Experiment 4: Extraction and Characterization of Casein from Milk PDF

EXPERIMENT 4 EXTRACTION AND CHARACTERIZATION OF CASEIN FROM MILK AND TEST OF ITS OTHER NUTRIENTS MILK - Most nutritionally complete food found in nature - Milk contains of animals and humans contain Vitamins, Minerals, Carboh...

EXPERIMENT 4 EXTRACTION AND CHARACTERIZATION OF CASEIN FROM MILK AND TEST OF ITS OTHER NUTRIENTS MILK - Most nutritionally complete food found in nature - Milk contains of animals and humans contain Vitamins, Minerals, Carbohydrates, Lipids VITAMIN MINERALS Principally Thiamine Calcium Riboflavin Potassium Pantothenic acid Sodium Vitamin A Phosphorus B12 Trace metals Vitamin D CARBOHYDRATES LIPIDS principally Lactose Fats Cow’s milk and Goat milk almost identical in every aspect Human milk contains half of the proteins and minerals of goat and cow milk, but almost 1.5 times as much sugar LACKING iron and Vitamin C GLOBULAR PROTEINS Casein Lactalbumin Lactoglobulin  - tend to fold back on themselves into compact - nearly spheroidal units - more easily solubilized in water as colloidal suspensions than fibrous proteins are “Complete Proteins” - They contain all amino acids essential for building blood and tissue - They can sustain life and provide normal growth even if they’re the only proteins in the diet CAESIN - Main proteins in milk - Phosphoprotein, phosphate groups are attached to the hydroxyl groups of some of the amino acid sidechains 3 similar proteins which differ primarily in molecular weight and the amount of phosphorus groups they contain: a-casein β-casein k-casein Insoluble in water = a-casein, β-casein k-casein - Solubilizing the other two casein in water by promoting formation of micelles Casein exists in milk as the calcium salt CALCIUM CASEINATE Isoelectric point of pH 4.6 Insoluble in solutions of pH less than 4.6 pH of Milk is about 6.6 casein has a negative charge on the outer surface of the casein micelles neutralized and the neutral proteins precipitates, with calcium ions remaining in solution A natural example of this process occurs when milk sours. The souring of milk is an intricate process started by the action of microorganisms on the principal carbohydrate in milk, lactose. The microorganisms hydrolyze the lactose into glucose and galactose. Once galactose has been formed, lactobacilli, a strain of bacteria present in milk, convert it to the sour-tasting lactic acid. Since the production of the lactic acid also lowers the pH of the milk, the milk clots when it sours due to the precipitation of casein. LACTALBUMIN - second most abundant protein types in milk - is a globular protein that is soluble in water and in dilute salt solutions. - denatured and coagulated by heat. Once the caseins have been removed, and the solution has been made acidic, the lactalbumin can be isolated by heating the mixture to precipitate them. LACTOGLOBULINS - Present in smaller amounts than the albumins - Denature and precipitate under the same conditions as the albumins. - Carry the immunological properties of milk. - They protect the young mammal until its own immune system has developed. I. EXTRACTION OF CASEIN II. CHARACTERIZATION OF CASEIN Biuret Test Ninhydrin Test Xanthoproteic Test Adamkiewicz Test Molich’s Test Phosphate test III. TEST FOR ORHER NUTRIENTS IN MILK Test For Lactose Test for Calcium Test for Chlorides Test for Sulfates