QUANTIFICATION OF THE POLYPHENOLIC CONSTITUENTS OF RETAIL SAMPLES OF RED WINE

ABSTRACT

The  study  sets-out   to  investigate   the  amount   of  some  selected   class  of  polyphenols   with cardiovascular  benefits,  present  in red wine.  The total phenolic  content of the freshly opened red wine samples  as determined  by Folin-Ciocalteau  Method  (FCM)  were  in the range  of 42-1625 mg/1 Gallic Acid Equivalents  (GAE) (Mean= 1084.6).  Samples J and N,  which were of Spanish and  Portuguese   origins,  respectively,  contained  the  highest  concentration   of  1625   mg/1  GAE each,  while  the  lowest  concentration   was  recorded  in  sample  C,  a  wine  of Nigerian  origin. Similarly,  the total anthocyanin  concentration  of freshly opened wine samples  was in the range of  20.5-166.7  mg/1  Malvidin-3-Glucoside  Equivalents   (Mean  =  109.4),  with  sample  R  (an American  wine) containing  the highest  concentration.  The total tannin  concentration  was in the range  of 225-2387  mg/l  Epicatechin  Equivalents   (Mean=   1653.1).  Wine  Q,  a  South  African wine,  had  the  highest  concentration  of tannin.  The  effect  of  air  exposure  resulted  in  a time• dependent  decline  in the total phenolic  concentration  of the wines,  with the decline  being  more pronounced  after 60 mins of air exposure.  Red wine samples  with lower phenolic  concentration were found to be less affected  by the reduction  in total phenol due to air exposure.  The maximum loss  in the  total  phenolic  concentration  on  air  exposure  was recorded  in  sample  S  (a  Spanish wine), whose phenol content decreased by as much as 87.4% after 120  mins.  Maximum  decrease in total anthocyanin  content  was observed  in sample A (a Spanish wine) which decreased  by as much as 58.5% after 120  mins.  Total tannin was found to be more stable than other polyphenolic compounds  present  in the  samples,  as the  total  tannin  concentration  showed  a less significant reduction  over  time.  Tannin  concentration   of sample  B  (an  Australian  wine)  and  sample  C, decreased  by  as  much  as  22%  over  the  course  of  120  mins.  A  similar  trend  in  decline  was observed during cold storage between  5-8C  after 96 hours at 24-hour  intervals.  Sample K lost as much as 87.6% of its total phenolic  content  after 96 hours.  A maximum  loss of74.9%  of the concentration  of total anthocyanin  was observed  in wine C.   For total tannin,  a loss of 47% was observed  in wine B after  120  mins.  The result  of the organoleptic  (sensory)  evaluation  and the total phenolic  concentration  were non-significantly  correlated,  r = 0.29, p < 0.05. Likewise,  there was a non-significant  correlation  between  the result of the organoleptic (sensory)  evaluation  and the total tannin concentration,  r = 0.39, p < 0.05. Total phenolic  concentration  and the retail price were  significantly  correlated,  r = 0.55, p  < 0.05.  Similarly,  Total  tannin  concentration  and the retail price  were  also significantly  correlated,  r = 0.50, p  < 0.05.  Comparing  the total phenolic content of the alcoholic  (M = 1201.60,  SD= 357.59) and non-alcoholic  brands (M = 967.50,  SD = 521.34),  showed a non-significant  difference  t (18) = 0.26, p  < 0.05 (p > 0.05).  In conclusion, the various wine brands differed  widely  in their content of all classes of polyphenols  tested.  The polyphenols  in the samples  also differed  in their  susceptibility  to oxidation  during  air exposure and  cold  storage  after  opening.  These  observations   could  be  useful  to  consumers  who  are interested  in wines  because  of their  content  of polyphenols,  which  are reported  to offer  some health benefits.

