Red Wine
Longevity
The news about wine keeps getting better. Dutch researchers say that a half-glass of wine per day might help you live longer--five years longer, in fact. (Remember, though, excessive drinking can lead to health problems that may shorten your life.) Though the researchers note that more study is needed, the theory is that light alcohol consumption--and especially red wine--may contribute to longevity because the "polyphenolic compounds contained in wine have been seen in animals to stop the build up of fatty tissue in the arteries that can result in stroke or heart attack."
Improves Heart Health
Japanese researchers believe that light to moderate drinking paired with socialization (enter happy hour) can significantly reduce your risk for heart disease. While the researchers mostly looked at men, it's easy to see why the findings could be true for women too. Most health experts are fine with light drinking--one glass per day (but not every day) for women. And aren't we all happier when we're spending time with friends?
Reduces Inflammation
Those who drink were found to have a significantly reduced risk of developing several arthritic conditions including Rheumatoid Arthritis (RA), Osteoarthritis (OA), reactive arthritis, psoriatic arthritis and spondylarthropathy, according to Dutch researchers. Researchers aren't exactly certain why alcohol consumption (note, no guidelines were given as to which type of alcohol and how much, but we can safely assume that the scientists are talking about moderate drinking here), but they speculate that alcohol may have inflammation-reducing effects.
Aids Weight Loss
Researchers at Brigham and Women's Hospital in Boston who studied the alcohol consumption of more than 19,000 women over 13 years found that women who drank a "light to moderate amount of alcohol" (defined by no more than two servings a day of wine, beer or liquor--I'll add that some studies have found that any more than one drink per day for females to be excessive, so just file that away) tended to gain less weight than women who didn't drink. The study was recently published in the journal Archives of Internal Medicine.
An explanation, please? "Women who drink moderate amounts of alcohol tend to eat less food, particularly carbohydrates," said cardiologist Lu Wang, lead researcher on the study and an instructor at Brigham and Women's Hospital, who spoke to USA Today.
Fights Osteoporosis
A new study reports that beer is a significant source of dietary silicon. Dietary what? It's an ingredient believed to increase bone mineral density, and researchers from the Department of Food Science & Technology at the University of California, Davis, say that beer is loaded with it.
They studied commercial beer production and found that most commercial beer--especially hoppy beer--is a rich source of dietary silicon. Based on these findings, the scientists suggest that moderate beer consumption may actually help fight osteoporosis.
Phenolic compounds in wineContents from Wikipedia encyclopedia
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The phenolic compounds in Syrah grapes contributes to the taste, color and mouthfeel of the wine.
The phenolic compounds in wine include a large group of several hundred chemical compounds, known as polyphenolics, that affect the taste, color and mouthfeel of wine. This large group can be broadly separated into two categories-flavonoids and non-flavonoids. Flavonoids include anthocyanins and tannins which contribute to the color and mouthfeel of the wine. Non-flavonoids include stilbenes such as resveratrol and compounds derived from acids in wine like benzoic, caffeic and cinnamic acid. In winegrapes, phenolics are found widely in the skin, stems and seeds. During the growth cycle of the grapevine, sunlight will increase the concentration of phenolics in the grape berries with the development of phenolics being an important component of canopy management. Most phenols are classified as secondary metabolites and are not active in the primary metabolism and function of the grapevine. They are water soluble and will often secrete into the vacuole of grape berries as glycosides. In winemaking, the process of maceration or "skin contact" is used to increase the influence of phenols in wine. Phenolic acids are found in the pulp or juice of the wine and can be commonly found in white wines which usually doesn't go through a maceration period. The process of oak agingcan also introduce phenolic compounds to wine, most notably in the form of vanillin which adds vanilla aroma to wines.[1]
Flavonoids
Main article: Flavonoids
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The process of maceration or extended skin contact allows the wine to extract phenolic compounds (including those that form a wine's color) from the skins of the grape.
In red wine, up to 90% of the wine's phenolic content fall under the classification of flavonoids. These phenols, mainly derived from the stems, seeds and skins are often leeched out of the grape during the maceration period of winemaking. The amount of phenols leeched is known as extraction. They contribute to the astringency, color and mouthfeel of the wine. In white wines the number of flavonoids is reduced due to less skin contact that they receive in winemaking. Within the flavonoid category is a subcategory known as flavonols, which includes the yellow pigment inducing phenol-quercetin. Like other flavonoids, the concentration of flavonols in the grape berries increases as they exposed to sunlight. Some viticulturalists will use measurement of flavonols like quercetin as an indication of a vineyard's sun exposure and the effectiveness of canopy management techniques. There is on going study in the health benefits of wine derived from the antioxidant and chemopreventive properties of flavonoids.[2]
Anthocyanins
Main article: Anthocyanin
Anthocyanins are phenolic compounds found throughout the plant kingdom, being responsible for the blue to red colors found inflowers, fruits and leaves. In wine grapes, they develop during the stage of veraison when the skin of red wine grapes change color from green to shading from red to black. As the sugars in the grape increase during ripening, so does the concentration of anthocyanins. In most grapes anthocyanins are found only in the outer cell layers of the skin, leaving the grape juice inside to be virtually colorless. Therefore to get color pigmentation in the wine, the fermenting must needs to be in contact with the grape skins in order to extract the anthocyanins. For this reason, white wine can be from red wine grapes as in the case for many white sparkling wines which are often made from the red wine grapes of Pinot noir and Pinot meunier. The exception to this is the small class of grapes known as teinturiers, such as Alicante Bouschet, which has a small amount of anthocyanins in the pulp which produces pigmented juice.[3]
There are several types of anthocyanins found in wine grapes which are responsible for the vast range of coloring found in wine grapes from ruby red to dark black. Ampelographers can use this observation to assist in the identification of different grape varieties. The European vine family Vitis Vinifera is characterized with anthocyanins that are composed of only one molecule of glucose while non-Vinifera vines such as hybrids and the American Vitis labrusca will have anthocyanins with two molecules. In the mid-20th century, French ampelographers used this knowledge to test the various vine varieties throughout France to identify which vineyards still contained non-Vinifera plantings.[3]
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Tempranillo has a high pH level which means that there is a higher concentration of blue and colorless anthocyanin pigments in the wine. The resulting wine's coloring will have more blue hues than bright ruby red hues.
The color variation in the finished red wine is partly derived from the ionization of anthocyanin pigments caused by the acidity of the wine. In this case, the three types of anthocyanin pigments are red, blue and colorless with the concentration of those various pigments dictating the color of the wine. A wine with low pH (and such greater acidity) will have a higher occurrence of ionized anthocyanins which will increase the amount of bright red pigments. Wines with a higher pH will have a higher concentration of blue and colorless pigments. As the wine ages, anthocyanins will react with other acids and compounds in wines such as tannins, pyruvic acid and acetaldehyde which will change the color of the wine, causing it to develop more "brick red" hues. These molecules will link up to create polymers that eventually exceed their solubility and become sediment at the bottom of wine bottles.[3]
Tannins
Main article: Tannin
Tannins refer to the diverse group of chemical compounds in wine that can affect the color, aging ability and texture of the wine. While tannins can not be smelt or tasted, they can be perceived during wine tasting by the tactile drying sensation and sense of bitterness that they can leave in the mouth. This is due to the tendency of tannins to react with proteins, such as the ones found in saliva. In food and wine pairing, foods that are high in proteins (such as red meat) are often paired with tannic wines to minimize the astringency of tannins. However, many wine drinkers find the perception of tannins to be a positive trait-especially as it relates to mouthfeel. The management of tannins in the winemaking process is a key component in the resulting quality of the wine.[4]
Tannins are found in the skin, stems and seeds of wine grapes but can also be introduced to the wine through the use of oak barrels and chips or with the addition of tannin powder. The natural tannins found in grapes are known as proanthocyanins due to their ability to release red anthocyanin pigments when they are heated in an acidic solution. The tannins are formed by enzymes during metabolic processes by the grapevine. The amount of tannins found naturally in grapes varies depending variety with Cabernet Sauvignon, Nebbiolo, Syrah and Tannat being 4 of the most tannic grape varieties. The reaction of tannins and anthocyanins with the phenolic compound catechins creates another class of tannins known as pigmented tannins which influences the color of red wine. The tannins derived from oak influence are known as "hydrolysable tannins" being created from the ellagic and gallic acid found in the wood.[4]
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Fermenting with the stem, seeds and skin will increase the tannin content of the wine.
