Phenolics in Food and Nutraceuticals is the first single-source compendium of essential information concerning food phenolics. This unique book reports the classification and nomenclature of phenolics, their occurrence in food and nutraceuticals, chemistry and applications, and nutritional and health effects. In addition, it describes antioxidant activity of phenolics in food and nutraceuticals as well as methods for analysis and quantification. Each chapter concludes with an extensive bibliography for further reading. Food scientists, nutritionists, chemists, biochemists, and health professionals will find this book valuable.

Phenolics in food and nutraceuticals

The most mysterious aspect of wine is the endless variety of flavours that stem from a complex, completely non-linear system of interactions among many hundreds of compounds. In its widest sense, wine flavour refers to the overall impression of both aroma and taste components. Aroma is usually associated with odorous, volatile compounds; the bouquet of wine refers to the more complex flavour compounds which evolve as a result of fermentation, elevage and ageing. With the exception of terpenes in the aromatic grape varieties and alkoxypyrazines in the herbaceous cultivars, perceived flavour is the result of absolute amounts and specific ratios of many of these interactive compounds, rather than being attributable to a single "impact" compound. Without underestimating the complexity of these interactive effects or negating the definitive role played by the accumulated secondary grape metabolites in the varietal character of wine, this review will focus mainly on the contribution of yeast fermentation to the sensorial quality of the final product. Yeast and fermentation conditions are claimed to be the most important factors influencing the flavours in wine. Both spontaneous and inoculated wine fermentations are affected by the diversity of yeasts associated with the vineyard and winery. During the primary alcoholic fermentation of sugar, the wine yeast, Saccharomyces cerevisiae, together with other indigenous non-Saccharomyces species, produce ethanol, carbon dioxide and a number of by-products. Of these yeast-derived metabolites, the alcohols, acetates and C4-C8 1tfatty acid ethyl esters are found in the highest concentration in wine. While the volatile metabolites contribute to the fermentation bouquet ubiquitous to all young wines, the production levels of these by-products are variable and yeast strain specific. Therefore, this article also highlights the importance of untapping the hidden wealth of indigenous yeast species present on grapes, and the selection and genetic development of yeast starter culture strains with improved flavour profiles. In the future, some winemakers may prefer to use mixtures of indigenous yeast species and tailored S. cerevisiae strains as starter cultures to reflect the biodiversity and stylistic distinctiveness of a given region. This will help winemakers to fullfil the consumer's demand for individual wines with intact local character and to ensure the survival of wine's most enthralling aspect - its endless variety.

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Yeast and its Importance to Wine Aroma - A Review

This review discusses the impacts of nitrogen addition in the vineyard and winery, and establishes the effects that nitrogen has on grape berry and wine composition and the sensory attributes of wine. Nitrogen is the most abundant soil-derived macronutrient in a grapevine, and plays a major role in many of the biological functions and processes of both grapevine and fermentative microorganisms. Manipulation of grapevine nitrogen nutrition has the potential to influence quality components in the grape and, ultimately, the wine. In addition, fermentation kinetics and formation of flavour-active metabolites are also affected by the nitrogen status of the must, which can be further manipulated by addition of nitrogen in the winery. The only consistent effect of nitrogen application in the vineyard on grape berry quality components is an increase in the concentration of the major nitrogenous compounds, such as total nitrogen, total amino acids, arginine, proline and ammonium, and consequently yeast-assimilable nitrogen (YAN). Both the form and amount of YAN have significant implications for wine quality. Low must YAN leads to low yeast populations and poor fermentation vigour, increased risk of sluggish/stuck/slow fermentations, increased production of undesirable thiols (e.g. hydrogen sulfide) and higher alcohols, and low production of esters and long chain volatile fatty acids. High must YAN leads to increased biomass and higher maximum heat output due to greater fermentation vigour, and increased formation of ethyl acetate, acetic acid and volatile acidity. Increased concentrations of haze-causing proteins, urea and ethyl carbamate and biogenic amines are also associated with high YAN musts. The risk of microbial instability, potential taint from Botrytis-infected fruit and possibly atypical ageing character is also increased. Intermediate must YAN favours the best balance between desirable and undesirable chemical and sensory wine attributes. ‘Macro tuning’, of berry nitrogen status can be achieved in the vineyard, given genetic constraints, but the final ‘micro tuning’ can be more readily achieved in the winery by the use of nitrogen supplements, such as diammonium phosphate (DAP) and the choice of fermentation conditions. This point highlights the need to monitor nitrogen not only in the vineyard but also in the must immediately before fermentation, so that appropriate additions can be made when required. Overall, optimisation of vineyard and fermentation nitrogen can contribute to quality factors in wine and hence affect its value. However, a better understanding of the effect of nitrogen on grape secondary metabolites and different types of nitrogen sources on yeast flavour metabolism and wine sensory properties is still required.