CHAPTER ONE

INTRODUCTION

Epidemiological studies have shown that a moderate  wine consumption  has beneficial  effect  on health.   Wine   consumption   reduces   the  susceptibility  of low  density   lipoprotein   (LDL)   to oxidation  which  is important for the prevention  of arteriosclerosis  development  (Harbome  and Williams,  2000;  Heim et al.,  2002).  The practice  of wine consumption  has a favorable  influence on the reduction  of cancer  incidence  and on chronic  inflammatory  diseases,  the development  of both  being  associated  with  oxygen  free radical  (Scalbert  et al.,  2005).  This  has  gained  more awareness  through  the famous “French  Paradox”  which observed  low death rates resulting  from coronary   heart   disease  (CHD)   despite  high  intake  of  dietary  cholesterol   and  saturated   fat (Renaud  and  de  Lorgeril,  1992).  The  more  remarkable   health  promoting   effect   of wine  in comparison  to  alcohol  alone  (in  addition  to  other  factors)  is due  to  some  biologically  active compounds,  present  especially  in  red  wine.  Among  alcoholic  beverages,  red  wine  has  been reported  to  be  more  protective  against  coronary  heart  disease  than  other  alcoholic  beverages (Gronbaek  et al.,  1995). More than 500 different  compounds,  of which  160 are esters,  have been

identified   in  different   wine  types.   These  include   water  (7487%,  w/w),  ethanol  (10 14%),

saccharides  (0.05-10%),  organic acids (0.05-0.7%),  phenols  (0.01-0.2%),  and glycerol  (Soleas et al., 1997).  Phenolic  compounds  have long been considered  to be basic  components  of wines and over 200 compounds  have been identified.  The concentration  of total phenolic  compounds  in commercially  available  red wines  is rarely  above  2.5 g/1 (Singleton  et al.,  1999). Two primary classes of phenolic  compounds  that occur in grapes and wine are flavonoids  and non-flavonoids. Flavonoids  commonly  constitute  > 85% of the phenolic  content  (2:  1   g/1)  in red wines.  In white wines,  flavonoids  typically  comprise  <  20% of the  total  phenolic  content  (<  50 mg/1).  Their

dietary  intake   has  been  shown  to  be  inversely   related  to  coronary  heart  disease  mortality

(Hoffmeister  et al.,  1999).

Phenolic compositions  is an important aspect in high quality red wines, and are responsible  for astringency  and  bitterness  (Margaret  et  al.,  2007),  and play  a role  in  colour  stability.  The phenolic profile of a wine has been shown to be influenced by different viticultural practices,  as well as different  enological techniques.  The variety,  vintage and region where the grapes are grown all affect the phenolic composition  of the wine (Brossaud et al.,  1999;  Yokotsuka et al.,

1999). The amount of flavonoids  extracted  during vinification  is influenced by many factors, including  temperature,   mixing,   parameters   of  the   fermentation   vessel,   duration   of  skin maceration,  ethanol concentration,  SO,  yeast strain,  pH,  and pectolytic  enzymes (Brossaud et al.,  1999).  The concentration of phenolic compounds in wine increases during skin fermentation and  subsequently  begins  to  decrease  as  phenols  bind  with  proteins  and  yeast  hulls  (cell remnants),   and  precipitate.   During   fining  and  maturation,  the  concentration   of phenolic compounds continues to decrease.  Their concentration is further substantially decreased at aging and cold storage (Stratil et al., 2008). Research on non-enzymatic wine oxidation by exposure to atmospheric  oxygen has been approached  on two major  scales;  from a macroscopic  point  of view,  and  a  step-by-step  mechanism  involved  in  oxidation.  This  advanced  exploration  of oxidation phenomena  in wine  has been  largely undertaken  since the beginning  of the  1990s (Atanasova et al.,  2002).  However,  while detrimental effects of excessive and prolong exposure are well established,  little is known about the exact impact on wine quality due to low and short levels of oxygen exposure.

