Macrowine 2021
IVES 9 IVES Conference Series 9 Application of ultrasonic and refractometric measurements in enological samples and related model solutions

Application of ultrasonic and refractometric measurements in enological samples and related model solutions

Abstract

AIM: The refractive index is a basic optical property of materials and a key tool for the determination of major components in musts, such as sugars. Ultrasonic based technology is emerging as a well-suited tool for monitoring food processes and quality, and in particular it has been applied in predicting the alcohol content and measuring the ultrasonic velocity in enological products. The aim of this study is to combine the applications of these two technologies to quantify alcohol and residual sugar in real and model enological samples. The effects of major wine and must components on the combined application of these analytical tools are investigated.

METHODS: Refractometric and sonic Brix values were determined using a LP10 sensor (Maselli Misure, Parma, Italy) working at controlled temperature. The selection of the real enological samples for the study has been made during the 2020 harvest in South Tyrol (Italy). The model solutions were prepared at different combinations of different levels of ethanol in water, glucose, tartaric acid, malic acid and gallic acid as major wine components. For these model solutions, firstly the levels of each component were chosen upon a likelihood criterium, then to reduce the number of analyses to run. A refined randomized selection of these combinations was chosen according to a D-Optimal experimental design, calculated on the R-based application CAT, with a large enough number of selected experiments to ensure representativeness. The statistical analysis of the results for the real and model samples has been performed on CAT and XLStat (Addinsoft, France).

RESULTS: A statistical analysis of the obtained results allowed to investigate the effects of the major constituents on the Brix and alcohol determinations by combined refractometric and acoustic analyses, in real and model enological samples. The calculated models showed that the effects of interactions between variables/chemical components and non-linear contributions cannot be a priori ruled out in order to accurately explain the instrumental responses to the variations of these major components. As an alternative, the evaluation of separate models for more limited experimental domains (e.g. only musts, only dry wines or musts undergoing fermentation) is also discussed. The effects of the residual sugar and alcohol content on the determination of refractive and sonic Brix are discussed in detail.

CONCLUSIONS

In samples collected during fermentations or in wines, the application of this combined technique for residual sugar and alcohol determinations could be feasible, provided that the full dependence of these refractometric and acoustic parameters on the major sample components and their interactions is well understood, and the related mathematical models validated over the widest possible range of enological samples. Some mathematical models have been proposed and discussed along with validation.

DOI:

Publication date: September 7, 2021

Issue: Macrowine 2021

Type: Article

Authors

Matteo Sesenna

Faculty of Science and Technology, Free University of Bozen-Bolzano, Piazza Università 5, 39100 Bolzano, Italy; Oenolab, NOITechpark, via Alessandro Volta 13, 39100 Bolzano BZ, Italy,Edoardo, LONGO, Faculty of Science and Technology, Free University of Bozen-Bolzano, Piazza Università 5, 39100 Bolzano, Italy; Oenolab, NOITechpark, via Alessandro Volta 13, 39100 Bolzano BZ, Italy  Alessandro, FORNASIER, University of Turin (Italy), DISAFA – Food Science and Technology  Luca ROLLE University of Turin (Italy), DISAFA – Food Science and Technology  Ulrich PEDRI, Institute for Fruit Growing and Viticulture, Laimburg Research Center, Laimburg 6, I-39051 Pfatten, Italy  Danila CHIOTTI, Institute for Fruit Growing and Viticulture, Laimburg Research Center, Laimburg 6, I-39051 Pfatten, Italy  Emanuele, BOSELLI, Faculty of Science and Technology, Free University of Bozen-Bolzano, Piazza Università 5, 39100 Bolzano, Italy; Oenolab, NOITechpark, via Alessandro Volta 13, 39100 Bolzano BZ, Italy

Contact the author

Keywords

refractometric brix; ultrasonic brix; sugars; ethanol

Citation

Related articles…

Impact of long term agroecological and conventional practices on subsurface soil microbiota in Macabeu and Xarel·lo vineyards

