Transcript Culinary Science - Westminster Kingsway College

Culinary Science
Second years
Lesson 1 – emulsions and flavour
Lab rules
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Work safely and hygienically
Cleaning and washing up
Lab clothing
Phones
Behaviour
No food and drink
Blue for soap
Red for sanitising
When cleaning, use blue then red
Flavour
What is the definition of flavour?
Aromas
Orthonasal
Retronasal
FAT-SOLUBLE
Neutral
Tastes
•Salty
•Sweet
•Bitter
•Acidic
•Umami
WATER-SOLUBLE
Charged
Emulsions
What is the definition of a emulsion?
An emulsion is a stable mixture of fat and water.
How does this link to flavour?
What ingredients are naturally emulsions?
Cream
Milk
Butter
What emulsions do you make?
Mayonnaise
Béarnaise
Gravy
Hollandaise
You need a source of water (any water based liquid), fat (oil or
melted butter), and an emulsifier
Emulsifiers
These work by having a part that loves water
(hydrophilic) and a part that loves fat (hydrophobic) –
so they hold the water and fat together
Green - water loving amino acids
Orange – fat loving amino acids
Phospholipids eg lecithin
Denatured proteins – by
whisking or heating
Natural emulsions - milk
Milk is composed mainly of water and fat molecules.
The water phase - the majority of the milk - contains the milk
proteins, dissolved substances including vitamins, mineral
salts, and some sugars (lactose, provides the sweet taste) nutritious part of the milk.
The fat phase has a very important function in
• the texture of the milk - creamy mouth-feel.
• the flavour - reservoir for milk flavour compounds.
What is the emulsifier?
A membrane containing phospholipids (contain both
hydrophobic and hydrophilic parts).
Cream formation
Stabilising effect provided by phosholipid membrane not enough
to prevent separation over time.
Fat droplets large enough to find each other and combine - rise
(lower density) → a separation of phases.
If left for a while, milk will completely separate out.
Therefore, usually treated first.
Milk processing
Pasteurisation: kills bacteria.
Homogenisation: squeezing the milk through very small holes to
reduce the size of the fat droplets.
Smaller droplets are less likely to find each other and combine.
Fat droplets
Casein micelles
Before
After
Butter
Butter, mainly water and fat BUT fat content is much greater than
water content (up to 80%).
So the water droplets, which are in the minority, are dispersed in
the fat phase (i.e. the emulsion is reversed).
Butter is produced from mechanically stirring cream.
When the cream is agitated, the fat droplets get broken up and
they release some fat and tend to stick together, and when they
have reached the desired size, the butter is removed from the
remaining water.
The emulsions that you make
Potential issues – a failed mayonnaise
1.
2.
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Not enough fat
Too much fat
If the fat is added too quickly
Not whisked sufficiently
The emulsion ingredients are too cold
Stabilising emulsions
The two golden rules for emulsification are:
1. Decrease the size of the fat droplets in the mixture - these
smaller droplets will find it harder to find each other and
separate out
Fat droplets
Water
droplets
Add oil slowly
When doing it by hand
This gives short term stability. For longer term stability.......
Stabilising emulsions
Require emulsifiers like egg yolk
What other emulsifiers are there?
Soy lecithin
Gelatine
The New Emulsions
All that is actually needed to make a stable emulsion therefore is
• a fat source (oil and butter, but cheese or fois gras could be
used instead)
• a water source (vinegar or stock, but any aqueous liquid
including tea, coffee, orange juice).
• source of tensioactive molecules (usually supplied by adding
egg yolks or gelatine, but any phosholipid or denatured
protein could act as an emulsifier)
Exercise: Come up with your own emulsion
The experiment
Part 1:
• Design an experiment to
show the emulsifying
ability of lecithin –
“vinaigrettes”
• Design an experiment to
show the emulsifying
ability of gelatine –
“mayonnaises”
How could the experiment
be improved?
Come up with a dish
Any questions?
Bibliography
• McGee on Food and Cooking. By Harold McGee
• The Science of Cooking. By Peter Barham
• Molecular Gastronomy manual from www.inicon.net