Macrowine 2021
IVES 9 IVES Conference Series 9 Impact of mannoproteins structural features on the colloid stability when facing different kinds of wine polyphenols

Impact of mannoproteins structural features on the colloid stability when facing different kinds of wine polyphenols

Abstract

The aim was to study the impact of structural features in the polysaccharide moiety of mannoproteins on their interaction with polyphenols and the formation of colloidal aggregates. To this end, mannoproteins fractions were extracted from four different yeast strains: a commercial enological strain (MP-com), the wild-type BY4742 strain (MP-WT) and its mutants ΔMnn4 (MP-Mnn4) and ΔMnn2 (MP-Mnn2). The Mnn4p and Mnn2p are responsible for mannosyl-phosphorylation and branching of the N-glycosylation backbone [1]. Enzymatic extraction was performed using a commercial Endo-beta-1,3-Glucanase of Trichoderma sp. (E-LAMSE, Megazym)[2]. Mannoprotein fractions were thoroughly characterized by composition of their polysaccharide and protein moieties, branching degree, net charge, molecular weight distribution, static and dynamic molecular parameters [3]. Their interactions with seed tannins and a pool of red wine polyphenols and the formation of colloidal aggregates were studied in model solutions at different polyphenol/mannoprotein ratios through Dynamic Light Scattering (DLS). Model solutions were followed during one month. The number and size distribution of colloidal aggregates was determined by Nanoparticle Tracking Analysis (NTA).The four Mannoprotein fractions had broad and high molecular weight distributions, as well as similar protein, polysaccharide mass % and amino acid composition. However, they showed different proportions of mannose and glucose and the structural characterization of the polysaccharide moiety confirmed the expected differences between MP-WT, MP-Mnn2, and MP-Mnn4. DLS and NTA experiments indicated a two-step interaction process between seed tannins and mannoproteins: an immediate formation of colloidal aggregates (150-300 nm), followed by a very progressive evolution related to a reversible aggregate flocculation. The number, dispersity and extent of flocculation were dependent on the tannin/MP ratio. So far, no notable differences were evidenced between the four MP fractions. With the polyphenol pool of red wine, neither DLS nor NTA experiments were able to evidence the formation of colloidal aggregates. This does not mean that interactions do not exist[4,5]. Although the mannoproteins used had different polysaccharide compositions, structures, and properties, no difference in terms of colloidal behavior when in solution with tannins or wine polyphenols was evidenced by the methods applied. Thus, neither the absence of mannosyl phosphate groups (MP-Mnn4) nor the absence of branching of the outer chains of the N-glycosylated carbohydrate structures (MP-Mnn2) seems to play a determining role in the colloidal behavior of mannoproteins in the presence of seed tannins or red wine polyphenols.

DOI:

Publication date: September 14, 2021

Issue: Macrowine 2021

Type: Article

Authors

Saul Assunção Bicca

UMR-SPO, University of Montpellier, INRAE, Montpellier Supagro, Montpellier, France,Thierry, DOCO, UMR-SPO, University of Montpellier, INRAE, Montpellier Supagro, Montpellier, France Céline, PONCET-LEGRAND, UMR-SPO, University of Montpellier, INRAE, Montpellier Supagro, Montpellier, France Pascale, WILLIAMS, UMR-SPO, University of Montpellier, INRAE, Montpellier Supagro, Montpellier, France Julie MEKOUE N’GUELA, UMR-SPO, University of Montpellier, INRAE, Montpellier Supagro, Montpellier, France & Lallemand SAS, Blagnac, France Aude VERNHET, UMR-SPO, University of Montpellier, INRAE, Montpellier Supagro, Montpellier, France