In the vineyards, there is also a growing distinction being made between "ripe" and "unripe" tannins present in the grape. This "physiological ripeness", which is roughly determined by tasting the grapes off the vines, is being used along with sugar levels as a determination of when to the harvest. The idea is that "riper" tannins will taste softer but still impart some of the texture components found favorable in wine. In winemaking, the amount of the time that the must spends in contact with the grape skins, stems and seeds will influence the amount of tannins that are present in the wine with wines subjected to longer maceration period having more tannin extract. Following harvest, stems are normally picked out and discarded prior to fermentation but some winemakers may intentionally leave in a few stems for varieties low in tannins (like Pinot noir) in order to increase the tannic extract in the wine. If there is an excess in the amount of tannins in the wine, winemakers can use various fining agents like albumin, casein and gelatin that can bind to tannins molecule and precipitate them out as sediments. As a wine ages, tannins will form long polymerized chains which come across to a taster as "softer" and less tannic. Oxygen can bind with tannin molecules to make them larger and seem also seem softer on the palate. The winemaking technique of micro-oxygenation and decanting wine use oxygen to partial mimic the effect of aging on tannins.[4]
[edit] Other Flavonoids
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Phenolic compounds like tannins and vanillin can be extracted from aging in oak wine barrels.
Catechins are flavonoids that contribute to the construction of various tannins and contribute to the perception of bitterness in wine. They are found in highest concentrations in grape seeds but are also in the skin and stems. Catechins play a role in the microbial defense of the grape berry, being produced in higher concentrations by the grape vines when it is being attacked by grape diseases such as downy mildew. Because of that grape vines in cool, damp climates produce catechins at high levels than vines in dry, hot climates. Together with anthocyanins and tannins they increase the stability of a wines color-meaning that a wine will be able to maintain its coloring for a longer period of time. The amount of catechins present varies amount grape varieties with varietals likeMerlot and Pinot noir having high concentrations while Syrah has very low levels. As an antioxidant, there are some studies into the health benefits of moderate consumption of wines high in catechins.[5]
Vanillin is a phenolic aldehyde most commonly associated with the vanilla notes in wines that have been aged in oak. Some trace amounts of vanillin are found naturally in the grapes themselves but they are most prominent in the lignin structure of oak barrels. Newer barrels will impart more vanillin, with the concentration present decreasing with each subsequent usage.[6]
[edit] Non-Flavonoids
See also: Wine and health
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Wines made from Pinot noir in a cooler climate tend to have more resveratrol than wines made from varieties like Cabernet Sauvignon from warmer climates.
Resveratrol is a phenolic compound found in highest concentration in the skins of wine grapes. Both red and white wine grape varieties have resveratrol but more frequent use of skin contact and maceration in red winemaking means that red wines will normally have 10 times more resveratrol than white wines. It generally produced by grape vines as a means of microbial defense, though production can be artificially stimulated by ultraviolet radiation. Grapevines in cool, damp regions with higher risk of grape diseases, such as Bordeaux and Burgundy, tend to produce grapes with higher levels of resveratrol than warmer, drier wine regions like California and Australia. Additionally, different grape varieties are prone to differing levels with Muscadines and the Pinot family having high levels while the Cabernet family being noted for lower levels of resveratrol. In the late 20th century, interest in the possible health benefits of resveratrol in wine was spurred by discussion of the French paradox involving the health of wine drinkers in France.[7]
See alsoReferences
Red wine and resveratrol: Good for your heart?
Red wine and something in red wine called resveratrol might be heart healthy. Find out the facts, and hype, regarding red wine and its impact on your heart.
By Mayo Clinic staff
Red wine, in moderation, has long been thought of as heart healthy. The alcohol and certain substances in red wine called antioxidants may help prevent heart disease by increasing levels of "good" cholesterol and protecting against artery damage.
While the news about red wine might sound great if you enjoy a glass of red wine with your evening meal, doctors are wary of encouraging anyone to start drinking alcohol. That's because too much alcohol can have many harmful effects on your body.
Still, doctors do agree that something in red wine appears to help your heart, though it's unclear just exactly what that "something" is. Researchers think antioxidants, such as flavonoids or a substance called resveratrol, have promising heart-healthy benefits.
Antioxidants aren't the only substances in red wine that look promising. The alcohol in red wine also appears to be heart healthy. Find out what's known — and not known — about red wine and its possible heart-health benefits.
How is red wine heart healthy?
Research studies on the heart-health benefits of red wine have reported mixed results. Some studies show that red wine seems to have even more heart-health benefits than other types of alcohol, while other studies show that red wine isn't any better than beer, white wine or liquor for heart health. There's still no clear evidence yet that red wine is superior to other forms of alcohol when it comes to possible heart-health benefits.
The studies supporting red wine suggest antioxidants in red wine called polyphenols help protect the lining of blood vessels in your heart. These antioxidants come in two main forms: flavonoids and nonflavonoids.
�Flavonoids. These antioxidants are found in a variety of foods, including oranges, grape juice, apples, onions, tea and cocoa. Other types of alcohol, such as white wine and beer, contain small amounts, too, but red wine has higher levels.
�Nonflavonoids. These antioxidants found in red wine have recently been of particular interest because they appear to help prevent arteries from becoming clogged with fatty blockages. However, these studies mostly involved mice — not humans. Resveratrol is the nonflavonoid that's received the most attention from researchers.
Resveratrol in red wine
Resveratrol might be a key ingredient in red wine that helps prevent damage to blood vessels, reduces "bad" cholesterol and prevents blood clots.
Most research on resveratrol has been conducted on animals, not people. Research in mice given resveratrol has indicated that the antioxidant might also help protect them from obesity and diabetes, both of which are strong risk factors for heart disease. However, those findings were reported only in mice, not in people. In addition, to get the same dose of resveratrol used in the mice studies, a person would have to consume 100 to 1,000 bottles of red wine a day.
Some research shows that resveratrol could be linked to a reduced risk of inflammation and blood clotting, both of which can lead to heart disease. More research is needed before it's known whether resveratrol was the cause for the reduced risk.
Some companies sell supplements containing resveratrol. However, not enough is known about resveratrol's effects to endorse resveratrol supplements. Research into the potential heart-health benefits of resveratrol is continuing.
Red wine and resveratrol: Good for your heart?
Resveratrol in grapes and other foods
The resveratrol in red wine comes from the skin of grapes used to make wine. Because red wine is fermented with grape skins longer than is white wine, red wine contains more resveratrol. Simply eating grapes, or drinking grape juice, has been suggested as one way to get resveratrol without drinking alcohol. Some studies have suggested that red and purple grape juices have some of the same heart-healthy benefits of red wine.
Other foods that contain some resveratrol include peanuts, blueberries and cranberries. It's not yet known how beneficial eating grapes or other foods might be compared with drinking red wine when it comes to promoting heart health. The amount of resveratrol in food and red wine can vary widely.
