Search Results (20)

The aim of the present study was to assess the qualitative and quantitative characteristics of the grapes and berries of seven different biotypes (A1–A7) of grapevine cultivar Assyrtiko, cultivated in Santorini. All biotypes of grapevine cultivar Assyrtiko are cultivated in the same soil and climatic conditions in the area of Akrotiri. Grapes from the different biotypes were collected during technological maturity. In the must of all samples, the following measurements were carried out: total soluble solids concentration, active acidity (pH), and total titratable acidity. Also, mechanical analyses of the grapes and berries of all the biotypes under study were performed. Moreover, using a spectrophotometer, the content of grape’s skin in total phenolics, condensed tannins, total ortho-diphenols, total flavonoids, total flavanols, total flavonols and flavones, and their antioxidant capacity with the use of FRAP and DPPH methods were quantified, while high-performance liquid chromatography (HPLC) identified the most important individual acids and individual sugars. The same measurements were also carried out for the grape seeds. The results of the present study revealed the effect of the biotype both in the qualitative and the quantitative characteristics of grape cultivar Assyrtiko, with statistically significant differences being observed among the different biotypes. Full article

The objective of this work was to investigate the effect of location on the composition and quality of wines from the viticultural zone PGI Drama. Grapes from two white (Sauvignon blanc, Assyrtiko) and three red varieties (Merlot, Cabernet Sauvignon, Agiorgitiko) were collected from nine locations within the zone during 2022. The vineyards span distances ranging from several hundred meters to 100 km, and their altitudes vary from 90 to nearly 820 m. Vinification was performed following the same protocol according to the type of wine. Wines were analyzed for quality parameters such as pH, total acidity, alcohol, and residual sugar content. In addition, elemental composition, phenolic content, antioxidant capacity, and sensory attributes of the wines were assessed. The obtained results suggested that besides the type of wine and variety, the location significantly affects the quality parameters of the wine. PCA analysis revealed that location is an important factor affecting the wine quality. The areas north and northwest proved more suitable for specific varieties, as they produce wines with more distinct organoleptic characteristics. The results provide insights into the behavior of international and native varieties in the face of global warming and assist in decisions concerning the most suitable plant material. Full article

Besides the other factors, the microclimate (terroir) influences the quality characteristics of wine. The Assyrtiko variety has adapted to the volcanic soil of Santorini but under climate change, finding an ideal location for full grape ripening represents a challenge in preserving the PDO quality of Santorini wines. Thus, this study aims to evaluate the effect of location and harvesting time on the quality of Assyrtiko wine. It assessed the location effect (three distant plots of land in three distant areas of the island) on the composition of grapes (water uptake, pH, sugar, and organic acid accumulation) during the ripening. The grapes were vinified using the same procedure. The aromatic volatile profile of the wines was evaluated with GC-MS. A two-way ANOVA revealed that besides location and harvest time, their interaction is also significant for the parameters studied, except for the interaction effect involving sugar content. The analysis of volatile aromatic compounds revealed that the wine from grapes harvested at a later date had a higher aromatic intensity with notes of citrus, white-fleshed, and tropical fruits. This wine surpasses the levels of 2-phenylethanol, isoamyl acetate, linalool, and 2-phenylethyl ester with 17.8%, 7.7%, 21.1%, and 15.6%, respectively, compared to the immediate next in descending order. Results suggest that the grape variety is better suited to the local climatic conditions when full grape ripeness is reached by the end of the growing season. Full article

