Production of White Wine from Grapes Using Sacharomyces cervisiae

 

P. Bangaraiah¹*, P. Ashok Kumar²

¹Department of Chemical Engineering, Vignan University, Vadlamudi.

²Department of Chemical Engineering, S.V. University, Tirupati.

 

ABSTRACT:

Wine is an alcoholic beverage often made of fermented grape juice. The natural chemical balance of grapes is such that they can ferment without the addition of sugars, acids, enzymes or other nutrients. Wine is produced by fermenting crushed grapes using various types of yeast which consume the sugars found in the grapes and convert them into alcohol. Different varieties of grapes and strains of yeasts are used depending on the types of wine being produced. Although other fruits such as apples and berries can also be fermented, the resultant wines are normally named after the fruit from which they are produced (for example, apple wine or elderberry wine) and are generically known as fruit wine or country wine. Wine is an undistilled product obtained after normal alcoholic fermentation of grapes by yeast. Wine is basically the transformation of sugars of grapes by yeast under anaerobic conditions in to ethanol, co₂, and small amounts of byproducts like D-Glucose, D-fructose. In our project, for the extraction of juice grapes must be stemed, cleaned, and crushed and then sodium or potassium metabiosulphate is added to check undesirable organisms. The crushed grape is called must. Fermentation is carried out by adding 2-5% of wine yeast namely sacharomyces cervisiae, anaerobic conditions favors the alcoholic fermentation liberating ethanol, co_2.  Main aim of this work is to produce white wine from grapes. A detailed study on grapes and different methods to produce wine is also reported. By analysis of wine, we reported the percentage purity, alcohol percentage in produced wine and different compound compositions.

 

 

 

1. INTRODUCTION:

1.1 History of wine:

Wine stems from an extended and rich history dating back about 8,000 years and is thought to have originated in present day Georgia or Iran. Wine is thought to have appeared in Europe about 6,500 years ago in present-day Bulgaria and Greece and was very common in classical Greece, Thrace and Rome. Wine has also played an important role in religion since ancient times. The Greek God Dionysos and the Roman God Bacchus represented wine^1,2.

 

Wine has also played an important role in religious ceremonies of Christianity and Judaism, such as the Eucharist and Kiddush, was also forbidden in the Islamic civilization, but after Geber and other Muslim chemists pioneered the distillation of wine, it was used for other purposes, including cosmetic and medical uses. In fact the 10th century Persian philosopher and scientist Al Biruni described recipes where herbs, minerals and even gemstones are mixed with wine for medicinal purposes. Wine was so revered and its effect so feared that elaborate theories were developed about which gemstone-cups would best counteract its negative side effects³. The word "wine" derives from the Proto-Germanic winam, an early borrowing from the Latin vinum, "wine" or "(grape) vine", itself derived from the Proto-Indo-European stem win-o- . Similar words for wine or grapes are found in the Semitic languages and in Georgian, and the term is considered an ancient wanderwort. The oldest known evidence of wine production in Europe is dated to 4500 BC and comes from archaeological sites in Greece. The same sites also contain the world’s earliest evidence of crushed grapes. In Ancient Egypt, six of 36 wine amphoras were found in the tomb of King Tutankhamun bearing the name "Kha'y", a royal chief vintner. Five of these amphoras were designated as from the King's personal estate with the sixth listed as from the estate of the royal house of Aten. Traces of wine have also been found in central Asian Xinjiang, dating from the second and first millennia BC⁴.

 

