Anthocyanins, flavan-3-ols, and flavonols are the three major classes of flavonoid compounds found in grape berry tissues. Several viticultural practices increase flavonoid content in the fruit, but ...the underlying genetic mechanisms responsible for these changes have not been completely deciphered. The impact of post-veraison sunlight exposure on anthocyanin and flavonol accumulation in grape berry skin and its relation to the expression of different transcriptional regulators known to be involved in flavonoid synthesis was studied. Treatments consisting of removing or moving aside the basal leaves which shade berry clusters were applied. Shading did not affect sugar accumulation or gene expression of HEXOSE TRANSPORTER 1, although in the leaf removal treatment, these events were retarded during the first weeks of ripening. Flavonols were the most drastically reduced flavonoids following shading and leaf removal treatments, related to the reduced expression of FLAVONOL SYNTHASE 4 and its putative transcriptional regulator MYB12. Anthocyanin accumulation and the expression of CHS2, LDOX, OMT, UFGT, MYBA1, and MYB5a genes were also affected. Other regulatory genes were less affected or not affected at all by these treatments. Non-transcriptional control mechanisms for flavonoid synthesis are also suggested, especially during the initial stages of ripening. Although berries from the leaf removal treatment received more light than shaded fruits, malvidin-3-glucoside and total flavonol content was reduced compared with the treatment without leaf removal. This work reveals that flavonol-related gene expression responds rapidly to field changes in light levels, as shown by the treatment in which shaded fruits were exposed to light in the late stages of ripening. Taken together, this study establishes MYB-specific responsiveness for the effect of sun exposure and sugar transport on flavonoid synthesis.
Astringency is a specific oral sensation dominated by a dryness and puckering feeling and is one of the main quality factors for red wines, teas as well as some fruit products. Various hypotheses ...have been proposed to explain the mechanisms of the astringency sensation; however which prevails is still unknown. Here we used a tribological system to determine if the astringency is predominantly a physical perception. Mixtures of whole human saliva and typical astringent compounds such as tannins and red wines were evaluated for their lubrication behavior. Friction coefficient was measured over a wide range of lubrication speed. By comparing friction coefficient with human sensory results of astringency, a positive correlation was found. In particular the highest correlation was observed (R2 = 0.93) at a sliding speed of 0.075 mm/s. Results from this work demonstrate that astringency of polyphenol‐rich products is a sensory perception via a physical stimulus and can be quantified using tribology techniques.
Practical Applications
There is an increasing interest in sensory astringency, particularly its signaling process in oral cavity and the quantitative assessment of its intensity. This is due to the fact that astringency is an important quality characteristic which strongly influences consumer's acceptability for many polyphenol‐rich foods. This research achieved the first experimental approach to sensory astringency determination on red wines by using a tribological technique. Results from this work positively confirm the hypothesis that astringency is a tactile sensation. The method established in this work provides a useful tool for efficient determination of astringent intensity both as industrial quality control and for the prediction of consumer's sensory perception.
Oral tribology receives growing attention in the field of food sciences as it offers great opportunities to establish correlations between physical parameters, such as the coefficient of friction, ...and sensory effects when interacting with components of the human mouth. One important aspect covers the astringency produced by wine, which can be described as the sensation of dryness and puckering in the mouth, specifically occurring between the tongue and the palate after swallowing. Therefore, this article aims at shedding some light on recent trends to correlate physical measures, such as the coefficient of friction derived by oral tribology, with prevailing theories on underlying physiological causes for sensory perception of wines. Some successful cases reported the potential of correlating wine astringency perception with the coefficient of friction in tribological experiments. Our critical assessment demonstrates that the findings are still contradictory, which urgently asks for more systematic studies. Therefore, we summarize the current challenges and hypothesize on future research directions with a particular emphasis on the comparability, reproducibility and transferability of studies using different experimental test-rigs and procedures.
Display omitted
•Critical evaluation of the correlation between wine astringency and physical measures•The coefficient of friction has been identified as a suitable parameter.•The correlation between wine astringency and the frictional behavior is elucidated.•Tribological testing methods have a noticeable influence on the results obtained.•More emphasis has to be put on comparability, reproducibility and transferability.