There is a growing trend on the transition from conventional to agroecological management of vineyards. However, the impact of practices, such as reduced-tillage, organic fertilization and cover crops, is not well-understood regarding the soil microbial diversity, and its relationship with the soil physicochemical properties in the subsurface depth near the rooting zone. Soil bacterial diversity is an important contributor towards plant health, productivity and response to environmental stresses. A field experiment was conducted by sampling subsurface soil bacterial community (NGS and qPCR) near to the root zone of Macabeu and Xarel·lo vineyards, located at the Penedes. 3 organic (ECO) and 3 conventional (CON) vineyards, with more than 10 years of respective management were sampled (n=5 each plot). ECO practices did not affect bacterial and fungal abundance but increased significantly the ammonium oxidizing bacteria and alpha-diversity (Inv.Simpson). Interestingly beta-diversity was significantly affected by the management strategy. ANOSIM-tests revealed a significative effect of the management (ecological vs conventional) and plot, on the soil microbial structure (ASV abundance). Main phyla depicted were Proteobacteria, Actinobacteria and Acidobacteria, whose relative abundances were not affected by the management. EdgeR assay revealed a significant increase of Cyanobacteria and decrease of Gemmatimonadetes and Firmicutes phyla in ECO. Interestingly, the grapevine variety was not correlated with the soil microbial community structure. Mantel-test revealed an important correlation (Spearman) of some physicochemical parameters with the soil microbiota structure, in order of importance: texture, EC, pH Ca/Mg, Mg/P, K+, Mg2+, Ca2+, SO42-, and OM. N-NH4 and NTK, which were higher in the ECO managed soils, did not correlated significantly with the soil microbiome population. The results revealed the importance of combining a deep physicochemical characterization of each replicate with the microbial diversity assessment to gain better insights on the relationship between soil microbiome and vineyard management.

Biodiversity in the vineyard agroecosystem: exploring systemic approaches

Biodiversity conservation and restoration are essential for guarantee the provision of ecosystem services associated to vineyard agroecosystem such as climate regulation trough carbon sequestration and control of pests and diseases. Most of published research dealing with the complexity of the vineyard agroecosystems emphasizes the necessity of innovative approaches, including the integration of information at different temporal and spatial scales and development of systemic analysis based on modelling. A biodiversity survey was conducted in the Franciacorta wine-growing area (Lombardy, Italy), one of the most important Italian wine-growing regions for sparkling wine production, considering a portion of the territory of 112 ha. The area was divided into several Environmental Units (EUs), defined as a whole vineyard or portion of vineyard homogenous in terms of four agronomic characteristics: planting year, planting density, cultivar, and training system. In each EU a set of compartments was identified and characterised by specific variables. The compartments are meteorology, morphology (altitude, slope, aspect, row orientation, and solar irradiance), ecological infrastructures and management. The landscape surrounding EU was also characterised in terms of land-use in a buffer zone of 500 m. For each component a specific methodology was identified and applied. Different statistical approaches were used to evaluate the method to integrate the information related to different compartments within the EU and related to the buffer zone. These approaches were also preliminarily evaluated for their ability to describe the contribution of biodiversity and landscape components to ecosystem services. This methodological exploration provides useful indication for the development of a fully systemic approach to structural and functional biodiversity in vineyard agroecosystems, contributing to promote a multifunctional perspective for the all wine-growing sector.

