shiraz, Sauvignon Blanc and Chardonnay. An initial five-factor (ethanol concentration in the extraction solvent, liquid:solid ratio, time, power and temperature), five-level orthogonal experimental array was designed and three factors (ethanol concentration in the extraction solvent, liquid:solid ratio and time) plus their best levels were chosen to optimise the extraction using a central composite rotatable design (CCRD) experiment. This revealed, after the use of response surface methodology, that the optimal extraction conditions were ethanol concentration (47.2%), liquid:solid ratio (45.3:1) and time (4.6min). Total polyphenols were determined by application of the Folin-Ciocalteau method. Sequential application of the optimal conditions to one sample revealed that approximately 92% of the total polyphenols were extracted in the first instance. In comparison with other extraction methods, MAE provided comparable or better extraction, but was very much quicker. One key finding was that varying the applied power to the extraction was essentially irrelevant; inspection of the applied power profile during extraction revealed that the power was strictly modulated to maintain a constant temperature in the reaction cell.Yinping Li, George K. Skouroumounis, Gordon M. Elsey and Dennis K. Taylorhttp://www.elsevier.com/wps/find/journaldescription.cws_home/405857/description#descriptio

Occurrence, sensory impact, formation, and fate of damascenone in grapes, wines, and other foods and beverages

Among plant-derived odorants, damascenone is one of the most ubiquitous, sometimes occurring as an apparent natural product but more commonly occurring in processed foodstuffs and beverages. It has been widely reported as a component of alcoholic beverages, particularly of wines made from the grape Vitis vinifera . Although damascenone has one of the lowest ortho- and retronasal detection thresholds of any odorant, its contribution to the sensory properties of most products remains poorly understood. Damascenone can be formed by acid-catalyzed hydrolyses of plant-derived apocarotenoids, in both aglycon and glycoconjugated forms. These reactions can account for the formation of damascenone in some, but not all, products. In wine, damascenone can also be subject to degradation processes, particularly by reaction with sulfur dioxide.Mark A. Sefton, George K. Skouroumounis, Gordon M. Elsey, and Dennis K. Taylo

New phenolic grape skin products from vitis vinifera cv. Pinot noir

Anthocyanins and their related compounds were extracted from grape skins of Pinot noir, using 50% aqueous methanol, and purified by solid phase extraction chromatography using XAD-7 resin to obtain a pigment-rich fraction. This fraction was subjected to multilayer coil countercurrent chromatography (MLCCC) using a quaternary solvent system consisting of tert-butyl methyl ether/n-butanol/acetonitrile/water acidified with 0.01% trifluoroacetic acid (2:2:0.1-1.8:5) (v/v/v/v) in a step gradient elution to separate anthocyanin oligomers from grape anthocyanins. In the process of the characterization of the MLCCC fractions by electrospray mass spectrometry, two noncolored anthocyanin derivatives were found and characterized on the basis of their mass spectral data. As a result, these compounds have been tentatively identified as coupling products between both hydrated malvidin-3-glucoside and peonidin-3-glucoside, with 2-S-glutathionyl caffeoyl tartaric acid (GRP). It is therefore proposed that grape skins contain this new class of coupling product, and a possible chemical pathway for their formation is suggested.Petros Kneknopoulos, George K. Skouroumounis, Yoji Hayasaka, and Dennis K. Taylo

Precursors to oak lactone: Synthesis of gallate ester derivatives of 3-methyl-4-hydroxyoctanoic acid

Copyright © 2001 Elsevier Science Ltd All rights reserved.(3R,4R- and 3S,4S)-3-Methyl-4-(3′-O-methylgalloyloxy)octanoic acid (2b), the corresponding methyl ester (2c) and the straight galloyl derivative, (3R,4R- and 3S,4S)-3-methyl-4-galloyloxyoctanoic acid (2a) were synthesised from cis-oak lactone (1). Analysis by TLC and mass spectrometry established that the original assignment of structure (2c) to a methylated natural oak component was in error. The gallate esters 2a and 2b have been synthesised. A previous assignment of structure 2b to an oak-derived substance is shown to be in error.Michael Raunkjær, D.Sejer Pedersen, Gordon M. Elsey, Mark A. Sefton, and George K. Skouroumounishttp://www.elsevier.com/wps/find/journaldescription.cws_home/233/description#descriptio

Generation of (E)-1-(2,3,6-Trimethylphenyl)buta-1,3-diene from C13-Norisoprenoid Precursors

Agnieszka Cox, George K. Skouroumounis, Gordon M. Elsey, Michael V. Perkins, and Mark A. Sefto

Mass spectrometric evidence for the existence of oligomeric anthocyanins in grape skins

Stéphane Vidal, Emmanuelle Meudec, Véronique Cheynier, George Skouroumounis and Yoji Hayasak

Accumulation of vanillin during barrel-aging of white, red, and model wines.

A method for the rapid and accurate analysis of vanillin in wine, using stable isotope dilution analysis and gas chromatography/mass spectrometry, has been developed and applied to 64 oak barrel-aged white, red, and model wines. Following barrel fermentation and maturation on yeast lees, the concentration of vanillin in the white wines was only about one-third of that in the model wines stored for the same period. Once the yeast lees were removed, however, the white and model wines accumulated vanillin at a similar rate, which indicated that biological reduction of vanillin occurred only prior to racking. After 93 weeks in barrels, the concentration of vanillin in the red wines was less than one-half that in the model wines, and vanillin was further depleted during subsequent bottle storage of the red wines for 2 years at cellar temperature. For the model and red wines, the mean concentration of vanillin in barrels made from French oak, seasoned and coopered in Australia, was significantly higher than that for wines stored in barrels made from the same wood, but seasoned and coopered in France. In the white wines, extensive biological transformation of vanillin associated with yeast activity during the initial weeks of maturation appears to have nullified this seasoning/ coopering effect. Oak origin had no significant influence on the final vanillin concentration in the wines.Philip J. Spillman, Alan P. Pollnitz, Dimitra Liacopoulos, George K. Skouroumounis, and Mark A. Sefto