MILK

1) Adultration of milk 1) Adultration of milk Objectives: To detect any adulteration of milk. Introduction and principle: One of the most common adulterants in milk is added water, which increase the bulk of the milk but decrease it's specific gravity. Normal whole cow's has a specific gravity of( ), while the specific gravity of the skim milk produced from this by removal of fat is since the milk fat globules have a specific gravity of less than 1, their removal in the manufacture of skim milk causes an increase in specific gravity.

specific gravity may be measured using a specific gravity bottle, taking care to carry out the whole procedure at a certain constant temperature, since specific gravity is dependant on temperature. Another way of detecting adulteration by water is to determine the total solids content of the milk.

Normal whole cow's milk contains 11.5% solids. The specific gravity of a milk adulterated with water might be maintained at a normal value by the addition of starch, another form of adulteration. Starch is easily detected by it's formation of a purple complex with iodine, I2

Pasteurization, a precisely specified heat treatment, is the only means commonly permitted for the preservation of milk. The growth of microorganisms may also be prevented, however, by the addition of numerous prohibited preservations, for each of which there is a specific method of detection. Alternatively, milk might be boiled in order to improve it's keeping quality. Such treatment destroys the native structure of peroxidase,

an enzyme present naturally in milk. Lack of peroxidase activity indicate excessive heat treatment of the milk. Unpasteurized milk left at room temperature suffers an increase in it ’ s acidity. This is caused mainly by the fermentation of the milk sugar, lactose, to lactate by bacteria present in the milk.

Cows milk consist water,fat,lactose,casine and mineral Fat 3-3.3% Solid not fat 8.5% Total solid 11.7%

Method: A) Determination of specific gravity: 1- weight an empty specific gravity bottle. 2- fill it with distilled water and weight. 3-empty the bottle and dry it in an oven. 4- fill it with milk and weight. 5- calculate the density of milk as weight of milk in S.G bottle weight of milk in S.G bottle = = Weigh of water held in S.G bottle Weigh of water held in S.G bottle

B) Determination of total solid: 1- take a weight of crucible. 1- weigh 5 g of milk in a crucible 2- put a crucible in a water bath until dryness. 3- after complete dryness put the crucible in an oven, and weigh after cooling. 4- determination the percent of total solid. %Of total solid = wt of crucible of the – wt of crucible/ wt of sample * 100 %Of total solid = wt of crucible of the – wt of crucible/ wt of sample * 100

C) Test for peroxidase: 1- prepare 2 test tubes. 1- prepare 2 test tubes. 2- in tube 1 add 3 ml milk, 5 drops of dilute acetic acid, and a few drops of alcoholic guaicium solution then add 1 ml of 3% hydrogen peroxide. 2- in tube 1 add 3 ml milk, 5 drops of dilute acetic acid, and a few drops of alcoholic guaicium solution then add 1 ml of 3% hydrogen peroxide. 3- in tube 2 add the same but use boiled milk. 3- in tube 2 add the same but use boiled milk. 4- a blue color develops in tube 1, this indicate the presence of peroxidase enzyme which is destroyed by boiling. 4- a blue color develops in tube 1, this indicate the presence of peroxidase enzyme which is destroyed by boiling.

2) Determination of fat in milk: objectives: The amount of fat in milk is a chrematistic property that is measured in this experiment. Introduction and principle: The determination of fat content in milk is based on releasing the fat from proteins present. Then the fat is extracted by diethyl ether. The ether extract is heated to evaporate the solvent leaving back the fat to be weighed.

Method: 1- Add 2ml of 0.8% ammonia, 3 ml ethanol, and 4ml distilled water to 8 g of milk in a long Stoppard boiling tube. 2- Slightly warm the contents and shake, for 7 min release the pressure, then cool, transfer into a seperatory funnel. 3- Add 25 ml diethyl ether and 25 ml petroleum ether. Extracted by gentle shaking, then take aweight of beaker, transfer the ether layer the upper layer to the beaker.

4- Evaporate the ether content.in water bath 5- Dry the flask in the oven for 2-3 hours and after cooling in a desiccators, weigh. 6. Calculate the fat content from the weight of material held in the flask. Of fat= wt of flask after drying – wt empty flask/ wt of sample * 100