Transcript B3.1 L3 Microorganisms and food

What is a Vegetarian?
Write down your ideas (2 mins)
Lesson 3
Objectives:
•To describe the production of the enzyme chymosin
•To recall the role of chymosin in the manufacture of
vegetarian cheese
•To describe microbial products used in food, including
vitamin C, carrageen extract, enzymes such as
invertase, citric acid, amino acids such as glutamic
acid, monosodium glutamate
Making Cheese
Rennet comes from the stomach of
slaughtered cows. Rennet contains
two protein digesting enzymes, one of
which is called CHYMOSIN.
These enzymes cause milk to
form
WHEY
CURDS: This raw cheese.
We can now genetically modify bacteria to produce CHYMOSIN.
What is the advantage of this?
Acceptable to vegetarians, AND GM free. CHYMOSIN is GM free,
only the bacteria used to make it are genetically modified.
Bacteria are responsible for curdling the milk. They get
into the milk and ferment the lactose sugar it contains.
As the fermentation proceeds, the pH of the milk is
lowered (the milk becomes acid) to the point where the
milk proteins coagulate forming curds.
1
a
b
Bacteria in milk ferment the sugar it contains.
Name the sugar.
Name the acid produced when bacteria ferment milk sugar.
2
3
4
a
b
Describe what happens when milk is curdled.
Why does curdled milk taste sour?
Chymosin is a vital part of the process of making cheese.
What is chymosin?
Why is chymosin a vital part of the process of making cheese?
5
In the UK most of the chymosin used to make hard cheese is produced
by genetically modified (GM) microorganisms. However, the cheese is rated as
‘GM free’.
a
Why is the cheese rated as ‘GM free’?
b
Suggest reasons why the makers of cheese might think it important
that their product is rated as ‘GM free’.
Task
• Use the textbooks to complete worksheet
B3.1 3b – Microorganisms and food.
• Micro-organisms break down protein
Body Mass Index = Body Mass (Kg)
(Body Height)2 (m2)
Can you think of any situations where the BMI
is not the best way to determine obesity?
http://www.blinkx.com/video/the-bmi-scale/cYxU9HhagD1tSSHk7uuAwA
Size 0 – BMI<18
Obesity
Exam Question
Describe the stages in the commercial production of soy
sauce. (4 marks)
Any four in correct sequence from:
1. cook soya bean;
2. mix with (ground) roasted wheat;
3. ferment with Aspergillus ;
4. brine is added;
5. yeast and/or Lactobacillus added;
6. second fermentation/refermentation;
7. filtered;
8. pasteurisation;
9. use sterile bottle;
[Ignore sterilising]
Max 3 marks if any points in wrong sequence.