How does alcohol help the heart?
Various studies have shown that moderate amounts of all types of alcohol benefit your heart, not just alcohol found in red wine. It's thought that alcohol:
�Raises high-density lipoprotein (HDL) cholesterol, the "good" cholesterol
�Reduces the formation of blood clots
�Helps prevent artery damage caused by high levels of low-density lipoprotein (LDL) cholesterol, the "bad" cholesterol
Drink in moderation — or not at all
Red wine's potential heart-health benefits look promising. Those who drink moderate amounts of alcohol, including red wine, seem to have a lower risk of heart disease. However, more research is needed before we know whether red wine is better for your heart than are other forms of alcohol, such as beer or spirits.
Neither the American Heart Association nor the National Heart, Lung, and Blood Institute recommend that you start drinking alcohol just to prevent heart disease. Alcohol can be addictive and is associated with other health issues.
Drinking too much increases your risk of high blood pressure, high triglycerides, liver damage, obesity, certain types of cancer, accidents and other problems. In addition, even small amounts of alcohol can cause cardiomyopathy — weakened heart muscle — causing symptoms of heart failure in some people. If you have heart failure or a weak heart, you should avoid alcohol completely. If you take aspirin daily, you should avoid or limit alcohol, depending on your doctor's advice. You also shouldn't drink alcohol if you're pregnant. If you have questions about the benefits and risks of alcohol, talk to your doctor about specific recommendations for you.
If you already drink red wine, do so in moderation. Moderate drinking is defined as an average of two drinks a day for men and one drink a day for women.
A drink is defined as 12 ounces (355 milliliters, or mL) of beer, 5 ounces (148 mL) of wine or 1.5 ounces (44 mL) of 80-proof distilled spirits.
The limit for men is higher because men generally weigh more and have more of an enzyme that metabolizes alcohol than women do.
Tannins - types and amounts in grapes and wines
Tom Collins
Senior Research Enologist
Beringer Blass Wine Estates
Formerly the Manager of East Coast Grower Relations and Vineyard Operations for Canandaigua Wine Company, Tom Collins is now a Senior Research Enologist with Beringer Blass Wine Estates in St. Helena, CA. His viticultural areas of interest while with Canandaigua included evaluation of new sprayer technology, vineyard mechanization and vineyard redevelopment. In his position with Beringer Blass, Tom oversees the development and implementation of a broad range of winemaking research projects, including yeast strain trials, yeast nutrition trials, color enhancement and stability trials for red wines and the winemaking evaluation of various vineyard research projects. He is also involved in the evaluation of new technologies for the winemaking laboratory, as well as lab proficiency training and testing in all of Beringer Blass' wineries in California.
Tannins are complex polymeric compounds that are responsible at least in part for many of the sensory attributes of wines, particularly red wines. Tannins are involved in the tactile sense of astringency in red wines, they play an important role in the intensity and stability of color in red and tannins are responsible in many cases for the brown color that develops with age in both red and white wines. The flavonoid compounds that polymerize to form some types of tannins are also thought to provide many of the health benefits associated with the moderate consumption of wines.
The grape berries themselves contain some tannin, particularly in the seeds and skins. Certain types of tannins arise from polymerization of monomeric phenols during wine processing and aging. Wines aged in wood cooperage or wines that have had exposure to oak dust, chips or staves will also extract some types of tannins from the wood. Finally, pure or relative pure mixtures of tannins may be added to the wine during processing or aging.
Tannins are polymers of simpler phenols, which can generally be classed as either flavonoid or non-flavonoid. The simplest of phenols is phenol itself, which consists of an aromatic ring and a single hydroxyl group.
Catechin is an example of a flavonoid, in this case a flavan-3-ol. Flavonoids have a common structure that consists of an aromatic “A” ring, an oxygen containing heterocyclic “C” ring and a second
Aromatic “B” ring. There are several classes of flavonoids that differ primarily in the structure of the heterocyclic ring. From these and similar building blocks, tannins are polymerized. There are two primary classes of tannins found naturally in grapes and wine. The first class, the hydrolysable tannins, is based on non-flavonoid phenolics. The basic unit in a hydrolysable tannin is a polyhydroxy molecul.
Gallic acid is usually a sugar, to which are bound multiple non-flavonoid phenols, often gallic acid (Figure 3) or ellagic acid, which is a dimer of gallic acid (Figure 4). Gallotannin (Figure 5) is an example of a hydrolysable tannin. These tannins are readily hydrolyzed under acidic or basic conditions, hence their name. Non-flavonoid phenols and hydrolysable tannins are also found primarily in the skins and in the pulp.
The second primary class of tannins in grapes and wines are the condensed tannins. These tannins are polymers of primarily flavan-3-ols (catechin and epicatechin), along with the anthocyanin pigments. If an anthocyanin is incorporated into the tannin, the resulting polymer is often colored. As a covalent bond is formed between the individual units within a condensed tannin, these tannins are not readily hydrolyzed. Typically the linkage occurs between the 4 position (on the heterocyclic ring) and the 8 position on the aromatic A ring, although it is possible for the linkage to occur at the 6 position as well.
An epicatechin tetramer consists of linkages just between the 4 position and the 8 position of the adjacent epicatechin units. These polymers can include both catechin and epicatechin units.
The epicatechin and catechin monomers are found primarily in the seed coat in grapes, and to a lesser extent in the skins. Polymers of these two compounds (condensed tannins) are found in the seeds, skins and to a lesser extent, in the pulp. Monomeric anthocyanins and polymeric pigments are found primarily in the skins of red grapes.
Polymerization of the condensed tannins continues as the juice is processed into wine and as the wine ages. As the number of units in the polymers increases, their color changes from colorless to yellow to brown. As the number of units increases, the solubility of the polymer decreases, and eventually the polymer will precipitate from solution. If the tannin incorporates an anthocyanin moiety, this precipitation will result in slowly declining color as the wine ages.
As tannins are very complex compounds, common methods for determining their concentrations in grape tissues or wines are often indirect or empirical in nature. Comparison of results from different studies can be problematic. Most analyses of tannins begin with an attempt to differentiate them from their monomeric building blocks. This may be done either by a separation based on the larger size of the tannins or by selective precipitation or extraction. Once separated from the monomeric phenols, the tannins may be analyzed by a number of available methods for the analysis of phenolic compounds. The most widely used is probably the Folin-Ciocalteu colorimetric method. Gallic acid is used as the standard for this method and results are reported as gallic acid equivalents (GAE). It is not possible, given the complex mixture of tannins present in grape tissue or wine samples to convert GAE into an exact amount of tannin, but GAE are never-the-less useful as a tool for comparisons amongst samples or treatments.
Using a low pressure chromatographic method for separation of non-polymeric and polymeric phenols, Kantz and Singleton (1991) reported that grape seeds contained the highest amount of polymeric phenols of the grape tissues they looked at, with polymeric phenols ranging from 21 to 27 mg GAE/g fresh weight. Polymeric phenols accounted for 60 to 70% of the total extractable phenolic content of the seeds. Grape skins contained much lower total and polymeric phenols and were much more variable, ranging from 0.1 to 5 mg GAE/g fresh weight of skins; polymeric phenols accounted for from 6% to 43% of the total extractable phenols in the skins. Thorngate and Singleton (1994) subsequently showed that most of the phenolic material in the seeds was actually in the outer layers of the seed, with very little found in the seed endosperm.
