1.1. The task

1. Define phenol matters in grape.

2. Prepare necessary reagents.

3. Draw up report about the effort

Theoretical part

Phenol compounds have one or more hydroxyl groups, connected with carbons of aromatic line. They assist in grape and wine in terms of monomers, oligomers and polymers. Phenol compounds take active part in oxidation-reduction processes, flowing in wort and wine, interact with proteins and metals, forming hard soluble compounds, inducing haze of wines. They take part in formation of bouquet, taste and color of wines. Content of phenol compounds is in white wine 200-1500 mg/dm³, in red wines 1500-5000 mg/dm³. Under technologic store of phenol matters of grape is implied that their part, which can pass into wort by correct processing of working of grape.

The order of performance of job

Necessary materials and facility:

Thermostable glass, volume 600-800 cm³; thermometer; thermostat; potassium permanganate KMnO₄ 0,01n solution; solution indigo carmine: 2,33 g matter dissolve in 100 cm³ water, add 5ml of concentrated H₂SO₄, bring up to 1 litre and filtrate; sodium hydroxide, 15% ;nitrate of plumbum, 50% solution

Separate grape by hand from comb, crush them. Carry over pulp in thermostable glass and quickly bring up temperature 70C by intimate mixing. Incubate by temperature 70 C 30min, from time to time mixing. Then cool pulp and pressing by hand through mull. In gotten wort determine content of anthocyans and phenol matters, as is described below. Method allow to see about dynamics of accumulation of coloring matters in the period of grape ageing and fix moment of maximum accumulation of coloring matters, and accordingly period of red sort vintage.

Definition of mass concentration of phenol matters in wort by permaganatemetric method. This method is founded on oxidation of phenol matters of wort by standard solution KMnO₄ by indicator indigo carmine. Find out volume of KMnO₄ used on titration, before and after removal of phenol matters. On the difference between first and second titrating estimate content of phenol matters.

Technique of definition. 50 cm³ red or 100 cm³ white wine boil out on water bath to half volume. By analysis of wort that operation isn’t conducted. Rinsings pour in delivery flask volume 100 cm³ and bring up to mark. 50 cm³ of gotten solution carry over in delivery flask volume 100 cm³, add 3-6 cm³ 15% solution of NaOH (to stoppage of color change) and much the same quantity solution Рb (NО3)₂, bring water to mark, filtrate.

In large porcelain cup pour 700-800 cm³ water, 20 cm³ solution indigo carmine, 20 cm³ filtrate and titrate 0,1n solution KMnO₄ with constant stirring to appearance of yellowness. To define total oxidizer 20 cm³ solution, gotten after dealcoholizing, but not discoloured, titrate how describe above. Calculation. Content of phenol matters (g/litre) estimate by formula:

0,00416(В₁-В₂) К· 10

Х = ---------------------------

В

where 0,00416 - quantity of anotanin, corresponding 1 ml 0,1 N permanganate solution, g;

В₁- quantity of permanganate solution used on titration 20 ml of test solution before discoloration, ml;

В₂- quantity of permanganate solution used on titration 20 ml of test solution after discoloration, ml;

K - multiplier for re-count on 1 liter wine (for red wines 100, for white- 50) ;

10 - quantity of oxalic acid, taken on titration, ml;

B- quantity of permanganate solution used on titration 10 ml 0,1 N solution oxalic acid, ml

A report on task performance

Test questions

1. How to prepare a standard solution of tannin

2. How to determine the total phenol content in the fruit.

3. How to build a calibration curve

Laboratory work # 7

Determination of ascorbic acid’ content by iodometric method.

Purpose of the work: experimental determination of ascorbic acid’ content by iodometric method.

1.1. The task

1. Learn the bases of iodometric method .

2. Define ascorbic acid’ content by iodometric method.

3. Draw up report about the effort.

1.2. Theoretical part

A redox titration, involving an iodometric method, will be used to do the analysis. The samples will be classified by their ascorbic acid content.

