Effect of a commercial tannin on the sensorial temporality of astringency

The composition and structure of plant fibers affect their fining performance in wines

In recent years, the wine industry has shifted towards plant-based fining agents for food safety reasons and consumer preferences. This study analysed the interaction of five plant fibers with red wine phenolic compounds to determinate their performance as fining agents. Chemical composition, polysaccharide profile, and physical properties were examined. Pea, cellulose, and Sauvignon Blanc pomace fibers effectively reduced tannin content while minimally affecting the concentration of anthocyanins, flavonols and wine color. Contrary to previous beliefs, the presence of pectins in fibers didn't play a crucial role in phenolic compound interaction since cellulose-rich fibers with low pectin concentration also bound tannins effectively, especially those with small particle size and high contact surface. Pea fiber, rich in cellulose and pectins, showed remarkable tannin retention while minimally affecting wine color. This research highlights the potential of plant fibers as effective fining agents in wine production and how their composition affects their performance.

Influence of Protective Colloids on Calcium Tartrate Stability and the Astringency Perception in a Red Wine

Calcium tartrate instability in wines has been a neglected topic for many years. However, it seems that this problem is gaining prominence, and the industry welcomes inputs to address this issue. Among the alternatives that winemakers use for tartrate salt stabilization, the addition of authorized protective colloids is one of the best choices because they are easy to apply and have a low energetic cost. In the present study, the same red wine was treated with five different commercially available protective colloids in triplicate. The effectiveness of such colloids on calcium tartrate potential instability was estimated, in addition to their side effects on the phenolic composition of the treated wines and their astringency perception, as assessed by sensory analyses of the treated wine. The results show that, under these trial conditions, carboxymethylcellulose is the best choice for reducing the risk of calcium tartrate precipitation in wine. Moreover, the application of protective colloids to the wines had little effect on their color, phenolic composition, or evolution during one year of bottle storage. Finally, the addition of protective colloids did not impact the astringency intensity, but it influenced the dynamic perception of astringency according to the temporal dominance of sensation analysis.

Different physicochemical interactions between varietal wines and human saliva: Correspondence with astringency

Astringency corresponds to the sensation of dryness and roughness that is experienced in the oral cavity in association with the interaction between salivary proteins and food polyphenols. In this study, the phenolic composition of seven varietal wines, the intensity of astringency they evoke and the physicochemical reactivity of these wines with whole human saliva were evaluated. Phenolic composition of wines was characterized by spectrophotometry and HPLC chromatography. Intensity of astringency was evaluated by trained sensory panels. Saliva from a single volunteer subject was used to assess wine-saliva interactions. To this end, binary mixtures were produced at different v/v wine/saliva ratios and each of them assayed for the ability of the salivary protein to diffuse on a cellulose membrane (diffusion test) and to remain in solution (precipitation test). Physicochemical reactivities between wine components and the protein fraction of saliva were contrasted against the astringency and the phenolic profile of each varietal wine. The study supports the view that astringency depends on physicochemical interactions between two complex matrices -wine and saliva- and not between some of their particular components.

Multi-attribute temporal descriptive methods in sensory analysis applied in food science: A systematic scoping review

Among descriptive sensory evaluation methods, temporal methods have a wide audience in food science because they make it possible to follow perception as close as possible to the moment when sensations are perceived. The aim of this work was to describe 30 years of research involving temporal methods by mapping the scientific literature using a systematic scoping review. Thus, 363 research articles found from a search in Scopus and Web of Science from 1991 to 2022 were included. The extracted data included information on the implementation of studies referring to the use of temporal methods (details related to subjects, products, descriptors, research design, data analysis, etc.), reasons why they were used and the conclusions they allowed to be drawn. Metadata analysis and critical appraisal were also carried out. A quantitative and qualitative synthesis of the results allowed the identification of trends in the way in which the methods were developed, refined, and disseminated. Overall, a large heterogeneity was noted in the way in which the temporal measurements were carried out and the results presented. Some critical research gaps in establishing the validity and reliability of temporal methods have also been identified. They were mostly related to the details of implementation of the methods (e.g., almost no justification for the number of consumers included in the studies, absence of report on panel repeatability) and data analysis (e.g., prevalence of use of exploratory data analysis, only 20% of studies using confirmatory analyses considering the dynamic nature of the data). These results suggest the need for general guidelines on how to implement the method, analyze and interpret data, and report the results. Thus, a template and checklist for reporting data and results were proposed to help increase the quality of future research.

