Question

With regard to temperature of operation, place the following unit operations in sequence in an increasing order of temperature:
(i) Sterilisation
(ii) Thermisation
(iii) Homogenisation
(iv) Bactofugation and
(v) HTST pasteurization.
Choose the correct answer from the options given below :

• A. Sterilisation, HTST pasteurization, Thermisation, Bactofugation, Homogenisation
• B. Sterilisation, HTST pasteurization, Homogenisation, Thermisation, Bactofugation
• C. Bactofugation, Homogenisation, Thermisation, HTST pasteurization, Sterilisation
• D. Bactofugation, HTST pasteurization, Homogenisation, Thermisation, Sterilisation

Hint:

To easily order thermal processes, remember their primary biological goals: 1. Physical separation (Bactofugation) requires the lowest heat.
2. Quality extension (Thermisation) requires mild heat.
3. Pathogen destruction (Pasteurization) requires medium heat.
4. Spore destruction (Sterilisation) requires the highest heat.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Various thermal and mechanical unit operations in dairy processing are carried out at specific, optimized operating temperatures to ensure efficacy, maintain milk stability, and prevent protein denaturation.

Step 2: Detailed Explanation:
Let us identify the typical operating temperatures for each of the given unit operations:
- Bactofugation (iv): This centrifugal separation process removes bacterial spores. It is carried out at \(55\ ^\circ\text{C}\) to \(60\ ^\circ\text{C}\), where the viscosity of milk is low enough for efficient separation without causing thermal damage.
- Homogenisation (iii): To ensure that milk fat is completely liquid and can be easily broken down, homogenization is performed at \(60\ ^\circ\text{C}\) to \(65\ ^\circ\text{C}\).
- Thermisation (ii): This mild heat treatment is used to extend the storage life of raw milk before processing. It is typically conducted at \(63\ ^\circ\text{C}\) to \(65\ ^\circ\text{C}\) for \(15\) seconds.
- HTST pasteurization (v): This standard heat treatment destroys all vegetative pathogens in milk. It operates at \(72\ ^\circ\text{C}\) to \(75\ ^\circ\text{C}\) for \(15\) seconds.
- Sterilisation (i): This intensive thermal process destroys all microorganisms and spores. It requires temperatures of \(115\ ^\circ\text{C}\) to \(121\ ^\circ\text{C}\) for \(15\) minutes (or \(135\ ^\circ\text{C}\) to \(150\ ^\circ\text{C}\) for UHT processing).
Arranging these operations in increasing order of temperature gives: Bactofugation \(\rightarrow\) Homogenisation \(\rightarrow\) Thermisation \(\rightarrow\) HTST pasteurization \(\rightarrow\) Sterilisation.
This sequence matches the order listed in option (C).

Step 3: Final Answer:
The correct increasing sequence of temperature of operation is Bactofugation, Homogenisation, Thermisation, HTST pasteurization, Sterilisation.