Search Results (35)

The Touriga Nacional grape variety is renowned in Portuguese red wines for its intense color and aromatic complexity, largely attributed to its rich phenolic composition. Several factors influence the phenolic profile of wines, including edapho-climatic conditions, grape variety, and winemaking techniques such as fermentation, maceration, barrel aging, and maturation. In this study, the technique for winemaking was the only controlled variable, allowing for a specific evaluation of its impact on phenolic composition and antioxidant capacity. Ten single-varietal Touriga Nacional wine samples from the 2019 vintage, produced in the Cima Corgo sub-region of the Douro by different wineries, were analyzed. The phenolic composition was determined using colorimetric methods to quantify total phenols, ortho-diphenols, flavonoids, anthocyanins, and tannins. Antioxidant capacity was assessed through the 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), and Ferric Reducing Antioxidant Power (FRAP) assays. Since all wines shared the same grape variety, region, and harvest year, the fermentation technique was the main differentiating factor, enabling a direct comparison of its influence on phenolic extraction and antioxidant properties. Additionally, Reversed-Phase High-Performance Liquid Chromatography with Photodiode Array Detection coupled with Mass Spectrometry (RP-HPLC-DAD-ESI-MS/MS) was employed to identify and quantify individual phenolic compounds. This study highlights the key role of winemaking techniques in modulating the phenolic composition and antioxidant potential of Touriga Nacional wines. Full article

Background/Objectives: Type 2 Diabetes Mellitus (T2DM) is characterized by hyperglycemia, increased risk of cardiovascular diseases, and oxidative imbalances. This study aimed to investigate the impact of dietary supplementations with ‘Arinto’ grape pomace flour (GPF) (WGPF) and ‘Touriga Nacional’ GPF (RGPF) in an animal model of T2DM. Methods: T2DM was induced by a high-fat diet (HFD) for 28 days and a single dose of streptozotocin (STZ) (35 mg/kg) on the 21st day. Forty adult male Wistar rats were divided into five groups: Control (CT), T2DM, T2DM + Metformin (250 mg/kg), T2DM + 10% ‘Arinto’ GPF (WGPF), and T2DM + 10% ‘Touriga Nacional’ GPF (RGPF). On the 21st day of the experimental protocol, animals were submitted to an oral glucose tolerance test. An oral glucose tolerance test, oxidative stress parameters, biochemical analysis, and pancreas histological analyses were performed. Results: T2DM impaired glucose tolerance, elevated serum triglycerides and cholesterol, increased oxidative damage in the liver, and induced pancreatic histological abnormalities. However, supplementation with WGPF and RGPF demonstrated positive effects, mitigating glycemic and lipid disruptions, ameliorating oxidative stress, and protecting pancreatic Islets β-cells. Conclusions: Our findings highlight the protective effects of WGPF and RGPF in the adverse impacts of T2DM. Additionally, our study emphasizes the innovative use of grape pomace, a winemaking by-product, promoting sustainability by transforming waste into functional foods with significant health benefits. Full article

According to the climate projections, drought will increase in frequency and severity. Since water stress (WS) impacts a grapevine’s physiology and yield negatively, the evaluation and selection of tolerant genotypes are needed. To analyse the WS effects on the morphology and cell division of three grapevines (Vitis vinifera L.) varieties, “Touriga Franca” (TF), “Touriga Nacional” (TN) and “Viosinho” (VS), in vitro-grown plants were exposed to 10% polyethylene glycol 6000 (PEG) (−0.4 MPa) or 20% PEG (−0.8 MPa), incorporated in the culture medium, for four weeks. Control plants were kept in culture media without PEG. The VS and TN plants showed the highest mean numbers of nodes, shoots and leaves and average mitotic indexes under 20% PEG. The TF and TN plants showed the lowest frequencies of mitotic anomalies under 10% PEG. The VS plant growth was less affected by WS, but TF and TN presented more regular mitosis under moderate WS. Globally, in vitro culture constitutes a cost-effective experimental system for studying grapevine responses to WS and the preliminary selection of resilient genotypes. These approaches could be applied to study plant responses to other abiotic stresses based on additional evaluation techniques (e.g., transcriptional analyses or genome-wide association studies). Full article