Implications of nitrogen nutrition for grapes, fermentation and wine

Ethylphenols are important aromatic compounds of red wines. These compounds are formed in wines by some yeast species belonging to the genus Brettanomyces/Dekkera in the presence of hydroxycinnamic acids. These volatile phenols are responsible for the ‘phenolic’, ‘animal’ and ‘stable’ off-odours found in certain red wines. The results presented show that the synthesis of the high quantities of ethylphenols found in the ‘phenolic’ red wines can occur during the ageing of wines having normally completed their alcoholic and malo-lactic fermentations. This olfactory fault caused by Brettanomyces/Dekkera is found more frequently than the classical ‘mousy-taint’ attributed to this yeast genus. In addition, the study of the mechanisms of biosynthesis of ethylphenols by Brettanomyces/Dekkera has shown the sequential activities of two enzymes. The first, is a cinnamate decarboxylase (CD), which assures the transformation of certain cinnamic acids into the correspondent vinylphenols; the second is a vinylphenol reductase, which catalyses the reduction of vinylphenols into ethylphenols. The CD activity of Brettanomyces/Dekkera is not inhibited by the polyphenolic compounds of red wines (procyanidins and catechins) while these compounds do inhibit the CD activity of Saccharomyces cerevisiae. On the other hand, the substrate specificities of the CD activities of Brettanomyces/Dekkera and Saccharomyces are different.

The origin of ethylphenols in wines

The aroma profile of five premium red wines has been studied by sensory descriptive analysis, quantitative gas chromatography−olfactometry (GC-O), and chemical quantitative analysis. The most relevant findings have been confirmed by sensory analysis. Forty-five odorants, including the most intense, were identified. At least 37 odorants can be found at concentrations above their odor threshold. A satisfactory agreement between GC-O and quantitative data was obtained in most cases. Isobutyl-2-methoxypyrazine, (E)-whiskey lactone, and guaiacol were responsible for the veggie, woody, and toasted characters of the wines, respectively. The sweet-caramel notes are related to the presence of at least five compounds with flowery and sweet notes. The phenolic character can be similarly related to the presence of 12 volatile phenols. The berry fruit note of these wines is related to the additive effect of nine fruity esters. Ethanol exerts a strong suppression effect on fruitiness, whereas norisoprenoids and dimethy...

Analytical characterization of the aroma of five premium red wines. Insights into the role of odor families and the concept of fruitiness of wines.

L'elevage des vins en barriques modifie profondement leur expression aromatique.L'etude par chromatographie en phase gazeuse et spectrometrie de masse permet d'identifier plusieurs substances volatiles appartenant a la fraction phenolique des aromes.Les vins rouges presentent naturellement une composition complexe en phenols volatils alors que celle des vins blancs est plus simple. L'elevage sous bois entraine une augmentation notable des phenols deja presents ainsi que l'apparition de molecules specifiques au bois dechene brule.L'interaction des levures et des bacteries avec le bois est mise en evidence.Les vins rouges se caracterisent par une presence parfois abondante d'ethyl phenols, les vins blancs qui ne subissent pas la fermentation malolactique s'en differencient par l'abondancede vinyl phenols.L'etude sensorielle de chaque substance permet de demontrer le role negligeable de certaines : furfural, methyl-5-furfural, alcool furfurylique et le role exceptionnel joue par d'autres : cis et trans β-methyl-γ-octalactone, vanilline et dans certains cas ethyl-4-phenol et ethyl-4-gaiacol.+++Wood storage of wines changes profondly their aromatic expression.Several volatile substances from wines and oak woods phenolic fraction of aroma are identified by gas chromatography and mass spectrometry. Wood storage increases natural phenols concentration. Simultaneously specific burned wood molecules appear.Yeast and bacterial interaction with wood is demonstrated. Ethyl phenols are characteristic of red wines and vinyl phenols of white wines without malolactic fermentation.The sensorial analysis of each substance demonstrates the negligible intervention in wine aroma of furfural, 5-methyl-furfural, and furfuryl alcohol, and the important participation of cis and trans β-methyl-γ-octalactone, vanilin 4-ethyl-phenol and 4-ethyl gaiacol.

