Dairy Packaging, Sensory & By-Products

Technological principles of whey powder manufacturing:

• Statement (A) is correct: pre-crystallization of lactose ($85\text{--}90\%$) into $\alpha$-lactose monohydrate prevents sticking and hygroscopicity, allowing concentrates up to $58\text{--}60\%\text{ TS}$ to be spray dried successfully.
• Statement (B) is correct: two-stage drying (spray chamber followed by vibrating fluid bed) permits drying at lower temperatures, preserving native whey protein functionality.
• Statement (C) is incorrect: two-stage drying reduces thermal energy consumption by $15\text{--}20\%$ because fluid-bed evaporative moisture removal is thermally far more efficient than chamber drying.
• Statement (D) is incorrect: operating processing cost is decreased, not increased, due to fuel and energy savings.

Two-stage enzymatic debittering of casein hydrolysates:

• Assertion (A) is true: enzymatic hydrolysis of casein generates bitter hydrophobic peptides; a two-stage sequential hydrolysis is widely applied to overcome this bitterness.
• Reason (R) is false: in two-stage hydrolysis, casein is first cleaved internally by an endopeptidase (e.g., alcalase, trypsin, or neutrase) into short oligopeptides, followed by secondary treatment with an exopeptidase (aminopeptidase or carboxypeptidase) that cleaves hydrophobic terminal residues to debitter the hydrolysate; the sequence in Reason (R) is completely inverted.
• Thus, Assertion (A) is true but Reason (R) is false.
• Therefore, option 3 is the correct answer.

Biosynthesis of Vitamin B12 from whey using Propionibacterium:

• Statement (A) is correct: cheese whey supplemented with cobalt and dimethylbenzimidazole is an efficient substrate for vitamin B12 biosynthesis by Propionibacterium freudenreichii subsp. shermanii.
• Statement (B) is incorrect: Propionibacteria are anaerobic to aerotolerant/microaerophilic microorganisms, not aerobic growers.
• Statement (C) is correct: accumulating propionic and acetic acids drop culture pH and arrest growth, requiring fed-batch neutralization (e.g., with ammonium hydroxide) to maintain cell growth.
• Statement (D) is correct: corrinoid precursor synthesis and final assembly of the cobalamin nucleotide loop occur maximally during late exponential and stationary phases.

Electrodialysis (ED) is an electrochemical membrane separation process used in the dairy industry primarily for the demineralization (desalting) of whey and infant formula ingredients. An electric potential gradient generated by Direct Current (DC) is applied across an alternating stack of cation-exchange membranes and anion-exchange membranes. Positively charged cations ($Na^+, K^+, Ca^{2+}$) migrate unidirectionally towards the negative cathode, and negatively charged anions ($Cl^-, H_2PO_4^-$) migrate towards the positive anode. Alternating current (AC) cannot be used because periodic reversal of polarity would simply oscillate ions back and forth without net directional separation.

Option analysis:

• DC: Correct. Direct current provides the fixed electric field necessary for unidirectional ion migration.
• AC: Incorrect. Oscillates ions without separation.
• Static charges: Incorrect.
• Sinusoidal: Incorrect.