experiment 4

• What is the most nutritionally complete food found in nature?

  Milk
• What vitamins are present in milk?

  thiamine

  riboflavin

  pantothenic acid

  vitamins A, B12, and D
• What minerals are present in milk?

  Calcium

  Potassium

  Sodium

  Phosphorous

  Trace Metals
• What proteins are present in milk?

  Casein

  Lactalbumin

  Lactoglobulin
• What lipids and carbohydrates are present in milk?

  Lactose (Carbohydrates)

  Fats (Lipids)
• Cow’s milk and goats’ milk are almost identical in every resepect. Human milk contains less than half of the proteins and minerals of cows’ or goats’ milk, but almost 1.5 times as much sugar.
• The only important nutrients lacking in milk are iron and vitamin C.
• All three types of proteins in milk are globular proteins. They are more easily solubilized in water as colloidal suspensions than fibrous proteins are.
• Proteins in milk are “complete proteins” because they contain all amino acids essential for building blood and tissue, they can sustain life and provide normal growth even if they are the only proteins in the diet. These proteins are not only contain more amino acids than plant proteins, but they contain greater amount of amino acids than the proteins in eggs and meats.
• What is the main protein in milk?

  casein
• What type of protein is casein?

  Phosphoprotein
• Casein is a phosphoprotein meaning that phosphate groups are attached to the hydroxyl groups of some of the amino acid side-chains.
• What are the types of casein?

  a-casein (alpha)

  b-casein (beta)

  k-casein (kappa)
• The phosphoproteins in milk is a mixture of three similar proteins which differ primarily in molecular weight and the amount of phosphorous groups they contain.
• a-casein and b-casein are both insoluble in water. K-casein is responsible for solubilizing the other two caseins in water by promoting the formation of micelles.
• Casein exists in milk as the calcium salt, calcium caseinate. Calcium caseinate has an isoelectric point of pH 4.6. Therefore, it is insoluble in solutions of pH less than 4.6.
• The pH of milk is 6.6. Casein has a negative charge at this pH and is solubilized as a salt. If acid is added to the milk, the negative charges on the outer surface of the casein micelles are neutralized and the neutral protein precipitates, with the calcium ions remaining in solution.
• What acid is produced when milk becomes sour?

  lactic acid
• What carbohydrate starts the process of the souring of milk?

  lactose
• The souring of milk is started by the principal carbohydrate, 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.
• What is the second most abundant protein in milk?

  lactalbumin
• Lactalbumin is a globular protein that is soluble in water and in dilute salt solutions. They are however, 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.
• It is present in smaller amounts than the albumins and generally denature and precipitate under the same conditions as albumins.

  lactoglobulins
• Lactoglobulins carry the immunological properties of milk. They protect the young mammal until its own immune system has developed.
• At what temperature is the hot plate heated to?

  55 degrees Celcius
• After heating it to 55degrees Celcius, what do you add?

  10% acetic acid, dropwise
• What appears after adding the 10% acetic acid?

  casein
• What is the obtained casein used for?

  characterization of casein:

  biuret test

  ninhydrin test

  xanthoproteic test

  adamkiewicz test

  molisch’s test

  phosphate test
• what is the whey solution (filtrate) used for?

  Test for other nutrients:

  Test for lactose, calcium, chlorides, and sulfates
• What is added to the casein to remove small quantities of fat that may have precipitated with the casein?

  1:1 ethyl ether and ethanol
• What is the casein solution composed of?

  35 mL of water and 0.5 mL of. 1M NaOH