Of the total pool of phenolic material available in the grape berry, only a part is subsequently found in the resulting wines. Incomplete extraction, adsorption with yeast lees and other solids, precipitation with grape or yeast proteins and a host of other reactions all tend to limit the total phenol and polymeric phenol levels in wine. Singleton and Draper (1964) studied the extraction of polymeric phenols from grape seeds into wine; complete extraction of the tannin in the seeds should result in a tannin content of 200 to 400 mg/L. Under typical red wine fermentation conditions about half that amount is common. That level is then further reduced by other reactions and by precipitation. They also showed that in the same length of time, more complete extraction is favored by increased temperature and increased ethanol content.
References:
Kantz, K. and V.L.Singleton. Isolation and determination of polymeric polyphenols using Sephadex LH-20 and analysis of grape tissue extracts. Am. J. Enol. Vitic. 42:309-16 (1991).
Singleton, V.L. and D.E. Draper. The transfer of polyphenolic compounds from grape seeds into wines. Am. J. Enol. Vitic. 15:34-40 (1964).
Thorngate, J.H. and V.L. Singleton. Localization of procyanidins in grape seeds. Am. J. Enol. Vitic. 45: 259-262 (1994).
32nd Annual New York Wine Industry Workshop
© 2007Albert R. Mann Library Cornell University Ithaca, NY 14853
Changes in Ellagic Acid and Other Phenols in Muscadine Grape (Vitis rotundifolia) Juices and Wines during Storage
M. N. Musingo 1, C. A. Sims 1, R. P. Bates 1, S. F. O’Keefe 1, and O. Lamikanra 2
1 Food Science and Human Nutrition Department, P.O. Box 110370, University of Florida, Gainesville, Florida, 32611-0370.
2 Center for Viticultural Sciences, CESTA, Florida A&M University, Tallahassee, Florida.
email: cas@gnv.ifas.ufl.edu
This study followed the changes in gallic acid, catechin, epicatechin, ellagic acid, epicatechin gallate, and ellagic acid sedimentduring storage of muscadine (Vitis rotundifolia) juices and wines. Juices and wines from cv. Carlos and Welder (both white) and juices from Noble (red) were produced following standard methods. Samples were heated at 94°C for 5 min to accelerate sediment formation and then stored at 25°C for up to 52 wk. Other studies examined the effects of spiking juice with 50mg/mL of gallic acid and hydrolyzing juices using trifluoroacetic acid. In white cultivars, all phenolic compounds, except catechin, were higher in Carlos than in Welder. Ellagic acid sediment formed in the juices from both white cultivars after approximately 2 wk, compared to 24 wk in the wines. In all samples, there was an increase in gallic acid immediately after heating, followed by a decrease. There was also an increase of ellagic acid in solution followed by a decrease, as the ellagic acid started to form a sediment. The amount of ellagic acid sediment didnot change much over time in the wine, whereas in the juice, the ellagic acid sediment increased over time. The ellagic acid in solution generally declined after appearance of ellagic acid sediment, and the ellagic acid sediment reached a maximum of 24 mg/mL in Carlos juice after 24 wk and 98 mg/mL in Noble hot press juice after 42 wk. When juice was spiked with 50 mg/mL gallic acid, there was no significant increase in ellagic acid in solution or in ellagic acid sediment. However, juice hydrolysis resulted in a significant increase in ellagic acid in solution and ellagic acid sediment. Ellagic acid is likely coming from hydrolysis of higher molecular weight compounds and perhaps some from the dimerization of gallic acid.
Note:
Acknowledgments: Paper No. R-07811 of the Florida Agricultural Experiment Station Journal Series.
Key words: Ellagic acid, phenols, Vitis rotundifolia, heating, storage, juice hydrolysis
Detection of Phenolic Compounds and Hydroxy Acids in Grapes, Wines, and Similar Beverages
K. Hennig 1 and R. Burkhardt 1
1 Institute of Biochemistry and Wine Chemistry of the Hessian Research Institute, Geisenheim Rhine
Solvents and developers for the detection of phenol-like compounds and hydroxy acids in grape juice, wine, pomace wine, and wine-like beverages have been listed.
The compounds are d-catechin, I-epicatechin, I-epigallocatechin, gallic acid, protocatechuic acid, and ellagic acid, in addition, gallocatechin in apples.
Among the polyphenols are: chlorogenic acid, isochlorogenic acid, cis- and trans-caffeic acid, and probably caffeic acid lactone.
Among the phenols were found cis- and trans-coumaric acid and probably a coumaric acid lactone.
The positions of the substances on the chromatograms, their Rf-values with various solvents and developers are reproduced.
In juice of green grapes were found: d-catechin, I-epicatechin, I-epigallocatechin, ellagic acid, chlorogenic-and isochlorogenic acids and shikimic acid. Absent in juice from green grapes are: free gallic acid, caffeic acid, p-coumaric acid, quinic acid, and flavonols.
Catechins are mostly in seeds and stems and in lesser amounts in skins. Chlorogenic acid was not found in these parts.
Chlorogenic acid is always present in wine and later also caffeic acid. Gallic acid disappears on maturation of wine. Old white winescontain as a rule no condensable tannins.
In the pomace wine are present condensable tannins of the woody parts and of the seeds. Free gallic acid and ellagic acid are present in large amounts. Chlorogenic acid is present in pomace wine in an insignificant amount.
A blend of wine and pomace wine cannot be identified with certainty because gelatine and egg white finings remove free gallic acid and catechins. When no condensabe tannins are present one is assured of the purity of grape wine.
Young apple wine contains much more chlorogenic acid than grape wine. Caffeic acid and quinic acid are also present. d-Catechin and I-epicatechin are present in small amounts.
Old apple wines contain no chlorogenic acid, instead very large amounts of caffeic, quinic, and shikimic acids are present. Some coumaric also is present.
Strawberry dessert wine contains no chlorogenic acid and normal amounts of caffeic acid. There is much quinic acid, but no shikimicacid. Gallic acid, d-catechin and I-epigallocatechin were found. There is also present a red-violet fluorescent spot characteristic of oak extracts used in brandy manufacture.
Cherry wine contains much chlorogenic, caffeic and quinic acids and little shikimic acid. d-Catechin, I-epicatechin and gallic acid were found.
Gooseberry dessert wine contains practically no chlorogenic acid but much caffeic, quinic and shikimic acids. Small amounts of gallicacid were found, but no condensable tannins.
Caffeic acid occupies a key position and serves, evidently, for the construction of the flavonoid structure. Chlorogenic acids are present in live plants in large amounts probably as reserve material for caffeic acid. Caffeic acid appears only in dead tissue of the plant—in must and in wine.
It was possible to separate the isomers of caffeic and coumaric acids with 2% solution of acetic acid as second solvent. Since three spots appear in each instance along with the cis- and transforms, the formation of a lactone is assumed.
Caffeic, p-coumaric, and ellagic acids are formed as secondary compounds.
Acetaldehyde and glucose are not the only substances that bind sulfurous acid. Derivatives of cinnamic acid such as caffeic and p-coumaric acids can also bind the acid.
The sulfurous acid is a poison for polyphenoloxidase and a reducing agent for the quinones formed from the polyphenols. Its reducing action can also be performed by ascorbic acid.
The caffeic acid lactone is identical with esculetin and the p-coumaric acid lactone is identical with umbeliferon. Therefore, these twoterms can be used for the designation of lactone.
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Longevity
The news about wine keeps getting better. Dutch researchers say that a half-glass of wine per day might help you live longer--five years longer, in fact. (Remember, though, excessive drinking can lead to health problems that may shorten your life.) Though the researchers note that more study is needed, the theory is that light alcohol consumption--and especially red wine--may contribute to longevity because the "polyphenolic compounds contained in wine have been seen in animals to stop the build up of fatty tissue in the arteries that can result in stroke or heart attack."