Background: “Touriga Franca” (TF) and “Touriga Nacional” (TN) are grapevine varieties cultivated in the ‘Douro Superior’ subregion (Northern Portugal) that experience stressful environmental conditions during the summer. Objectives: Aiming to profile the expression of stress-responsive genes by quantitative real-time PCR (qPCR) in TF and TN plants growing naturally, three candidate reference genes were first tested under controlled conditions. Methods: To simulate a summer’s day, TF and TN in vitro plants were exposed to 32 °C–3 h (heat acclimation) and 42 °C–1 h (severe heat stress, HS) followed by two recovery periods (32 °C–3 h and 24 °C–24 h). Leaf samples were collected at the end of each phase. Control plants were kept at 24 °C. Results: Among the candidate reference genes, the UBC and VAG pair showed the highest stability. The suitability of these genes for qPCR was validated by heat shock protein 17.9A (HSP17.9A) gene profiling. The HSP17.9A expression was up-regulated in both varieties and all experimental phases except in TF control plants. TN showed the highest HSP17.9A relative expression ratio after severe HS. Conclusions: TN responded faster than TF to the induced heat shocks. The UBC, VAG, and HSP17.9A genes revealed to be suitable for further qPCR assays in TF and TN grapevine varieties. Full article

Vitis vinifera is the grape variety used in the production of wine and other products. In the wine production process, many of the vine’s by-products are wasted, namely seeds and stems. Given the proportion of wine production worldwide, the quantity of by-products is beginning to be an environmental problem, making it urgent to take measures for their use to obtain bioactive compounds with health benefits. The aim of this work was to study the antioxidant and antimicrobial activities of extracts from the seeds and stems of four Portuguese grape varieties: Touriga Franca, Touriga Nacional, Viosinho, and Tinta Roriz. Total phenolic (TPC) and total flavonoids (TFC) contents present in the different extracts were evaluated, as well as the antioxidant activity, by DPPH and FRAP methods. TPC and TFC values of the stem’s extracts are much higher than those of the seeds of the same grape variety in the same solvent. The antioxidant activity of aqueous and ethanolic stem extracts is higher than that obtained for the seeds, showing that antioxidant activity is related to the content of polyphenols. The antimicrobial activity of different stem and seed extracts was determined against yeasts and Gram-positive and Gram-negative bacteria, and the effect was determined based on the minimal inhibitory concentrations calculated (MIC). In general, the ethanol:water (1:1) extract of the seeds from the different varieties tested inhibited C. albicans ATCC10231 and C. krusei ATCC6258 growth even at 200 μg/mL, and the effect was fungicidal at 200 μg/mL. The same type of extract showed selective antimicrobial activity, inhibiting S. aureus ATCC29213 growth but having no effect against E. coli ATCC25922 even at 200 μg/mL. The effect against S. aureus was bactericidal (at 200 μg/mL) for Touriga Franca, Touriga Nacional, and Viosinho. Taking all these results into account, it can be concluded that the by-products of the grape varieties tested are important sources of bioactive products, particularly as antioxidants and antimicrobials. Full article

Environmental degradation leads to an unsustainable food system. In addition to this issue, the consumption of foods that improve people’s health and well-being is recommended. One of the alternatives is undoubtedly the use of by-products of winemaking, namely in the form of grape pomace flour (GPF). To verify the benefits of using the Touriga Nacional and Arinto (Vitis vinifera L.) flour varieties, analytical determinations were made to identify and quantify different components. In terms of nutritional characterization, the Touriga Nacional GPF showed results that indicate better nutritional quality than the Arinto GPF. The Touriga Nacional and Arinto samples had protein contents of 10.13% and 8.38%, polyunsaturated fatty acids of 6.66% and 5.18%, soluble dietary fiber of 14.3% and 1.7%, and insoluble dietary fiber of 55.1% and 46.4%, respectively. The anthocyanins, proanthocyanidins, and flavonols presented in samples were detected by HPLC-DAD/ESI-MS. Atomic absorption spectrometry revealed elevated concentrations of certain elements in Touriga Nacional compared to Arinto, with the former showing higher levels of aluminum (130 mg/kg) and iron (146 mg/kg) against the latter’s Al (120 mg/kg) and Fe (112 mg/kg) content. GPF could become a valuable ingredient due to its nutritional quality and high content of various polyphenols. Full article

