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Milk, Cheese & Frozen Desserts

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Jacqui Toumbas

on 5 May 2013

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Transcript of Milk, Cheese & Frozen Desserts

Safety First - Please ensure hair is tied back and covered with a hair net
- Closed in shoes & lab coat must be worn at all times
- Wash hands as entering & exiting the kitchen
- We will be using gas stoves- make sure you are
familiar with how to light the stove. If unsure please
ask your demonstrator
- Electrical equipment and sharp knives will be
used, please take care.

- Milk, Cheese & Frozen Desserts Experiment 1 - Coagulation of fresh milk Aim:
To observe and explain the effect of heat and the effect of acid on fresh whole milk

Amendments: Conversion of American Tbsp to Australian Tbsp (As per students' notes)

Key Terms: Clot, Denaturation, Whey Proteins

Concept on Coagulation of Milk:

Pre-lab Questions:
Which protein in milk is most affected by heat?
Which protein is most affected by acid? Experiment 2 - Milk Foams Experiment 4 - Low Fat & Regular Vanilla Ice Cream (p245/248) Aim:
To gain experience in preparing agitated frozen desserts
Discover the effects of varying the level of sugar
Become accustomed to low-fat ice cream- comparing the different variations and types.

Vanilla Ice Cream experiment- completing variations 1&2 ONLY

Key Terms: Gelato, Sorbet

Concept Preparation of Frozen Dessert:

Pre-lab Questions:
Can crushed ice alone freeze ice cream? Why is rock salt used for homemade ice cream preparation?
How does agitation affect the texture of frozen dessert?
What interfering agents are used in ice cream preparation? Experiment 3 - Preparation of Cottage Cheese Aim:
To gain experience in the preparation of milk foams
To compare the ease of preparation, stability and characteristics of various milk foams
To investigate the effect of temperature on the preparation of whipped cream

Heavy Whipping Cream - completion of variations a and b only
Evaporated Milk - completion of variations a and b only

Key Terms: Casein, Coagulation, Colloid, Curdled, Precipitate

Concept: Whipped milk products

Pre-lab Questions:
Will heavy whipping cream, evaporated milk or reconstituted non-fat milk solids result in a foam with the largest volume? Why? Experiment 5 - Effect of heat on cheese Enjoy Mixture Heating & Ageing Overrun Preparation of
Frozen Desserts Frozen Desserts differ from each other by ingredient type & proportion of fat, milk solids-not-fat (MSNF), protein & lactose. Commercial preparation of Ice cream consists of combining liquid ingredients in a mixing vat and heat to 43 degrees;
fat solidifies
swelling of milk proteins, gelatin & other stabalizers
This has an effect on the texture, body and resistance to melting. Churning & Freezing During freezing the ingredients are churned:
promotes formation of small nuclei
crystal formation
encourage homogenized fat globules
incorporates air Heat Shock After ice cream is produced, repeated cycles of temperature fluctuations from cold to hot and back cause larger ice crystals to grow, reducing the quality Due to pumping air into the original frozen dessert mixture is to expand it and cause overrun. This is the volume over and above the volume of the original frozen dessert mix. Heat (Surface of milk) Heat (Bottom of saucepan) Acid Enzyme Coagulation of Milk
- Heat
- Acid
- Enzyme Evaporation - losing of water content Increase the concentration of casein, fat and mineral salt Form a thin film on the surface of the milk Precipitate formed on the bottom of the saucepan
- Whey protein
- Lactaibumin
- Lactogobulin Become insoluble and mesh with calcium phosphate from milk Adding acid to milk cause the casein in it to coagulate. - At pH 4.6
- Casein becomes very insoluble
- Precipitates into a curd Milk coagulates and form curds when enzyme is added into milk. Examples:
- Rennin
Most common enzyme use in production of cheese
- Pepsin in swine's stomach
- Protease form fungus Aim: (as per the lab manual page 76)
To compare cottage cheeses prepared by rennin vs. acid coagulation
To observe the formation and separation of curd and whey in cottage cheese production
To compare homemade cottage cheese with a commercial cottage cheese

Amendments: n/a

Key Terms: Rennet, Rennin, Curd, Gel, Mould-ripened, Syneresis, Whey

Concept: Acid & Enzyme Coagulation of milk in cheese production

Pre-lab Questions:
What is cheese?
What occurs during the curing & ripening process of cheese? How does the length of the curing period impact the flavour & cooking characteristics of cheese?
What is rennin? Describe rennin's effect on milk. Aim:
to observe how cheese react with heat
to learn about different ingredients affect the result of heating

Amendments: n/a

Key Terms: Natural Cheese, Processed Cheese

Concept: Effect of heat on cheese

Pre-lab Questions:
Predict the difference in the cooking quality of cheddar cheese compared to that of fat-free cheddar cheese. Why do you expect these outcomes?
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