FOOD TECHNOLOGY
Micro-organisms in Food Production
FOOD SAFETY IN INDUSTRY
Microbial Risk Assessment
Why do manufacturers carry out regular microbiological tests on
products?
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They have a legal responsibility to their consumers to ensure
foods are fit for human consumption and of a high standard.
Consumers will remain loyal if the company has a good
reputation.
In order to regulate their practices, microbiological testing is built
into the manufacturing process as part of the Quality Assurance
programme.
This testing enables the manufacturer to sample each batch of
product to check for any contamination and identify it’s source.
If a batch proves to produce too many undesirable bacteria,
producing dangerous levels of toxins, the batch can be removed
from the shelves until the contamination source can be identified.
FOOD SAFETY IN INDUSTRY CONT..
How is Microbial Testing carried out?
 A sample is taken from a batch of product.
 The sample is made into a liquid solution using a stomacher
which mirrors the action of the stomach by pulverising food.
 This liquid is then smeared onto agar jelly and left to incubate
for several days.
 The dishes are then placed under a strong microscope and
colonies of micro-organisms are identified and counted. The
counting is done using a clicker pen and a grid (may be
computers now).
FOOD SAFETY IN INDUSTRY CONT..
How are the results of microbiological testing used?
 If large amounts of pathogens are identified, the products
may be deemed unsafe for human consumption and
removed from circulation.
 Use by and Best before dates are calculated by microbiologists who plot the rate of bacteria growth in certain
conditions and mathematically predict the point at which a
product becomes unfit for human consumption. They will
always be cautious in their estimation.
THE USE OF MICROORGANISMS IN FOOD
MANUFACTURE: YOGURT
Yogurt is milk, often concentrated or with added
milk powder, which has developed a characteristic
acidity.
 The flavour of yogurt is made by 2 microorganisms,
-Lactobacillus
- Streptococcus
 These two microorganisms must be in equal
amounts and one must not out grow the other
(bitter/ too acid product made)
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HOW IS YOGURT MADE?
Ingredients in yoghurt:
Milk, bacteria, fruit flavours, stabilizers and
thickeners
 Yogurt is homogenised then pasteurised at 90°C
for 30 minutes or by HTST (high temperature, short
time) method to kill microorganisms.
 It s then cooled to 44°C then inoculated with the
starter culture.
To make set yogurt – the mix is incubated at 44°C for
1 ½ hours, then poured into containers which are
warm until the yogurt has coagulated. It is then
cooled to 5°C- 8°C until consumed within 14 days.
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HOW IS YOGURT MADE? CONT..
To make stirred yogurt – the incubation is at a
slightly lower temperature. The yogurt becomes
thicker but not coagulated, it is then
continuously stirred to prevent a curd from
forming. Fruit and syrup are metered into
containers followed by the yogurt mix, it is then
cooled and stored.
New developments:
 Frozen yogurt, long life yogurt
 Bio yogurt - a health advantage as there are
more living cultures. The microorganism
Bifidobacterium bifidium helps the stomach
problems.
HOW MICROORGANISMS ARE USED FOR
CHEESE
Cheddar
Pasteurised milk is placed in a large stainless Vat (tub).
Lactic acid forming bacteria (Lactococcus cremoris and
Lactococcus lactis) is added together with colouring.
Milk held slightly above room temperature (25°C) and lactic acid is
produced to about 0.17% - 0.2%.
Rennet (enzyme) is added to coagulate protein at approximately 20
minutes.
The temperature of Vat is now about 40°C to make curd contract and
expel the liquid which is drained.
The curd is cut into slabs (30cm x 60cm)
‘Cheddering’ involves piling up slabs and turning them every 15
minutes for a firm temperature
The slabs are chopped into pieces again, allowing extra liquid to be
removed.
Salt is added and the cheddar is stored at 10°C for 3 months to
ripen or cure.
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HOW MICROORGANISMS ARE USED FOR
CHEESE CONT..
Blue Cheese
It is not pressed but gently packed into moulds so that
penicillium blue mould can grow through the
cheese lumps.