Contact the author

Keywords

mannoproteins, colloidal stability, wine interactions

Citation

Related articles…

Climate ethnography and wine environmental futures

Globalisation and climate change have radically transformed world wine production upsetting the established order of wine ecologies. Ecological risks and the future of traditional agricultural systems are widely debated in anthropology, but very little is understood of the particular challenges posed by climate change to viticulture which is seen by many as the canary in the coalmine of global agriculture. Moreover, wine as a globalised embedded commodity provides a particularly telling example for the study of climate change having already attracted early scientific attention. Studies of climate change in viticulture have focused primarily on the production of systematic models of adaptation and vulnerability, while the human and cultural factors, which are key to adaptation and sustainable futures, are largely missing. Climate experts have been unanimous in recognising the urgent need for a better understanding of the complex dynamics that shape how climate change is experienced and responded to by human systems. Yet this call has not yet been addressed. Climate ethnography, coined by the anthropologist Susan Crate (2011), aims to bridge this growing disjuncture between climate science and everyday life through the exploration of the social meaning of climate change. It seeks to investigate the confrontation of its social salience in different locations and under different environmental guises (Goodman 2018: 340). By understanding how wine producers make sense of the world (and the environment) and act in it, it proposes to focus on the co-production of interdisciplinary knowledge by identifying and foreshadowing problems (Goodman 2018: 342; Goodman & Marshall 2018). It seeks to offer an original, transformative and contrasted perspective to climate change scenarios by investigating human agency -individual or collective- in all its social, political and cultural diversity. An anthropological approach founded on detailed ethnographies of wine production is ideally placed to address economic, social and cultural disruptions caused by the emergence of these new environmental challenges. Indeed, the community of experts in environmental change have recently called for research that will encompass the human dimension and for more broad-based, integrated through interdisciplinarity, useful knowledge (Castree & al 2014). My paper seeks to engage with climate ethnography and discuss what it brings to the study of wine environmental futures while exploring the limitations of the anthropological environmental approach.

Analysis of some environmental factors and cultural practices that affect the production and quality of the Manto Negro, Callet and Prensal Blanc varieties

45 non irrigated vineyards distributed in the DO (Denomination) Pla i Llevant de Mallorca and the DO Binissalem Mallorca were used to investigate the characteristics of production and quality and their relationships certain environmental factors and cultural practices. The grape varieties investigated are autochthonous to the island of Mallorca, Manto Negro and Callet as red and Prensal Blanc as white. All plants were measured for four consecutive years in the main production and quality parameters. Among the environmental factors, the type of soil has been studied, more specifically its water retention capacity, the planting density, the age of the vineyard and the level of viral infection. The presence or absence of virus seems to have no effect on any component studied in the varieties studied. For the white variety Prensal Blanc age is negatively correlated with production and the number of bunches, nevertheless it does not cause any effect on the required quality parameters. However, for the red varieties Callet and Manto Negro, the age of the plantation is the variable that best correlates with the quality parameters, therefore the old vines should be the object of preservation by the viticulturists and winemakers in order to guarantee its contribution to the quality of the wines made with these varieties.

Climate change impacts on Douro Region viticulture and adaptation measures

Climate has a significant impact in the success of any agricultural system, with a direct influence on the crops suitability to a given region, interfering on yield and quality and also with the economic sustainability of the productive activity. In the Douro Demarcated Region (RDD), as in most regions of the Mediterranean climate, the scarce precipitation (33% has less than 600 mm per year), and your high variability, associated with high rates of evapotranspiration during the summer, is usually one of the fundamental factors that limit the grapevine development, as well as the production and quality of the harvest. Thus, facing the scenario in temperature changes for the next decades (1.5-2.5°C) and confirming the predictions of precipitation decreases and/or great variability in the occurrence of heat waves and intense rainfall, the consequences for slope stability in mountain viticulture and sustainability of all operations involved, are risks to be taken into account. In this way, a deepest and sustained knowledge regarding the adaptation measures to adverse environmental conditions is of a crucial importance, enabling a more efficient adaptation of plant growth conditions and the optimization of production and quality of the grapevines. The development of this work, carried out in two commercial vineyards, one located in Soutelo do Douro, São João da Pesqueira, Cima Corgo sub-region, and another located in Numão, Vila Nova de Foz Côa, Douro Superior sub-region, it seeks to establish a relationship between climatic elements and physiological, productive and qualitative parameters, as well as to evaluate the effectiveness of adaptation measures, including different types of deficit irrigation (2002-2019) and the application of shading nets (2019-2020) in the physiological, viticultural and oenological behavior in the Touriga Nacional and Moscatel Galego Branco varieties, respectively. The results showed that the application of deficit irrigation allowed to significantly reduce the impact of the adverse weather conditions at key moments in the development of the grapevine, particularly in the period immediately before veráison and maturation, reducing the negative effects on the physiological processes and productivity, without compromise the must quality parameters. On the other hand, the application of shading nets significantly reduced de leaves temperature, allowing to increase the water potential, stomatal conductance and photosynthetic rate of grapes, which was reflected in the yield increase in the 2nd year of the study. For the maturation indicators, higher levels of total acidity, malic acid and assimilable nitrogen were obtained. The last measure presents a huge potential, being essential to carry out more years of trials to obtain stronger conclusions in terms of production parameters, but also in characteristics as important as the grape ripening components and the organoleptic characteristics of wines.