Improves Heart Health
Japanese researchers believe that light to moderate drinking paired with socialization (enter happy hour) can significantly reduce your risk for heart disease. While the researchers mostly looked at men, it's easy to see why the findings could be true for women too. Most health experts are fine with light drinking--one glass per day (but not every day) for women. And aren't we all happier when we're spending time with friends?
Reduces Inflammation
Those who drink were found to have a significantly reduced risk of developing several arthritic conditions including Rheumatoid Arthritis (RA), Osteoarthritis (OA), reactive arthritis, psoriatic arthritis and spondylarthropathy, according to Dutch researchers. Researchers aren't exactly certain why alcohol consumption (note, no guidelines were given as to which type of alcohol and how much, but we can safely assume that the scientists are talking about moderate drinking here), but they speculate that alcohol may have inflammation-reducing effects.
Aids Weight Loss
Researchers at Brigham and Women's Hospital in Boston who studied the alcohol consumption of more than 19,000 women over 13 years found that women who drank a "light to moderate amount of alcohol" (defined by no more than two servings a day of wine, beer or liquor--I'll add that some studies have found that any more than one drink per day for females to be excessive, so just file that away) tended to gain less weight than women who didn't drink. The study was recently published in the journal Archives of Internal Medicine.
An explanation, please? "Women who drink moderate amounts of alcohol tend to eat less food, particularly carbohydrates," said cardiologist Lu Wang, lead researcher on the study and an instructor at Brigham and Women's Hospital, who spoke to USA Today.
Fights Osteoporosis
A new study reports that beer is a significant source of dietary silicon. Dietary what? It's an ingredient believed to increase bone mineral density, and researchers from the Department of Food Science & Technology at the University of California, Davis, say that beer is loaded with it.
They studied commercial beer production and found that most commercial beer--especially hoppy beer--is a rich source of dietary silicon. Based on these findings, the scientists suggest that moderate beer consumption may actually help fight osteoporosis.
Phenolic compounds in wineContents from Wikipedia encyclopedia
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The phenolic compounds in Syrah grapes contributes to the taste, color and mouthfeel of the wine.
The phenolic compounds in wine include a large group of several hundred chemical compounds, known as polyphenolics, that affect the taste, color and mouthfeel of wine. This large group can be broadly separated into two categories-flavonoids and non-flavonoids. Flavonoids include anthocyanins and tannins which contribute to the color and mouthfeel of the wine. Non-flavonoids include stilbenes such as resveratrol and compounds derived from acids in wine like benzoic, caffeic and cinnamic acid. In winegrapes, phenolics are found widely in the skin, stems and seeds. During the growth cycle of the grapevine, sunlight will increase the concentration of phenolics in the grape berries with the development of phenolics being an important component of canopy management. Most phenols are classified as secondary metabolites and are not active in the primary metabolism and function of the grapevine. They are water soluble and will often secrete into the vacuole of grape berries as glycosides. In winemaking, the process of maceration or "skin contact" is used to increase the influence of phenols in wine. Phenolic acids are found in the pulp or juice of the wine and can be commonly found in white wines which usually doesn't go through a maceration period. The process of oak agingcan also introduce phenolic compounds to wine, most notably in the form of vanillin which adds vanilla aroma to wines.[1]
Flavonoids
Main article: Flavonoids
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The process of maceration or extended skin contact allows the wine to extract phenolic compounds (including those that form a wine's color) from the skins of the grape.
In red wine, up to 90% of the wine's phenolic content fall under the classification of flavonoids. These phenols, mainly derived from the stems, seeds and skins are often leeched out of the grape during the maceration period of winemaking. The amount of phenols leeched is known as extraction. They contribute to the astringency, color and mouthfeel of the wine. In white wines the number of flavonoids is reduced due to less skin contact that they receive in winemaking. Within the flavonoid category is a subcategory known as flavonols, which includes the yellow pigment inducing phenol-quercetin. Like other flavonoids, the concentration of flavonols in the grape berries increases as they exposed to sunlight. Some viticulturalists will use measurement of flavonols like quercetin as an indication of a vineyard's sun exposure and the effectiveness of canopy management techniques. There is on going study in the health benefits of wine derived from the antioxidant and chemopreventive properties of flavonoids.[2]
Anthocyanins
Main article: Anthocyanin
Anthocyanins are phenolic compounds found throughout the plant kingdom, being responsible for the blue to red colors found inflowers, fruits and leaves. In wine grapes, they develop during the stage of veraison when the skin of red wine grapes change color from green to shading from red to black. As the sugars in the grape increase during ripening, so does the concentration of anthocyanins. In most grapes anthocyanins are found only in the outer cell layers of the skin, leaving the grape juice inside to be virtually colorless. Therefore to get color pigmentation in the wine, the fermenting must needs to be in contact with the grape skins in order to extract the anthocyanins. For this reason, white wine can be from red wine grapes as in the case for many white sparkling wines which are often made from the red wine grapes of Pinot noir and Pinot meunier. The exception to this is the small class of grapes known as teinturiers, such as Alicante Bouschet, which has a small amount of anthocyanins in the pulp which produces pigmented juice.[3]
There are several types of anthocyanins found in wine grapes which are responsible for the vast range of coloring found in wine grapes from ruby red to dark black. Ampelographers can use this observation to assist in the identification of different grape varieties. The European vine family Vitis Vinifera is characterized with anthocyanins that are composed of only one molecule of glucose while non-Vinifera vines such as hybrids and the American Vitis labrusca will have anthocyanins with two molecules. In the mid-20th century, French ampelographers used this knowledge to test the various vine varieties throughout France to identify which vineyards still contained non-Vinifera plantings.[3]
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Tempranillo has a high pH level which means that there is a higher concentration of blue and colorless anthocyanin pigments in the wine. The resulting wine's coloring will have more blue hues than bright ruby red hues.
The color variation in the finished red wine is partly derived from the ionization of anthocyanin pigments caused by the acidity of the wine. In this case, the three types of anthocyanin pigments are red, blue and colorless with the concentration of those various pigments dictating the color of the wine. A wine with low pH (and such greater acidity) will have a higher occurrence of ionized anthocyanins which will increase the amount of bright red pigments. Wines with a higher pH will have a higher concentration of blue and colorless pigments. As the wine ages, anthocyanins will react with other acids and compounds in wines such as tannins, pyruvic acid and acetaldehyde which will change the color of the wine, causing it to develop more "brick red" hues. These molecules will link up to create polymers that eventually exceed their solubility and become sediment at the bottom of wine bottles.[3]
Tannins
Main article: Tannin
Tannins refer to the diverse group of chemical compounds in wine that can affect the color, aging ability and texture of the wine. While tannins can not be smelt or tasted, they can be perceived during wine tasting by the tactile drying sensation and sense of bitterness that they can leave in the mouth. This is due to the tendency of tannins to react with proteins, such as the ones found in saliva. In food and wine pairing, foods that are high in proteins (such as red meat) are often paired with tannic wines to minimize the astringency of tannins. However, many wine drinkers find the perception of tannins to be a positive trait-especially as it relates to mouthfeel. The management of tannins in the winemaking process is a key component in the resulting quality of the wine.[4]
Tannins are found in the skin, stems and seeds of wine grapes but can also be introduced to the wine through the use of oak barrels and chips or with the addition of tannin powder. The natural tannins found in grapes are known as proanthocyanins due to their ability to release red anthocyanin pigments when they are heated in an acidic solution. The tannins are formed by enzymes during metabolic processes by the grapevine. The amount of tannins found naturally in grapes varies depending variety with Cabernet Sauvignon, Nebbiolo, Syrah and Tannat being 4 of the most tannic grape varieties. The reaction of tannins and anthocyanins with the phenolic compound catechins creates another class of tannins known as pigmented tannins which influences the color of red wine. The tannins derived from oak influence are known as "hydrolysable tannins" being created from the ellagic and gallic acid found in the wood.[4]
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Fermenting with the stem, seeds and skin will increase the tannin content of the wine.