1.2 Wine

Wine is  an alcoholic   beverage   (containing   ethyl   alcohol,   which   is  commonly   referred   to as ethanol) made  from fermented grapes or  other  fruits.  Wine  is  a  complex  liquid.  Although water,  ethanol,  glycerol,  and  various  organic  acids  comprise  the  major  portion  of wine,  the distinct identity comes from the organic compounds (such as terpenes, esters, and alcohols), polysaccharides  and phenolics  (such as anthocyanins  and tannins) present  in the wine (Eti~vant,

1991).  Some aromatic  compounds  are present  in the grapes  from which the wine  is made,  and some are synthesized as by-products of fermentation by the yeast that turns the sugar in the grape must into ethanol. Still others are formed only after wine has been aged and are the result of oxidation    and    acid-catalyzed    reactions    (Peyrot    des   Gachons    and    Kennedy,    2003).

Polysaccharides  are polymeric  un-fermentable  sugars that lend body and viscosity to a wine.

Without  them,  a wine might  seem thin or watery.  These compounds  are formed during  fruit ripening when the grape berry softens. The riper the grape, the more these components are found in the final wine (Goldberg,  1995). Polyphenolic compounds are widely distributed in vegetables and fruit trees. They are present in complex polymeric and glycosidic forms, that could not easily be degraded by digestive juices and so their absorption could be limited. In wine, during fermentation, these aggregates are broken down to monomeric forms (Peyrot des Gachons and Kennedy,  2003).  The  alcohol  content  of 10%  or  more  contained  in  most  table  wines  gives stability to phenols present in bottled wines, allowing their absorption (Goldberg,  1995).

1.2.1    Classification of Wine

Wines are grouped by employing  a number  of different  methods. They could be grouped  into different classes by grape variety, region of origin,  colour, production technique, by the name of the wine maker or viticulturist (Liger-Belair,  2005).  For the consumer,  basically three (3) main

classes of wines  are most  easily discernible:  table wines,  sparkling  wines,  and fortified wines. Table wines (still or natural wines) make up the majority of wines available in the market.

1.2.1.1 Table Wines

Table wines contain between 10 and 14 percent alcohol and are traditionally consumed as part of a meal.  They are further grouped by their colour,  sugar content,  the variety and origin of the grapes that were used (Don~che,  1993). Wines can be white, red, or pink in colour, depending on the grape variety and wine-making technique.  Most of the table wines made fit for consumption are fermented until they are dry-this  means that,  the entire grape sugar moiety present  in the grape must has been turned to alcohol by the yeast. Off-dry (slightly sweet) wines are made by stopping the fermentation before all the sugar is converted or by adding grape juice to the wine afterwards.  In  other wine-producing regions  outside  of Europe,  California  and  Australia  in particular, table wines are most times classified by the grape variety from which they are made (Cerdan et al.,  2002).  As a rule,  at least  75 percent of the grapes used in the production of the particular wine must be of the named grape variety (Don~che,  1993).  For example,  Chardonnay is  wine  made  from  at  least  75  percent  chardonnay  grapes.  Wines  classified  this  way  are sometimes called varietals,  and include wines such as Riesling,  Cabernet sauvignon,  and Merlot. The traditional European classification system puts more emphasis on the region or appellation; where the wine  is from.  The French system of Appellation  d’Origine  Control~e  labels wines according to their geographical pedigree (Cerdan et al., 2002). The most famous wine-producing regions in France, and probably in the world, are Burgundy, in central France, and Bordeaux, a region  on  the  southwestern  coast  of the  country.  Bordeaux  ranks  its  best  wineries,  called chdteaux,   and their  vineyards-crus,   into  five classes  called grand  crus:  Ch~teau Margaux,

Ch~teau Latour, Ch~teau Mouton-Rothschild and Ch~teau Lafite-Rothschild in Pauillac, plus Ch~teau  Haut-Brion  in  Graves.  Wines  from  these  vineyards  in  France  are  considered  to  be among the highest-quality wines in the world (Prectorius and Hoj,  2005).