Greek wines made from the indigenous grape varieties Assyrtiko, Malagousia, Moschofilero and Roditis are attracting the interest of wine producers and consumers due to their aromatic characteristics. However, there are few studies that focus on the unique wine characteristics of each variety and the relationship between the composition of volatile compounds and sensory properties. Monovarietal white wines (2018 vintage) were analyzed by gas chromatography–mass spectrometry to quantify 34 volatile compounds. Multivariate statistical analyses were used to investigate correlations between volatiles and sensory attributes identified by a trained panel. The results showed that the strongest aroma compounds were a group of terpenes, isoamyl acetate and phenylethyl acetate. Terpenes such as geraniol, α-terpineol, linalool and cis-rose oxide correlated with floral notes, especially in Moschofilero wines. In addition, isoamyl acetate contributed to the aroma of tropical fruits, especially banana, in the Roditis wines, while phenylethyl acetate correlated with rose, vanilla and fruity notes in both the Moschofilero and Roditis samples. The Assyrtiko wines and the Malagousia wines were mainly associated with compounds such as cis-3-hexen-1-ol and cis- and trans-furan linalool oxides, which may enhance fresh fruit and citrus aromas through synergistic effects. The common background aroma of the studied wines was mainly determined by higher alcohols, fatty acids and ethyl esters. This study provides a basis for understanding the typical aroma of white wines from indigenous Greek grape varieties, which will help producers develop targeted wine styles and will be useful for consumer promotion. Full article

The honeydew moth, Cryptoblabes gnidiella Millière (Lepidoptera: Pyralidae), is native to the Mediterranean Basin. However, it has recently been reported as an emerging grapevine pest in southern European Union countries and in the Middle East, North Africa, and South America. This may be attributed to the global warming trends. In this brief communication, we present the first documented cases of honeydew moth infestation of grapevine in Greece, specifically in two organic vineyards in the Regional Unit of Drama in Northeastern Greece in 2024. Notably, the infestations were limited to the late-ripening grape cultivar ‘Xinomavro’, harvested in October, while other cultivars such as ‘Assyrtiko’, ‘Malagousia’, ‘Cabernet sauvignon’, ‘Sauvignon blanc’, ‘Limniona’, ‘Chardonnay’, and ‘Agiorgitiko’, harvested in late August and early September, showed no signs of infestation. This suggests that the actual impact of C. gnidiella in Greece may be underestimated, as previous late summer infestations of lepidopteran larvae in vineyards were likely misattributed to L. botrana. We discuss the potential implications and concerns regarding the occurrence and management of this pest in Greece. Full article

Adaptive laboratory evolution (ALE) is a non-GMO technique utilized for the amelioration of wine yeast strains. Employing two-step ALE strategies, we recently acquired six evolved Saccharomyces cerevisiae populations with improved fermentative abilities compared to their parental strains in synthetic broths. Herein, we evaluated the qualities of the abovementioned evolved populations under real winemaking conditions, using the grape musts Assyrtiko and Roditis. The ethanol-tolerant populations evolved solely with glucose delayed to complete the fermentation due to slow fructose assimilation, albeit showing improved ethanol yields, compared to their parental strains. The volatile compounds of the evolved populations were significantly different from those of parental strains. Statistically significant differences were observed in the organoleptic profiles between the evolved populations’ and parental strains’ wines. Notably, wine from one evolved population (BLR200) was rated higher in overall aroma and quality. This study supports the magnitude of ALE strategies for the generation of novel wine yeasts. Full article

Assyrtiko is a rare ancient grape variety of Greece, which is known to produce Protected Designation of Origin (PDO) Santorini white wines. Besides the famous character of the volcanic terroir, Assyrtiko of Santorini is also marked by a low pH value and sharp acidity. The aim of the present study was to apply a new inoculation procedure that modulates the fermentation process by maintaining the unique sensorial characteristics of Assyrtiko wines based on acidity. For this purpose, the Lachancea thermotolerans species, known for the formation of lactic acid, was tested in sequential fermentation with three different Saccharomyces cerevisiae strains. At the end of the fermentation process, implantation control for S. cerevisiae strains (interdelta sequence profile analysis) was performed, oenological parameters were determined according to the OIV protocols, and the volatile compounds produced were measured by gas chromatography–mass spectrometry (GC/MS). Finally, all produced wines were evaluated by quantitative descriptive analysis by two groups of experts; the Greek team of oenologists from Santorini Island specialized in Assyrtiko wines, and the French team of oenologists specialized in wine from Bordeaux. As expected, the inoculated strain was the one that dominated the fermentation process, but nine S. cerevisiae indigenous strains were also identified in the produced wines. Lachancea thermotolerans produced 1 g/L of lactic and also modulated the volatile profile of the wines independently of the S. cerevisiae strain used. The origin of the panelists played an important role in bringing up sensorial traits, such as acidity. Our results led to a new interesting application of L. thermotolerans for white wine production adapted to climate change claims. Full article