Although most mammals can synthesize vitamin C, or ascorbic acid (C6H8O6), from sugars, man must ingest considerable quantities of this substance. The National Academy of Sciences recommends the consumption of 60 mg of ascorbic acid per day. Vitamin C deficiency refers to a condition where the body does not have enough vitamin C to perform important functions. Humans, unlike many animals, cannot manufacture vitamin C on their own — they must consume it as part of their diet. This vitamin helps build and maintain healthy bones and teeth; build tendons, cartilage, skin, and collagen; and heal wounds.

Technique definition.

5-10g of coarsely cut product pour by 1% spirit of salt (not above 20ml) in mortar, grind until indiscrete mass and carry over into 100ml measuring flask. Wash the mortar and add 2% solution of metaphosphoric acid till mark, leave to stand for 10min and filter at once into dry flask. Then take out three 5-20ml’ samples of filtrate (according to content of ascorbic acid). Add a small crystal of potassium iodide (KJ) and several drops of 1% amylase in two parallel samples and titrate from microburet by 0,001mol/dm³solution of iodic potassium(KJO₃) until violet color.

If you determine ascorbic acid’ content in colored solutions, put the3d flask nearby to compare color. The volume 1ml of 0,001mol/dm³solution of iodic potassium corresponds 0,088ml of ascorbic acid.

Calculation of ascorbic acid’ content (X_a) is carried by formula:

X_a= V·T ·V₁·100/ m·V₂, where

V- quantity of 0,001mol/dm³solution of iodic potassium, taken for titration of extract, ml;

T- titre -0,088 mg of ascorbic acid, responding 1 ml of 0,001mol/dm³solution of iodic potassium;

100- correction coefficient of ascorbic acid’ content;

V₂- volume of filtrate of being investigated product, taken for titration, ml;

m-weighed amount of product, g.

Test questions

1.What is the formula of ascorbic acid?

2. Why man must ingest considerable quantities of this substance?

3.Why it is necessary to add a small crystal of potassium iodide (KJ)?

Laboratory work #8

Analysis of reducing properties of ascorbic acid.

Purpose of work: analyze reducing properties of ascorbic acid.

1.1. The task

1. Learn the bases of reducing properties of ascorbic acid..

2. Define reducing properties of ascorbic acid.

3. Draw up report about the effort.

1.2. Theoretical part

Ascorbic acid is a naturally occurring organic compound with antioxidant properties. It is a white solid, but impure samples can appear yellowish. It dissolves well in water to give mildly acidic solutions. Ascorbic acid is one form ("vitamer") of vitamin C. It was originally called L-hexuronic acid, but when it was found to have vitamin C activity in animals ("vitamin C" being defined as a vitamin activity, not then a specific substance), the suggestion was made to rename L-hexuronic acid. The new name for L-hexuronic acid is derived from a- (meaning "no") and scorbutus (scurvy), the disease caused by a deficiency of vitamin C. Because it is derived from glucose, many animals are able to produce it, but humans require it as part of their nutrition. Other vertebrates lacking the ability to produce ascorbic acid include other primates, guinea pigs, teleost fishes, bats, and birds, all of which require it as a dietary micronutrient (that is, a vitamin).^[2]

Chemically, there exists a D-ascorbic acid which does not occur in nature. It may be synthesized artificially. It has identical antioxidant properties to L-ascorbic acid, yet has far less vitamin C activity (although not quite zero).^[3] This fact is taken as evidence that the antioxidant properties of ascorbic acid are only a small part of its effective vitamin activity. Specifically, L-ascorbate is known to participate in many specific enzyme reactions which require the correct epimer (L-ascorbate and not D-ascorbate).

1. Reaction with methylene blue. Ascorbic acid in the light reduces by methylene blue to uncolored compound , acidifing to dehydroascorbic acid.

Reagents and facility: cabbage or potatoes juice; test tube; grate from nonrusting steel; mull; methylene blue,0,01% sol.; natrium carbonate, 5% sol..

Technique definition.

Potato tuber or part of cabbage head grate on grater from nonrusting steel. Ground mass squeeze out through mull, mounted in two layers.

To 1ml of new- succus of potatoes or cabbage add drop wise of methylene blue and 2-3 drops of soda solution. Test tube slightly heat. See after discoloration of blue color.