Sustainable and efficient agricultural production is a growing priority in modern society. Viticulture, an important agricultural and food sector, also faces this challenge. Precision Viticulture (PV) has gained prominence as it aims to foster high-quality, efficient, and environmentally sustainable practices. The Soluble Solids Content (SSC) is essential for assessing grape ripeness and quality in the winemaking process. Conventional methods for determining SSC values (expressed in °Brix) are invasive, expensive, and labour-intensive, necessitating sample preparation, making large-scale analysis impractical. In response to these limitations, this study presents an innovative approach within the field of Precision Viticulture. It focuses on the non-invasive prediction of SSC using low-cost proximal hyperspectral optical sensors. These sensors rely on spectral reflectance measurements in the range of 340–850 nm. This study was conducted in a commercial vineyard in the Demarcated Douro Region, Cima-Corgo sub-region, Portugal, over six weeks during ripening. In total, 169 grape berries from Touriga Nacional vines were analysed under three irrigation regimes (no irrigation, 30% ETc, and 60% ETc). After organising and preprocessing the data, machine learning algorithms, namely Partial Least Squares Regression (PLS), Random Forest (RF), and the Generalised Linear Model (GLM), were applied to predict SSC values. These models’ performance was thoroughly evaluated using cross-validation techniques. The performance of different models was evaluated, showing significant differences according to the metrics used (R2, RMSE, and MAPE). The RF model demonstrated effectiveness and precision. A high R² value of 0.9312, coupled with low RMSE (0.9199 °Brix) and MAPE (3.88%), signifies a strong fit to the data and accurate predictive capabilities. The results of this benchmarking study on predictive models of SSC provide valuable insights into the performance of various models, aiding winegrowers and winemakers in decision making. Full article

Predawn leaf water potential (Ψ_pd) is the main parameter to determine plant water status, and it has been broadly used to support irrigation management. However, the Scholander pressure chamber methodology is laborious, time-consuming and invasive. This study examined a low-cost hyperspectral proximal sensor to estimate the Ψ_pd in grapevine (Vitis vinifera L.). For this, both the Ψ_pd and spectral reflectance (340–850 nm) were accessed in grapevines in a commercial vineyard located in the Douro Wine Region, northeast Portugal. A machine-learning algorithm was tested and validated to assess grapevine’s water status. The experiment was performed in a randomized design with 12 grapevines (cv. Touriga Nacional) per irrigation treatment: non-irrigated, 30% crop evapotranspiration (Etc), and 60% Etc. The dataset was analyzed using Principal Component Analysis (PCA), and the machine-learning regression algorithm applied was Extreme Gradient Boosting (Xgboost). Results from the validation dataset (n = 108) for the Xgboost tested exhibited a root mean square error (RMSE) of 0.23 MPa, a mean absolute error (MAPE) of 16.57% and an R² value of 0.95. These results demonstrate that the hyperspectral sensor and Xgboost algorithm show potential for predicting the Ψ_pd in vineyards, regardless of a plant’s water status. Full article

This study aims to take advantage of the wine industry by-products and extract bioactive compounds from grape pomace by applying methodologies susceptible to be integrated easily into industrial workflows because of the association with standard instrumentation and facilities, while the main factors affecting the efficiency of the process have been optimized. The sampling consisted of two grape varieties: ‘Touriga Nacional’ and ‘Sousão’. A response surface methodology (RSM) method was used to optimize the extraction conditions based on three independent variables according to the chemical characteristics and stability/lability traits associated with polyphenols; the main bioactive phytochemical in grape pomace: solvent (50%, 70%, and 90% ethanol); temperature (20 °C, 40 °C, and 60 °C); and pH (0.5% HCl, 2% HCl, and 3.5% HCl). The phytochemical profile, as well as the radical scavenging and reducing powers were determined on 27 different samples. The highest yield and antioxidant activity corresponded to extracts obtained at 60 °C using 3.5% HCl and 70% ethanol. The values for total phenols and flavonoids were 44.93 mg of gallic acid equivalents (GAE) and 22.95 mg of catechins equivalents (CE) per gram, respectively. Concerning the evaluation of antioxidant capacity using various assays such as ABTS, DPPH, and FRAP, the results obtained were 0.30, 0.43, and 0.36 mmol of Trolox equivalent antioxidant capacity (TEAC) per gram, correspondingly. The analysis of the extract obtained with the best extraction performance using these parameters via High-Performance Liquid Chromatography–Mass Spectrometry has been also performed, allowing us to identify fourteen (14) compounds, including phenolic acids (n = 3), flavonols (n = 7), and anthocyanins (n = 4). As a result of this process, the best conditions for the production of a natural and environmentally friendly dye, not only avoiding waste but also reusing these by-products, were achieved. Full article