American  wineries use a tag on their wine bottle labels called Appellation  of Origin to indicate where the grapes were grown. An appellation  can be a country, state, county, or geographically defined as American Viticultural Area (AVA).  At least 85 percent of the grapes used to produce the  wine  must  be  from  the  viticultural  area  stated  on the  label (Don~che,  1993).  The United States  currently  recognizes  about   150  AVAs,  distinguishable  by  geographical  features.  The largest growing region in the United States,  California,  has at least 85 AVAs,  including  the Napa and Sonoma valleys (Don~che,  1993).

1.2.1.2 Sparkling Wine

Sparkling wine is a modification of table wine by subjecting table wine to a second fermentation. The wine maker achieves this by adding a measured amount of sugar and fresh yeast to the dry wine (Liger-Belair,  2005).  This can be carried out in a closed tank,  or directly in the bottle. French  champagne,  the  most  famous  sparkling  wine,  is produced  in this  way  (Liger-Belair,

2005).  The fresh yeast ferments the freshly added sugar,  but this time the carbon dioxide gas remains in the sealed bottle, creating carbonation.  The basic material is usually a dry white, rose, or red table wine.  Sufficient sugar is added to the basic wine to produce a pressure of about five (5) or six (6) atmospheres. The gas bubbles to the surface when the sparkling wine is poured into a glass  (Pernot  and Valade,   1995).  Under the Appellation   d’Origine  Control~e  system,  only sparkling wines produced in the Champagne region of northeastern France can officially use the name  champagne.   Sparkling  wines  produced  in  all other  regions  of the  world,  even  those

produced  using  the  traditional  champagne  method,  are  simply  referred  to  as  sparkling  wines

(Pemot and Valade,  1995).

1.1.1.3 Fortified Wines

Fortified wines contain  additional  alcohol  and  are  usually  consumed  in  small  amounts  as aperitifs before meals or dessert wines after a meal (Cristovam and Paterson, 2003). Two (2) famous examples are port and sherry.  In port (originated in Portugal) wine making,  the grapes are crushed and the fermentation started but then stopped through the addition of more alcohol, which as a result kills the yeast. The resulting wine is sweet and has an alcohol content that is about  5-10% higher than table wine.  Fortification  has two purposes:  (1) to raise the alcohol content  sufficiently  (usually  17-21 %) to prevent  fermentation  of all of the  sugar  and (2) to produce  types  with  a special  alcohol  character.  The  alcohol  used  for fortification  is usually (legally required  in most countries) distilled from wine (Cristovam and Paterson,  2003; Liddle and Boero,  2003).  The distillation  of the fortifying spirits is made to a high percent  alcohol, usually 95-96%. Industrial alcohol has also been employed in a few countries. Sherry (originally from  Spain)  is likewise  produced  by adding  alcohol  to  a young  dry wine  in  an oak barrel intentionally filled only halfway.  Special yeasts called flor yeast grow on the surface of the wine and create the distinct nutty flavour characteristic of sherry (Martinez et al.,  1998).

Brandy is produced from wine but is classified as distilled liquor, not as wine.  Brandy is distilled from wine to concentrate the alcohol in the wine. After distillation the brandy is aged. Bottled brandy typically contains 40 percent alcohol and has been aged in oak barrels for several years (Singleton,  1995; Bertrand, 2003; Cantagrel, 2003)

