Equipment, devices and technical means

The cow's milk, milk fat-free; 40% - й solution of chloride calcium; 1% - й solution of abomasal enzyme; ferment for cottage cheese; glass capacities with a capacity of 1 l, funnels, mylar bags, thermometers, thermostat, Chizhova's device, centrifuge, bath water, scales analytical, titrating installation; acid sulfuric with a density of 1, 81-1, 82 g/ml, alcohol izoamilovy, a fenolftalein 0, 1% spirit solution, 0, 1n sodium hydroxide solution, 2, 5% solution of sulfate of cobalt, zhiromer dairy, traffic jams rubber for zhiromer, a pipette on 10, 77 ml, 10 ml, 1 ml, devices for measuring off of sulfuric acid and izoamilovy alcohol on 10 ml and 1 ml, flasks conic with a capacity of 150-200 ml, traffic jams rubber, cylinders, funnels, mortars porcelain with pestles.

Work performance order

The set amount of whole milk will be pasteurized at 80 ⁰C with endurance 20–30 with, cooled to 32 ⁰C, spill 0, 5 l in glass capacities. Bring 1% of bacterial ferment in milk: in capacity No. 1, 2 and 3 – the ferment for cottage cheese giving to a clot of skvashenny milk the pricked consistence in capacity No. 4 – the ferment giving to a clot a viscous consistence. Then add 1% to capacities No. 2 and 3 - й solution of abomasal enzyme at the rate of 1 g of dry powder on 1 t of milk. Bring 40% in capacity No. 3 - й Sas2 solution at the rate of 400 g of dry salt on 1 t of milk. After hashing of contents all samples of inoculated milk place in the thermostat with a temperature of 30 ⁰C where they have to be before emergence of a clot and achievement of acidity 60-65 ⁰T. Then measured cylinders with funnels number and put a mylar sack in each funnel. The received samples of skvashenny milk cut so that on a surface of a clot squares with the party of 1 cm have turned out. Having sustained samples at rest within 30 min., observing numbering of glasses and cylinders, transfer clots to mylar sacks. Note time of the beginning of a filtration of serum and every 5 min. write down her quantity in measured cylinders. After the termination of spontaneous office of serum the cottage cheese which is in mylar sacks is podpressovyvat, taken from them and estimated on organoleptic and physical and chemical indicators (define mass fractions of fat, moisture, titrable acidity).

Definition of a mass fraction of moisture and dry rest. For definition of moisture content in a product use Chizhova's device. Prepare a package of 150х150 mm in size from newsprint, put on diagonal, fold corners and edges approximately on 15 mm. The package is put in a leaf of parchment and dried up in the device within 3 minutes at a temperature of 150-152 °C. The dried-up packages cool and store in an eksikator.

The prepared package is weighed with a margin error by no more than 0, 01 g, give in it 5 g of a product with a margin error no more than 0, 01 g, evenly distributing on all surface of a package. The package of a hinge plate is closed, placed in the device between the tiles heated to temperature of 150-152 °C and maintained within 5 minutes. It is at the same time possible to dry up two packages. When drying products with rather high humidity at the beginning of drying in order to avoid a rupture of a package the plate of the device is raised and supported in such situation before the termination of plentiful release of vapors which usually lasts 30-50 seconds. Then the plate is lowered and continue drying. Packages of the dried-up prokba cool in an eksikator of 3-5 minutes and weigh.

The mass fraction of moisture in a product is determined by a formula:

,

where W - a mass fraction of moisture in a product, %;

m - the mass of a package of a hinge plate before drying;

m1 - the mass of a package of a hinge plate after drying;

5 - product hinge plate.

 

The mass fraction of solid in a product (With, %) is calculated on a formula:

 

C =100 -W.

The divergence between parallel definitions has to be no more than 0, 5%.

Definition of acidity of cottage cheese. In a porcelain mortar give 5 g of cottage cheese. Carefully pound a pestle, add in the small portions 50 cm3 of the water which is warmed up to 35-40 °C add three drops of solution of a fenolftalein and titrut 0, 1 N solution of a caustic natr (heat) before emergence of the slabok-pink coloring which isn't disappearing within 1 minute.

Acidity (°Т) is equal in Turner's degrees to the quantity of milliliters of 0, 1 N of solution of a caustic natr spent for neutralization of 5 g of a product, increased on 20.

The divergence between parallel definitions shouldn't exceed 4 °Т.

To issue results of observations of process of a sinerezis of cottage cheese clots in the table form in the form presented in tab. 12.1, and also in a graphic look.

Dynamics of office of serum from cottage cheese clots

 

Registration of results of work Table 12.1

Number sample	It is brought, ml	Duration of observation, min.
ferments	СаСl2	abomasal enzyme
Amount of the emitted serum, ml

 

 

To provide data on definition of indicators of quality of cottage cheese in the table form in the form presented in tab. 12.2

 

Characteristic of prototypes of cottage cheese Table 12.2

Number sample	Titrable acidity, °Т	Mass fraction, %	Organoleptic indicators
Moisture	Fat	Taste and aroma	Consistence

 

In conclusion of the report to draw conclusions on work in general.

Control questions:

1. Ways of production of cottage cheese.

2. Ways of release of protein from milk by production of cottage cheese and their influence on an exit of a ready-made product.

3. The factors causing efficiency of coagulation and processing of a clot.

4. The mode of thermal treatment of milk by production of cottage cheese, his justification.

5. The factors influencing clot dehydration.

6. What substances cause taste and a smell, characteristic of cottage cheese.

 

Laboratory work №13

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