The control experiment

Weigh 10 g of potato pulp, carry it in a flask with a capacity of 100 cm3, add 70 cm3 cylinder with water and with frequent shaking to stand for 40 min. Then wash the upper part of the flask 10 cm3 of distilled water, reagent - illuminated light, which is used mainly experiment. Add 5 ml of 10 % solution of tannin, 5 ml of lead acetate, shaken for 5 min., Bring the contents of the flask to the mark with distilled water, mix and filter. Sampling is a pipette 50 cm3 filtrate is transferred to a volumetric flask of 100 cm3, add 2 cm3 of 25 % solution of HCl, stand 15 minutes. in a boiling water bath, cooled to 20 ° C, polarize the tube length of 200 mm Saccharimeters. Prepared showing polarization P2.

Starch content calculated using the formula:

,

where:

Kp - mass fraction of starch, % by weight of dry matter;

P1 value of the angle of rotation of the polarization, which is optically active substances mainly experiment, ° L;

P2 - the angle of rotation of the polarization plane, which is water soluble optically active substances (non- starch) in the control experiment, ° L;

(P1 - P2) - the angle of rotation of the polarization plane, which is soluble starch sample, ° L;

m - mass of the product is taken for analysis, 5 g;

L - length of polarimetric cell, 2dm;

[α] d20 - rotating relative ability of potato starch in degrees of arc;

W - moisture content in potatoes,%;

0.3462 - conversion factor from degrees to degrees of arc sugar scale.

When taken for analysis navazhtsi 5g mass m and length polarimetric cuvette 2 dm formula takes the form:

where F - Evers factor, which is 1000 0,3462 / [α] A20

When calculating the mass fraction of starch using Table 1, which shows the value of specific capacity rotating [α] d20 coefficient and Evers (F) for the main types of starch.

Laboratory work 7

Дата добавления: 2015-11-14