Question

"Feathering" of coffee cream is NOT influenced by

• A. pH
• B. Temperature
• C. Potassium ions
• D. Calcium ions

Hint:

Coffee Cream Feathering: Promoted by Acidic pH, High Temperature, and Divalent CALCIUM ($ ext{Ca}^{2+}$) ions. NOT influenced by MONOVALENT POTASSIUM ($ ext{K}^+$) ions.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Colloidal destabilization in coffee cream: feathering (curdling/flocculation of cream in hot coffee) is driven by low coffee pH, high water temperature, and high divalent calcium/magnesium ion concentrations ($ ext{Ca}^{2+}, ext{Mg}^{2+}$); monovalent potassium ($ ext{K}^+$) does not bridge micellar caseins and does not influence feathering.
Key Formula or Approach:
\[ \text{Feathering Risk} \propto \frac{\text{High Coffee Temp} \times [\text{Ca}^{2+} + \text{Mg}^{2+}]}{\text{pH} \times [\text{Citrate} + \text{Phosphate}]} \quad [\mathbf{Potassium \text{ (K}^+) \text{ has NO Effect}}] \]

Step 2: Detailed Explanation:
In the physical chemistry and colloidal stability of coffee cream:
- Feathering of Coffee Cream: A major physical defect characterized by curdling, clumping, and flake/feather formation when cream is poured into hot brewed coffee.
- Factors that strongly influence and promote feathering include:
1. pH of Coffee (A): Highly acidic coffee ($\text{pH} < 5.0$) brings micellar caseins close to their isoelectric point ($4.6$), inducing rapid acid flocculation.
2. Temperature (B): High coffee temperature ($> 85^\circ ext{C}$) accelerates protein thermal coagulation.
3. Calcium and Magnesium ions (D): High divalent cation hardness in water/coffee bridges negative phosphoserine residues, collapsing micellar steric stabilization.
4. Potassium ions ($ ext{K}^+$) (C): Monovalent alkali cations do not form divalent bridges between casein micelles and have NO influence on coffee cream feathering.

Step 3: Final Answer:
Therefore, feathering is NOT influenced by Potassium ions, corresponding to option (C).