Lecture 10 Flashcards
Four fractions of casein:
αs1 : β : κ : αs2 = 3:3:1:0.8
αs and β caseins
Calcium sensitive and are very hydrophobic
κ caseins
Contains only one phosphate group. Are hydrophilic because it contains an acidic carb section
True or false. Hydrophilic κ caseins exist on the surface.
True
Why do κ caseins stabilize the micelle?
Negative charge and
hydration.
Charged hydrophilic
carbohydrate group.
Hairlike structure which
confer steric stability
True or False. Acid coagulation of milk proteins is a reversible process.
False. It is irreversible.
True or False. Acid coagulation is accompanied by demineralization, reduction of electrostatic interactions between protein molecules, and aggregation of caseins through hydrophobic interaction and calcium bridging.
True
What is the pI value of casein micelles?
4.6
What is rennet-like protease?
Zingibain
During enzyme-induced milk coagulation, k-casein is broken down into what?
CMP and para-k-casein
What is soluble and thus diffuses away from the micelle?
CMP
Para-k-casein is _____________.
Hydrophobic
What is another name for zingibain?
Ginger protease
Optimal temp: 70°C
Temperature range: 40 to 70 °C
What are the applications of zingibain and limitations?
Meat tenderizer and rennet substitute. Limitations are low stability and easily inactivated.
What temp will be used when making ginger milk curd?
80 °C
Zingibain is a substitute for _________.
Rennet
What is the function of enzymes on milk protein coagulation?
Cleave the hydrophilic carbohydrate group on k casein and destabilize milk proteins.
What results do we see from enzymes destabilizing milk proteins?
The k-casein coagulates and forms a solid curd
Explain the principle of acid effects on milk protein coagulation.
Acid-induced coagulation involves the precipitation of casein.
During acid-induced coagulation, what is involved?
Demineralization, aggregation of caseins, and reduction of electrostatic interactions.
What pI does acid coagulation occur?
4.6
True or false. Ultimately, enzymes reduce steric repulsion.
True
Enzyme-induced coagulation cleaves k-casein resulting in ______ and ___________.
CMP and para-k-casein
Why is fresh ginger juice needed to make ginger curd milk?
The enzyme is not very stable and is easily inactivated.
