miércoles, 1 de octubre de 2014

Diffusion of oxygen throughout the stave of a barrel

This time we have filmed the diffusion of oxygen throughout the stave of a barrel


For the first time, the dissolved oxygen dynamics and two-dimensional distribution of oxygen within the thickness of a barrel stave have been demonstrated. Wood water saturation is a key factor in the diffusion of oxygen through wood with barrel OTR decreasing during the ageing period.

This work has been just pulished in the Australian Journal of Grape and Wine Research in an article entittled Imaging of oxygen transmission in the oak wood of wine barrels using optical sensors and a colour camera

Background and Aims: Wine ageing in oak barrels is characterised by a series of physical and chemical processes, in many of which oxygen plays an important role. Therefore, to control better this phase of winemaking, it is not enough to know that oxygen penetrates into the barrel through the oak wood; it is also important to know how oxygen moves through the wood into the barrel, in what quantity and which factors are involved.

Methods and Results: We attempted to answer these questions with a high-resolution colour camera, ratiometric calibration and a planar optode with which the two-dimensional distribution and dynamics of oxygen within an oak barrel stave were studied. It was possible to make two-dimensional measurements when combined with microscopic optics and an appropriate camera, which permitted the measure of the transmission of oxygen into the barrel through the oak stave and the study of the mechanism of transmission. The trial was applied to both dry and wet oak wood, which revealed how the moisture content of the wood influenced oxygen transmission. The measurements were made in an airtight chamber under controlled temperature and pressure, which accurately reproduced the conditions of a stave in an oak wood barrel filled with liquid.

Conclusion: We were able to visualise the diffusion of oxygen in both dry and in wet French oak wood under conditions similar to those operating in a barrel. The moisture content of the wood influenced the oxygen transmission rate (OTR) through the wood.

lunes, 1 de septiembre de 2014

Oxygen pick-up in wine making

The influence of selected winemaking equipment and operations on the concentration of dissolved oxygen in wines

by Juan F. Calderón, María del Alamo-Sanza, Ignacio Nevares, Felipe Laurie

Oxygen has a determining effect on the quality and longevity of wines. In spite of its importance, there are only a limited number of reports examining the levels of dissolved oxygen during wine production and the enrichments produced by different operations. In this study, the contribution of selected winemaking equipment and operations (i.e., pumping, centrifugation, tartrate stabilization, filtration and bulk wine transportation) on the concentration of dissolved oxygen in wines was assessed using a photoluminescence-based oxygen meter. For example, winemaking equipment such as diatomaceous earth filtration and membrane filtration caused dissolved oxygen increases between 0.100 and 0.200 mg/L, and pad filtration and centrifugation showed average oxygen enrichments of approximately 0.350 mg/L. However, operations such as filtration with rotary vacuum equipment and continuous tartrate stabilization produced oxygen enrichments up to ~2.8 mg/L. A better awareness of the levels of oxygen incorporated by different winemaking practices will help incorporate the necessary safeguards to protect wines from oxidation and estimate the magnitude of the cumulative exposure to oxygen during winemaking.

jueves, 21 de agosto de 2014

OTR dynamics in new oak barrels: A new approach


Recent Advances in the evaluation of the oxygen transfer rate in oak barrels


Few weeks ago we publised an article related to wine ageing in HDPE tanks, now we came back to you with a deep study focused in the evolution of the OTR of new oak barrels. The entry of atmospheric oxygen into wine barrels is one aspect of the wine aging process. The oxygen transfer rate regulates changes in wine and can affect aging rates because some barrels may result in greater wine oxygenation. This study measured the transfer rate and oxygen distribution within a barrel. The analysis indicated the presence of a dissolved oxygen concentration gradient in the liquid, with greater concentrations near the bung. The study of the transfer rate of oxygen over time, in 12 barrels of different types, showed that wetting wood reduces oxygen diffusion and the oxygen transfer rate. These results are the first to determine the kinetics of oxygen entry into wine barrels and can be used to quantify the annual rate of oxygen entry in wine barrels.