1.2. Classification of wine:

Regulations govern the classification and sale of wine in many regions of the world. European wines tend to be classified by region, while non-European wines are most often classified by grape. More and more, however, market recognition of particular regions is leading to their increased prominence on non-European wine labels. Examples of non-European recognized locales include Napa Valley in California, Willamette Valley in Oregon, Barossa Valley and Hunter Valley in Australia, Central Valley in Chile and Marlborough in New Zealand⁵. Wines are categorized using a number of different methods. Sometimes they are grouped into different categories by grape variety, region of origin, by color, by the name of the wine maker or viticulturalist, or by production technique. Three basic groups of wines are most easily distinguishable for the consumer: table wines, sparkling wines, and fortified wines. Table wines, also known as still or natural wines, are produced in many different styles and make up the majority of wines on the market. Traditionally consumed as part of a meal, table wines contain between 10 and 14 percent alcohol and are further classified by their color, sugar content, and the variety and origin of the grapes that were used. Depending on the grape variety and wine-making technique, wines can be white, red, or pink in color. Most table wines are fermented until they are dry that is, all the grape sugar has been turned to alcohol by the yeast⁶.  Slightly sweet or off-dry wines are made by stopping the fermentation before all the sugar is gone or by adding grape juice back to the wine afterwards. In wine-producing regions outside of Europe, particularly California and Australia, table wines are often classified by the grape variety they are made from. At least 75 percent of the grapes used to produce the wine must be of the named grape variety. Chardonnay, for example, is wine made from at least 75 percent chardonnay grapes. Wines classified this way are sometimes called varietals, and include^7,8. Sparkling wine is made from table wine that has undergone a second fermentation. The wine maker adds a measured amount of sugar and fresh yeast to the dry wine. This can happen in a closed tank, or directly in the bottle, which is the way the most famous sparkling wine, French champagne, is produced. The yeast ferments the added sugar, but this time the carbon dioxide gas remains in the sealed bottle, creating carbonation. When the sparkling wine is poured into a glass, the gas bubbles form on to the surface⁹.  Fortified wines contain additional alcohol and are usually consumed in small amounts as aperitifs before meals or dessert wines after a meal. Popular examples are port and sherry. In port wine making, which originated in Portugal, the grapes are crushed and the fermentation started but then stopped by the addition of more alcohol, which kills the yeast. The resulting wine is sweet and has an alcohol content that is 5 to 10 percent higher than table wine. Originally from Spain, sherry is made by adding alcohol to a young dry wine in an oak barrel intentionally filled only halfway. Special yeasts called floor yeast grow on the surface of the wine and create the distinct nutty flavor characteristic of sherry. About 8 million cases of fortified wines are produced in the United States each year¹⁰.  Brandy is made from wine but is classified as distilled liquor, not as wine. Brandy is distilled from wine to concentrate the alcohol in the wine. To make a distillate, wine is heated in an enclosed copper pot until it boils and the alcohol evaporates. The alcoholic vapor passes through a coiled pipe where it is cooled down until it forms a liquid again, or condenses. After distillation the brandy is aged. Bottled brandy typically contains 40 percent alcohol and has been aged in oak barrels for several years.

 

1.3.1. Europe classification:

France has an appellation system based on the concept of terroir, with classifications which range from Vin de Table ("table wine") at the bottom. Portugal has something similar and, in fact, pioneered this technique back in 1756 with a royal charter which created the "Demarcated Douro Region" and regulated wine production and trade. Germany did likewise in 2002, although their system has not yet achieved the authority of those of the other countries'. Spain and Italy have classifications which are based on a dual system of region of origin and quality of product.

 

1.3.2. Beyond Europe:

New World wine wines from outside of the traditional wine growing regions of Europe tend to be classified by grape rather than by terroir or region of origin, although there have been non-official attempts to classify them by quality.

 

2. EXPERIMENTATION:

2.1. Experimentation:

After the harvest, the grapes are crushed and allowed to ferment. Red wine is made from the must of red or black grapes that undergo fermentation together with the grape skins, while white wine is usually made by fermenting juice pressed from white grapes, but can also be made from must extracted from red grapes with minimal contact with the grapes' skins. Rosé wines are made from red grapes where the juice is allowed to stay in contact with the dark skins long enough to pick up a pinkish color, but little of the tannins contained in the skins.

 

Chemical Reaction:

C₆H₁₂O₆ -->2C₂H₅OH+2 CO_2:

During this primary fermentation, which often takes between one and two weeks, yeast converts most of the sugars in the grape juice into ethanol. After the primary fermentation, the liquid is transferred to vessels for the secondary fermentation. Here, the remaining sugars are slowly converted into alcohol and the wine becomes clear¹¹.. Wine is then allowed to age in oak barrels before bottling, which add extra aromas to the wine, while others are bottled directly. The time from harvest to drinking can vary from a few months for Beaujolais nouveau wines to over twenty years for top wines. However, only about 10% of all red and 5% of white wine will taste better after five years than it will after just one year. Depending on the quality of grape and the target wine style, some of these steps may be combined or omitted to achieve the particular goals of the winemaker. Many wines of comparable quality are produced using similar but distinctly different approaches to their production; quality is dictated by the attributes of the starting material and not necessarily the steps taken during vinification.