1.2.2    The Wine Grapes and Vineyards

The main grapevine cultivated for wine production  is the European wine grape is Vitis vinifera which probably  originated  in the Caucasus Mountains  (Aguero et al.,  2006).  Today there are more than 5,000  varieties  of Vitis vinifera grown  in the world  basically  localized  along the Black,  Caspian,  and Mediterranean seas.V. labrusca and V.  rotundifolia have been domesticated in the eastern United States,  the domestication of V.  amurensis has been reported in Japan,  and various interspecies hybrids have been used for wine production (Aradhya et al.,  2003). The high sugar content of most V.  vinifera varieties at maturity is the major factor in the selection of these varieties for use in much of the world’s wine production.  Their natural sugar content,  providing necessary material for fermentation,  is sufficient to produce a wine with alcohol content of 10 percent  or higher;  wines  containing  less alcohol  are unstable  because  of their  sensitivity  to bacterial  spoilage (Bertsch et al.,  2005).This grape plant prefers warm,  dry summers and mild winters,  and successful cultivation is limited only to temperate climates in both the northern and southern  hemispheres.  One  of the  major  factors  attracting  wine  makers  to  this  grape  is  its tremendous range in composition  (Bertsch et al.,  2005).  The pigment pattern of the skin varies from light  greenish  yellow to russet,  to pink,  red,  reddish  violet,  or blue-black;  the juice  is generally colourless,  although some varieties have a pink to red colour,  and the flavour varies from quite neutral to strongly aromatic (examples include Gewiirztraminer,  Cabernet Sauvignon, and Zinfandel).  Some varieties, such as Pinot Noir, having rather neutral flavoured juice, develop a characteristic flavour when fermented on the skins and aged (Bouquet et al.,  2006). The species V.  labrusca and V.  rotundifolia seldom contain sufficient natural sugar to produce a wine with alcohol  content  of 10 percent  or higher  and  additional  sugar  is usually  required.  The  most popular red varieties in the United  States  are zinfandel,  cabernet  sauvignon,  grenache,  merlot,

and pinot  noir.  The  most  popular  white  grapes  are  colombard,  chardonnay,  cheninblanc,  and sauvignon  blanc. Factors  associated  with  a particular  region  or areas make the wine  from  that location  unique  (Bowers  and  Meredith,   1996).  These  factors  (terroir)  include  local  climate (rainfall,   sunlight  and  temperature),   location   of grapevines  (altitude  and  slope),   and  soil

(structure,  composition,  and water drainage).  From studies,  it has been observed that a grapevine

produces the best of its fruits when the moderate climate provides much sunshine and cool nights without frost, and the soil is well drained (Bowers and Meredith,  1997).  Grapevines grow best in sandy, chalky, or rocky soils. Wine grapes are grown in vineyards, where individual vines are cultured and nurtured on a system of stakes and wires,  called a trellis,  to maximize exposure to the sun.  The first harvest of grapes can be collected in the third year after the planting,  and a full crop suitable for commercial use can be expected after five years (Bowers and Meredith, 1997). Grapevines may produce fruit for 20 to over 100  years.  The grapevine growth cycle begins in early spring when new shoots appear on the buds of the grapevine.  Grapes begin their growth cycle in the spring when average daily temperature  is about  10° C (50° F).  To reach maturity, they require a certain amount of heat above 10°  C during the growing season.  This amount of heat,  called the heat summation,  is calculated by totaling the number of degrees of average daily temperature  over  10° C for each  day of the  growing  season  (Fanizza  et al.,  2005).  A heat summation of about 1,800°  is required for successful growth.  If the heat summation is less than required,  the  grapes  will  not  ripen;  they  will  reach  the  end  of the  growing  season  with insufficient  sugar  and  too  much  acidity  (Franks  et  al.,  2002).  This  condition,  frequently occurring in the eastern United States, Switzerland, and other cool regions, can be corrected by adding sugar to the crushed grapes.  Where the heat summation is much greater than required,  as in Algeria and parts of California, the grapes mature earlier and with less acidity and colour than

those  produced  under  cooler  conditions  (Maletic  et al.,  2004).  The grapes begin  to ripen  in midsummer and are ready to be harvested in midfall, depending on the location, grape variety, weather,  and the type of wine to be produced.  By the end of fall,  the vines lose their leaves and become dormant until the following spring.  The particular character of wine is strongly affected by viticultural practices such as training,  trellising,  harvesting,  and pruning (Prectorius and Hoj,

