UHT Process Steps

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Questions and Answers

What is the primary purpose of the UHT process?

To extend the shelf life of food products (correct)

To change the color of food products

To increase the nutritional value of food

To enhance the flavor of dairy products

What is the typical temperature required to kill spores in milk during UHT processing?

150°C (302°F)

100°C (212°F)

180°C (356°F)

135°C (275°F) (correct)

What is the typical holding time at sterilization temperature during UHT processing?

1-2 seconds (correct)

1-2 minutes

5-10 minutes

15-30 seconds

What is the primary difference between UHT and HTST pasteurization?

Holding time Signup and view all the answers

What is a common side effect of high heat during the UHT process?

Maillard browning Signup and view all the answers

What is the typical shelf life of UHT milk?

Six to nine months Signup and view all the answers

What is an alternative position for homogenisation in the UHT process?

After initial cooling Signup and view all the answers

What is the most common UHT product?

Milk Signup and view all the answers

What is the main advantage of infusion direct heating method?

Suitability for low and higher viscosity products Signup and view all the answers

What is the purpose of flash cooling in vacuum chamber in direct heating?

To remove water equivalent to the amount of condensed steam used Signup and view all the answers

What is the main limitation of direct heating injection method?

It is energy intensive Signup and view all the answers

What is the principle of membrane processing?

Particles are separated based on their molecular size and shape Signup and view all the answers

What is the main advantage of indirect heating systems?

The heating medium and product are not in direct contact Signup and view all the answers

What is the purpose of membrane processing in whey?

To produce whey protein concentrate (WPC) Signup and view all the answers

What is the main difference between concentrated and dried dairy products?

Concentrated milk products have less water removed than dried dairy products Signup and view all the answers

What is the water content of fluid milk?

Approximately 88% water Signup and view all the answers

What happens to the skim milk during separation?

It moves outwards and leaves through a separate outlet Signup and view all the answers

How is the desired fat content achieved during direct standardization?

By automatically remixing the cream and skim at the separator Signup and view all the answers

What was the original application of the pasteurization process?

Wine Signup and view all the answers

What is the primary purpose of milk pasteurization from a public health aspect?

To make milk and milk products safe for human consumption Signup and view all the answers

What is the minimum temperature required for pasteurization of milk for at least 30 minutes?

63° C Signup and view all the answers

What is used to determine if milk has been pasteurized?

A test for alkaline phosphatase Signup and view all the answers

What is an additional benefit of pasteurization besides making milk safe for consumption?

Improving the shelf life of milk Signup and view all the answers

How often can the shelf life of pasteurized milk be extended?

By up to 16 days Signup and view all the answers

Study Notes

UHT Process

The UHT process involves preheating, homogenization, heating to sterilization temperature, holding, initial cooling, homogenization, final cooling, and aseptic packaging.
The sterilization temperature is above 135°C (275°F) for an extremely short period, around 1–2 seconds.

UHT Processing

UHT stands for ultra-high temperature processing, ultra-heat treatment, or ultra-pasteurization.
It is used for milk, fruit juices, cream, soy milk, yogurt, wine, soups, and stews.
UHT milk was invented in the 1960s and became available in the 1970s.
High heat can cause Maillard browning and change the taste and smell of dairy products.
UHT milk has a typical shelf life of six to nine months, until opened.

UHT Methods

There are two principal methods of UHT treatment: direct heating and indirect heating.

Direct Heating Systems

There are two methods of direct heating: injection and infusion.
Injection involves high-pressure steam injection into pre-heated liquid, rapid heating, and flash cooling.
Infusion involves pumping food into a chamber of high-pressure steam, instantaneous heating, and rapid cooling.
Infusion has several advantages, including no localized overheating or burn-on, and suitability for low and higher viscosity products.

Indirect Heating Systems

The heating medium and product are not in direct contact, but separated by equipment contact surfaces.
Several types of heat exchangers are applicable, including plate, tubular, and scraped surface.

Membrane Processing of Milk

Membrane processing is a technique that permits concentration and separation without heat.
It separates particles based on their molecular size and shape using pressure and specially designed semi-permeable membranes.
It can be used for protein separation in whey, milk concentration before cheesemaking, and other applications.

Concentrated and Dried Dairy Products

Fluid milk contains approximately 88% water.
Concentrated milk products are obtained through partial water removal.
Dried dairy products have even greater amounts of water removed to usually less than 4%.

Standardization

The streams of skim and cream after separation must be recombined to a specified fat content.
This can be done by adjusting the throttling valve of the cream outlet or through direct standardization.

Pasteurization

The process of pasteurization was named after Louis Pasteur.
It involves heating every particle of milk or milk product to a specific temperature for a specified period.
The purpose is to make milk and milk products safe for human consumption and to improve their keeping quality.
Pasteurization can destroy pathogens, undesirable enzymes, and spoilage bacteria.
Typical pasteurization regulations for milk include heating to 63°C for at least 30 minutes or 72°C for at least 16 seconds.

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Description

Learn about the major steps involved in the UHT (Ultra High Temperature) process, including preheating, homogenisation, and heating to sterilisation temperature.