 

The quality of the grapes determines the quality of the wine more than any other factor. Grape quality is affected by variety as well as weather during the growing season, soil minerals and acidity, time of harvest, and pruning method. The combination of these effects is often referred to as the grape's terroir. Grapes are usually harvested from the vineyard in the autumn, in the northern hemisphere from early September until the beginning of November, or the middle of February until the beginning of March in the southern hemisphere. The most common species of wine grape is Vitis vinifera, which includes nearly all varieties of European origin¹². Harvest is the picking of the grapes and in many ways the first step in wine production. Grapes are either harvested mechanically or by hand. The decision to harvest grapes is typically made by the winemaker and informed by the level of sugar, acid and pH of the grapes. Other considerations include phenological ripeness, berry flavor, tannin development. Overall disposition of the grapevine and weather forecasts are taken into account.

 

2.1.1. Crushing and primary fermentation:

Crushing is the process of gently squeezing the berries and breaking the skins to start to liberate the contents of the berries. Desteming is the process of removing the grapes from the rachis. In traditional and smaller-scale wine making, the harvested grapes are sometimes crushed by trampling them barefoot or by the use of inexpensive small scale crushers. These can also destem at the same time. However, in larger wineries, a mechanical crusher/destemmer is used. The decision about desteming is different for red and white wine making. Generally when making white wine the fruit is only crushed, the stems are then placed in the press with the berries. The presence of stems in the mix facilitates pressing by allowing juice to flow past flattened skins. These accumulate at the edge of the press. For red winemaking, stems of the grapes are usually removed before fermentation since the stems have relatively high tannin content; in addition to tannin they can also give the wine a vegetal aroma. On occasion, the winemaker may decide to leave them in if the grapes themselves contain less tannin than desired. This is more acceptable if the stems have 'ripened' and started to turn brown. If increased skin extraction is desired, a winemaker might choose to crush the grapes after destemming. Removal of stems first means no stem tannin can be extracted. In these cases the grapes pass between two rollers which squeeze the grapes enough to separate the skin and pulp, but not so much as to cause excessive shearing or tearing of the skin tissues. In some cases, notably with "delicate" red varietals such as Pinot noir or Syrah, all or part of the grapes might be left uncrushed to encourage the retention of fruity aromas through partial carbonic maceration¹³.

 

During the primary fermentation, the yeast cells feed on the sugars is the most and multiplies, producing carbon dioxide gas and alcohol. The temperature during the fermentation affects both the taste of the end product, as well as the speed of the fermentation. For red wines, the temperature is typically 22 to 25 °C, and for white wines 15 to 18 °C. For every gram of sugar that is converted, about half a gram of alcohol is produced, so to achieve a 12% alcohol concentration, the must should contain about 24% sugars. The sugar percentage of the most is calculated from the measured density, the must weight, with the help of a saccharometer. If the sugar content of the grapes is too low to obtain the desired alcohol percentage, sugar can be added. In commercial winemaking, capitalization is subject to local regulations. During or after the alcoholic fermentation, malolactic fermentation can also take place, during which specific strains of bacteria convert malolactic into the milder lactic acid. This fermentation is often initiated by inoculation with desired bacteria.

 

2.1.2. Cold and heat stabilization:

Cold stabilization is a process used in winemaking to reduce tartrate crystals in wine. These tartrate crystals look like grains of clear sand, and are also known as "wine crystals" or "wine diamonds". They may appear to be sediment in the wine, but they are not. During the cold stabilizing process, the temperature of the wine, after fermentation, is dropped to close to freezing for 1-2 weeks. This will cause the crystals to separate from the wine and stick to the sides of the holding vessel¹⁴. When the wine is drained from the vessels, the tartrate is left behind. During "heat stabilization", unstable proteins are removed by adsorption onto bentonite, preventing them from precipitating in the bottled wine.

