Introduction: Casein is a major milk phosphoprotein integral to pharmaceutical science, encompassing chemistry, sources, preparation, evaluation, preservation, storage, therapeutic uses and commercial utility. B.Pharm students should understand casein chemistry (phosphoserine residues, amphiphilic domains, casein micelle architecture), common sources (bovine, caprine milk), preparation methods (acid precipitation, rennet coagulation, spray drying), analytical evaluation (Kjeldahl, SDS-PAGE, FTIR, phosphorus assays), and preservation/storage strategies (low moisture, controlled temperature, vacuum packaging). Casein’s biodegradable, mucoadhesive and film-forming properties underpin therapeutic applications (drug carriers, controlled release, wound films) and commercial uses (cheese, adhesives, coatings, nutraceuticals). Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What type of protein is casein?
- Milk albumin
- Phosphoprotein
- Glycoprotein
- Collagen
Correct Answer: Phosphoprotein
Q2. Which are the principal casein fractions found in bovine milk?
- Alpha-, beta- and kappa-casein
- Gamma-, delta- and epsilon-casein
- Albumin, globulin and lactoferrin
- Actin, myosin and tropomyosin
Correct Answer: Alpha-, beta- and kappa-casein
Q3. Around which pH does casein reach its isoelectric point and precipitate?
- pH 2.0
- pH 4.6
- pH 7.0
- pH 9.5
Correct Answer: pH 4.6
Q4. What is a characteristic solubility property of native casein at neutral pH?
- Highly soluble in water
- Insoluble in water, dispersible as micelles
- Soluble only in organic solvents
- Soluble only at pH below 3
Correct Answer: Insoluble in water, dispersible as micelles
Q5. Which casein fraction primarily stabilizes the micelle surface?
- Alpha-casein
- Beta-casein
- Kappa-casein
- Gamma-casein
Correct Answer: Kappa-casein
Q6. Which common method is employed for laboratory preparation of casein from milk?
- Ammonium sulfate fractionation
- Acid precipitation at pH 4.6
- Soxhlet extraction with hexane
- Ion-exchange chromatography as primary step
Correct Answer: Acid precipitation at pH 4.6
Q7. How does rennet cause milk coagulation during casein preparation?
- By hydrolyzing beta-lactoglobulin
- By cleaving kappa-casein to destabilize micelles
- By oxidizing phosphoserine residues
- By reducing disulfide bonds in casein
Correct Answer: By cleaving kappa-casein to destabilize micelles
Q8. Which industrial drying method is most commonly used to produce casein powder?
- Lyophilization (freeze-drying) only
- Spray drying
- Vacuum oven drying at 150°C
- Sublimation without atomization
Correct Answer: Spray drying
Q9. For long-term preservation of purified casein with minimal structural change, which approach is preferred?
- Storage in aqueous suspension at 4°C
- Freeze-drying (lyophilization)
- Heating at 80°C for 30 minutes
- Maintaining at pH 4.6 in solution
Correct Answer: Freeze-drying (lyophilization)
Q10. Which analytical method is typically used to determine total protein content of casein?
- Kjeldahl nitrogen estimation
- Bradford assay without calibration
- UV absorbance at 280 nm only
- Thin layer chromatography
Correct Answer: Kjeldahl nitrogen estimation
Q11. Which technique is most appropriate for assessing casein polypeptide molecular weight distribution?
- Gas chromatography
- SDS-PAGE electrophoresis
- Optical microscopy
- Refractometry
Correct Answer: SDS-PAGE electrophoresis
Q12. Which spectroscopic method helps evaluate secondary structure changes in casein?
- FTIR spectroscopy
- Flame photometry
- Polarography
- Atomic absorption spectroscopy
Correct Answer: FTIR spectroscopy
Q13. Which residue in casein is primarily responsible for calcium binding?
- Hydroxyproline
- Phosphoserine
- Tyrosine
- Histidine
Correct Answer: Phosphoserine
Q14. Which enzyme is commonly used to enzymatically cross-link casein in formulations?
- Pepsin
- Transglutaminase
- Lipase
- Amylase
Correct Answer: Transglutaminase
Q15. Enzymatic hydrolysis of casein can release bioactive peptides such as:
- Insulin-like growth factor
- Casomorphins
- Collagen peptides
- Albumin fragments
Correct Answer: Casomorphins
Q16. Which property of casein makes it attractive as a pharmaceutical drug carrier?
