Post Nº 100

This is the post number 100. One hundred of weekends that I spend writing, reading, illustrating, editing and publishing the posts. The time that I spent do it is just part of the time I stole to the family, special to my youngest daughter, so today I decided to involve her in this project. The illustration is her authorship.

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Enological repercussions of non-Saccharomyces species in wine biotechnology

The use of non-Saccharomyces yeasts in enology has increased since the beginning of the current century because of the potential improvements they can produce in wine sensory quality. Several review articles have described the potential of some non-Saccharomyces species and the suitable criteria to select them according to the effects of the species on wine color, aroma, body or structure.

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Exploring the diversity of a collection of native non-Saccharomyces yeasts to develop co-starter cultures for winemaking

Winemaking involves the inoculation of Saccharomyces cerevisiae starter cultures in grape musts. Currently other yeast species are being investigated as co-starters with the aim of improving wine complexity. In this post the authors summarize the results of a study carried out to discover new strains that can be used to enhance wine quality. The results show that wine quality depend on both species and strains which indicate that mixed fermentation strategies using new generation of co-starters can improve the overall quality of regional wine.

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Immobilization of yeasts in oak chips or cellulose powder for use in bottle-fermented sparkling wine

Sparkling wine production comprises two successive fermentations performed by Sacharomyces cerevisiae strains. This post is about a project aimed to develop yeast immobilisation processes on two wine-compatible supports, study the effects of yeast type (IOC 18–2007 and 55A) and the immobilisation support type (oak chips and cellulose powder) on the fermentation kinetics, the deposition rate of lees and the volatile composition of the finished sparkling wine; compare the fermentation parameters of the wines inoculated with immobilised or non-immobilised cells.
According with the last post of the year the use of immobilization supports reports the advantages of rapid yeast elimination and not adding bentonite and does not have a negative impact on the wine sensory profile.

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Understanding the green character in red wines by a sensory-directed approach

This post results from a study done with the aim of define the “green character” of red wines and characterise the groups of molecules potentially involved in that perception. Wines were screened by wine experts for different levels of green character. Phenolic fractions were obtained by liquid chromatography (LC) and further submitted to sensory and chemical characterisation. The volatile fraction was screened by semipreparative LC, gas chromatography-olfactometry (GC-O) and quantitative analysis. The green character was associated to vegetal aroma, astringency, green and dry tannins. No specific aroma compounds were identified in the GC-O evaluation of green wines, however the wines contained higher levels of fusel alcohols. The interaction between isoamyl alcohol and the anthocyanin-derivative fraction and/or tannins is suggested to be involved in the formation of green character in red wines.

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Modulation of wine astringency by mannoproteins –salivary protein/mannoprotein/polyphenol interactions

The oral sensation called astringency is commonly described as drying, roughing and puckering in the mouth epithelia. Since some polyphenols are able to bind salivary proteins, namely PRPs, they can form insoluble tannin-protein precipitates in the mouth, causing a loss of lubrication and increased friction in the oral cavity, which would explain its astringency. This mechanism is thought to be the main responsible of wine astringency. A recent study has evaluated the effect of the addition of yeast mannoproteins (MP) on the interaction between a flavonol glucoside (quercetin 3-O-glucoside) and human salivary proteins, combining sensory analysis and analytical techniques such as quenching fluorescence, dynamic light scattering and isothermal titration calorimetry. Results obtained indicate the existence of interactions between mannoproteins and flavonols but also between mannoproteins and salivary proteins, suggesting a possible formation of protein/polyphenol/polysaccharide ternary complex that probably affects the astringency perception.

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Professional highlights in wine area

Today ended the “Mostra da Universidade do Porto” that is an annual exhibition where the University of Porto schools promote their educational offer. The most repeated question made by high school students was “What can I do with that degree?”. I always answer, “All that you want”. I really believe it! Someone with cognitive and hard work capacities, can do anything with the tools acquire during the course. Joining creativity and courage, then are congregated the conditions to a brilliant career. Of course, that a personal career also depends in the networks that each one can establish.

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