Investigating wine astringency profiles by characterizing tannin fractions in Cabernet Sauvignon wines and model wines

Contribution of various phenols on wine astringency profiles was far from clear explanations. To effectively describe wine astringency profiles and determined the function of tannins/matrix (pH and ethanol), multiple chemical analyses combined RATA (Rate-all-that-apply) sensory method were applied in Cabernet Sauvignon and model wines. Results showed that polymeric flavanols determined the bulk of wine astringency intensity, oligomeric tannins enriched the smoothness and periodontium astringency, and monomeric phenol enhanced overall astringency intensity through synergistic effect. Astringency balance was effectively quantification, and its potential correlation relationship with epicatechin extension subunit (0.83) and fluorescence peak shift (0.75) cannot be ignored. The astringency profiles of condensed tannins with anthocyanins were enhanced. Low-pH (from 3.8 to 3.0) enhanced astringency by increasing the tannins affinity to proteins, while ethanol (from 10.0 % ∼ 15.0 %) decreased the hydrophobicity bond between tannins-protein interaction. This paper provided new insights to explain wine astringency profiles and a reference for astringency modification during winemaking.

Karakterisasi Fisiko-Kimia Biji dan Kulit Ari Kacang Bogor Asal Jampang-Sukabumi Jawa Barat

The traditional cultivation and limited use of bambara groundnut (Vigna subterranea) seed and coat have encouraged the development of this commodity. The aim of this research was to characterize the seed and coat of bambara groundnut from Jampang, Kab. Sukabumi, West Java. Analysis on bambara groundnut seed including proximate analysis, in vitro protein digestibility, starch content, and dietary fiber, as well as analysis on its coat including anthocyanin, total phenolic, antioxidant activity, phytic acid and tannin, were examined in this study. The results showed that bambara groundnut seed from Jampang-Sukabumi contained 16.53% proteins, 3.04% ash, 7.83% fats and 55.22% carbohydrates in dry basis (db). The carbohydrates consisted of starch 52.71% and dietary fiber 7.47% (db). The protein had an in vitro protein digestibility of 41.65% db. The purple seed coat contained of 1.51% anthocyanin, 25.85 mg/g total phenolic content (as gallic acid equivalent), antioxidant activity at 82.75% inhibition of free radical DPPH, 6.37 mg/g phytic acid, and 96.79 mg/g tannin (as tannic acid equivalent) in dry basis. The relatively high content of tannin and antioxidant activity but very low phytic acid content, make the bambara seed coat a potential source for tannin, meanwhile the bambara groundnut is potential as a nutrition source.

Structural Equation Modeling (SEM) and Temporal Dominance of Sensations (TDS) in the Evaluation of DOC Douro Red Wine's Sensory Profile

In the Portuguese Douro region, several DOC (Denomination of Controlled Origin) Douro red wines are produced and, due to the peculiar characteristics of the three Douro sub-regions, present particular imprinted terroirs, that can be perceived when tasted. Considering the DOC Douro wine’s sensory profile and terroir, this study aimed to analyze the sensory characteristics of red wines produced in the three Douro sub-regions (Baixo Corgo, Cima Corgo, and Douro Superior) by a single point sensory technique, a Quantitative Descriptive Analysis—QDA^® and also applying a temporal method-TDS (Temporal Dominance of Sensations). The use of QDA and TDS methods proved to be efficient in the wine’s sensory profile characterizing. The QDA^® method allowed a detailed classification of attributes; however, the TDS method proved to be much more efficient. Moreover, the wines of the three sub-regions presented profiles with characteristics very similar in olfactory and taste/flavor aspects, pointing out a huge relation between the characteristics of the three sub-regions and the grape varieties present in the wines. Globally, the olfactory profile of wines is characterized by Fruity, Floral, and Balsamic aromatic notes, while the taste/flavor profile stands out, highlighting Astringency and Acidity and, again, Fruity as the main in-mouth aroma. It was also possible to conclude that TDS is a fast method that is easy to apply and has excellent results in the evaluation of the olfactory and taste/flavor profile of wines and, with a larger set of samples, it would be possible to obtain characteristic TDS curves for each Douro sub-region, providing a wine’s fingerprint that could be used for authentication and traceability purposes.