2005).  Training and trellising  enable the viticulturist  to control the sun exposure to ensure an even grape ripening.  Grapes harvested when they are not ripe may be low in sugar and may not ferment properly.  On the other hand,  overly ripe  grapes  are very high  in sugar  content  and produce wine high in alcohol (Regner et al.,  2000).  Once the vines are dormant, the viticulturist prunes the vines to remove all the dead wood. Pruning enables the grower to control the size and shape of the vines,  and also the number  of buds that will develop the next year. Just as plants have   pests   that   affect   the   quality   and   number   of  their   products,   grapevines   in   like manner have many natural enemies:  insects,  molds,  bacteria,  viruses,  and animals such as deer and birds that eat the young shoots or the sweet grapes (Regner et al.,  2000).  These pests will affect the produce from the grapevine and can as well contaminate the wine due to by-products of metabolism as remnants  from these pests.    Certain soil-borne pests,  such as the root louse Phylloxera,  destroy the roots of European grapevines.  Vines native to North and South America have a natural resistance to this insect, but they often produce grapes with an undesirable flavour (Bowers and Meredith,  1997).  To circumvent this problem,  American vineyards use grapevines grown from two different parts:  the roots from resistant American vines and the part above the ground  from European  vines by a process known  as grafting  and works  much  like healing a “broken bone”.  There are about 8 million hectares (20 million acres) of vineyards in the world producing 69 million tons of grapes each year. About 29 billion liters (8 billion gallons) of wine

are made from those grapes.  Countries that produce large quantity of wine include  France,  Italy, Germany,   the  United   States,   Australia,   and   South  Africa.   Many   other   countries  produce enormous  quantities  of  table  wines  (Bowers  and  Meredith,   1997).   In  Europe  there  are,   for example,  Spain,  Portugal,  Switzerland,  Hungary,  Romania,  Bulgaria,  Greece,  and  Georgia.  In North Africa and the Middle East there are Algeria,  Tunisia,  and Israel. In South America there are Brazil,  Peru,  Chile,  and Argentina.  The  largest  wine producers  worldwide  are  France  (19 percent),  Italy (17 percent),  and Spain (13 percent).  The United  States  of America  (USA) is the fourth largest  producer  in the world,  producing  about  9 percent  of the world’s  wine.  California produces   90  percent  of  all  the  wine  in  the  United   States,   with  enologists   in  New  York, Washington,  Oregon,  and at least 41  other states making the remainder  of U.S.  wine.  In Asia the largest producer is Japan ((Bowers and Meredith,  1997; Fanizzaet al.,  2005; Franks et al.,  2002).

1.3 Red Wine

Red wine is a type of wine made from dark-coloured grape varieties.  Its colour can be derived from a vast assortment of grape varietals ranging from grapes that are reddish,  deep purple,  and even a beautiful blue on the colour scale (Boulton,  1996). These grapes give rise to a wine that is colour classified with  such descriptors  as garnet,  almost black,  dark red,  light red,  ruby red, opaque purple,  deep violet and maroon.  The actual colour of the wine can range from intense violet,  typical of young wines,  through to brick red for mature wines and brown for older red wines.  It is the grape skins that are responsible for the red wine’s  distinct colour spectrum.  The skins  are  in  contact  with  the  grape’s  juice  during  the  fermentation  process,   allowing  the dispersion of both colour and tannins (Bird, 2005).The juice from most black grapes is greenish• white;  the red colour comes from anthocyan pigments (also called anthocyanins) present in the skin of the grape;  exceptions are the relatively uncommon teinturier varieties,  which produce a xxiii

red  coloured juice.  Much  of the red-wine  production  process  therefore  involves  extraction  of colour and flavour components  from the grape skin (Jeff,  1999).  The individual wine’s particular red  hue  depends  on  the  grape  type  used  in  the  process  and  the  length  of time  the  skin’s pigmentation  is  in  contact  with juice.  There  are  right  around  50 key  red  wine  varietals  that consistently manifest themselves in today’s worldwide wine market.

