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Analytical Chemistry Experiment: Preparation of Alcoholic Beverages from Fresh Fruits

December 21, 2008

Analytical Chemistry Experiment

Preparation of Alcoholic Beverages from Fresh Fruits

Abstract

About one kilogram of Pineapple was washed, peeled and cut off in small cube to osterize in a blender. A fruit extract was obtained. Together with the addition of desirable amount of sugar and yeast, the fruit extract was placed in a high-neck bottled and been fermented for at least two weeks. It was been pastured through the use of traditional katsa (filter).  Pineapple wine was produced and placed to observation about its taste, color, odor, textured and transparency . 100ml of the wine with raisins was set aside for distillation and boiling point experiments…

I. Introduction

Fermentation come form a Latin word fermentum means to leaven. Fermentation is the anaerobic enzymatic conversion of organic compounds, especially carbohydrates, to simpler compounds, especially to ethyl alcohol, resulting in energy in the form of adenosine triphosphate (ATP); the process is used in the production of alcohol, bread, vinegar, and other food or industrial products. It differs from respiration in that organic substances rather than molecular oxygen are used as electron acceptors. Fermentation occurs widely in bacteria and yeasts, the process usually being identified by the product formed; e.g., acetic, alcoholic, butyric, and lactic fermentation are those that result in the formation of acetic acid, alcohol, butyric acid, and lactic acid.

On the other hand, fermentation can also define as the conversion of a carbohydrate such as sugar into an acid or an alcohol. More specifically, fermentation can refer to the use of yeast to change sugar into alcohol or the use of bacteria to create lactic acid in certain foods. Fermentation occurs naturally in many different foods given the right conditions, and humans have intentionally made use of it for many thousands of years.

II. Review of Related Literature

Alcoholic Beverages

May be divided into fermented drinks including beer and wines, and distilled drinks or spirits which are obtained from the former by distillation. Spirits usually contain about fifty per cent. of alcohol, beer and wines from one to twenty per cent. The alcohol in all cases results from the breaking up of the sugar in the fermenting liquid.

Sugars

Ordinary sugar, or cane sugar, uncrystallizable, or fruit sugar; and grape sugar, or glucose, are the three most important varieties. Fruit sugar exists in all the sub-acid fruits as grapes, currants, apples, peaches, etc. When these are dried, it changes to grape sugar forming the whitish grains which are seen on the outside of prunes, raisins, etc. Grape sugar is found to a limited extent in fruits associated with fruit sugar. Cane sugar is readily changed by the action of acids or ferments into fruit sugar, and the latter into grape sugar, but the process cannot be reversed. Grape sugar is the only fermentable variety, the others becoming changed into it before fermentation.

Transformation of Starch

Under the influence of acids, or diastare, a principle existing in germinating grains, starch is changed first into gum (dextrine) and afterwards into grape sugar. Hence one of our most important sources of alcohol is to be found in the starch of barley, corn, wheat, potatoes, etc. Wood may be converted into grape sugar by the action of strong sulphuric acid which is afterwards neutralized. An attempt to produce alcohol in this way on a commercial scale was made in France, but was not successful.

Ferment

A solution of pure sugar will remain unchanged for an indefinite period of time. To induce fermentation, a portion of some nitrogenous body, itself undergoing decomposition, must be added. Such ferments are albumen (white of egg), fibrin (fibre of flesh), casein (basis of cheese), gluten (the pasty matter of flour). Yeast consists of vegetable egg-shaped cells, which is increased during its action as a ferment.

Circumstances influencing Fermentation

In order that fermentation shall begin we require, besides the contact of the ferment, the presence of air. The most easily decomposed articles of food may be preserved for an indefinite period by hermetically sealing them in jars, after drawing out the air. When once begun, however, fermentation will go on, if the air be excluded. Temperature is important. The most favorable temperature is between 68 and 77 Fahr. At a low temperature fermentation is exceedingly slow. Bavarian or lager beer is brewed between 32 and 46 1/2 Fahr. A boiling heat instantly stops fermentation, by killing the ferment.

To check fermentation we may remove the yeast by filtration. Hops, oil of mustard, sulphurous acid (from burning sulphur), the sulphites, sulphuric acid, check the process by killing the ferment.

Too much sugar is unfavorable to fermentation, the best strength for the syrup is ten parts of water to one of sugar.

Changes during Fermentation

The grape-sugar breaks up into carbonic acid which escapes as gas, alcohol and water which remain. In malting the grain is allowed to germinate, during which process the starch of the grain is changed into gum and sugar: the rootlets make their appearance at one end and the stalk or acrospire at the other. The germination is then checked by heating in a kiln; if allowed to proceed a certain portion of the sugar would be converted into woody matter, and lost.