Vitis vinifera, an economically significant grapevine species, is known for wine, juice, and table grape production. The berries of wine grapes host a diverse range of microorganisms influencing both grapevine health and the winemaking process. Indigenous to Greece, the emblematic variety Assyrtiko, renowned for high-quality white wines, originated from Santorini and spread to various Greek regions. Despite existing studies on the microbiota of several varieties, the carposphere microbiota of Assyrtiko grapes remains unexplored. Thus, we conducted a spatiotemporal metagenomic study to identify the epiphytic microbial community composition of Assyrtiko grapes. The study was conducted in two consecutive vintage years (2019 and 2020) across three different and distinct viticulture regions in Greece (Attica, Thessaloniki, Evros). We performed amplicon sequencing, targeting the 16S rRNA gene for bacteria and the ITS region for fungi, with subsequent comprehensive bioinformatic analysis. Our data indicate that the distribution and relative abundance of the epiphytic carposphere microbial communities of the Assyrtiko variety are shaped both by vintage and biogeography. Full article

Flow cytometry (FCM) is a widely used technique to study genome size (C-value), but recalcitrant metabolites in grapevines often hinder its efficiency in grapevine research. The aim of the present study was (i) to develop a novel buffer tailormade for the nuclei isolation of grapevines and (ii) to characterize a Cypriot germplasm collection based on C-values. A local cultivar “Xinisteri” was used as a pilot test to evaluate a Sorbitol-based buffer, while sprouting, young, and fully matured leaves were examined to evaluate the developmental parameter. The novel Sorbitol buffer was shown to have a coefficient of variation (CV) of 4.06%, indicating improved properties compared to other commonly used FCM buffers [WPB (7.69%), LB01 (6.69%), and LB (7.13%), respectively]. In addition, a significant variation in genome size between genotypes was found in a comprehensive application with 24 grape varieties. Nucleic content (2C) ranged from 0.577/1C pg for the “Assyrtiko” cultivar up to 0.597/1C pg for the “Spourtiko” cultivar, revealing a 17.6/1C Mbp difference. The lowest coefficient of variation (CV) across all entries was found in the variety “Ofthalmo” (2.29%), while the highest was observed in “Pinot Noir” (3.44%). Anova analysis revealed several distinct clusters, showing that in several cases, C-values can be used as a simple method to distinguish grapevine cultivars. Full article

Six wild-type non-Saccharomyces strains, belonging to the species Zygosaccharomyces bailii, Priceomyces carsonii, Trigonopsis californica, and Pichia manshurica, were evaluated for white wine production using Assyrtiko grapes from Santorini in Greece. Fermentation kinetics, in terms of glucose and fructose consumption and sensory analysis, was first employed to test the enological potential of the yeast strains. Based on their performance, two strains of Z. bailii (Zb-A19Y5 and Zb-K29Y2) and one strain of T. californica (Tc-A9Y1) selected for further analysis. The selected strains were tested in larger fermentation volumes for sugar consumption, while the produced wines were assessed for classical enological parameters, volatile compounds (GC/MS), and sensory analysis. Tc-A9Y1 could lead to dry wine (1 g/L of residual sugars) with 1.6 vol (12%) less alcohol than the other experimental wines. The wines that were fermented with the strain Zb-K29Y2 exhibited very high concentrations of isoamyl alcohol (604.33 ± 76.8 mg/L), but at the same time, they were characterized by low fruity notes. None of the produced wines presented any off-flavor aromas. Exploiting non-Saccharomyces strains with great fermentation capacity, which are able to produce high-quality wines and adapted to global warming conditions, is a new challenge for the wine industry. Full article

