Investigating the Phenolic Composition of Merlot and Shiraz Grape Extracts and Wines Produced from Grapes With Different Seed-to-skin Ratios

Forecasting wine phenolic composition from infrared spectra of grapes extracts and monitoring of fermentations with optimised time-specific prediction models

This study aimed to investigate the impact of leaf removal on concentrations of anthocyanin, tannin, and methoxypyrazines (MPs) in Pinot noir grapes and wines. Leaf removal after 7 days (LR7), 30 days (LR30), and 60 days (LR60) of flowering were compared with no leaf removal control (LRC). Grapes and resultant wines were analysed for tannin and aroma composition using liquid chromatography and two-dimensional gas chromatography–mass spectrometry. All leaf removal treatments increased anthocyanin concentration in grapes and reduced MP levels in grape stems compared to LRC, indicating the effectiveness of both early and late leaf removal. Leaf removal after 7 days and 30 days were more effective in enhancing colour density, polymeric pigments, and tannin concentration in wines. Higher grape skin tannin and anthocyanin concentrations, along with lower seed tannin concentration in berries, correlated with higher tannin concentrations in wines. LR7 showed significantly higher skin-originated tannin proportion than LRC, suggesting a useful tool to manage tannin extraction. Aroma composition of resultant wines was influenced by leaf removal, although these differences were not evident in the sensory evaluation.

Pulsed electric field (PEF) is a non-thermal technology able to promote color and polyphenols extraction from grape skins. Most of the publications about PEF in winemaking report data concerning international varieties, poorly considering minor cultivars and the medium/long-term effects of the treatment on wine composition during storage. PEF was applied at different specific energies (2, 10, and 20 kJ kg−1) on grapes of the low-color red cv. Rondinella, after crushing-destemming. Pressing yield, the evolution of color, and total phenolic index (TPI) were measured during skin maceration. Moreover, the wines were characterized for basic compositional parameters, color, anthocyanin profile, phenolic composition (glories indices), metal content (Fe, Cr, and Ni), and sensory characters, two and twelve months after the processing, in comparison with untreated samples and pectolytic enzymes (PE). PEF did not affect fermentation evolution, nor did it modify wine basic composition or metal content. Treatments at 10 and 20 kJ kg−1 led to higher color and TPI in wines, in comparison to PE, because of increased content of anthocyanins and tannins. The sensory evaluation confirmed these findings. Modifications remained stable in wines after twelve months. Glories indices and vitisin A content highlighted greater potential stability of wine color in PEF-treated wines.

The aim of this work is mainly to determine the effect of the pedoclimatic conditions (“terroir”) on the phenolic composition of wine originated from three French red grape varieties Cabernet Sauvignon, Merlot and Syrah, cultivated in the region of Thessaloniki (Northern Greece); simultaneously a study of its evolution during aging in a stainless steel tank, in oak barrels of different origin and in bottles is conducted. Additionally, in this work, we try to compare the evolution of phenolic composition of wines during aging in French medium toast oak barrel and in American heavy toast oak barrel. For this reason, 20 red wine samples originated from this area were analyzed. The color markers were measured by UV-spectrometry, while the phenolic acids and catechin content of the wine samples and their evolution during aging were determine by UVis-High performance liquid chromatography. Significant differences detected among the three grape varieties regarding color parameters, total anthocyanins and some phenolic acids. The increase of the extraction time during vinification affected the amounts of phenolic acids, catechin, total phenolic index (TPI) and tannin content. Gallic acid and catechin were the most abundant phenolic compounds and their amounts, as well as the concentrations of several phenolic acids were significantly affected during the storage period. Finally, the phenolic composition and the amounts of phenolic acids did not appear to be affected by the origin of oak barrels.

A simple standardized technique for two-dimensional paper chromatographic "mapping" and estimation of the relative amounts of the phenolic substances in grape extracts was presented. This technique was applied to the study of weekly harvests of 12 grape varieties. The berry pulp tended to reflect the juice and seeds in phenolic composition. The juice phenolics, as a rule, were predominantly blue-fluorescing substances resembling chlorogenic acid and its analogs. Calzin and one of its parents, Refosco, were unique among 34 varieties tested in having a considerable content of astringent tannin in the juice. Skin extracts were quite variable in qualitative phenolic composition by variety, especially considering, but in addition to, the presence or absence of anthocyanins. The phenolic composition of the seeds, however, followed a similar pattern in red or white grapes and in varieties with parentage from two species of <i>Vitis</i>. Among a total of about 25 differentiated substances readily oxidized by FeCl₃-K₃Fe-(CN)₆ and considered as phenols, the majority were present in the seeds of all varieties at similar stages, and usually in roughly similar proportions. Varietal differences did occur with respect to the presence or absence of a few of the substances and the relative amounts of those present per unit of total phenol. The nature of several of the substances was outlined, and, in particular, evidence was presented that one was catechin, one was epicatechin, and a third was epicatechin gallate. Although these flavanols have been reported in grapes (4, 6) previously, epicatechin gallate has not always been found in seeds (6). A considerable metabolism of phenolic substances in seeds during ripening was found even up to the last stages, as shown by the appearance or increase of some and the decrease of others in relation to a unit of total phenol.