In the vineyards, there is also a growing distinction being made between "ripe" and "unripe" tannins present in the grape. This "physiological ripeness", which is roughly determined by tasting the grapes off the vines, is being used along with sugar levels as a determination of when to the harvest. The idea is that "riper" tannins will taste softer but still impart some of the texture components found favorable in wine. In winemaking, the amount of the time that the must spends in contact with the grape skins, stems and seeds will influence the amount of tannins that are present in the wine with wines subjected to longer maceration period having more tannin extract. Following harvest, stems are normally picked out and discarded prior to fermentation but some winemakers may intentionally leave in a few stems for varieties low in tannins (like Pinot noir) in order to increase the tannic extract in the wine. If there is an excess in the amount of tannins in the wine, winemakers can use various fining agents like albumin, casein and gelatin that can bind to tannins molecule and precipitate them out as sediments. As a wine ages, tannins will form long polymerized chains which come across to a taster as "softer" and less tannic. Oxygen can bind with tannin molecules to make them larger and seem also seem softer on the palate. The winemaking technique of micro-oxygenation and decanting wine use oxygen to partial mimic the effect of aging on tannins.[4]
[edit] Other Flavonoids
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Phenolic compounds like tannins and vanillin can be extracted from aging in oak wine barrels.
Catechins are flavonoids that contribute to the construction of various tannins and contribute to the perception of bitterness in wine. They are found in highest concentrations in grape seeds but are also in the skin and stems. Catechins play a role in the microbial defense of the grape berry, being produced in higher concentrations by the grape vines when it is being attacked by grape diseases such as downy mildew. Because of that grape vines in cool, damp climates produce catechins at high levels than vines in dry, hot climates. Together with anthocyanins and tannins they increase the stability of a wines color-meaning that a wine will be able to maintain its coloring for a longer period of time. The amount of catechins present varies amount grape varieties with varietals likeMerlot and Pinot noir having high concentrations while Syrah has very low levels. As an antioxidant, there are some studies into the health benefits of moderate consumption of wines high in catechins.[5]
Vanillin is a phenolic aldehyde most commonly associated with the vanilla notes in wines that have been aged in oak. Some trace amounts of vanillin are found naturally in the grapes themselves but they are most prominent in the lignin structure of oak barrels. Newer barrels will impart more vanillin, with the concentration present decreasing with each subsequent usage.[6]
[edit] Non-Flavonoids
See also: Wine and health
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Wines made from Pinot noir in a cooler climate tend to have more resveratrol than wines made from varieties like Cabernet Sauvignon from warmer climates.
Resveratrol is a phenolic compound found in highest concentration in the skins of wine grapes. Both red and white wine grape varieties have resveratrol but more frequent use of skin contact and maceration in red winemaking means that red wines will normally have 10 times more resveratrol than white wines. It generally produced by grape vines as a means of microbial defense, though production can be artificially stimulated by ultraviolet radiation. Grapevines in cool, damp regions with higher risk of grape diseases, such as Bordeaux and Burgundy, tend to produce grapes with higher levels of resveratrol than warmer, drier wine regions like California and Australia. Additionally, different grape varieties are prone to differing levels with Muscadines and the Pinot family having high levels while the Cabernet family being noted for lower levels of resveratrol. In the late 20th century, interest in the possible health benefits of resveratrol in wine was spurred by discussion of the French paradox involving the health of wine drinkers in France.[7]
See alsoReferences
- ^ J. Robinson (ed) "The Oxford Companion to Wine" Third Edition pg 517-518 Oxford University Press 2006 ISBN 0198609906
- ^ J. Robinson (ed) "The Oxford Companion to Wine" Third Edition pg 273-274 Oxford University Press 2006 ISBN 0198609906
- ^ a b c J. Robinson (ed) "The Oxford Companion to Wine" Third Edition pg 24 Oxford University Press 2006 ISBN 0198609906
- ^ a b c J. Robinson (ed) "The Oxford Companion to Wine" Third Edition pg 680 Oxford University Press 2006 ISBN 0198609906
- ^ J. Robinson (ed) "The Oxford Companion to Wine" Third Edition pg 144 Oxford University Press 2006 ISBN 0198609906
- ^ J. Robinson (ed) "The Oxford Companion to Wine" Third Edition pg 727 Oxford University Press 2006 ISBN 0198609906
- ^ J. Robinson (ed) "The Oxford Companion to Wine" Third Edition pg 569 Oxford University Press 2006 ISBN 0198609906
Red wine and resveratrol: Good for your heart?
Red wine and something in red wine called resveratrol might be heart healthy. Find out the facts, and hype, regarding red wine and its impact on your heart.
By Mayo Clinic staff
Red wine, in moderation, has long been thought of as heart healthy. The alcohol and certain substances in red wine called antioxidants may help prevent heart disease by increasing levels of "good" cholesterol and protecting against artery damage.
While the news about red wine might sound great if you enjoy a glass of red wine with your evening meal, doctors are wary of encouraging anyone to start drinking alcohol. That's because too much alcohol can have many harmful effects on your body.
Still, doctors do agree that something in red wine appears to help your heart, though it's unclear just exactly what that "something" is. Researchers think antioxidants, such as flavonoids or a substance called resveratrol, have promising heart-healthy benefits.
Antioxidants aren't the only substances in red wine that look promising. The alcohol in red wine also appears to be heart healthy. Find out what's known — and not known — about red wine and its possible heart-health benefits.
How is red wine heart healthy?
Research studies on the heart-health benefits of red wine have reported mixed results. Some studies show that red wine seems to have even more heart-health benefits than other types of alcohol, while other studies show that red wine isn't any better than beer, white wine or liquor for heart health. There's still no clear evidence yet that red wine is superior to other forms of alcohol when it comes to possible heart-health benefits.
The studies supporting red wine suggest antioxidants in red wine called polyphenols help protect the lining of blood vessels in your heart. These antioxidants come in two main forms: flavonoids and nonflavonoids.
�Flavonoids. These antioxidants are found in a variety of foods, including oranges, grape juice, apples, onions, tea and cocoa. Other types of alcohol, such as white wine and beer, contain small amounts, too, but red wine has higher levels.
�Nonflavonoids. These antioxidants found in red wine have recently been of particular interest because they appear to help prevent arteries from becoming clogged with fatty blockages. However, these studies mostly involved mice — not humans. Resveratrol is the nonflavonoid that's received the most attention from researchers.
Resveratrol in red wine
Resveratrol might be a key ingredient in red wine that helps prevent damage to blood vessels, reduces "bad" cholesterol and prevents blood clots.
Most research on resveratrol has been conducted on animals, not people. Research in mice given resveratrol has indicated that the antioxidant might also help protect them from obesity and diabetes, both of which are strong risk factors for heart disease. However, those findings were reported only in mice, not in people. In addition, to get the same dose of resveratrol used in the mice studies, a person would have to consume 100 to 1,000 bottles of red wine a day.
Some research shows that resveratrol could be linked to a reduced risk of inflammation and blood clotting, both of which can lead to heart disease. More research is needed before it's known whether resveratrol was the cause for the reduced risk.
Some companies sell supplements containing resveratrol. However, not enough is known about resveratrol's effects to endorse resveratrol supplements. Research into the potential heart-health benefits of resveratrol is continuing.
Red wine and resveratrol: Good for your heart?