The aim of this study was to evaluate consumers' perception of a complex set of stimuli as aromatically enriched wines. For that, two consumer based profiling methods were compared, concurrently run ...with overall liking measurements: projective mapping based on choice or preference (PM-C), a newly proposed method, and check-all-that-apply (CATA) questions with an ideal sample, a more established, consumer-based method for product optimization. Reserve bottling and regular bottling of Sauvignon Blanc wines from three wineries were aromatically enriched with natural aromas collected by condensation during wine fermentation. A total of 144 consumers were enrolled in the study. The results revealed that both consumer-based highlighted the positive effect of aromatic enrichment on consumer perception and acceptance. However, PM-C generated a very detailed description, in which consumers focused less on the sensory aspects and more on the usage, attitudes, and reasons behind their choices. Providing a deeper understanding of the drivers of liking/disliking of enriched Sauvignon Blanc wines.
Display omitted
•Sauvignon Blanc wines were enriched with natural aromas collected from fermentation.•Projective mapping based on choice and CATA questions were performed by consumers.•Both methods showed the positive effect of aromatic enrichment on consumer perception.•Projective mapping based on choice generated a more detailed description than CATA.
G. A., Diaz, J., Auger, X., Besoain, E., Bordeu, and B. A. Latorre, 2013. Prevalence and pathogenicity of fungi associated with grapevine trunk diseases in Chilean vineyards. Cien. Inv. Agr. 40(2): ...327-339. Trunk diseases in grapevine (Vitis vinifera) have been identified as a major problem in the wine and table grape industries around the world, reducing the productivity, quality and longevity of vineyards. The present study examined 694 wood samples from the cordons and trunks of vines with trunk disease symptoms in 67 Chilean vineyards located between Copiapó (27°18' S) and Los Angeles (37°42' S). A total of 1,363 fungal isolates were obtained from diseased cordons and trunks with dark brown streaking, yellowish soft-spongy cankers and brown hard V-shaped cankers. Using molecular identification, a total of 12 fungal genera were identified in Chile at varying frequencies: Phaeomoniella chlamydospora (85%); Botryosphaeriaceae (56%) including Diplodia mutila, D. seriata, Neofusicoccum parvum and Spencermartinsia viticola; Inocutis sp. (47%); Diatrypaceae (Cryptovalsa ampelina and Eutypella leprosa) (4.8%); Seimatosporium botan (1.7%); Phomopsis viticola (0.4%); Cylindrocarpon sp. (0.4%); and Phaeoacremonium aleophilum (0.2%). All species were pathogenic, inducing dark brown streaking on various aged grapevine wood tissue. In conclusion, several fungal species are associated with grapevine trunk diseases in the Chilean vineyards being Pa. chlamydospora, D. seriata and Inocutis sp. the most frequent isolated species. These are pathogens that can be found alone or they can coexist in the same plant. This is the first report of Pho. viticola associated with trunk diseases in Chile.
Red grape musts from overripe grapes are characterised by high pH and sugar concentration. Corrections with organic acids are commonly used to secure the alcoholic fermentation and improve the ...organoleptic characteristics of the wine. In this study we test an alternative biological acidification method using the ability of
Lactobacillus plantarum
to produce high concentrations of lactic acid. The time course of sugars, organic acids and pH were measured. Available sugars were consumed by
L. plantarum
producing up to 8.3 g L
−1
of lactic acid. Lactic acid changed the pH from 3.9 to 3.4 after 14 days post-inoculation without yielding a relevant concentration of acetic acid (0.34 g L
−1
).
Thirty-seven red wines from different varieties, origins, and styles were characterized to identify the chemical parameters that better correlate with wine astringency. Principal Component Analysis ...showed that tannin content was the most important parameter influencing overall astringency and its sub-quality dryness, followed by polyphenolic content, color index and, to a lesser extent, pH and alcoholic degree. Given that astringency is a textural sensation caused by the interaction between salivary proteins and tannins, a comparison between two tannin precipitation assays (i.e., methylcellulose, MCP; and Harbertson-Adams assays, HA) were performed to evaluate their ability as estimators of red wine astringency. Results of the sensory correlations showed that MCP and HA have a different behavior toward intensity of astringency and dryness, mainly influenced by the tannin concentration. HA exhibited a sigmoidal behavior with a better astringency predictive performance at low and mid tannin concentration range, whilst MCP showed a linear behavior with a better performance at high tannin concentration range.
•Astringency estimation is an important tool for quality management in red winemaking.•Tannin content is one of the most important parameters influencing astringency and its sub-quality dryness.•Polyphenolic content and color index are also positively correlated with astringency perception.•Tannin concentration influences the performance of analytical methods as estimators of wine astringency.
PDF