Oxygen contribution to phenolic evolution during aging of red wines

Background. The use of faba bean (Vicia faba L.) as a feed and food plant is hindered by the presence of antinutritional substances and in particular phenolic compounds – tannins – in the seed coat. The existence of low-tannin or zero-tannin forms in the faba bean gene pool allows breeders to promote this trait. The aim of this work was to carry out biochemical validation of a known morphological marker of low tannin content and identify relationships of some phenotypic traits characterized by accumulation of phenolic compounds (tannins and anthocyanins) with their concentration for use as additional morphological markers of the low content of these antinutrients in bean seeds.Materials and methods. Associations of the presence/absence of anthocyanin in seedlings, pigmentation on petals, and dark extrafloral nectaries on stipules with the content of tannins and anthocyanins were analyzed in 10 faba bean accessions with different seed coat colors from the VIR collection. The plants were grown and evaluated in Leningrad Province in 2020–2021. Tannins in seeds were assessed using Leventhal’s method. Anthocyanins were analyzed in the green biomass of plants using a spectrophotometric method.Results and conclusion. Different combinations of the studied morphological features associated with the coloration of the studied organs were found. A high positive correlation between the levels of anthocyanins and tannins (r = 0.79) was identified as well as a direct connection of the high value of these traits with the presence of a dark extrafloral nectary on stipules and anthocyanin in seedlings. The absence of anthocyanin staining on seedlings and the absence of dark-colored extrafloral nectaries on stipules can serve as markers of low-tannin genotypes in the early stages of plant development. The light seed coat color that does not darken for a long time may also be the evidence of low tannin content.

Propolis, a type of resin produced by honey bees, has many medicinal properties. Various extraction methods and conditions had been studied to extract the bioactive compounds from raw propolis. However, different extraction methods and extraction conditions were reported to exhibit different extraction efficiencies. Hence, in this study, different extraction methods, namely maceration, ultrasound-assisted extraction and combination of maceration and ultrasound-assisted extraction, as well as extraction solvents and extraction times, were examined to investigate the effects on the amount of total phenolic content, total flavonoid content and antioxidant activity of Tetrigona apicalis Malaysian propolis extract. Experimental results showed that combination method of maceration and ultrasound-assisted extraction is the best method for extracting the highest amount of total phenolic content with 70% aqueous ethanol as solvent and obtained at the longest extraction time (24 h of maceration and 60 min of ultrasound-assisted extraction). While for total flavonoid content, maceration exhibited the best extraction method and the highest amount of flavonoid was obtained from 80% aqueous ethanol at the lowest extraction time (8 h). Meanwhile, antioxidant activity was found to have strong correlations with phenolic and flavonoid contents. In conclusion, it is crucial to develop effective extraction method and conditions depending on the targeted compounds and desired properties to enhance the extraction efficiency.

Flavonoids impart color and mouthfeel to grapes and wine and are very sensitive to environmental conditions. Growth chamber experiments were performed to investigate the effect of temperature regimes and the differences between day/night temperatures on anthocyanins and flavonols in Merlot grapes. Among the regimes tested, the ones with diurnal 20°C determined the highest levels of anthocyanins and flavonols. Higher diurnal temperatures decreased those levels but increased the proportion of methoxylated and acylated species. When regimes with the same day temperature but different night temperatures were compared, differences between day/night temperatures did not affect anthocyanins, unless a difference of 25°C between day and night temperatures was imposed. When regimes with the same night temperature but different day temperatures were compared, the regime with higher day temperature had a lower anthocyanin level. No relationships were observed between the effects of temperature regimes on anthocyanin level and the expression of key anthocyanin genes. However, the effects on anthocyanin acylation level were consistent with the effects on the acyltransferase expression, and the effects on flavonol level were consistent with the effects on the expression of key flavonol genes. This study indicates that, in Merlot grapes, anthocyanins and flavonols are mostly sensitive to day temperatures.