1.2.1 Red Wine Styles and Varieties

Red wines are made into a variety of styles.  The stylistic differences are based on differences  in wine characteristics such as grape variety, colour, flavour, body, mouth-feel, and aging potential. The styles range  from simple,  fruity,  fresh,  light coloured blushes  and roses to complex,  full bodied, rich and dark red, with long aging potential. Many factors such as a variety, soil, climate, growing conditions, and viticultural practices influence the fruit composition, and therefore, the style of wine that can be produced.  In addition to fruit composition, winemaking techniques also play an important role in determining the wine style.

Many  varieties  are  available  for  red  wine  production.  The  wines  are  usually  produced  as varietals,  or as blends containing several varieties.  A list of commonly used red wine varieties is given in Table 1.

Table 1:  Commonly Used Red Wine Varieties

VINIFERA GROUP     LABRUSCA    FRENCH HYBRIDS    OTHERS

Cabernet Sauvingnon    Concord

Baco Noir

Northon/Cynthiana

Merlot

Pinot

Steuben

Chambourcin

Chancelor

St. Vincent

Vincent

Zinfandel Syrah  (shiraz) Grenache Cabernet Franc Barbera

Gamay

Foch Rougeon Villard no ir colobel

Source: Bird, 2005

Varieties from the Vinifera group are most widely used for winemaking (Bird, 2005). In regions where Vinifera  grapes are not grown,  French hybrids,  Labrusca,  and other varieties  are often used. Among the Vinifera group, Cabernet Sauvignon alone, or in combination with Merlot or Cabernet Franc is used in premium red wine production (Boulton,  1996).  Pinot noir,  the famous grape of Burgundy,  makes excellent red wine.  When grown in other parts of the world, the wine does not always attain the same level of quality as found in Burgundy. Zinfandel, though popular for blush wine, can also make dark, full-bodied, and flavourful red wine (Jeff, 1999). Syrah, the popular  grape of Rhone and Australia  makes fruity wines with softer tannins.  Concord  is  the leading  red  wine  variety  among  American  grapes.  Wines  from these  grapes  have  a strong flavour,  which  is often  referred  to  as  a “foxy”  aroma.  Another  American  red  wine  grape, Cynthiana/ Norton,  does not have the foxy aroma and can make full-bodied,  dark red wines (Bird, 2005). Among the varieties in the French hybrid category, Baco, Chambourcin, Foch, and Rougeon are commonly used for red wines.  These varieties,  with proper handling,  make good red table wines.  Fresh grapes make the best raw material for making red wine (Boulton,  1996). In a situation where fresh grapes are unavailable,  frozen grapes or grape concentrate can be used, particularly for making smaller lots of wine (Jeff,  1999

1.4 Phenolics

Phenols   are  a  large  and  complex   group   of  compounds   of pnmary importance  to  the characteristics  and quality of red wine.  They are also significant  in white wines,  but occur at much lower concentrations (Waterhouse and Edeler, 1999). Phenols and related compounds can affect   the  appearance,  taste,  mouth-feel,  fragrance,  and  antimicrobial  properties   of wine. Although primarily  of grape origin,  smaller amounts may be extracted from wood cooperage. Only trace amounts are derived from yeast metabolism (Waterhouse and Edeler,  1999).

1.4.1   Polyphenols

Polyphenols   also   described   as   Polyhydroxyphenolsare    a   group   of  orgamc   chemicals characterized by the presence  of large multiples  of phenol  structural units.  They are basically natural, but  can also be synthetic.  The unique  physical,  chemical,  and biological  (metabolic, toxic,  therapeutic,  etc.) properties of a particular  class are characteristic of the number of these phenol structures bonding together to form the polyphenol (Quideau, 2011). The major polyphenolics  found  in  wine  are  either  members  of the  diphenylpropanoids  (flavonoids)  or phenylpropanoids (non-flavonoids). In addition, there are related (phenyl) compounds that do not possess one or more hydroxyl groups on the phenyl ring (and are correspondingly  strictly not phenols).

₦5,000.00 – DOWNLOAD FULL PROJECT DOWNLOAD FULL PROJECT Added to cart

---

---

---

---

Related Project Topics :