Lab

Question 1

What is the Beer Lambert Law?

Answer 1

𝐴 = 𝜀 × 𝑙 × 𝑐
𝐴: absorbance
𝜀: extinction coefficient
𝑙: path length
𝑐: concentration

Question 2

What are the two applications of the Beer-Lambert Law?

Answer 2

1. Compare protein concentration with KNOWN ABSORBANCE for two different samples —-> proteins with higher concentrations show higher absorbance
2. Calculate the protein concentration with KNOWN EXTINCTION COEFFICIENT AND PATH LENGTH

Question 3

At what temperature do egg whites denature, coagulate, and become solid at room temperature?

Answer 3

63-65 Celsius

Question 4

What are 4 factors in denaturation and coagulation?

Answer 4

1. Temperature
2. pH
3. Sugar
4. Salt

Question 5

Effect of pH on denaturation

Answer 5

As pH shifts, strong intramolecular electrostatic repulsion causes swelling and unfolding

Question 6

Effect of sugar on denaturation

Answer 6

exerts a protective effect on egg by controlling denaturation rate and ultimate formation of intermolecular bonds
RAISES THE TEMPERATURE REQUIRED FOR COAGULATION

Question 7

Effect of salt on denaturation

Answer 7

• promotes denaturation, coagulation, and gelation
• DECREASES DENATURATION TEMPERATURE

Question 8

What is the process of acid-induced milk coagulation?

Answer 8

• achieved by 1) adding acids: citric acid, lactic acid, lemon juice 2) fermentation through culture
• accompanied by dimineralization, reduction of electrostatic interactions between protein molecules, and aggregation of caseins through hydrophobic interaction and calcium bridging

At pH = 4.6
1. colloidal calcium phosphate dissociates from casein molecules
2. surface charge of casein micelles decreases
3. collapse of k-casein layer and reduction in the stability of the micelles
4. aggregation of caseins and the formation of gel structure in unheated milk

Question 9

What is the process of Enzyme-induced milk coagulation

Answer 9

• enzymes: zingibain, rennet
• when enzyme mixed with milk, enzyme cleaves hydrophilic carbohydrate group on k-casein to break it down into CMP and para-k-casein
• CMP is soluble/hydrophilic and diffuses away from micelle
• para-k-casein is hydrophobic, stick together and form milk curds
• enzymes decrease steric repulsion between casein molecules

Question 10

Why do some fats have better H2O-absorbing capacity?

Answer 10

Mono and di glycerides have polar OH groups, which can interact with water through hydrogen bonding
- the more mono and di glycerides, the higher water absorption capacity

Question 11

Why do some fats have better creaming ability?

Answer 11

• they can incorporate and retain air bubbles better
• temperature matters: not too cold, not too warm