Experiment 11: Milk

Milk

Most complete food

Contains fats, proteins, carbohydrates, vitamins, and inorganic salts

Why is milk the most complete food?

fat globules, casein micelles; whey protein, salts, lactose, and soluble casein

Milk contains complex dispersion of ____________________ and ____________________ suspended in an aqueous solution of ____________________, ____________________, ____________________, and ____________________

catalase, lactase, enzymes, lipase, peroxidase, phosphatase, lipase, protease

What does fresh unboiled milk contain?

casein

Chief protein in milk

acid; milk fat

Casein is precipitated by _____________, carrying with it the ____________

Phosphoprotein - a type of conjugated protein

What class of protein is casein?

through organic solvents

How is fat extracted in milk?

soluble constitutuents like lactose and inorganic salts

What does filtrate from casein and fat contains?

amino acids from blood; mammary glands

Where does proteins from milk derived from and where is it synthesized?

phospholipid in blood

Where does milk fat originate?

derived from glucose of blood

Where does lactose of milk originate?

calcium, magnesium, sodium, phosphates, citrates, and chlorides

What are inorganic salts present in milk?

blood; filtration

Inorganic salts from milk are derived from ______________ through the process: ________________

bone

Reserve supply of calcium

Human milk is:

-less casein and ash

-more albumin and lactose

How does human milk differs from cow's milk?

lactic acid

What causes slight acidity of milk?

6.7 [slightly acidic]

pH of fresh milk

No color changes

Result of litmus paper when exposed to milk

red/pink solution indicating redox reaction

Result when congo red was added to milk

Colorless solution

Result when phenolphthalein was added to milk

desimeter

Device used to measure specific gravity

skimmed milk, absence of milk fat. fat makes the milk lighter removing it makes the milk denser

Which has a high specific gravity, fresh milk or skimmed milk? and why?

canned milk

Which milks forms a film, sour or canned milk?

proteins have been denatured by acetic acid

Why is there no film formation in sour milk?

1. temperature

2. stirring/whisking

3. presence/absence of milk fat

4. type of milk

What are factors that affect film formation?

lactoderm or milk skim caused by denturation of proteins (beta-globulin)

What is the cause of film formation in boiling milk?

acetic acid

What is used to acidify in the coagulation test for milk?

Presence of whey protein which is composed of beta-lactoglobulin

Why is there coagulation in milk upon addition of acid?

allows proteins to reach isoelectric point, lowering the intermolecular repulsion between proteins, leading to coagulation when heated

How does acid help in coagulation of milk?

1. Rennin converts caseinogen into paracasein

2. Calcium salts present in milk precipitate paracasein as casein

Two process of casein formation

presence of brown solution and caramel odor due to reducing sugar glucose

Result of action of hot alkali

NaOH

What was used as oxidizing agent for hot alkali action?

Noore's test

What carbohydrate test used the same principles with hot alkali reaction?

1. dilute HAc

2. ethyl alcohol

3. ether

Reagent used in preparation of casein

whey

In preparation of casein, what does the supernatant liquid contains?

Remove milk fat

What is the purpose of ether in preparation of casein?

to remove moisture

What is the purpose of ethyl alcohol in preparation of ether?

water, NaOH, NaCL

Which solvents is casein soluble to?

HCl

Which solvent is casein insoluble to?

yes, due to denatured proteins that forms tyrosine

Is casein positive for millon's test? why?

lactalbumin and lactoglobin

What does coagulum consists of?

Yes

Is the whey filtrate postive for biuret test?

P - ammonium phosphomolybdate

Ca - ammonium oxalate

RC - cuprous oxide

What precipitates confirms the presence of P, Ca, and reducing sugar

milk fat

What does presence of residue indicate?

translucent spot

What can be observed in the white paper after placing it with milk fat residue?