Centrifugation of Milk: Take the Quiz and Flashcards

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Questions and Answers

What is the primary purpose of clarification in centrifugation?

Separation of cream from skim milk

Removal of solid impurities from milk prior to pasteurization (correct)

Butter oil purification

Standardizing whey separation

What is the function of the discharge slots in a self-cleaning centrifuge bowl?

To allow ejection of sediment during continuous separation/clarification (correct)

To introduce milk towards the disc stack

To separate cream from skim milk

To move dense particles back to the perimeter

Which phase moves towards the bowl wall in a centrifuge?

Cream phase

Dense phase (correct)

Light phase

Whey phase

How many discs can be stacked together in a centrifuge?

Up to 120 discs Signup and view all the answers

What is the result of self-cleaning in a centrifuge on milk processing?

Loss of 25 L/hr of milk for one dairy Signup and view all the answers

Which process involves the separation of bacteria from milk in centrifugation?

Bactofuge treatment Signup and view all the answers

What is the purpose of keeping the pasteurized milk at least 1 psi higher than raw milk in the regenerator?

To prevent contamination of pasteurized milk with raw milk in case of a pin-hole leak. Signup and view all the answers

What is the function of the balance or constant level tank in an HTST pasteurizer?

It provides a constant milk supply. Signup and view all the answers

Why must the overflow level be kept below the lowest milk passage in the regenerator?

To maintain a higher pressure on the pasteurized side of the heat exchanger. Signup and view all the answers

How does the balance tank prevent air from entering the pasteurizer?

By creating a downward slope of at least 2% on the outlet pipe. Signup and view all the answers

What is one of the functions of a regenerator in a pasteurizer?

Utilizes the heat content of pasteurized milk to warm incoming milk. Signup and view all the answers

Why must the holding tube slope upwards in the direction of flow?

To eliminate air entrapment and ensure uniform flow velocity. Signup and view all the answers

Which method of UHT processing involves heating by injecting steam directly into the product?

Injection heating Signup and view all the answers

What is the primary function of homogenization in milk processing?

To create an oil-in-water emulsion Signup and view all the answers

Which packaging method for aseptic processing involves erecting, sterilizing, filling, and sealing knocked-down blanks?

Erect, fill and seal Signup and view all the answers

What is the primary drawback of a lack of equipment for particulate sterilization?

Settling of solids Signup and view all the answers

In the context of UHT processing, what results in a more pronounced cooked flavor in milk?

Injection heating Signup and view all the answers

What is a distinguishing feature of indirect heating systems used in UHT processing?

Scraped surface method Signup and view all the answers

What is the primary purpose of pasteurization in milk and milk products?

Destroying harmful bacteria (pathogens) Signup and view all the answers

Which method of pasteurization saves time and energy compared to the vat method?

Continuous method Signup and view all the answers

What is commonly used as the heating medium in an HTST pasteurizer?

Steam Signup and view all the answers

Which equipment is essential in an HTST pasteurizer to facilitate heat exchange?

Plate heat exchanger Signup and view all the answers

For continuous pasteurizing, what is crucial to maintain in the heat exchanger?

Higher pressure on the pasteurized side Signup and view all the answers

What is the holding time required for milk inside the heat exchanger during pasteurization at 72°C?

15 seconds Signup and view all the answers

Study Notes

Centrifugation and Separation

Centrifugation is used in the dairy industry for clarification, skimming, standardizing, whey separation, bactofuge treatment, quark separation, and butter oil purification.
Centrifuges can separate and clarify at the same time, with dense particles thrown to the perimeter, forming solids that collect in the centrifuge.
Modern self-cleaning centrifuges allow for continuous separation/clarification, with a specially constructed bowl that can eject 8 to 25 L of sediment every 60 min.

Centrifuge Components

A centrifuge consists of up to 120 discs stacked together at a 45 to 60 degree angle.
Milk is introduced towards the inner edge of the disc stack through vertically aligned distribution holes.
Dense phase moves towards the bowl wall, along the underside of the discs, while light phase moves towards the center, along the upper faces of the discs.

HTST Pasteurizer Components

Balance tank provides a constant milk supply, with a float valve assembly controlling the liquid level.
Regenerator utilizes the heat content of pasteurized milk to warm the incoming milk.
Timing pump draws product through the raw regenerator and pushes milk under pressure through the pasteurized regenerator.
Holding tube must slope upwards 1/4″/ft in direction of flow to eliminate air entrapment.
Indicating thermometer is the most accurate temperature measurement.

Pasteurization

Pasteurization is used to make milk and milk products safe for human consumption by destroying all bacteria that may be harmful to health (pathogens).
It improves the keeping quality of milk and milk products, destroying some undesirable enzymes and many spoilage bacteria.
Shelf life can be 7, 10, 14, or up to 16 days.

Pasteurization Methods

Batch method: milk is heated to 63°C for 30 min, then cooled to 4°C.
Continuous process method: saves time and energy compared to the vat method, using a high temperature short time (HTST) pasteurizer with a plate heat exchanger.
HTST pasteurizer maintains a higher pressure on the pasteurized side of the heat exchanger, with a holding time of 15s at 72°C.

UHT Methods

Direct heating systems: injection, infusion
Indirect heating systems: plate, tubular, scraped surface

Packaging for Aseptic Processing

Fill and seal: preformed containers made of thermoformed plastic, glass, or metal are sterilized, filled in aseptic environment, and sealed.
Form, fill, and seal: roll of material is sterilized, formed in a sterile environment, filled, and sealed.
Erect, fill, and seal: using knocked-down blanks, erected, sterilized, filled, and sealed.
Thermoform, fill, and seal: roll stock sterilized, thermoformed, filled, and sealed aseptically.
Blow mold, fill, and seal

Homogenization

Homogenization is a mechanical treatment of the fat globules in milk, achieved by passing milk under high pressure through a tiny orifice.
Milk is an oil-in-water emulsion, with fat globules dispersed in a continuous skim milk phase.

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Description

Explore the process of centrifugal separation in the dairy industry, including its various uses such as clarification, skimming, whey separation, bactofuge treatment, quark separation, and butter oil purification. Test your knowledge on this essential technique for dairy production.

Centrifugation in the Dairy Industry

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