Resveratrol in grapes and other foods
The resveratrol in red wine comes from the skin of grapes used to make wine. Because red wine is fermented with grape skins longer than is white wine, red wine contains more resveratrol. Simply eating grapes, or drinking grape juice, has been suggested as one way to get resveratrol without drinking alcohol. Some studies have suggested that red and purple grape juices have some of the same heart-healthy benefits of red wine.
Other foods that contain some resveratrol include peanuts, blueberries and cranberries. It's not yet known how beneficial eating grapes or other foods might be compared with drinking red wine when it comes to promoting heart health. The amount of resveratrol in food and red wine can vary widely.
How does alcohol help the heart?
Various studies have shown that moderate amounts of all types of alcohol benefit your heart, not just alcohol found in red wine. It's thought that alcohol:
�Raises high-density lipoprotein (HDL) cholesterol, the "good" cholesterol
�Reduces the formation of blood clots
�Helps prevent artery damage caused by high levels of low-density lipoprotein (LDL) cholesterol, the "bad" cholesterol
Drink in moderation — or not at all
Red wine's potential heart-health benefits look promising. Those who drink moderate amounts of alcohol, including red wine, seem to have a lower risk of heart disease. However, more research is needed before we know whether red wine is better for your heart than are other forms of alcohol, such as beer or spirits.
Neither the American Heart Association nor the National Heart, Lung, and Blood Institute recommend that you start drinking alcohol just to prevent heart disease. Alcohol can be addictive and is associated with other health issues.
Drinking too much increases your risk of high blood pressure, high triglycerides, liver damage, obesity, certain types of cancer, accidents and other problems. In addition, even small amounts of alcohol can cause cardiomyopathy — weakened heart muscle — causing symptoms of heart failure in some people. If you have heart failure or a weak heart, you should avoid alcohol completely. If you take aspirin daily, you should avoid or limit alcohol, depending on your doctor's advice. You also shouldn't drink alcohol if you're pregnant. If you have questions about the benefits and risks of alcohol, talk to your doctor about specific recommendations for you.
If you already drink red wine, do so in moderation. Moderate drinking is defined as an average of two drinks a day for men and one drink a day for women.
A drink is defined as 12 ounces (355 milliliters, or mL) of beer, 5 ounces (148 mL) of wine or 1.5 ounces (44 mL) of 80-proof distilled spirits.
The limit for men is higher because men generally weigh more and have more of an enzyme that metabolizes alcohol than women do.
Tannins - types and amounts in grapes and wines
Tom Collins
Senior Research Enologist
Beringer Blass Wine Estates
Formerly the Manager of East Coast Grower Relations and Vineyard Operations for Canandaigua Wine Company, Tom Collins is now a Senior Research Enologist with Beringer Blass Wine Estates in St. Helena, CA. His viticultural areas of interest while with Canandaigua included evaluation of new sprayer technology, vineyard mechanization and vineyard redevelopment. In his position with Beringer Blass, Tom oversees the development and implementation of a broad range of winemaking research projects, including yeast strain trials, yeast nutrition trials, color enhancement and stability trials for red wines and the winemaking evaluation of various vineyard research projects. He is also involved in the evaluation of new technologies for the winemaking laboratory, as well as lab proficiency training and testing in all of Beringer Blass' wineries in California.
Tannins are complex polymeric compounds that are responsible at least in part for many of the sensory attributes of wines, particularly red wines. Tannins are involved in the tactile sense of astringency in red wines, they play an important role in the intensity and stability of color in red and tannins are responsible in many cases for the brown color that develops with age in both red and white wines. The flavonoid compounds that polymerize to form some types of tannins are also thought to provide many of the health benefits associated with the moderate consumption of wines.
The grape berries themselves contain some tannin, particularly in the seeds and skins. Certain types of tannins arise from polymerization of monomeric phenols during wine processing and aging. Wines aged in wood cooperage or wines that have had exposure to oak dust, chips or staves will also extract some types of tannins from the wood. Finally, pure or relative pure mixtures of tannins may be added to the wine during processing or aging.
Tannins are polymers of simpler phenols, which can generally be classed as either flavonoid or non-flavonoid. The simplest of phenols is phenol itself, which consists of an aromatic ring and a single hydroxyl group.
Catechin is an example of a flavonoid, in this case a flavan-3-ol. Flavonoids have a common structure that consists of an aromatic “A” ring, an oxygen containing heterocyclic “C” ring and a second
Aromatic “B” ring. There are several classes of flavonoids that differ primarily in the structure of the heterocyclic ring. From these and similar building blocks, tannins are polymerized. There are two primary classes of tannins found naturally in grapes and wine. The first class, the hydrolysable tannins, is based on non-flavonoid phenolics. The basic unit in a hydrolysable tannin is a polyhydroxy molecul.
Gallic acid is usually a sugar, to which are bound multiple non-flavonoid phenols, often gallic acid (Figure 3) or ellagic acid, which is a dimer of gallic acid (Figure 4). Gallotannin (Figure 5) is an example of a hydrolysable tannin. These tannins are readily hydrolyzed under acidic or basic conditions, hence their name. Non-flavonoid phenols and hydrolysable tannins are also found primarily in the skins and in the pulp.
The second primary class of tannins in grapes and wines are the condensed tannins. These tannins are polymers of primarily flavan-3-ols (catechin and epicatechin), along with the anthocyanin pigments. If an anthocyanin is incorporated into the tannin, the resulting polymer is often colored. As a covalent bond is formed between the individual units within a condensed tannin, these tannins are not readily hydrolyzed. Typically the linkage occurs between the 4 position (on the heterocyclic ring) and the 8 position on the aromatic A ring, although it is possible for the linkage to occur at the 6 position as well.
An epicatechin tetramer consists of linkages just between the 4 position and the 8 position of the adjacent epicatechin units. These polymers can include both catechin and epicatechin units.
The epicatechin and catechin monomers are found primarily in the seed coat in grapes, and to a lesser extent in the skins. Polymers of these two compounds (condensed tannins) are found in the seeds, skins and to a lesser extent, in the pulp. Monomeric anthocyanins and polymeric pigments are found primarily in the skins of red grapes.
Polymerization of the condensed tannins continues as the juice is processed into wine and as the wine ages. As the number of units in the polymers increases, their color changes from colorless to yellow to brown. As the number of units increases, the solubility of the polymer decreases, and eventually the polymer will precipitate from solution. If the tannin incorporates an anthocyanin moiety, this precipitation will result in slowly declining color as the wine ages.
As tannins are very complex compounds, common methods for determining their concentrations in grape tissues or wines are often indirect or empirical in nature. Comparison of results from different studies can be problematic. Most analyses of tannins begin with an attempt to differentiate them from their monomeric building blocks. This may be done either by a separation based on the larger size of the tannins or by selective precipitation or extraction. Once separated from the monomeric phenols, the tannins may be analyzed by a number of available methods for the analysis of phenolic compounds. The most widely used is probably the Folin-Ciocalteu colorimetric method. Gallic acid is used as the standard for this method and results are reported as gallic acid equivalents (GAE). It is not possible, given the complex mixture of tannins present in grape tissue or wine samples to convert GAE into an exact amount of tannin, but GAE are never-the-less useful as a tool for comparisons amongst samples or treatments.
Using a low pressure chromatographic method for separation of non-polymeric and polymeric phenols, Kantz and Singleton (1991) reported that grape seeds contained the highest amount of polymeric phenols of the grape tissues they looked at, with polymeric phenols ranging from 21 to 27 mg GAE/g fresh weight. Polymeric phenols accounted for 60 to 70% of the total extractable phenolic content of the seeds. Grape skins contained much lower total and polymeric phenols and were much more variable, ranging from 0.1 to 5 mg GAE/g fresh weight of skins; polymeric phenols accounted for from 6% to 43% of the total extractable phenols in the skins. Thorngate and Singleton (1994) subsequently showed that most of the phenolic material in the seeds was actually in the outer layers of the seed, with very little found in the seed endosperm.
