Macrowine 2021
IVES 9 IVES Conference Series 9 Grape seed flavanols extraction and mechanical-acoustic properties as influenced by maceration time and ethanol content

Grape seed flavanols extraction and mechanical-acoustic properties as influenced by maceration time and ethanol content

Abstract

AIM: Grape flavanols are involved in wine quality markers such as in-mouth sensations and colour stability. In particular, seed flavanols are characterized by low molecular weight and high galloylation ratio, which are correlated respectively with bitterness and astringency. Their release during maceration is derived from the seed hydration and the ethanol-driven disassembly of cell walls that is promoted by maceration time. In this study, acoustic and mechanical parameters were tested to investigate the effect of maceration length and ethanol content on seed flavanols extraction. The magnitude of the changes observed in seeds hardness in the different maceration conditions was evaluated in the attempt to establish correlations with the extracted compounds.

METHODS: Pinot noir seeds were macerated in a wine-like solution (pH 3.40, 5 g/L tartaric acid) with different ethanol content (0, 5, 10, 15 and increasing addition up to 15% v/v). After 3, 7, and 10 days, total polyphenols (A280), condensed tannins (methylcellulose assay), flavanol composition as mean degree of polymerization (mDP), and monomeric content by HPLC were determined in the resulting solutions. Mechanical and acoustic parameters of macerated seeds were evaluated through compression test by instrumental texture analysis.

RESULTS: Seed tannins extraction was influenced by both ethanol and maceration time, in different extent depending on the specific compound. In all macerations, an initial seed deformation together with a loss of elasticity was reported. As well, seed hardness (as seed break force, N) increased in all macerations except for 15% ethanol samples that showed a significant decrease. In accordance, some acoustic parameters (as average acoustic energy, dB) increased significantly during maceration, and this last parameter was positively correlated with total polyphenols and condensed tannins extractions.

CONCLUSIONS:

Initial ethanol content and maceration length influenced flavanols richness and composition in the maceration extract. However, limited differences in both phenolic composition and texture parameters were found between the samples with no ethanol content and gradually-increasing alcohol strength

DOI:

Publication date: September 10, 2021

Issue: Macrowine 2021

Type: Article

Authors

Maria Alessandra Paissoni

University of Torino, Italy,Susana RÍO SEGADE, University of Torino, Italy Luca ROLLE, University of Torino, Italy Simone GIACOSA, University of Torino, Italy

Contact the author

Keywords

grape seeds, tannins, maceration, texture analysis, mechanical-acoustic properties

Citation

Related articles…

Legal and economic evolution of the Japanese wine industry in the 21st century

Historically bounded by strict regulations with a focus on taxation since the 19th century, the japanese wine industry stands at a crossroads in the 21st century, necessitated by alignment with international standards and opening towards global markets.

Deconstructing the soil component of terroir: from controversy to consensus

Wine terroir describes the collectively recognized relation between a geographical area and the distinctive organoleptic characteristics of the wines produced in it. The overriding objective in terroir studies is therefore to provide scientific proof relating the properties of terroir components to wine quality and typicity. In scientific circles, the role of climate (macro-, meso- and micro-) on grape and wine characteristics is well documented and accepted as the most critical. Moreover, there has been increasing interest in recent years about new elements with possible importance in shaping wine terroir like berry/leaf/soil microbiology or even aromatic plants in proximity to the vineyard conferring flavors to the grapes. However, the actual effect of these factors is also dependent on complex interactions with plant material (variety/clone, rootstock, vine age) and with human factors.
The contribution of soil, although a fundamental component of terroir and extremely popular among wine enthusiasts, remains a much-debated issue among researchers. The role of geology is probably the one mostly associated by consumers with the notion of terroir with different parent rocks considered to give birth to different wine styles. However, the relationship between wine properties and the underlying parent material raises a lot of controversy especially regarding the actual existence of rock-derived flavors in the wine (e.g. minerality). As far as the actual soil properties are concerned, the effect of soil physical properties is generally regarded as the most significant (e.g sandy soils being associated with lighter wines while those on clay with colored and tannic ones) mostly through control of water availability which ultimately modifies berry ripening conditions either directly by triggering biosynthetic pathways, or indirectly by altering vigor and yield components. The role of soil chemistry seems to be weakly associated to wine sensory characteristic, although N, K, S and Ca, but also soil pH, are often considered important in the overall soil effect.
Recently, in the light of evidence provided by precision agriculture studies reporting a high variability of vineyard soils, the spatial scale should also be taken into consideration in the evaluation of the soil effects on wines. While it is accepted that soil effects become more significant than climate on a local level, it is not clear whether these micro-variations of vineyard soils are determining in the terroir effect. Moreover, as terroir is not a set of only natural factors, the magnitude of the contribution of human-related factors (irrigation, fertilization, soil management) to the soil effect still remains ambiguous. Lastly, a major shortcoming of the majority of works about soil effects on wine characteristics is the absence of connection with actual vine physiological processes since all soil effects on grape and wine chemistry and sensorial properties are ultimately mediated through vine responses.
This article attempts to breakdown the main soil attributes involved in the terroir effect to suggest an improved understanding about soil’s true contribution to wine sensory characteristics. It is proposed that soil parameters per se are not as significant determining factors in the terroir effect but rather their mutual interactions as well as with other natural and human factors included in the terroir concept. Consequently, similarly to bioclimatic indices, composite soil indices (i.e. soil depth, water holding capacity, fertility, temperature etc), incorporating multiple soil parameters, might provide a more accurate and quantifiable means to assess the relative weight of the soil component in the terroir effect.

Predicting consumers’ organic wine consumption behaviour

Organic wine production and consumption is one of the sustainable practices contributing to a number of sustainable development goals (SDGs).

Embracing innovation for a future-ready wine industry: insights from Moldova’s AI-powered pilot project

In 2023–2024, the Republic of Moldova launched its first AI-powered wine pilot, integrating artificial intelligence into the vitivinicultural value chain.

Directed Evolution of Oenococcus oeni: optimising yeast-bacteria interactions for improved malolactic fermentation

Malolactic fermentation (MLF) is a secondary step in the vinification process and it follows alcoholic fermentation (AF) which is predominantly carried out by Saccharomyces cerevisiae. These two processes result in the degradation of metabolites to produce secondary metabolites which also contribute to the final wine flavour and quality. AF results in the production of ethanol and carbon dioxide from sugars and MLF stems from the degradation of L-malic acid (a dicarboxylic acid) to L-lactic acid (a monocarboxylic acid). The latter process results in a smoother texture as the acidity of the wine is reduced by the process, it also adds to the flavour complexity of the wine.