Studies on regulation of production of phenolics in strawberry (Fragaria X ananassa Duch,) fruit were initiated by monitoring phenylalanine ammonia-lyase (PAL) activity and levels of anthocyanins, flavonoids, tannins, and other soluble phenols throughout fruit ontogeny in `Tillikum'. PAL catalyzes the first step in the biosynthesis of phenylpropanoids, which are further modified into a wide variety of phenolic compounds. Peak in PAL activity (1 mol· s -1 = 1 kat) of 90 pkat· mg -1 protein was detected at 5 and 27 days after anthesis (DAA), when fruit was green and nearly ripe, respectively. PAL activity was only ≈10% of peak values in the white berry stage, when. fruit growth was most rapid. The second peak in PAL activity was followed by a rapid drop, to nearly zero in red-ripe fruit at 30 DAA. Total soluble phenols reached a maximum level soon after anthesis, just before the first peak in PAL activity, then declined to a low constant value well in advance of fruit ripening. Similar changes were observed in levels of tannins and flavonoids that, at anthesis, accounted for 44% and 51% of the soluble phenols, respectively. The concentration of anthocyanin was very low throughout most of fruit development, but beginning at 23 DAA it increased from &lt;0.03 to &gt;0.53 mg·g -1 fresh weight in 3 days. This accumulation paralleled the second rise in PAL activity. Accordingly, strawberry fruit have a developmental-dependent expression of PAL activity and accumulation of phenolic substances derived from the phenylpropanoid pathway.

White turmeric (Curcuma zedoaria (Christm.) Roscoe) is one of Indonesian herbal medicine. The extraction process to get active compound was influenced by some factor such as solvent, temperature, time, and method of extraction. The objective of this study was to determine the significant factor of extraction that is solvent, temperature and time of extraction on the polyphenol content and antioxidant activity of white turmeric (Curcuma zedoaria (Christm.) Roscoe) rhizome. Extraction was done by dynamic maceration method with variations (23 factor variable design) of solvent (ethanol 95% and water), temperature (25°C and 70°C), time (6 and 24 hours). The method of analysis of polyphenol content using Folin Ciocalteu reagent, and the antioxidant activity using DPPH free radical reduction method. The experiment design and data analysis using software Design Expert ver.10. The result showed that extraction using ethanol 95% at 70°C for 24 hours was gave high polyphenol content and antioxidant activity. Data analysis was showed that polyphenol content and antioxidant activity was influenced only by solvent of extraction. This study indicated that solvent is significant extraction factor for polyphenol content and antioxidant activity of white turmeric (Curcuma zedoaria (Christm.) Roscoe) rhizome. Keywords: Antioxidant, Curcuma zedoaria (Christm.) Roscoe, extraction, polyphenol

Natural dyes from mahogany are usually obtained by conventional extraction. This extraction process requires a large solvent, a long duration of the process so that the energy requirements are also higher. Therefore, the use of "green techniques" to extract natural dyes with a minimum of energy and solvent should be considered. One extraction method that has been developed is the microwave-assisted extraction (MAE) method. In this work, the effects of microwave power, material to solvent ratio, and the heating time on the extraction results and the pigment components of the extract were examined. A comparison of the time required for reflux extraction and Soxhlet was also made. In microwave extraction, the highest yield was obtained at optimum extraction conditions such as microwave power of 600 W, the ratio of material to solvent of 0.02 g/mL, extraction time of 30 min. While for reflux and Soxhlet extraction, the extraction time needed to obtain optimum yield was 120 min and 720 min, respectively. Identification of compound components by the phytochemical test. Descriptions of the effects of microwave and conventional extraction are shown by damage to the surface structure of solid materials using Scanning Electron Microscopy (SEM).

Astringency is one of the most important sensory attributes in red wine and is attributed to the presence of phenolic compounds. The objective of this study was to determine the relationship between tannin, anthocyanin, and small (SPP) and large (LPP) polymeric pigment concentrations in numerous Washington State red wines and to relate these values to perceived astringency. Three groups of wines were formed from a larger collection of wines based on tannin concentration: low (&lt;400 mg/L CE), medium (400–800 mg/L CE), and high (&gt;800 mg/L CE). Cabernet Sauvignon wines representing low, medium, and high tannin concentrations were selected and evaluated by 18 untrained panelists. Sensory results indicated that panelists gave significantly higher astringency ratings to wines high in tannin concentration compared with wines low in tannin concentration (<i>p</i> ≤ 0.05). In a second study, a trained panel evaluated Cabernet Sauvignon and Merlot wines representing combinations of low, medium, and high tannin, anthocyanin, SPP, and LPP concentrations. Results indicated that perceived astringency was significantly correlated with tannin, SPP, and LPP levels, while bitterness was significantly correlated with SPP, LPP, and tannin levels (<i>p</i> ≤ 0.05). These results indicated a relationship between polyphenolic compounds (tannins, SPP, and LPP) and the sensory attributes of astringency and bitterness.

Evaluation of the antimicrobial activity of grape extract against Bacillus cereus in rice

In this current special issue, different aspects related to phenolic compounds in fruit beveragesare presented.[...]