This work is fully developed in our last manuscript entittled Recent advances in the evaluation of the oxygen transfer rate in oak barrels in the Journal of Agricultural and Food Chemistry.

jueves, 31 de julio de 2014

We tested the Flextank vessels, now named Flexcube

High-density polyethylene tanks for red wine maturing with oak staves

Recently our group has published the analysis of the performance of the high-density polyethylene tanks from Flextank (Melbourne, Australia). The work has been just accepted in the Journal of the Science of Food and Agriculture where you can read the whole paper Wine evolution and spatial distribution of oxygen during storage in high-density polyethylene tanks.



Background

Porous plastic tanks are permeable to oxygen due to the nature of the polymers with which they are manufactured. In the wine industry, these types of tanks are used mainly for storing wine surpluses. Lately, their use in combination with oak pieces has also been proposed as an alternative to mimic traditional barrel aging.

Results

In this study, the spatial distribution of dissolved oxygen in wine-like model solution, and the oxygen transfer rate (OTR) of high-density polyethylene tanks (HDPE), was analysed by means of a non-invasive opto-luminescence detector. Also, the chemical and sensory evolution of red wine, treated with oak pieces, and stored in HDPE tanks was examined and compared against traditional oak barrel aging. The average OTR calculated for these tanks was within the commonly accepted amounts reported for new barrels. With regards to wine evolution, a number of compositional and sensory differences were observed between the wines aged in oak barrels and those stored in HDPE tanks with oak barrel alternatives.

Conclusion

The use of HDPE tanks in combination with oak wood alternatives is a viable alternative too for ageing wine.

viernes, 13 de junio de 2014

El oxígeno en la crianza del vino tinto




El pasado 16 de enero de 2014, en el museo Würth de La Rioja se celebró una jornada sobre el oxígeno y el vino. Todas las conferencias fueron de gran nivel y las podéis encontar en la web de Coloquio Ciencia y Vino.

De entre las conferencias queremos destacar la ofrecida por nuestro grupo que versaba sobre el oxígeno en la crianza del vino tinto, y más concretamente sobre los últimos avances que desde UVaMOX hemos realizado en el estudio en detalle de la barrica de roble. En concreto en esta presentación se muestra la visualización de la difusión del oxígeno a través de la duela de roble en la situación de madera seca y lo que es más interesante cuando la madera está humedecida. Este punto es importante ya que hasta ahora las diferentes teorías que se han formulado despreciaban la entrada de oxígeno por la madera. Esperamos que la disfrutéis.




viernes, 24 de enero de 2014

¿Miden bien nuestros sistemas de medida de oxígeno disuelto?

Investigación y corrección de las interferencias de etanol, azúcar y fenoles en la medida del oxígeno disuelto en vino

UVaMOX  

 

El oxígeno disuelto en vinos es un parámetro que se mide de forma habitual para el control y seguimiento de diferentes procesos enológicos. En el mercado encontramos equipos de medida basados en diferentes tecnologías y con prestaciones diferentes, lo que permite al usuario elegir el equipo que mejor se adapta a sus necesidades. Sin embargo, el mosto y el vino son muestras que presentan una composición compleja y variable con el tiempo, aspecto que unido a la importancia de las condiciones atmosféricas, hace necesario tener en cuenta una serie de factores para realizar una medida correcta del oxígeno disuelto presente en la muestra.

 Corrección del error cometido en la medida



Aunque en las especificaciones técnicas de la mayoría de los sensores no se establece cross-sensitivity al etanol o a otros componentes mayoritarios de vinos, el uso continuado de equipos de medida de oxígeno disuelto en enología ha hecho sospechar que sí existen ciertas interferencias en la medida del oxígeno disuelto debidas a estos compuestos, y por ello se hace necesario compensar la medida con el nivel de concentración de estos analitos. Este trabajo evalúa el efecto que el contenido en etanol, azúcar y fenoles tiene sobre la medida del oxígeno disuelto en vinos, y establece un valor de compensación para cada equipo con el fin corregir el error de la medida. En la figura se reflejan los errores cometidos en las medidas realizadas en vinos reales antes (naranja) y después de la corrección (azul) con los sistemas ópticos estudiados. Si quieres leer este trabajo en toda su extensión, lo puedes encontrar Science Direct