An overview of the perception and mitigation of astringency associated with phenolic compounds

Astringency, as a kind of puckering, drying, or rough sensation, is widely perceived from natural foods, especially plants rich in phenolic compounds. Although the interaction and precipitation of salivary proteins by phenolic compounds was often believed as the major mechanism of astringency, a definitive theory about astringency is still lacking due to the complex oral sensations. The interaction with oral epithelial cells and the activation of trigeminal chemoreceptors and mechanoreceptors also shed light on some of the phenolic astringency mechanisms, which complement the insufficient mechanism of interaction with salivary proteins. Since phenolic compounds with different types and structures show different astringency thresholds in a certain regularity, there might be some relationships between the phenolic structures and perceived astringency. On the other hand, novel approaches to reducing the unfavorable perception of phenolic astringency have been increasingly emerging; however, the according summary is still sparse. Therefore, this review aims to: (a) illustrate the possible mechanisms of astringency elicited by phenolic compounds, (b) reveal the possible relationships between phenolic structures and perception of astringency, and (c) summarize the emerging mitigation approaches to astringency triggered by phenolic compounds. This comprehensive review would be of great value to both the understanding of phenolic astringency and the finding of appropriate mitigation approaches to phenolic astringency in future research.

The Oxygen Consumption Kinetics of Commercial Oenological Tannins in Model Wine Solution and Chianti Red Wine

One property of oenological tannins, oxygen reactivity, is commonly exploited in winemaking. The reactivity is mediated by the presence of catalysts (i.e., transition metals and sulfur dioxide) and protects wine against oxidation. This work compares the oxygen consumption rate (OCR) of four commercial oenological tannins (two procyanidins from grape skin and seed, an ellagitannin from oak wood and a gallotannin from gallnut) in a model wine solution and Chianti red wine. All samples were subjected to consecutive cycles of air saturation at 20 °C to increase the total level of oxygen provided. After each cycle, the oxygen level was measured by means of a non-invasive luminescent sensor glued to a transparent surface (sensor dots) until there was no further change in substrate reactivity. The OCR followed first-order kinetics, regardless of the tannin. As expected, the ellagitannin showed the fastest OCR, followed by the two from grape seeds and skins and finally the gallotannin. The total O₂ consumption in the red wine was almost double that of the model solution, due to the oxidation of wine substrates. The measurement of OCR is helpful for setting up an advanced winemaking protocol that makes use of tannins to reduce the use of sulfur dioxide.

Sensory characterization of cucumbers pickled with verjuice as novel acidifying agent

Verjuice is an acidic unfermented unripe grape juice that has recently been proposed as an alternative to vinegar in different food preparations. In this study, pickled cucumber preserves were industrially prepared using two dilutions of verjuice as acidifying agent and compared with the traditional vinegar-pickled samples. Samples were chemically characterized and subjected to sensory analyses using a trained panel and consumers. The different acidifying agents resulted in pickled cucumbers giving different olfactory and gustatory evaluations. No differences in appearance and texture were found. Despite showing chemical and sensory differences, pickles preserved with verjuice and vinegar had similar overall liking scores for visual, olfactory and gustatory aspects. A key feature of pickles prepared with verjuice is their lack of acetic acid potentially conferring them an additional value, suggesting that verjuice represents a viable alternative to vinegar for the production of pickles with distinctive sensorial properties.

Evaluation of Yeast Derivative Products Developed as an Alternative to Lees: The Effect on the Polysaccharide, Phenolic and Volatile Content, and Colour and Astringency of Red Wines

Due to the increase of the use of yeast derivatives (YDs) in winemaking to improve the technological and sensory properties in wines, in this work we evaluated the effect of the post-fermentation application of different yeast derivative products on the physical and chemical properties and astringency of red wines during two consecutive harvests. A commercial and two experimental new yeast derivatives were applied at a medium‒high dosage (30 g/hL). The addition of different yeast derivatives in red wine increased the concentration of different polysaccharide fractions and, therefore, the total polysaccharide content, producing a decrease in the duration of the wine astringency perception over time. The use of yeast derivatives could produce an adsorption/clarification and/or protective effect on the phenolic compounds. However, it did not produce an important modification of the colour parameters. An intensification or a lower decrease of the most volatile compound groups was produced, but it depended on the YDs and yeast strain used in fermentation and post-fermentation processes.