The wine industry generates large amounts of by-products that are usually destined as waste. Grape pomace is the residue of the winemaking process and is rich in compounds with functional properties, such as dietary fiber and phenolic compounds. The aim of this research was to study the influence of white and red grape pomace flour (GPF) addition in the enhancement of functional properties of savory crackers. Different levels of incorporation were tested (5%, 10% and 15% (w/w)). Analysis of physical properties, nutritional composition and sensory acceptability were conducted to evaluate the effect of GPF incorporation. GPF cracker stability throughout a four-week period was achieved with regard to firmness and color. These products presented distinctive and appealing colors, ranging from a violet (GPF of Touriga Nacional variety) to a brown hue (GPF of Arinto variety). Concerning nutritional composition, both crackers incorporated with 10% GPF of Arinto or Touriga Nacional varieties could be considered “high in fiber”, as per the Regulation (EC) No. 1924/2006, suggesting a functional food. GPF crackers demonstrated an overall great acceptance of this kind of innovative foods, with the majority indicating that they would certainly/probably buy them. Moreover, the cracker with 10% Arinto GPF achieved the most balanced and overall preference. Full article

Grape pomace (grape skin and seeds) and stems are major by-products of winemaking, of lignocellulosic nature. The aim of this study was to value grape pomace and stems to produce prebiotic oligosaccharides (OS). Grapes from Touriga Nacional and Marselan cultivars (Vitis vinifera L.) were used for conventional red winemaking. The total of extractives, obtained by sequential extraction with dichloromethane, ethanol, and water, was approx. 64.0% (d.w.) for both pomaces, and 46.2% and 59.5% for Marselan and Touriga Nacional stems, respectively. Lignin contents in Marselan stems (26.4%) and pomace (20.4%) were higher than in Touriga Nacional pomace (19.3%) or stems (17.3%). Polysaccharides (hemicelluloses and cellulose) represented 9 and 8.2% of Marselan and Touriga pomaces, and 22.3 and 18.7% of respective stems. After extractives removal, the pomaces and stems were submitted to a hydrothermal treatment (autohydrolysis) to release oligosaccharides from the hemicellulose fraction. Autohydrolysis was carried out following a central composite rotatable design (CCRD) as a function of temperature (142–198 °C) and time (48–132 min). For all materials of both varieties, the production of sugars by autohydrolysis could be described by second-order models. Highest sugar productions were: 81.2 g/kg (d.w.) extracted Marselan pomace; 76.3 g/kg (d.w.) extracted Touriga Nacional pomace; 116.3 g/kg (d.w.) extracted Marselan stems; and 168.4 g/kg (d.w.) extracted Touriga Nacional stems. Yields of 99% OS were obtained by autohydrolysis at 170 °C/90 min. Full article

Climate-smart agriculture involves practices and crop modelling techniques aiming to provide practical answers to meet growers’ demands. For viticulturists, early prediction of harvest dates is critical for the success of cultural practices, which should be based on accurate planning of the annual growing cycle. We developed a modelling tool to assess the sugar concentration levels in the Douro Superior sub-region of the Douro wine region, Portugal. Two main cultivars (cv. Touriga-Nacional and Touriga-Francesa) grown in five locations across this sub-region were studied. Grape berry sugar data, with concentrations between 170 and 230 g L⁻¹, were analyzed for the growing season campaigns, from 2014–2020, as an indicator of grape ripeness conditioned by temperature factors. Field data were collected by ADVID (“Associação Desenvolvimento Da Viticultura Duriense”), a regional winemaker association, and by Sogrape, the leading wine company from Portugal. The “Phenology Modeling Platform” was used for calibrating the model with sigmoid functions. Subsequently, model optimizations were performed to achieve a harmonized model, suitable for all estates. Model performance was assessed through two metrics: root mean square error (RMSE) and the Nash–Sutcliffe coefficient of efficiency (EFF). Both a leave-one-out cross-validation and a validation with an independent dataset (for 1991–2013) were carried out. Overall, our findings demonstrate that the model calibration achieved an average EFF of 0.7 for all estates and sugar levels, with an average RMSE < 6 days. Model validation, at one estate for 15 years, achieved an R² of 0.93 and an RMSE < 5. These models demonstrate that air temperature has a high predictive potential of sugar ripeness, and ultimately of the harvest dates. These models were then used to build a standalone easy-to-use computer application (GSCM—Grapevine Sugar Concentration Model), which will allow growers to better plan and manage their seasonal activities, thus being a potentially valuable decision support tool in viticulture and oenology. Full article

