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SUBMITTED TO : DR. HAIDER ALI
SUBMITTED BY: Syed wasi haider, Zaid waheed,
Amir Sharif, imran khan
What is Food processing
Food processing is the transformation of cooked ingredients, by physical or chemical means intofood, or
of food into other forms. Food processing combines raw food ingredients to produce marketable food
products that can be easily prepared and served by the consumer.
WHY DO WE NEED TO PRESERVE FOOD?
So that surplus foods from good harvests can be stored and then used in times of
shortage. So that we can enjoy seasonal fruits and vegetables all year round. To
enable it to be transported long distances without it decaying. To allow it to be
stored in the home for long periods without going off
Uses heat sterilisation to destroy micro-organisms that cause food spoilage. The
cans are heated which drives out any air before it is sealed with a double seam to
prevent leakage or the re-entry of bacteria. Foods preserved by this method have
a long shelf life and can be stored at ambient temperatures. The severity of the
heat treatment can be lessened if the food contains acid, salt or sugar. The most
important pH is 4.5, as below this the very dangerous organism Clostridium
botulinum is inhibited. Cans are cooled in chlorinated water to prevent any
possible contamination in cans which may have a slight defect. This could infect
the food and cause an outbreak of food poisoning some time later.
A process by which the form of a food is changed
Such as changing corn to corn chips
Not a preservation measure
In this process, the food is heated, ground, and pushed through
various kinds of screens to yield different shapes
Use of microorganisms to convert foods
(raw commodities) into a more
Typically the conversion of
carbohydrates into acid or alcohol.
Some additional antimicrobial
compounds may be formed.
THEORY: Reduce the pH of the food or
produce substances which make the
environment uninhabitable by other
1. Type of organism
º natural or starter
º acid, oxygen,
º salt tolerance
2. Source of energy
3. Oxygen availability
Toughened glass is used because it can be taken to high temperatures for heat
treatment methods such as bottling fruit and vegetables. It is easy to sterilise
glass. The bottle (or jar) can be filled either with raw foods and then heated slowly
to boil the foods, destroying bacteria and spores. Air is expelled through a
specially designed lid, and as the jar cools down, a vacuum is formed. The sealed
jar prevents the re-entry of bacteria. As there is no oxygen present, bacteria are
unable to multiply. Bottling can also be used for high temperature methods such
as jamming, pickling and chutney production. Glass is non-reactive and therefore
suitable for use with acidic mixtures. Bottled food has a very long shelf life at
PASTEURISATION/ UHT (ULTRA HEAT
Food is heated to temperatures in excess of 100C to ensure that spores are
destroyed. In the case of milk the product is heated to not less than 132.2C and is
packaged under aseptic conditions. It is similar to pasteurised milk in terms of
nutritive value and the heat is so quick the colour and flavour changes are not so
obvious as in sterilised milk. The storage life is vastly longer however, for all
products that are heated there will be some loss of colour, flavour and texture to a
greater or lesser extent. Heat sensitive vitamins e.g. thiamine, riboflavin, niacin
and vitamin C will be affected. There’s a reduction of 10-20% of amino acid lysine
in high protein foods. Fruit juices may be fortified with additional vitamin C.
Packages are hermetically sealed. The packaging materials used are robust and
prevent entry of air unless opened or pierced
This process uses a temperature in excess of 100C in order to destroy nearly all
micro-organisms present in a food. This is important as some micro-organisms
can form spores which have the ability to survive at high temperatures. If the
correct temperature is not reached there is the possibility that the spores will
germinate and grow and food poisoning could result. Some organisms can survive
the sterilisation process if not processed for enough time or a high enough
temperature, e.g. Clostridium botulinum. The product is packed in air-tight
containers either before or after heat treatment. If packaging follows heating, the
containers must be sterilised before use and filled under aseptic conditions.
