Relation between Fatty Acid Content and Its Evolution during Fermentation and Utilization of Free Amino Acids in Vacuum-Filtered Viura Must

Evolution of volatile compounds treated with selected non-Saccharomyces extracellular extract during Pinot noir winemaking in monsoon climate

The dynamic pattern of volatiles during Pinot Noir winemaking in monsoon climate with yeast extracellular extract (EE) treatment was analyzed. EE from selected Pichia fermentans and Rhodotorula mucilaginosa strains, and almond β-glucosidase were added after 12-h alcohol fermentation, and the volatiles were determined every 24 h by GC-MS. After 6-month storage, wine aroma was evaluated instrumentally as well as by well-trained panelists. Results showed that enzyme treatments improved the contents of both varietal and fermentative volatiles. The levels of C₆ compounds, terpenes, and higher alcohols increased constantly during alcohol fermentation, whereas acetates, short and medium chain fatty acid ethyl esters, phenylethyls, and fatty acids increased first, followed by gradual decrease. EE treatment retarded the decrease of fruity ester content in wine. Mathematical regression between wine aroma and volatiles showed that the relatively higher contents of acetates, ethyl esters, and C₁₃-norisoprenoids in 6-month EE-treated wine were responsible for the improvement in floral aroma intensity.

Effects of simple rain-shelter cultivation on fatty acid and amino acid accumulation in 'Chardonnay' grape berries

BACKGROUND

Fatty acids and amino acids are the precursors of aliphatic and aromatic volatile compounds, higher alcohols and esters. They are also nutrition for yeast metabolism during fermentation. However, few reports have been concerned about the effect of viticulture practices on the accumulation of fatty acids and amino acids in wine grapes. This study aimed to explore the accumulation of these compounds in developing Vitis vinifera L. cv. Chardonnay grape berries under two vintages, and compare the influences of the rain-shelter cultivation and open-field cultivation.

RESULTS

Fifteen fatty acids and 21 amino acids were detected in total. The rain-shelter cultivation led to an increase in the total concentration of fatty acids, and a decrease in the total concentration of amino acids compared with the open-field cultivation in 2012, while no significant difference was observed between two cultivation modes in 2013 vintage. Concentrations of palmitoleic acid, isoleucine and cysteine were significantly promoted in the rain-shelter grape berries, whereas those of tyrosine and ornithine were markedly reduced in both vintages.

CONCLUSION

The rain-shelter cultivation of wine grapes in the rainy region is beneficial for improving grape quality and fermentation activity by influence on the concentration of fatty acids and amino acids. © 2017 Society of Chemical Industry.

Influencia de la clarificación por sedimentación en el contenido de ácidos grasos en mostos garnacha y Viura y su evolución durante la fermentación / Influence of clarification by sedimentation on the content of fatty acids in garnacha and Viura musts and their changes during the fermentation

The influence of static sedimentation of garnacha and Viura musts on the concentration of fatty acids and their changes during fermentation is evaluated. A non-sedimented must was used as a control sample. The sedimentation of garnacha must reduced the concentration of saturated fatty acids (mainly stearic acid), although it did not totally eliminate any single one. During the first half of the fermen tation (up to 50% of sugar consumption) the medium-chain fatty acids excreted their highest concen tration in the sample being clarified. The long-chain fatty acids, both saturated and unsaturated, were consumed in both samples, although the saturated acids showed a higher rate of consumption in the contrul sample (57%) than in the sedimented sample (10%). The polyunsaturated fatty acids were consumed at a high rate in both samples. During the second half of the fermentation (from 50% sugar consumption until the end of the fermentation) the consumption of long-chain fatty acids, both saturated and unsaturated, was similar in the control sample and in the sedimented sample. The clarification of the Viura must reduced all the above unsaturated fatty acids, particularly linoleic (84%). In the first half of the fermentation, the consumption of long-chain fatty acids, both saturated and unsaturated, was greater in the control sample than in the sedimented sample; the same oc curred during the second half of the fermentation.

Influencia de la filtración a vacío en el contenido de cationes de un mosto de la variedad Viura y en su evolución durante la fermentación y conservación del vino / The influence of vacuum-filtration on the content of cations of a must of the Viura variety and on its evolution during the fermentation and the bottle-aging of wine

This work examines the influence of vacuum-filtration on the concentration of cations in a must from the Viura variety, and their changes during fermentation and bottle aging of the wine. The clarifica tion treatment eliminated potassium (17 %) while the concentrations of calcium and magnesium did not change. The sodium content in the filtered must increased through contamination with diatoma ceous earth. Filtration eliminated mainly iron (84 %), and to a lesser extent copper (17 %), but had no influence on the concentrations of zinc and manganese in the must. Most of the studied cations evolved in a similiar way during the fermentation process, both in the filtered must and in the control sample. Most of the concentrations of cations in the white wines stabilized by refrigeration and stored for one year in the bottle were higher in the sample control than in one from filtered must. However, in both cases the limits were within the normal limits outlined for wine.

SO(2) protects the amino nitrogen metabolism of Saccharomyces cerevisiae under thermal stress

Thermal stress conditions during alcoholic fermentation modify yeasts' plasma membrane since they become more hyperfluid, which results in a loss of bilayer integrity. In this study, the influence of elevated temperatures on nitrogen metabolism of a Saccharomyces cerevisiae strain was studied, as well as the effect of different concentrations of SO₂ on nitrogen metabolism under thermal stress conditions. The results obtained revealed that amino nitrogen consumption was lower in the fermentation sample subjected to thermal stress than in the control, and differences in amino acid consumption preferences were also detected, especially at the beginning of the fermentation. Under thermal stress conditions, among the three doses of SO₂ studied (0, 35, 70 mg l⁻¹ SO₂), the highest dose was observed to favour amino acid utilization during the fermentative process, whereas sugar consumption presented higher rates at medium doses.

Use of nitrogen compounds in spontaneous and inoculated wine fermentations

In this paper the use of nitrogen compounds in garnacha must inoculated with active dry wine yeast Saccharomyces cerevisiae subsp. cerevisiae strain Na33 has been studied. The results are compared to garnacha must fermented with indigenous yeasts (control must). In the samples where the inoculated yeast predominated, no qualitative differences were appreciated in the use of amino acids with respect to the control samples, although there were quantitative differences. In the musts where the Na33 strain dominated, a lesser quantity of amino acids were consumed at the beginning of fermentation than in the control samples. For that reason, probably, this yeast showed problems in competing for the nitrogen nutrients of the must; this could have made its implantation in one of the inoculated samples more difficult. At the end of fermentation the Na33 strain continued to consume amino acids at high concentrations of ethanol. Its high tolerance to this toxic could be favored by the production and rehydration of dry wine yeast in the presence of air.