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Influence du bois sur certaines substances odorantes des vins

Au-dela de son action de cintrage, le chauffage du bois de chene provoque une thermodegradation de certains de ses composants. Les auteurs etudient l'influence de l'intensite de brulage du bois de chene sessile Quercus sessilis sur certains composes extractibles. Afin de se rapprocher des conditions d'extraction par un vin, le bois brule a differents degres est place au contact d'une solution hydroalcoolique modele.La thermolyse des principaux polymeres parietaux du bois, produit de nombreux composes volatils et odorants (aldehydes furaniques, phenols volatils, aldehydes phenols, phenyl cetones). La concentration en β-methyl-y-octalactone augmente notablement avec le chauffage du bois et simultanement les tanins hydrolysables sont en partie degrades.La chauffe legere ne produit que de faibles variations. La chauffe moyenne correspond au maximum de synthese de la majorite des composes aromatiques etudies. A partir et au-dela de la chauffe forte, les reactions de thermodegradation, mais tres vraisemblablement aussi une modification de la structure de la lignine vers une forme moins reactive, entrainent une diminution de l'ensemble des composes extractibles.

Incidence du traitement thermique du bois de chêne sur sa composition chimique. 2e partie : évolution de certains composés en fonction de l'intensité de brûlage

This study is dedicated to quantification, by gas chromatography combined with mass spectrometry, of some volatile compounds founded during ageing of sweet natural wines. Besides determination of the thresholds olfactory perception enable us knowing better the more active compound in sweet natural wines aroma. The results enable to know better volatile compounds which are able to produce ageing aromas characteristic of sweet natural wines. These products are always rich in sugar and grown up in a more or less oxidising environment. Logically, many of the compounds identified in this work (derived furanic compounds and many others) are linked with chemical like Maillard reactions between sugars and amino-acids. Others compounds as a sotolon need oxidising phenomena to increase in the environment. Comparatively, oldest Port wines have been analysed. The compounds measured in these Port wines also exist in French sweet natural wines of type Banyuls and Rivesaltes, keeped under oxidising environment. But the differences of concentrations in some compounds discriminate them from the Port wines.

Étude sur l'arôme des vins doux naturels non muscatés. 2e partie: Dosages de certains composés volatils intervenant dans l'arôme des vins doux naturels au cours de leur vieillissement

Pendant le sechage des merrains sur parc a l'air libre, on assiste a une profonde modification de la composition chimique et du profil aromatique du bois de chene. La teneur en eugenol, en aldehydes phenols et en Β-methyl-y-octalactone augmente regulierement pendant le vieillissement du bois. Principalement sous forme trans au debut du sechage, la Β-methyl-y-octalactone s'accumule finalement sous la forme cis plus aromatique. Dans le meme temps, on observe egalement une accumulation importante du precurseur inodore de Β-methyl-y-octalactone. L'intervention des micro-organismes frequemment isoles sur le bois en cours de sechage naturel sur la formation de composes aromatiques a ete etudiee. La culture de diverses moisissures isolees de bois en cours de sechage naturel sur extraits de bois et directement sur sciure de chene aboutit dans tous les cas a une forte diminution des teneurs en aldehydes phenols, notamment de la vanilline. En effet, tous les micro-organismes etudies (Penicilium sp., Trichoderma sp., Aureobasidium sp.) sont incapables de degrader la lignine car ils ne possedent pas d'activite ligninase. En revanche, ces champignons possedent une forte activite oxydo-reductase capable de reduire la vanilline en alcool vanillique inodore. En consequence, les aldehydes phenols apparaissant au cours du sechage naturel du merrain ne derivent pas d'une attaque enzymatique mais plus vraisemblablementde l'acidolyse et de l'oxydation chimique de la lignine du bois. Le stockage du bois a l'air libre en presence d'eau et d'oxygene doit permettre une evolution favorable de son potentiel aromatique tant que la vanilline et la cis Β-methyly-octalactone s'accumulent.

Monique Pons

Papers

The origin of ethylphenols in wines

Influence du bois sur certaines substances odorantes des vins

Incidence du traitement thermique du bois de chêne sur sa composition chimique. 2e partie : évolution de certains composés en fonction de l'intensité de brûlage

Étude sur l'arôme des vins doux naturels non muscatés. 2e partie: Dosages de certains composés volatils intervenant dans l'arôme des vins doux naturels au cours de leur vieillissement

Evolution de certains composés volatils du bois de chêne au cours de son séchage premiers résultats