Grapevine leaves contain abundant CaO_x crystals located either within the mesophyll in the form of raphides, or in the bundle sheaths as druses. CaO_x crystals function as internal carbon pools providing CO₂ for a baseline level of photosynthesis, named “alarm photosynthesis”, despite closed stomata; thus, preventing the photoinhibition and the oxidative risk due to carbon starvation under adverse conditions. Structural and functional leaf traits of acclimated grapevine plants (Vitis vinifera L. cv. Assyrtiko) were investigated in response to water availability, in order to evaluate the dynamic functionality of CaO_x. Leaf water potential, leaf area, leaf mass per area, stomatal properties, gas exchange parameters and performance index (PI) were decreased in leaves of vines acclimated to water deficit in comparison to the leaves of well-irrigated vines, although the chlorophyll fluorescence parameters showed that the operational efficiency of the photosystem II (PSII) photochemistry (F_v/F_m) did not change, indicating that the photosynthetic apparatus was not subjected to water stress. During the afternoon, more than half of the morning’s existing druses disappeared in the drought-acclimated leaves. Also, the raphides’ area of the drought-acclimated leaves was reduced more than that of the well-watered leaves. The substantial decomposition of druses under water deficit conditions compared to that of the raphides may have important implications for the maintenance of their different though overlapping roles. According to the results, it seems likely that, under water deficit conditions, a mechanism of “alarm photosynthesis” provides an additional tolerance trait in the leaves of Vitis vinifera cv. Assyrtiko; hence, leaf structure relates to function. Full article

In the viticulture sector, robots are being employed more frequently to increase productivity and accuracy in operations such as vineyard mapping, pruning, and harvesting, especially in locations where human labor is in short supply or expensive. This paper presents the development of an algorithm for grape maturity estimation in the framework of vineyard management. An object detection algorithm is proposed based on You Only Look Once (YOLO) v7 and its extensions in order to detect grape maturity in a white variety of grape (Assyrtiko grape variety). The proposed algorithm was trained using images received over a period of six weeks from grapevines in Drama, Greece. Tests on high-quality images have demonstrated that the detection of five grape maturity stages is possible. Furthermore, the proposed approach has been compared against alternative object detection algorithms. The results showed that YOLO v7 outperforms other architectures both in precision and accuracy. This work paves the way for the development of an autonomous robot for grapevine management. Full article

Non-Saccharomyces (NS) yeasts are gaining popularity in modern winemaking for improving wine quality. Climate change is one of the biggest challenges winegrowing now faces in warm regions. Here, Lachancea thermotolerans LtS1 and Torulaspora delbrueckii TdS6 combined with Saccharomyces cerevisiae ScS13 isolated from Assyrtiko grapes from Santorini island were evaluated in grape must fermentation with the aim to mitigate major consequences of temperature rise. Different inoculation protocols were evaluated, including simultaneous and sequential mixed-strain inoculations, displaying significant variation in the chemical and kinetic characteristics. Both LtS1 and TdS6 could raise the titratable acidity (TA). TdS6 also reduced the volatile acidity (VA) and was thus chosen for further evaluation in microvinifications and pilot-scale fermentations. Consistent with lab-scale trials, sequential inoculation exhibited the longest persistence of TdS6 resulting in minimum VA levels. Diethyl succinate, ethyl propanoate, and ethyl isobutyrate were significantly increased in sequential inoculations, although a decline in the net total ester content was observed. On the other hand, significantly higher levels of TA, succinic acid, and 2-methylpropanoic were associated with sequential inoculation. The overall performance of TdS6 coupled with a high compatibility with S. cerevisiae suggests its use in the fermentation of Santorini-Assyrtiko or other high sugar musts for the production of structured dry or sweet wines. Full article

