Pasteurisation and UHT Processing

Questions and Answers

What is the impact of pasteurisation on the nutritional value of milk?

Pasteurisation does not significantly affect the nutritional value of milk.

How does homogenisation affect the physical properties of milk?

Homogenisation reduces the size of fat globules, preventing them from clumping and rising to the surface.

Explain the pasteurisation process and its purpose.

Pasteurisation involves heating milk to 72 degrees Celsius for 15 seconds to destroy pathogenic bacteria.

What is UHT processing and how does it affect milk storage?

UHT processing involves heating milk to 138-149 degrees Celsius for 2-6 seconds, allowing it to be stored without refrigeration for at least 3 months. Signup and view all the answers

Why can't sweetened condensed milk be substituted for whole milk?

Sweetened condensed milk contains 60% less water and 40-45% sugar, making it unsuitable as a direct substitute for whole milk. Signup and view all the answers

What is the primary use of a paddle in mixing applications?

A paddle is primarily used for mixing heavier ingredients that do not require much aeration, such as creaming butter and sugar. Signup and view all the answers

How does a dough hook differ from other mixing tools?

A dough hook is specifically designed to knead bread doughs and develop gluten efficiently. Signup and view all the answers

What distinguishes a food processor from a blender in terms of liquid requirement?

A food processor typically requires little to no liquid, while a blender needs a set amount of liquid to function properly. Signup and view all the answers

What role does an immersion blender play in food preparation?

An immersion blender is used to blend ingredients or purée food directly in the container where they are being prepared. Signup and view all the answers

What is the purpose of an ice cream churner during the freezing process?

An ice cream churner simultaneously freezes the mixture and aerates it by keeping the ice crystals small. Signup and view all the answers

Study Notes

Milk Processing

Pasteurisation involves heating milk to 72°C for 15 seconds to destroy pathogenic bacteria and increase shelf life.
Pasteurisation also destroys spoilage-causing enzymes, but has no significant effect on nutritional value.
Ultra High Temperature Processing (UHT) involves heating milk to 138-149°C for 2-6 seconds, allowing for storage without refrigeration for at least 3 months.
UHT gives milk a slightly cooked taste, but no significant effect on nutritional value.
Homogenisation reduces fat globules in whole milk, preventing them from clumping and rising to the surface.

Storage of Milk

Fluid milk should be refrigerated at or below 4°C to prevent bacterial growth.
Shelf life is reduced by half for every 5°C rise in temperature above 4°C.
Milk containers should be kept closed to prevent absorption of odours or flavours.

Concentrated Milks

Concentrated milk products are produced by removing water from whole milk using a vacuum.
Resulting products have a high concentration of milk fat and solids, and an extended shelf life.

Condensed Milk

Condensed milk has 60% of its water removed and contains 40-45% sugar.
Sweetened condensed milk is canned and has a caramel flavour, but cannot be substituted for whole milk due to its sugar content.

Mixing Equipment

Paddle: used for generic mixing applications, particularly those that are too heavy for whips.
Hook or dough arm: used for mixing and kneading bread doughs, developing gluten quickly and efficiently.
Bench models range in capacity from 4 to 18 litres, while floor mixers can hold up to 140 litres.

Food Processors

Food processors are similar to blenders, but require little to no liquid during use.
Used for blending, chopping, dicing, and slicing, allowing for quicker meal preparation.

Immersion Blenders

Immersion blenders are kitchen blade grinders used to blend ingredients or purée food in the container.
Can be used while a pan is on the stove.

Ice Cream Churners

Ice cream churners are electric or manual equipment that freezes a mixture and simultaneously churns it to aerate and keep ice crystals small.
There are three types: countertop, floor, and manual.

Countertop Ice Cream Makers

Use a double-walled bowl filled with a liquid of urea and distilled water to freeze the machine to well below the normal freezing range of water in about 24 hours.

Ovens

OTG (Oven Toaster Grill) uses heating coils, radiation, and conduction to bake, toast, grill, or reheat small amounts of food.

Microwaves

Use microwaves (radiowaves) at a particular frequency to break water molecules, releasing heat and cooking food.

Dough Sheeter

The Dough Sheeter is an electric appliance that mechanically rolls dough and pastry to a uniform thickness.
Consists of a cloth conveyor belt that moves beneath a stationary rolling pin.

Planetary Mixers

The electric mixer is indispensable in the commercial kitchen, with several types found in most professional kitchens.
Selection of mixer depends on various factors such as the type of products being mixed and the volume of production required.
Vertical planetary mixers are most common due to their versatility and come in various sizes.

Mixing Attachments

Whisk: used for aeration or foaming applications, such as egg whites for meringue or whipping cream.
Paddle: used for generic mixing applications.
Hook or dough arm: used for mixing and kneading bread doughs.

Description

This quiz explores the processes of pasteurisation and ultra high temperature (UHT) processing of milk. It details the implications for bacterial destruction, spoilage prevention, and nutritional value. Understanding these methods is crucial for food safety and shelf life extension.