Changes in the volatile composition of red wines during aging in oak barrels due to microoxygenation treatment applied before malolactic fermentation

Microoxygenation is a wine-making technique consisting in the addition of small and controlled amounts of oxygen. This study has examined the effect of this technique on the volatile composition of two red single variety wines during two successive vintages. The microoxygenation treatment was applied at the end of alcoholic fermentation and before beginning malolactic fermentation. Once the microoxygenation treatment had finished, wines were aged in new American oak barrels for 12 months. The results obtained showed that the microoxygenation treatment did not cause significant changes in the varietal and fermentation volatile compounds, however microoxygenation slowed down the extraction of some of the volatile compounds extracted from wood. A varietal and vintage effect was also observed for some of the compounds studied.     

Antioxidant potential of single-variety red wines aged in the barrel and in the bottle

Wine constitutes a dynamic system in continuous evolution, in which numerous reactions involving polymerization and condensation take place between its phenolic compounds during the ageing process, which undoubtedly affect its structure and, very probably, its antioxidant effect. This study set out to evaluate the effect of ageing on the antioxidant potential of wine. A group of 162 wines were studied, of varying ages, which had undergone different ageing processes, both in the barrel and in the bottle, and which were prepared from different grape varieties and vintages. Total antioxidant capacity (ABTS, DPPH, DMPD, ORAC and FRAP), scavenger activity (HRSA and SRSA) and the biomarkers of oxidative stress (DNA-damage and ABAP-LP) were all analysed. The assay methods showed different behaviours for the same wines, thus the young wines presented higher indices for ABTS, DPPH and DMPD, whereas those that were aged showed higher indices for ABAP-LP and ORAC. Finally, the antioxidant potential of the wines in the study appeared not to be influenced by other factors, such as microoxygenation or grape variety.     

Colour stabilization of red wines by microoxygenation treatment before malolactic fermentation

Microoxygenation allows the addition of small, continuous and controlled amounts of oxygen, in order to improve wine quality. Then, the effect of this treatment on colour stabilization and phenolic composition was studied. Four single varietal red wines were elaborated during three consecutive vintages. One part of them was microoxygenated before malolactic fermentation, the other part being maintained in stainless steel tanks without microoxygenation.     

Antioxidant profile of red-single variety wines microoxygenated before malolactic fermentation

The controlled addition of oxygen before malolactic fermentation involves stability of wine colour and an improvement in their organoleptic quality. This study has examined its effect on the “in vitro” antioxidant profile of a variety of Spanish red-single variety wines of different ages. Total antioxidant capacity scavenger activity and the biomarkers of oxidative stress were all analysed. Neither antioxidant capacity, nor scavenger activity were influenced by the microoxygenation. However, the biomarkers of oxidative stress showed some effect of this technique. The controlled addition of small amounts of oxygen produced an increase in the prevention of DNA-damage and seems to decrease the capacity to inhibit lipid peroxidation. The effect on the capacity to protect DNA-damages was statistically significant in the groups of young and one year old wines, where microoxygenated wines showed higher values than their respective control ones. Furthermore, the effect on the prevention of lipid peroxidation was only qualitative, any statistical significant difference was found. A varietal effect was observed in analyzing the results, being Tinta del País wines the most influenced by this technique.     

微氧作用下天然酯变压器油热老化特性研究

天然酯变压器油因不饱和脂肪酸含量较高而易氧化,而变压器因储油罐与空气作用或密封设备产生泄漏等原因,会导致油中溶解微量的氧气.基于此,文章研究了微氧作用下天然酯变压器油的热老化特性,并分析了不同老化时间下油样的电气性能、油色谱特性以及两者之间的皮尔逊相关系数.结果 表明:适时微氧作用能在一定程度上延缓天然酯变压器油电气性能的降低;天然酯变压器油纸绝缘热老化的特征气体为CO2和C2 H6;天然酯变压器油的电气性能与油色谱中CO2-C2H6(油样中溶解的CO2与C2H6的百分比之差)之间存在强相关性.