 IVES 9 IVES Conference Series 9 Are my bubbles shrinking? A deeper look at oxygen desorption in wine

Are my bubbles shrinking? A deeper look at oxygen desorption in wine

Abstract

In the past decade, there has been an increasing amount of work dedicated to understanding micro-oxygenation in wine. Oxygen desorption into nitrogen gas is a similar process, but there has been little work focusing on this process and no work explicitly examining the effect that changes in wine components have on the process. The removal of excess dissolved oxygen from wine prior to bottling is commonly done in winemaking. A widely used method involves sparging nitrogen through the wine, in a process known as desorption. An indicator of the rate of oxygen desorption is the oxygen volumetric mass transfer coefficient (kla), which can be determined experimentally. The aim of the study was to examine how temperature, superficial gas velocity, and ethanol and glycerol levels affected the kla of dissolved oxygen into nitrogen gas in an aqueous solution of ethanol and glycerol. For the experiment, ethanol and glycerol concentrations were varied between 9 and 15% v/v, and 5 and 25 g/L respectively. The temperature was varied between 10 and 20C. The superficial gas velocity was varied between 0.15 and 0.32 cm/s. The experiments were performed in a 15L bubble column with a stone sparger. Before each run, the column was sparged with air in order to saturate the solution. Nitrogen was sparged until the concentration of oxygen was below 0.1 mg/L. DO levels were measured with an oxygen probe. The mean bubble size was determined using a high speed camera. The results showed that in the ranges tested, ethanol and glycerol concentration had no effect on the kla. A strong correlation was shown between superficial gas velocity, temperature and the kla The kla varied between 0.0139 and 0.0236s^-1. It was expected that the varying ethanol and glycerol concentrations would have an effect as the physico-chemical properties changed. Consequently an experiment was done in which ethanol concentration was incrementally increased from 0 to 10% v/v. It was found that raising the ethanol concentration to 0.1% increased the kla significantly relative to water. Beyond this the kla did not increase significantly. It was found that at ethanol concentrations of 0 to 0.02% the mean bubble size was nearly 2 times greater than at 0.05%. This suggests that the rise in kla is as a result of smaller bubbles. Preliminary tests performed on white wine showed that the kla was lower than in the ethanol/glycerol solutions under the same conditions. The kla range was 0.0094 and 0.012 s^-1 at 10 and 20 C respectively. The use of an aqueous solution of ethanol and glycerol overestimates the oxygen desorption rate in wine. This indicates that other unexamined properties within wine have a significant effect on kla. Oxygen desorption is significantly improved with the introduction of 0.05 % ethanol. Examining how wine proteins, acids and phenols affect the oxygen kla may give a better estimate of the desorption process in wine.

DOI:

Publication date: September 7, 2021

Issue: Macrowine 2021

Type: Article

Authors

Steven Sutton

Stellenbosch University,Prof. Wessel Du Toit, Stellenbosch University Prof. Robbie Pott, Stellenbosch University

Contact the author

Keywords

oxygen desorption, wine processing, volumetric mass transfer coefficient, nitrogen sparging, wine sparging, micro-oxygenation keyword3)

Citation

‘Cabernet Sauvignon’ (Vitis vinifera L.) berry skin flavonol and anthocyanin composition is affected by trellis systems and applied water amounts

Trellis systems are selected in wine grape vineyards to mainly maximize vineyard yield and maintain berry quality. This study was conducted in 2020 and 2021 to evaluate six commonly utilized trellis systems including a vertical shoot positioning (VSP), two relaxed VSPs (VSP60 and VSP80), a single high wire (SH), a high quadrilateral (HQ), and a guyot (GY), combined with three levels of irrigation regimes based on different crop evapotranspiration (ETc) replacements, including a 25% ETc, 50% ETc, and 100% ETc. The results indicated SH yielded the most fruits and accumulated the most total soluble solids (TSS) at harvest in 2020, however, it showed the lowest TSS in the second season. In 2020, SH and HQ showed higher concentrations in most of the anthocyanin derivatives compared to the VSPs. Similar comparisons were noticed in 2021 as well. SH and HQ also accumulated more flavonols in both years compared to other trellis systems. Overall, this study provides information on the efficacy of trellis systems on grapevine yield and berry flavonoid accumulation in a currently warming climate.

The modification of cultural practices in grapevine cv. Syrah, does it modify the characteristics of the musts?

The work shows the results of a year of experimentation (2020) in a Syrah variety vineyard in La Roda (Castilla-La Mancha, Spain). The trial approach was on a randomized block design with two factors: Irrigation (I) and Pruning (P).
Irrigation schedules were adjusted to apply amounts close to 1,500 m3/ha. With this provision, 2 different irrigation treatments were proposed: I1) Start of irrigation from pea-sized grape to post-harvest (providing at least 20 % of the total amount of irrigation water to be provided post-harvest); I2) Start of irrigation from pea-sized grape to harvest (usual irrigation practice in the study area). Pruning was proposed with two treatments, one at the end of January (P1), which is pruning on a conventional date; and P2) pruning carried out at the beginning of budding. In total, 4 repetitions were designed with 4 elementary plots, each one of them representing one of the proposed treatments (I1P1; I1P2; I2P1; I2P2). In total, 16 plots were worked on and each elementary plot consisted of 30 strains, distributed in 3 lines.
The productive response was evaluated with the yield results of the harvest harvested at 23 ºBrix. The qualitative response was measured in the musts through the indices of technological (acidity, pH and potassium) and phenolic maturity and aromatic compounds in free and glycosylated fractions. The treatments tested had, in general, an effect on the different variables analyzed.