The mould produces proteolytic enzymes and often
ammonia is released which is a characteristic of the
flavour of some of these cheeses.
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HOW MICROORGANISMS ARE USED FOR
CHEESE CONT..
Camembert and Brie
It is a soft cheese.
Penicillium camembertii (mould) which produces
white growth allows the mould to grow.
Enzymes from mould act on the curd and produces
soft and creamy texture of ripened cheese.
Shelf life is short.
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QUORN
Mycoprotein is the ingredient common to all
QuornTM products.
 It is a healthy meat-free source of protein and is
also a good source of dietary fibre.
 Mycoprotein is low in fat and saturate and
contains no cholesterol and no trans fats at all.
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MYCOPROTEIN
Fusarium Venenatum:
 The principle ingredient of Mycoprotein is an
ascomycota, one of the largest groups within the fungi
family, which also includes truffles and marels.
 It is one of a genus of filamentous fungi, meaning it is
comprised of a web of finely spun strands (hyphae).
Texture of Mycoprotein:
 Products made with Mycoprotein have a meat-like
texture because the harvested strands (hyphae) have
a similar structure to animal muscle cells (i.e they are
filamentous with a high length/diameter ratio).
HOW MYCOPROTEIN IS MADE
Made in 40 metre high fermenters which run
continuously for 5 weeks at a time.
 The fermenter is sterilised and filled with a
water and glucose solution.
 A batch of fusarium venenatum is introduced.
 Once the organism starts to grow a continuous
feed of nutrients, including potassium,
magnesium and phosphate as well as trace
elements, are added to the solution.
 The pH balance, temperature, nutrient
concentration and oxygen are all constantly
adjusted in order to achieve the optimum growth
rate.
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HOW MYCOPROTEIN IS MADE CONT..
The organism and nutrients combine to form
Mycoprotein solids and these are removed
continuously from the fermenter after an average
residence time of 5 to 6 hours.
 Once removed, the Mycoprotein is heated to 65°C
to breakdown the nucleic acid.
 Water is then removed in centrifuges, leaving the
Mycoprotein looking rather like pastry dough.
 The Mycoprotein is then mixed with a little free
range egg and seasoning to help bind the mix.
 It is then steam cooked for about 30 minutes and
then chilled, before being chopped into pieces or
mince.
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HOW MYCOPROTEIN IS MADE CONT..
The product is then frozen.
 This is a crucial step in the process because the ice
crystals help to push the fibres together, creating
bundles that give Mycoprotein its meat-like texture.
 The pieces and mince are then sold under the
QuornTM brand and also in wide array of products
ranging from escallops to ready meals, deli slices to
sausages.
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FOOD POISONING
The increased use of microwaves:
 Food cooked in a microwave doesn’t always heat
up as evenly as it should.
 Because of this, cold spots can remain in the food.
If you happen to be cooking a piece of frozen
chicken infected with the Salmonella bacteria, the
bacteria may not be killed in the cold spots which
can result in a bad case of food poisoning when the
food is eaten.
FOOD POISONING CONT..
The increase in the market share of cook chill
foods:
 These products require a short cooking time and
often can be cooked from frozen. If they are not
heated until piping hot right through then they may
cause food poisoning.
The increase in eating out:
 More people are eating out either in take aways or
restaurants. Although the council has responsibility
for the hygiene of these establishments there may
be times when the hygiene is not as it should be.
Often individuals will order a take away and reheat
it at some point.
FOOD POISONING CONT..
How it is caused:
 Lack of cooking knowledge at home
 More ready meals
 More take aways
 Lack of trained catering staff
 More eating out
 More foreign food transported from around the
world
 Factory farming
LOOK AT THE BACTERIA SLIDE FOR MORE
INFO ON:
Salmonella
 Listeria Monocytogenes
 Campylobactor
 Staphylococcus Aureus
 Escherichia Coli (E Coli)
 Clostridium Perfingens
 Clostridium Botulinum
 Bacillus Cereus
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