In brewing the sacharine matter is extracted from the malt during the mashing. Yeast is added to cause fermentation; an infusion of hops afterwards, to add to the flavor and to check fermentation. In wine making there is sufficient albuminous matter in the grape to cause fermentation without the use of yeast.

Distillation separates the alcohol in great part from the water. Alcohol boils at 179 Fahr., and water at 212. It is not possible, however, to separate entirely alcohol and water by distillation.

(The Household Cyclopedia of General Information, 1881)

III. Methodology

A.     Preparation of Juice Extract

1.)    Wash 1k of fruit. Peel off skin, or remove the seeds or pits when present. Cut small cubes, and osterize into a smooth consistency using a blender.

2.)    Add boiled water (cooled before adding). If the fruit extract obtained is viscous or too thick in consistency.

3.)    Add about brown or white sugar (amount added is relative to your taste) as he fruit is osterized and mixed thoroughly.

4.)    Transfer the juice into a high-necked bottle and cover tightly.

B.     Fermentation

1.)    Follow the set-up given by the instructor.

2.)    Add about 2 tablespoons of yeast to the fruit extract.

3.)    Allow fermentation of the mixture for 2-3 weeks.

C.     Pasteurization

1.)    Using clean cheesecloth (katsa), filter the fermented mixture, receiving the filtrate in a clean container.

2.)    Warm the filtrate to about 60-65 C. Add raw egg white and stir until the egg white is cooked. The egg white acts as a coagulant for any left-over residue in the filtrate.

3.)    Filter the cooked mixture again, using the cheesecloth. Dispose any coagulated substance retained by the cloth.

4.)    Place a small amount of the fermented mixture in a clean container and observe the following properties:

a.) taste                               b.) color               c.) odor                                d.) texture          e.) transparency

5.) Set aside 100ml of the fermented mixture for the distillation and boiling point experiments. Keep this portion in a tightly sealed bottle and refrigerate.


IV. Discussions of Data and Interference from Results

After doing the experiment, we observed the following properties:

Taste

Sweet pineapple taste with pinch of an alcoholic taste.

Color

It comes in bright yellow in color.

Odor

Strong Pineapple.  Too much smell can make you feel dizzy.

Texture

It was just fine.

Transparency

It comes in a slimy bright yellow .  I think sugar is the cause why it is slimy.

The wine was alcoholic because of the sugar or glucose that was broken down by the yeast. Without the presence of oxygen, the product of the glucose becomes ethyl alcohol and carbon dioxide.

V. Answers to Guide Questions

1.) Write the balanced chemical equation that represents the fermentation of sugar.

C6H12O6 → 2 C2H5OH + 2 CO2

This chemical equation summarizes ethanol fermentation, in which one hexose molecule is converted into two ethanol molecules and two carbon dioxide molecules

2.) What is the role of the yeast in the process?

Yeast are unicellular fungi that reproduce asexually by budding or fission. Yeast is what causes primary fermentation to take place. The role of yeast in the chemical process is that it will eat the sugars in the pineapple juice and the end products are CO2 and alcohol.

3.) Why should the fermentation set-up be alright?

Set-up should be alright in order to have accurate result of the experiment since fermentation is an anaerobic process, and oxygen will cause the organisms to produce different products.

If the set-up for fermentation is not properly assembled, like if the cover in the set-up is not properly sealed, the result of the fermentation may be contaminated or worse if the fermentation process will not take effect because of the presence of oxygen converting glucose to carbon dioxide and water.

4.)    What is the use of the limewater in the process?

Lime water also known as  saturated calcium hydroxide solution Ca(OH)2 can be used to test the presence of carbon dioxide because lime water reacts with carbon dioxide to produce a precipitate of calcium carbonate:

Ca(OH)2 (aq) + CO2 (g) → CaCO3 (s) + H2O (l)

Lime water is also used in fermentation, to determine whether carbon dioxide was produced. When lime water reacts with CO2 it becomes milky.

5.) What must be the average pH of the product of fermentation to qualify as “alcoholic”?

The resulting alcohol is 100 to 200 proof (200 proof is pure alcohol). Yeasts are able to grow in foods with a low pH, (5.0 or lower) and in the presence of sugars, organic acids and other easily metabolized carbon sources.

VI. Bibliography

  • Zubrick, James W. The Organic Chemistry Lab Survival Manual: A Student’s Guide to Techniques 6th Edition. New York: John Wiley & Sons Canada, Ltd.; 5th edition.
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One comment

  1. I like this



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