Elucidating vineyard site contributions to key sensory molecules: Identification of correlations between elemental composition and volatile aroma profile of site-specific Pinot noir wines

The reproducibility of elemental profile in wines produced across multiple vintages has been previously reported using grapes from a single scion clone of Vitis vinifera L. cv. Pinot noir. The grapevines were grown on fourteen different vineyard sites, from Oregon to southern California in the U.S.A., which span distances from approximately hundreds of meters to 1450 km, while elevations range from near sea level to nearly 500 m. In addition, sensorial (i.e. aroma, taste, and mouthfeel) and chemical (i.e. polyphenolic and volatile) differences across the different vineyard sites have also been observed among these wines at two aging time points. While strong evidence exists to support that grapes grown in different regions can produce wines with unique chemical and sensorial profiles, even when a single clone is used, the understanding of growing site characteristics that result in this reproducible differentiation continues to emerge. One hypothesis is that the elemental profile that a vineyard site imparts to the grape berries and the resulting wine is an important contributor to this differentiation in chemistry and sensory of wines. For example, various classes of enzymes that catalyze the formation of key aroma compounds or their precursors require specific metals. In this work, we begin to report correlations between elemental and volatile aroma profiles of site-specific Pinot noir wines, made under standardized winemaking conditions, that have been previously shown to be distinguished separately by these chemical analyses.

Rootstock regulation of scion phenotypes: the relationship between rootstock parentage and petiole mineral concentration

Grapevine is grown as a graft since the end of the 19th century. Rootstocks not only provide tolerance to Phylloxera but also ensure the supply of water and mineral nutrients to the scion. Rootstocks are an important mean of adaptation to environmental conditions, because the scion controls the typical features of the grapes and wine. However, among the large diversity of rootstocks worldwide, few of them are commercially used in the vineyard. The aim of this study was to investigate the extent to which rootstocks modify the mineral composition of the petioles of the scion. Vitis vinifera cvs. Cabernet-Sauvignon, Pinot noir, Syrah and Ugni blanc were grafted onto 55 different rootstock genotypes and planted in a vineyard as three replicates of 5 vines. Petioles were collected in the cluster zone with 6 replicates per combination. Petiolar concentrations of 13 mineral elements (N, P, K, S, Mg, Ca, Na, B, Zn, Mn, Fe, Cu, Al) at veraison were determined. Scion, rootstock and the interaction explained the same proportion of the phenotypic variance for most mineral elements. Rootstock genotype showed a significant influence on the petiole mineral element composition. Rootstock effect explained from 7 % for Cu to 25 % for S of the variance. The difference of rootstock conferred mineral status is discussed in relation to vigor and fertility. Rootstocks were also genotyped with 23 microsatellite markers. Data were analysed according to genetic groups in order to determine whether the petiole mineral composition could be related to the genetic parentage of the rootstock. Thanks to a highly powerful design, it is the first time that such a large panel of rootstocks grafted with 4 scions has been studied. These results give the opportunity to better characterize the rootstocks and to enlarge the diversity used in the vineyard.

Spatial determination of areas in the Western Balkans region favorable for organic production

In problematic conditions for production of grapes and wine caused by the COVID-19 pandemic and the resulting occurrence of wine surpluses, producers are increasingly turning to the innovative viticulture and winemaking of products that are more appealing to the market and the consumers. On the other hand, consumption of the food safety or organic products, and therefore of organic grapes and wine, is increasingly common in the world, in particular in Europe. The Regional Rural Development Standing Working Group (SWG RRD), as a regional intergovernmental organization gathers actors in the viticulture and winemaking sector from states and territories of the Western Balkans (South-East Europe) in the Expert Working Group for Wine, with the aim of improving viticulture and winemaking in this region through joint activities. In accordance with the aforementioned, the SWG RRD is working on advancing organic production of grapes and wine, and on recognition of specificities of the terroir of wine-growing areas in Western Balkans. In addition, as part of the project “Facilitation of Exchange and Advice on Wine Regulations in Western Balkan Countries” helmed by the German Federal Ministry of Food and Agriculture, in addition to harmonization of relevant legislation with EU regulations, efforts are being invested towards recognition of organic wines. Within activities and project implemented by this organization, expert analyses and scientific research of the terroir of Western Balkans were carried out, and some of the results are presented in this paper.