In modern wine-making technology, there is an increasing concern in relation to the preservation of the biodiversity, and the employment of “new”, “novel” and wild-type Saccharomyces cerevisiae strains as cell factories amenable for the production of wines that are not “homogenous”, expressing their terroir and presenting interesting and “local” sensory characteristics. Under this approach, in the current study, several wild-type Saccharomyces cerevisiae yeast strains (LMBF Y-10, Y-25, Y-35 and Y-54), priorly isolated from wine and grape origin, selected from the private culture collection of the Agricultural University of Athens, were tested regarding their biochemical behavior on glucose-based (initial concentrations ca 100 and 200 g/L) shake-flask experiments. The wild yeast strains were compared with commercial yeast strains (viz. Symphony, Cross X and Passion Fruit) in the same conditions. All selected strains rapidly assimilated glucose from the medium converting it into ethanol in good rates, despite the imposed aerobic conditions. Concerning the wild strains, the best results were achieved for the strain LMBF Y-54 in which maximum ethanol production (EtOH_max) up to 68 g/L, with simultaneous ethanol yield on sugar consumed = 0.38 g/g were recorded. Other wild strains tested (LMBF Y-10, Y-25 and Y-35) achieved lower ethanol production (up to ≈47 g/L). Regarding the commercial strains, the highest ethanol concentration was achieved by S. cerevisiae Passion Fruit (EtOH_max = 91.1 g/L, yield = 0.45 g/g). Subsequently, the “novel” strain that presented the best technological characteristics regards its sugar consumption and alcohol production properties (viz. LMBF Y-54) and the commercial strain that equally presented the best previously mentioned technological characteristics (viz. Passion Fruit) were further selected for the wine-making process. The selected must originated from red and white grapes (Assyrtiko and Mavrotragano, Santorini Island; Greece) and fermentation was performed under wine-making conditions showing high yields for both strains (EtOH_max = 98–106 g/L, ethanol yield = 0.47–0.50 g/g), demonstrating the production efficiency under microaerophilic/anaerobic conditions. Molecular identification by rep-PCR carried out throughout fermentations verified that each inoculated yeast was the one that dominated during the whole bioprocess. The aromatic compounds of the produced wines were qualitatively analyzed at the end of the processes. The results highlight the optimum technological characteristics of the selected “new” wild strain (S. cerevisiae LMBF Y-54), verifying its suitability for wine production while posing great potential for future industrial applications. Full article

The effect of oxidation on the organoleptic properties of white wines mostly involves increased browning color, loss of the fruity aromas, and appearance of unpleasant odors. Browning, however, is known to be related with polyphenol oxidation and therefore it may be delayed by the presence of antioxidants such as selenium (Se) and SO₂. On the other hand, the presence of oxidants such as metal ions and H₂O₂ can accelerate browning and oxidation phenomena. The browning capacity, the phenolic composition (both total and individual contents of flavanols and hydroxycinnamic acids), the antioxidant activity, and the SO₂ content of Assyrtiko white wines were studied after the addition of Fe²⁺ and H₂O₂ and Se at two temperatures, employing an accelerated test. Browning was approached from a kinetic point of view, and the study was focused on the implication of oxidants and antioxidants on browning rate, paying particular attention to the content of major redox-active polyphenols, including substances with an o-diphenol feature, such as flavanols and hydroxycinnamic acids. The results showed that after the addition of oxidants it was possible to significantly accelerate the rate of browning development (up to 4.7 and six times) depending on the temperature and the concentration of the added compounds. The presence of Se protected wine color and preserved total SO₂ at 35 °C, while at 50 °C, these effects were not observed. Total flavanol content decreased upon heating, while total hydroxycinnamic content showed a slight increase. Similarly, the content of the individual phenolic compounds (with the exception of caffeic acid and (+)-catechin at 35 °C) was decreased with oxidant addition, while Se addition was not adequate to prevent or even promote their oxidation. Full article