II. Preparation of the indicator

1) Preparation of 0.1-normal solution of NaOH. To do this, 1 ampoule standard titer NaOH is flown out in flask 1 liter, than the flask is "scrubbed " with distilled water and the volume of the solution is being brought to 1 liter.

2) 210 g of urea dissolved in 370 ml of distilled water, into this solution is flown out 70 ml of 0.1-normal solution of NaOH, also add 1.4 g of phenol red indicator and then fill with 3 liters of distilled water. Solution turns bright red colour.

3) Preparation of 0.1-normal solution of H2SO4. To do this, 1 ampoule of standard titer H2SO4 flown out into a flask 1l, than the flack is \"scrubbed \" with distilled water and the volume of the solution is being brought to 1 liter.
4) 0.1-normal solution of H2SO4 is being flown out into burette.
5) Fill the 25 ml of ready phenol solution in a beaker and titratу 0.1-normal solution of H2SO4 from the burette to the straw-yellow color of the solution.

III. Determination of urease activity

Into Petri dish throw 11 g of soya extrudate and fill with the previously prepared solution of straw-yellow color. Keep for 5 minutes until appear bright red dots:
1) separate dots - the activity of urease 0,05 pH;
2) the dots are of 25% - urease activity 0,1 pH;
3) dots of 50% - urease activity 0,1 - 0,15 pH;
4) dots of 75% - urease activity 0,2 - 0,3 pH.

Note: Regulatory activity of urease pH 0,10-0,20
Shelf life of phenol solution - 15 days.