- High crystallinity and insolubility
- Biodegradability and mucoadhesion
- Strong enzymatic resistance in vivo
- High thermal stability at 200°C
Correct Answer: Biodegradability and mucoadhesion
Q17. Which statement about casein and allergies is correct?
- Casein never causes allergic reactions
- Casein is a common milk allergen in susceptible individuals
- Casein allergy is identical to lactose intolerance
- Casein only causes contact dermatitis, not systemic allergy
Correct Answer: Casein is a common milk allergen in susceptible individuals
Q18. Which commercial application uses casein as a traditional adhesive?
- Casein-based wood glue
- Silicone sealants
- Epoxy resins
- Polyurethane foams
Correct Answer: Casein-based wood glue
Q19. In cheese production, what is the critical role of casein?
- Acting as the sole carbohydrate source
- Coagulation to form curd and structure
- Providing emulsification of lipids only
- Preventing microbial growth entirely
Correct Answer: Coagulation to form curd and structure
Q20. What structural role does the C-terminal region of kappa-casein perform on micelles?
- Forms the hydrophobic core
- Creates a hydrophilic “hairy” layer stabilizing micelles
- Binds DNA to micelle surface
- Forms covalent disulfide-linked shells
Correct Answer: Creates a hydrophilic “hairy” layer stabilizing micelles
Q21. During isoelectric precipitation of casein, which fraction remains in the supernatant?
- Casein curd
- Whey proteins and lactose (whey)
- Pure fat only
- Denatured casein pellet
Correct Answer: Whey proteins and lactose (whey)
Q22. Which statement correctly contrasts casein and whey?
- Casein remains soluble at pH 4.6 while whey precipitates
- Casein precipitates at pH 4.6; whey proteins remain in solution
- Whey proteins have higher phosphorus content than casein
- Casein is predominantly globular while whey is fibrous
Correct Answer: Casein precipitates at pH 4.6; whey proteins remain in solution
Q23. What is the approximate molecular weight of alpha-casein?
- ~5 kDa
- ~24 kDa
- ~100 kDa
- ~250 kDa
Correct Answer: ~24 kDa
Q24. What is the typical diameter range of casein micelles in milk?
- 1–10 nm
- 100–200 nm
- 10–20 micrometers
- 1–5 mm
Correct Answer: 100–200 nm
Q25. Optimal storage conditions for commercial casein powder include:
- High humidity and room temperature
- Low moisture, airtight packaging, cool and dark environment
- Exposed to air in open containers
- Storage at 60°C to prevent microbial growth
Correct Answer: Low moisture, airtight packaging, cool and dark environment
Q26. Which analytical method is commonly used to quantify phosphorus bound to casein?
- Colorimetric molybdenum blue assay
- Ninhydrin test for amino groups
- Biuret test for peptide bonds
- Benedict’s test for reducing sugars
Correct Answer: Colorimetric molybdenum blue assay
Q27. What molecular characteristic gives casein good emulsifying properties?
- High carbohydrate content
- Amphiphilic nature with hydrophobic and hydrophilic domains
- High content of aromatic rings only
- Extensive intra-chain disulfide bonding
Correct Answer: Amphiphilic nature with hydrophobic and hydrophilic domains
Q28. How does casein typically respond to thermal treatment compared with whey proteins?
- Casein is relatively heat-stable and resists unfolding
- Casein denatures at much lower temperatures than whey
- Casein forms rigid crystals upon heating
- Casein vaporizes before denaturation
Correct Answer: Casein is relatively heat-stable and resists unfolding
Q29. Which pharmaceutical role is casein commonly used for?
- As a non-biodegradable metal chelator only
- As a binder, film-former and controlled-release matrix
- As a primary antiseptic agent
- As an inorganic bulking agent
Correct Answer: As a binder, film-former and controlled-release matrix
Q30. Prior to casein extraction from milk, how is the fat generally removed?
- Chemical hydrolysis of lipids in situ
- Centrifugation/cream separation
- Adding large volumes of ethanol only
- Ultraviolet irradiation to degrade fats
Correct Answer: Centrifugation/cream separation
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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