 

2.1.3. Secondary fermentation and bulk aging:

During the secondary fermentation and aging process, which takes three to six months, the fermentation continues very slowly. The wine is kept under an airlock to protect the wine from oxidation. Proteins from the grape are broken down and the remaining yeast cells and other fine particles from the grapes are allowed to settle¹⁵. The secondary fermentation usually takes place in either large stainless steel vessels with a volume of several cubic meters of wine, or oak barrels, depending on the goals of the winemakers. Un oaked wine is fermented in a barrel made of stainless steel or other material having no influence in the final taste of the wine. Depending on the desired taste, it could be fermented mainly in stainless steel to be briefly put in oak, or have the complete fermentation done in stainless steel. Oak could be added as chips used with a non-wooden barrel instead of a fully wooden barrel. This process is mainly used in cheaper wine¹⁵.

 

2.2. Experimental procedure:

a.        Since the starter culture of s. cervisiae is not available. Wheat is used for initiating fermentation. As their surface usually contains the fermenting yeast. The wheat is soaked for 2-3 hours in water and then used for initiating the fermenting mature ripe and fleshy grapes are stored out and soaked in 5% salt water for 15-20 min to destroy unwanted microorganisms.

b.       Grapes are then washed with distilled water. Grapes are crushed in a blender after adding good quality water along with stirred seeds. This is known as must. This is transfer to fermenting water previously sterilized with alcohol. 8-10% of sugar syrup was added to the must.

c.        200-300 ppm of sodium Meta bisulphate is added to the must as preservative. This favors the growth of yeast and suppresses the growth of undesirable microorganisms.

d.       2- 3 hrs of soaked wheat of s. cervisiae is added to start fermentation.

e.        To clear the thickening of must and to get elasticity egg white is added.

f.         The fermented shaken vigorously. The mouth of bottle was cleaned and dry. Air lock is applied and it is air tight with paraffin wax.

g.       The water level in the air lock was checked, commencing of air bubble is indicative of commencement of fermentation.

h.       The fermented was kept in dark place and shaken well every day. The fermentation is continued for 3- 4 weeks or until ceasing of bubbles coming from the must.

i.         The temperature and pH we maintained during  the fermentation time is 15⁰c,3-4

 

3. RESULTS:

Raw Materials:

Grapes   = 2kg

Sugar     = 1kg

Egg white = 3 eggs

Soaked Wheat (yeast) = 20gms

Sodium Meta bisulphate = 2gms

 

Conditions Maintained:

Temperature = 15⁰c

PH = 3-4

Period of fermentation = 3 weeks

Aging = 60 days

We produced the white wine by using chemicals and maintaining conditions like temperature, pressure and foam at optimum levels. Then the produced wine is purified by using filtration, clarification and distillation. After purification we did analysis by using HPLC.

 

ANALYSIS BY HPLC:

Working of HPLC:

·         Mobile phase is drawn out of the reservoir bottle and pumped through the tubing by the pump.

·         The degasser removes dissolved air from the mobile phase, preventing air bubbles and consequent rise, drift or other baseline irregularities caused by dissolved air.

·         The pump sends the mobile phase through the manual injector.

·         In the column, the components are separated by means of the mutual interactions of the mobile phase and the column packing.

·         The detector detects the components eluted from the column, and sends the signals data to a chromatographic or pc.

·         Mobile phase from the detector drains into the waste container.

 

Analysis Report:

Alcohol = 2%

Glucose = 100 gm/lit

Fructose =100gm/lit

Nitrogen compounds = 900.7 mg/lit.

Purity of wine is 80%

 

4. CONCLUSION:

a.        By maintaining the all conditions in fermentation and by conducting all the purification steps we produced the wine with the following compositions

b.       Alcohol = 2%

c.        Glucose = 100 gm/lit

d.       Fructose =100gm/lit

e.        Nitrogen compounds = 900.7 mg/lit.

f.         By seeing the above results we concluded that our produced wine had 80 % purity.

 

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