Macrowine 2021
IVES 9 IVES Conference Series 9 Colour assessment of port wines using colorimetric and spectrophotometric methods

Colour assessment of port wines using colorimetric and spectrophotometric methods

Abstract

Colour is an important quality parameter in wines and is the result of a complex mixture of pigments (including anthocyanins and their derivatives, quinones, xanthyllium compounds, etc.). Red wine colour changes over time as pigments react between themselves and with other wine macromolecules (particularly polyphenols). During wine tasting, colour is normally assessed on the outer rim of the wine profile in a tilted glass, since most wines are too opaque to be analysed in the middle of the glass. Therefore, depending on the depth of observation considered, the perception of wine colour can be different. The precise measurement of wine colour is usually done using molecular (UV-VIS) spectrophotometric methods. In the current official (OIV) method, the transmittance spectrum of a particular sample is measured and used to calculate CIE L*a*b* parameters, which define a single (predominant) colour for a particular wine. Reflectance colorimetry is an alternative well-established method for measuring colour in foodstuffs, which can also be used in transparent samples (such as wines) as long as a reflective background is used. In this work, a reflectance colorimeter was used to measure CIE L*a*b* colour parameters of Port wine samples of different categories at different depths, in Petri dishes. The obtained results were compared with the parameters obtained using the OIV method. Representative profiles of Lightness (L*), Hue (H*) and Chroma (C*) vs. wine depths were obtained using Port wine samples from different categories and ages. Wines from the same category exhibited similar colour (depth) profiles, with Tawny-styled wines showing a more linear profile than Ruby-styled wines regarding the L* and H* parameters. Good correlations between the colorimetric and OIV methods were obtained for the L* (Ruby:R >= 0.97; Tawny:R > 0.86) and H* parameters (Ruby:R >= 0.90; Tawny >= 0.91) with the C* parameter giving inferior results, particularly in Tawny-style wines (Ruby:R >= 0.87; Tawny >= 0.29). The results suggest the colorimetric method can be used as an alternative to the OIV method for estimating the L* and H* parameters (the most important for wine colour definition), being quicker and more informative.

Publication date: May 17, 2024

Issue: Macrowine 2016

Type: Poster

Authors

Francisco Silva*, Bento Amaral, Cristina Silva, Francisco Campos, Manuel Ferreira, Natalia Ribeiro, Tomas Simões

*Escola Sup. Biotecnologia – UCP

Contact the author

Tags

IVES Conference Series | Macrowine | Macrowine 2016

Citation

Related articles…

Partial dealcoholisation of red wine by reverse osmosis-evaporative perstraction: impact on wine composition

Around the world, the alcohol content of wine has been steadily increasing; partly as a consequence of climate change, but also due to improvements in viticultural management practices and winemaking techniques [1,2]. Concurrently, market demand for wines with lower alcohol levels has increased as consumers seek to reduce alcohol intake for social and/or health reasons [3]. As such, there is increasing demand for both innovative methods that allow winemakers to produce ‘reduced alcohol wines’ (RAW) and a better understanding of the impact of such methods on the composition of RAW. This study therefore aimed to investigate compositional changes in two red wines resulting from partial alcohol removal following treatment by one such method, involving a combination of reverse osmosis and evaporative perstraction (RO-EP).

Use of glutathione under different grape processing and winemaking conditions and its impact on the formation of sulfide off-flavors, colour, and sensory characteristics of Riesling, Sauvignon blanc, and Chardonnay

The use of glutathione (GSH) in winemaking has been legitimated recently, according to OIV resolutions OENO 445-2015 and OENO 446-2015 a maximum dose of 20 mg/L is now allowed to use in must and wine. Several studies have proven the benefits of GSH, predominantly in Sauvignon blanc. Thus, oxidative coloration of must and wine is limited, aroma compounds such as volatile thiols are preserved, and the development of ageing flavors such as sotolon and 2-aminoacetophenone is impeded. The protective effect may be explained by the high affinity of GSH to bind o-quinones which are formed during phenolic oxidation and which are known to initiate browning and other oxidative changes. Some researchers have proposed the hydroxycinnamic acid to GSH ratio (HGR) as an indicator of oxidation susceptibility of must and could show that lower ratios yielded lighter musts.

Evaluation of Polarized Projective Mapping as a possible tool for attributing South African Chenin blanc dry wine styles

Multiple Factor Analysis (MFA) According to the Chenin blanc Association of South Africa, there are three recognized dry wine styles, Fresh and Fruity (FF), Rich and Ripe Unwooded (RRU), and Rich and Ripe Wooded (RRW), classically attributed with the help of sensory evaluation. One of the “rapid methods” has drawn our attention for the purpose of simplifying and making style attribution for large sample sets, evaluated during different sessions, more robust. Polarized Projective Mapping (PPM) is a hybrid of Projective Mapping (PM) and Polarised Sensory Positioning (PSP). It is a reference-based method in which poles
(references) are used for the evaluation of similarities and dissimilarities between samples.

Multivariate strategies for red wines classification using stilbenes and flavonols content

Bioactive polyphenols from grapes and wines, like stilbenes and flavonols (SaF), are often determined to nutritional evaluation, but also for many other purposes. The objective of this study was to quantify SaF in red wines from “Campanha Gaúcha”, a large and young viticultural region from South Brazil. Moreover, through statistical analysis, evaluate the influence of these compounds according to varieties, production process, harvest years and micro-regions of cultivation. A total of 58 samples of red wines were analyzed by high-performance liquid chromatography coupled to diode array detector (HPLC-DAD) for determination of trans-resveratrol (R), quercetin (Q), myricetin (M), kaempferol (K), trans-e-viniferin (V) and their precursor, cinnamic acid (C).

A preliminary study of clonal selection in cv. Viura in relation to varietal aroma profile

Viura is a synonym for Macabeo and currently it is the most widely planted white grape variety in D.O.Ca. Rioja, with 3,569 ha, representing 84% of the white grape cultivated area. It is a generous-yielding grape, presenting low values of titratable acidity and with large and compact clusters which makes it susceptible to Botrytis cinerea. Thus, this variety not always satisfies the wine grower’s prospects. Nowadays, the available plant material is scarce, moreover, it was selected on the basis of other quality criteria, not currently requested.