Grapevine trunk diseases constitute one of the major problems for viticulture worldwide, with Botryosphaeria dieback considered as one of the most important of these diseases. In this work, we aimed to (i) evaluate the effect of the combination of two products, Esquive^® (a Trichoderma-based product) and LC2017 (a low-copper-based product), in the control of Lasiodiplodia theobromae, by evaluating the internal lesion length caused by inoculation of this pathogen on greenhouse kept grapevines of cvs Cabernet Sauvignon and Touriga Nacional and, (ii) investigating their elicitor effect on plant defense responses, through the analysis of the expression of a set of genes. The pathogen was always re-isolated from the infected tissues and was able to cause wood discoloration. Touriga Nacional exhibited longer lesions than Cabernet Sauvignon, and the application of both products did not appear to reduce lesion length when compared to LC2017 applied alone. The elicitor effect of LC2017 on plant defense was confirmed by gene expression analysis, and no significant differences were found between plants treated with LC2017 and with both products. Moreover, a specific response related to the cultivar was verified, but this apparently unique interaction between product, cultivar and pathogen remains to be further investigated. Full article

Grapes and grape/wine byproducts such as non-fermented/semi-fermented or fermented grapes, skins, and seeds are a rich source of polyphenols, known to have nutraceutical properties. Grape byproducts present a great potential for the development of new beverages, such as infusions and tisanes. This work aimed to study the effects of different drying temperatures on the sensory and chemical properties of fermented grape pomace infusions, and to evaluate the same sensory and chemical characteristics on infusions of dried–minced grapes coated with different organic matrices. At the end of the work, it was possible to conclude that the presence of some coating agents results in changes in the sensory characteristics of the infusions, also altering the recorded antioxidant activity. However, all matrices seemed suitable for coating, and none showed negative characteristics in the infusions. Furthermore, of the three infusions (50, 60, and 70 °C), the one prepared with dehydrated grape pomace at 70 °C was the one with the highest pH value, highest °Brix value, and significantly greater concentration of phenolic compounds. In the sensory analysis, the constant presence of a bitter taste and astringent sensation stood out, which are not positive aspects from a sensory point of view. However, the addition of natural flavors—especially honey—made the infusion more sensorially pleasant. Overall, grape pomace dehydrated at 70 °C made it possible to obtain a product with phenolic compounds and antioxidant capacity that is more promising to integrate into human food, particularly via the preparation of infusions. Furthermore, the consumer may, if they so choose, add honey or another agent as a natural flavoring, making the final infusion more pleasant from a sensory point of view. Full article

Grapevine (Vitis vinifera L.) is one of the most economically important crops worldwide, especially due to the economic relevance of wine production. Abiotic stress, such as drought, may contribute to low yield, shifts in quality, and important economic loss. The predicted climate change phenomena point to warmer and dryer Mediterranean environmental conditions; as such, it is paramount to study the effects of abiotic stress on grapevine performance. Deficit irrigation systems are applied to optimize water use efficiency without compromising berry quality. In this research, the effect of two deficit irrigation strategies, sustained deficit irrigation (SDI) and regulated deficit irrigation (RDI), in the grape berry were assessed. The effects of different levels of drought were monitored in Touriga Nacional at key stages of berry development (pea size, véraison, and full maturation) through RNA-Seq transcriptome analysis and by specific differentially expressed genes (DEGs) monitoring through RT-qPCR. Handy datasets were obtained by bioinformatics analysis of raw RNA-Seq results. The dominant proportion of transcripts was mostly regulated by development, with véraison showing more upregulated transcripts. Results showed that primary metabolism is the functional category more severely affected under water stress. Almost all DEGs selected for RT-qPCR were significantly upregulated in full maturation and showed the highest variability at véraison and the lowest gene expression values in the pea size stage. Full article