Sterilising enables milk to be kept for 2-3 weeks unopened, but results in a burnt,
caramelised flavour and browning
Not to be confused with AFD (Accelerated freeze-drying) Rapid drying systems
cause the outer edges and corners of food to become dried out and rigid thus fix
the shape of the food pieces early in the process. Water is removed from the
centre of the food to produce a light honeycomb product, which readily rehydrates
when added to water (slow drying allows the product to shrink further and produce
a dense dried food, which is difficult to rehydrate). As the food is porous the food
is excellent for rehydration e.g. coffee, meat, fruit and vegetables. The water-
soluble vitamins may be lost from freeze-dried foods. Some odours are lost as a
result of this process. Out of all the drying processes, this is the most effective
way of maintaining the original characteristics of a product. This is a more costly
process, but where colour, texture, flavour, shape and reconstitutability properties
are of paramount importance (e.g. cuppa soups, snack pots, coffee), this process
gives the most organoleptic results.
Process primarily used for meat and fish in combination with salt to add flavour
and delay spoilage. The degree of preservation is minimal with this process,
because high levels of salt and smoke make the food less palatable and not so
good for health reasons. Therefore, in order to preserve smoked products,
additional methods such as chilling and vacuum packing are used. Smoking is
either hot or cold. In cold smoking the product remains uncooked. The
temperature doesn’t exceed 30C. Most products are then cooked, except salmon,
which is eaten raw. The organoleptic qualities are considered desirable. In hot
smoking the temperature is allowed to rise so that the food cooks. Smoked foods
are often coloured yellowy as a result of the process. They are partially dried and
salty, so the texture and flavour are distinctive.
Wood Smoking: It contains a number of substances that have antimicrobal
activity e.g. formaldehyde and higher aldehydes, phenols and methanol, all of
which are highly inhibitory to micro-organism
Micro-organisms cannot live, grow and reproduce without moisture. It is the
removal of moisture by warmth or high temperature. This is an effective method of
preservation. Foods can be dried using commercial methods e.g. spray drying,
freeze-drying, AFD, tunnel drying and sunlight e.g. tomatoes and fruits or by oven
drying e.g. herbs, coffee and vegetables. Dried foods have a long shelf life and
can be stored
Foods are prepared and then packed into a pouch or foil wrapper and the air is
sucked out, forming a vacuum inside the pack. Removing air takes away oxygen
and moisture which bacteria require in order to survive and multiply. Some
vacuum packs can be stored at ambient temperatures e.g. coffee and have a
medium shelf life. Others stored at chill temperatures e.g. smoked fish, cheese
and cured meats. These have a short shelf life. Organoleptic qualities are often
MAP (MODIFIED ATMOSPHERE PACKAGING)
Also known as ‘Controlled Atmosphere Packaging’ Preserves food in sealed gas
flushed packs In the packs oxygen level can be lowered or the carbon dioxide
level or nitrogen levels increased Carbon dioxide retards the growth of bacteria.
Oxygen helps retain the colour of the food e.g. meat stays red and nitrogen is
used to reduce the rate of oxidation. The ratio of these gasses depends upon the
food being packaged. Food is prepared and placed in the container. Container is
flushed with selected gas for the food type and is hermetically sealed. MAP is
often carried out in conjunction with chilling in case of chilled meals
Once the packaging is opened the food has a normal shelf life and must be stored
accordingly. The packaging used must not be reactive and sufficiently strong to
resist damage through piercing or splitting. The most commonly used materials
are plastics, which may be ovenable, with a film cover.
This method of preservation is where ionising radiations are applied to foods to kill
bacteria. There is said to be no risk of residual radioactivity and the process
should not be confused with radioactive contamination or radioactivity. It is
expensive to carry out and as yet is only permitted in the UK for use with some
vegetables, spices and poultry products. It extends shelf life by delaying ripening
(bananas), inhibiting sprouting (potatoes and onions) and killing moulds
(strawberries). It reduces significantly the numbers of pathogenic parasites in
meat. No visible changes to irradiated food other than reduction of undesirable
factors above. At permitted doses of irradiation, the organoleptic properties of
most foods are unaffected
WHY PRESERVE FOOD (ADVANTAGES)
Saves money, home preserves cheaper.
Food available out of season.
Variety in the diet.
Preserved food can be more convenient.
Preserved foods can be transported long distances.
Creates new flavours, salting, smoking, jam etc.
GENERAL PRINCIPLES OF PRESERVATION
To destroy or inactivate enzymes.
To destroy or inactivate micro-organisms.
To prevent the re-entry of new microbes by sealing food.
To maintain the nutritive value, colour, flavour, texture of the
food as far as possible.