Sustainable fertilisation of the vineyard in Galicia (Spain)

Excessive fertilization of the vineyard leads to low quality grapes, increased costs and a negative impact on the environment. In order to establish an integrated management system aimed at a sustainable fertilization of the vineyards, nutritional reference levels were established. For this purpose, 30 representative vineyards of the Albariño variety were studied, in which soil and petiole analyses were carried out for two years and grape yield and quality at harvest were measured. In both years of study, soil pH, calcium, sodium and cation exchange capacity were positively correlated with calcium content and negatively correlated with manganese in grapes. Irrigated vineyards had higher levels of aluminium in soil and lower levels of calcium in petiole. Climatic conditions were very different in the years of the study. The year 2019 was colder than usual, in 2020 there was a marked water stress with high summer temperatures. This resulted in medium-high acidity in grapes in 2019 and low acidity in 2020, with sugar levels being similar both years. A very marked decrease in must amino nitrogen was observed in 2020, with ammonia nitrogen remaining stable. The correlation of acidity and sugar values in grapes with soil and petiole analysis data made it possible to establish reference levels for the nutritional diagnosis of the Albariño variety in this region. Based on these results, an easy-to-use TIC application is currently being created for grapegrowers, aimed at improving the sustainability of the vineyard through reasoned fertilization. This study has now been extended to other Galician vine varieties.

Rapid damage assessment and grapevine recovery after fire

There is increasing scientific consensus that climate changeis the underlying cause of the prolonged dry and hot conditions that have increased the risk of extreme fire weather in many countries around the world. In December 2019, a bushfire event occurred in the Adelaide Hills, South Australia where 25,000 hectares were burnt and in vineyards and surrounding areas various degrees of scorching and infrastructure damage occurred. The ability to coordinate and plan recovery after a fire event relies on robust and timely data. The current practice for measuring the scale and distribution of fire damage is to walk or drive the vineyard and score individual vines based on visual observation. The process is time consuming, subjective, or semi-quantitative at best. After the December 2019 fires, it took many months to access properties and estimate the area of vineyard damaged. This study compares the rapid assessment and mapping of fire damage using high-resolution satellite imagery with more traditional ground based measures. Satellite imagery tracking vineyard recovery in the season following the bushfire is being correlated to field assessments of vineyard productivity such as canopy health and development, fertility and carbohydrate storage. Canopy health in the seasons following the fires correlated to the severity of the initial fire damage. Severely damaged vines had reduced canopy growth, were infertile or had very low fertility as well as lower carbohydrate levels in buds and canes during dormancy, which reduced productivity in the seasons following the bushfire event. In contrast, vines that received minor damage were able to recover within 1-2 years. Tools that rapidly and affordably capture the extent and severity of damage over large vineyard area will allow producers, government and industry bodies to manage decisions in relation to fire recovery planning, coordination and delivery, improving the efficiency and effectiveness of their response.