Of the total pool of phenolic material available in the grape berry, only a part is subsequently found in the resulting wines. Incomplete extraction, adsorption with yeast lees and other solids, precipitation with grape or yeast proteins and a host of other reactions all tend to limit the total phenol and polymeric phenol levels in wine. Singleton and Draper (1964) studied the extraction of polymeric phenols from grape seeds into wine; complete extraction of the tannin in the seeds should result in a tannin content of 200 to 400 mg/L. Under typical red wine fermentation conditions about half that amount is common. That level is then further reduced by other reactions and by precipitation. They also showed that in the same length of time, more complete extraction is favored by increased temperature and increased ethanol content.
References:
Kantz, K. and V.L.Singleton. Isolation and determination of polymeric polyphenols using Sephadex LH-20 and analysis of grape tissue extracts. Am. J. Enol. Vitic. 42:309-16 (1991).
Singleton, V.L. and D.E. Draper. The transfer of polyphenolic compounds from grape seeds into wines. Am. J. Enol. Vitic. 15:34-40 (1964).
Thorngate, J.H. and V.L. Singleton. Localization of procyanidins in grape seeds. Am. J. Enol. Vitic. 45: 259-262 (1994).
32nd Annual New York Wine Industry Workshop
© 2007Albert R. Mann Library Cornell University Ithaca, NY 14853
Changes in Ellagic Acid and Other Phenols in Muscadine Grape (Vitis rotundifolia) Juices and Wines during Storage
M. N. Musingo 1, C. A. Sims 1, R. P. Bates 1, S. F. O’Keefe 1, and O. Lamikanra 2
1 Food Science and Human Nutrition Department, P.O. Box 110370, University of Florida, Gainesville, Florida, 32611-0370.
2 Center for Viticultural Sciences, CESTA, Florida A&M University, Tallahassee, Florida.
email: cas@gnv.ifas.ufl.edu
This study followed the changes in gallic acid, catechin, epicatechin, ellagic acid, epicatechin gallate, and ellagic acid sedimentduring storage of muscadine (Vitis rotundifolia) juices and wines. Juices and wines from cv. Carlos and Welder (both white) and juices from Noble (red) were produced following standard methods. Samples were heated at 94°C for 5 min to accelerate sediment formation and then stored at 25°C for up to 52 wk. Other studies examined the effects of spiking juice with 50mg/mL of gallic acid and hydrolyzing juices using trifluoroacetic acid. In white cultivars, all phenolic compounds, except catechin, were higher in Carlos than in Welder. Ellagic acid sediment formed in the juices from both white cultivars after approximately 2 wk, compared to 24 wk in the wines. In all samples, there was an increase in gallic acid immediately after heating, followed by a decrease. There was also an increase of ellagic acid in solution followed by a decrease, as the ellagic acid started to form a sediment. The amount of ellagic acid sediment didnot change much over time in the wine, whereas in the juice, the ellagic acid sediment increased over time. The ellagic acid in solution generally declined after appearance of ellagic acid sediment, and the ellagic acid sediment reached a maximum of 24 mg/mL in Carlos juice after 24 wk and 98 mg/mL in Noble hot press juice after 42 wk. When juice was spiked with 50 mg/mL gallic acid, there was no significant increase in ellagic acid in solution or in ellagic acid sediment. However, juice hydrolysis resulted in a significant increase in ellagic acid in solution and ellagic acid sediment. Ellagic acid is likely coming from hydrolysis of higher molecular weight compounds and perhaps some from the dimerization of gallic acid.
Note:
Acknowledgments: Paper No. R-07811 of the Florida Agricultural Experiment Station Journal Series.
Key words: Ellagic acid, phenols, Vitis rotundifolia, heating, storage, juice hydrolysis
Detection of Phenolic Compounds and Hydroxy Acids in Grapes, Wines, and Similar Beverages
K. Hennig 1 and R. Burkhardt 1
1 Institute of Biochemistry and Wine Chemistry of the Hessian Research Institute, Geisenheim Rhine
Solvents and developers for the detection of phenol-like compounds and hydroxy acids in grape juice, wine, pomace wine, and wine-like beverages have been listed.
The compounds are d-catechin, I-epicatechin, I-epigallocatechin, gallic acid, protocatechuic acid, and ellagic acid, in addition, gallocatechin in apples.
Among the polyphenols are: chlorogenic acid, isochlorogenic acid, cis- and trans-caffeic acid, and probably caffeic acid lactone.
Among the phenols were found cis- and trans-coumaric acid and probably a coumaric acid lactone.
The positions of the substances on the chromatograms, their Rf-values with various solvents and developers are reproduced.
In juice of green grapes were found: d-catechin, I-epicatechin, I-epigallocatechin, ellagic acid, chlorogenic-and isochlorogenic acids and shikimic acid. Absent in juice from green grapes are: free gallic acid, caffeic acid, p-coumaric acid, quinic acid, and flavonols.
Catechins are mostly in seeds and stems and in lesser amounts in skins. Chlorogenic acid was not found in these parts.
Chlorogenic acid is always present in wine and later also caffeic acid. Gallic acid disappears on maturation of wine. Old white winescontain as a rule no condensable tannins.
In the pomace wine are present condensable tannins of the woody parts and of the seeds. Free gallic acid and ellagic acid are present in large amounts. Chlorogenic acid is present in pomace wine in an insignificant amount.
A blend of wine and pomace wine cannot be identified with certainty because gelatine and egg white finings remove free gallic acid and catechins. When no condensabe tannins are present one is assured of the purity of grape wine.
Young apple wine contains much more chlorogenic acid than grape wine. Caffeic acid and quinic acid are also present. d-Catechin and I-epicatechin are present in small amounts.
Old apple wines contain no chlorogenic acid, instead very large amounts of caffeic, quinic, and shikimic acids are present. Some coumaric also is present.
Strawberry dessert wine contains no chlorogenic acid and normal amounts of caffeic acid. There is much quinic acid, but no shikimicacid. Gallic acid, d-catechin and I-epigallocatechin were found. There is also present a red-violet fluorescent spot characteristic of oak extracts used in brandy manufacture.
Cherry wine contains much chlorogenic, caffeic and quinic acids and little shikimic acid. d-Catechin, I-epicatechin and gallic acid were found.
Gooseberry dessert wine contains practically no chlorogenic acid but much caffeic, quinic and shikimic acids. Small amounts of gallicacid were found, but no condensable tannins.
Caffeic acid occupies a key position and serves, evidently, for the construction of the flavonoid structure. Chlorogenic acids are present in live plants in large amounts probably as reserve material for caffeic acid. Caffeic acid appears only in dead tissue of the plant—in must and in wine.
It was possible to separate the isomers of caffeic and coumaric acids with 2% solution of acetic acid as second solvent. Since three spots appear in each instance along with the cis- and transforms, the formation of a lactone is assumed.
Caffeic, p-coumaric, and ellagic acids are formed as secondary compounds.
Acetaldehyde and glucose are not the only substances that bind sulfurous acid. Derivatives of cinnamic acid such as caffeic and p-coumaric acids can also bind the acid.
The sulfurous acid is a poison for polyphenoloxidase and a reducing agent for the quinones formed from the polyphenols. Its reducing action can also be performed by ascorbic acid.
The caffeic acid lactone is identical with esculetin and the p-coumaric acid lactone is identical with umbeliferon. Therefore, these twoterms can be used for the designation of lactone.
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