Vineyards and clay minerals: multi-technique analytical approach and correlations with soil properties

Purpose of this research is to quantitatively assess the mineral component of vineyard soils, with particular attention to the mineralogical analysis of clays, which represent an element of high importance in the vineyard culture as well as in general agriculture. An X-ray diffraction (XRD) / thermogravimetric (TG) multi-technique analytical approach was developed, tested on soil samples taken from vineyards around the world. This codified analytical procedure was necessary to obtain precise qualitative and quantitative mineralogical data, globally comparable to distinguish the geopedological identity of the vineyards. Soil samples from vineyards of various locations were analysed, in very different geological conditions. The bulk-rock quantitative phase analysis (QPA) was obtained by the Rietveld method while the detailed composition of the clay-sized fraction was determined by modelling of the oriented X-ray diffraction patterns. The research provided a precise classification of the mineral component of soils, distinguishing the mineral phases of the clays and the so-called mixed-layer clay minerals. We found that the content in mixed layers can be directly correlated with the water retention and the cation exchange capacity of the soil, while the presence of other clayey minerals and phyllosilicates in this research did not affect this CEC parameter, which codes the fertility level of the soils. The study demonstrates that terroir, in particular soils formed in complex or very different geological conditions, can only be effectively interpreted by properly analysing its mineral phases, in particular the mixed-layer clay component. These are characteristic abiotic ecological indicators, which may have specific eco-physiological influences on the plant.

Use of multispectral satellite for monitoring vine water status in mediterranean areas

The development of new generations of multispectral satellites such as Sentinel-2 opens possibilities as to vine water status assessment (Cohen et al., 2019). Based on a three years field campaign, a model of Stem Water Potential (SWP) estimation on vine using four satellite bands in Red, Red-Edge, NIR and SWIR domains was developed (Laroche-Pinel et al., 2021). The model relies on SWP field measures done using a pressure chamber (Scholander et al., 1965), which is a common, robust and precise method to assess vine water status (Acevedo-Opazo et al., 2008). The model was mainly developed from from SWP measures on Syrah N (Laroche Pinel E., 2021).

A large scale monitoring was organized in different vineyards in the Mediterranean region in 2021. 10 varieties amongst the most represented in this area were monitored (Cabernet sauvignon N, Chardonnay B, Cinsault N, Grenache N, Merlot N, Mourvèdre N, Sauvignon B, Syrah N, Vermentino B, Viognier B). The model was used to produce water status maps from Sentinel-2 images, starting from the beginning of June (fruit set) up to September (harvest). The average estimated SWP for each vine was compared to actual field SWP measures done by wine growers or technicians during usual monitoring of irrigation programs. The correlations between mean estimated SWP and mean measured SWP were at the same level than expected by the model. (Laroche Pinel, 2021) The general SWP kinetics were comparable. The estimated SWP would have led to same irrigation decisions concerning the date of first irrigation in comparison with measured SWP.

Acevedo-Opazo, C., Tisseyre, B., Ojeda, H., Ortega-Farias, S., Guillaume, S. (2008). Is it possible to assess the spatial variability of vine water status? OENO One, 42(4), 203.
Cohen, Y., Gogumalla, P., Bahat, I., Netzer, Y., Ben-Gal, A., Lenski, I., … Helman, D. (2019). Can time series of multispectral satellite images be used to estimate stem water potential in vineyards? In Precision agriculture ’19, The Netherlands: Wageningen Academic Publishers, pp. 445–451.
Laroche-Pinel, E., Duthoit, S., Albughdadi, M., Costard, A. D., Rousseau, J., Chéret, V., & Clenet, H. (2021). Towards vine water status monitoring on a large scale using sentinel-2 images. remote sensing, 13(9), 1837.
Laroche-Pinel,E. (2021). Suivi du statut hydrique de la vigne par télédétection hyper et multispectrale. Thèse INP Toulouse, France.
Scholander, P.F., Bradstreet, E.D., Hemmingsen, E.A., & Hammel, H.T. (1965). Sap pressure in vascular plants: Negative hydrostatic pressure can be measured in plants. Science, 148(3668), 339–346.

Short-term relationships between climate and grapevine trunk diseases in southern French vineyards

[lwp_divi_breadcrumbs home_text="IVES" use_before_icon="on" before_icon="||divi||400" module_id="publication-ariane" _builder_version="4.19.4" _module_preset="default" module_text_align="center" module_font_size="16px" text_orientation="center"...