Title: EFFECT OF FOOD PROCESSING ON NUTRIENT CONTENT OF FOOD
1- EFFECT OF FOOD PROCESSING ON NUTRIENT CONTENT OF
FOOD -
- FOOD SPOILAGE
- By
- AYUSHI JAIN
- 2010BT04
2FOOD PROCESSING
- Set of methods and techniques used to transform
raw ingredients into food or to transform food
into other forms for consumption by humans or
animals
3AIM
- To make food safe (microbiologically,
chemically). - To provide products of the highest quality
(flavour, colour, texture) - To make food into forms that are convenient (ease
of use)
4Different Methods Employed
- Various heat processes such as
- Cooking
- Baking
- Frying
- Microwave cooking
- Toasting
- Pasteurisation
- Smoking
- Milling
- Concentration
- Salting
- Blanching
- Addition of preservatives (sulphites, etc)
- Freezing
- Canning
- Irradiation
- Dehydration/drying
5..Continued
- Cutting, trimming and peeling
- Soaking, germination and fermentation
- Controlled atmosphere storage, ripening and waxing
6Effect of Food Processing on Nutrient Content
- Depend on
- Chemical stability of nutrient content
- Extent of processing
- Environmental factors
- Form in which the foods are delivered
7Heat Processing
- Merits
- improves the digestibility of foods, making some
nutrients more available. - Demerits
- Malliard reaction(non-enzymatic browning)
- Affects bioavailability of minerals
- Loss of vitamins
8Cooking
- Merits
- Provides desired texture, flavor and palatability
to food. - Starchy foods such as potatoes, corn, beans, and
lentils are made more digestible. - Destroys substances that would otherwise
interfere with the digestibility of the protein. - Decreases toxic effect of raw food and increases
availability of vitamin content. - Ensures that food is free from harmful levels of
micro-organisms
9- Demerits
- Leads to most important nutrient losses
- Mineral loss- leaching out in cooking
water(especially Zn and Cu loss, about 10-27) - The largest vitamin loss during cooking is
usually due to destruction of vitamin C, and to a
lesser extent vitamin B-1 and the other
water-soluble vitamins.
10Baking
11Frying
12Microwave Cooking
- Much quicker than conventional cooking
- Thiamine-better retained
- Niacin and Riboflavin are relatively stable.
- Mineral composition is minimally affected.
- Toasting
- A loss of about 10 to 30 per cent of the vitamin
B-1 present in bread occurs on toasting.
13Pasteurisation
- Nutrient losses are generally small.
- HTST and UHT result in greater nutrient retention
for those nutrients affected by the
pasteurisation treatment( thiamine, vit C, vit
B12) - Smoking
- Usually follows salting or curing.
- Reduces the oxidative changes that take place in
fats, proteins and vitamins- acts as an
antioxidant. - Causes nutrient loss due to the associated heat,
flow of gases and interaction of the smoke
components with proteins.
14Milling
15Concentration
- The nutrient changes that occur during
concentration will depend on - the contents of the mixture and
- the temperature at which the process takes place.
- There is a decreased water content and
corresponding increase in other nutrients.
16Salting
- Results in liquid exuding from the flesh, taking
with it some of the water-soluble proteins,
vitamins and minerals. - Some proteins are also denatured by the salt.
17Blanching
- The nutrient losses will depend on several
factors - the food item
- surface area exposed
- the method used (steam blanching or hot water
blanching) - contact time
- amount of agitation
18Losses of Nutrients during Blanching
NOTE When blanching fruits or vegetables the
addition of sodium bicarbonate(or other alkali)
to the blanching water for preserving the colour
should be considered carefully, as while
preserving the colour, it also has the effect of
softening the texture of the vegetable and
increasing destruction of vitamin C and thiamine.
19Sulphites
- Act as an anti-oxidant and prevent browning
- Increases the loss of thiamine.
- Use of sulphite on meat is restricted in some
countries and there is also a limit to the amount
that is used in the preservation of fruits and
seafood, as this may result in allergic reactions
in some consumers.
20Freezing
- The major nutrient losses that occur in frozen
foods are not due to freezing as such but due to
the blanching that occurs before freezing, and
then during subsequent thawing and cooking. - It is important that frozen foods are stored at
-18C to prevent their rapid deterioration. If
this temperature is not maintained then some
nutrient losses will occur, which are not
regained by refreezing.
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23Canning
- Nutrient losses occur from destruction during
heating and storage stages. - Water-soluble vitamins and minerals, may dissolve
in the water in the can, but they are lost only
if this liquid is not consumed. - We can reduce losses of vitamins during storage
by storing the cans in a cool place.
24Irradiation
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26Dehydration
- Losses during the drying process will depend on
- preparation procedures before drying (e.g.
slicing, blanching) - drying temperature,
- drying time,
- storage conditions
- Nutrient losses during drying can be decreased by
- drying at a low temperature and shortening drying
time. - After drying ensure that foods are stored under
dry conditions and at low oxygen levels.
27Demerits
28Cutting, trimming and peeling
- . Discarding the outer leaves of vegetables such
as cabbage, spinach and lettuce and peeling
fruits and vegetables such as apples, peaches,
pears, potatoes and carrots, lead to a
disproportionate loss of many vitamins- as
vitamins and minerals are presesnt just beneath
the skin.
29Effect of Processing on Nutrient
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31How To Minimize Water Input and Output
- Choose fresh foods that are not over-ripe,
bruised, cut or scraped. - Store foods in a cool, dark place.
- Unless the peel or outer layer is unpalatable,
damaged or contaminated, cook the food whole. - If it is necessary to slice the raw food. then
try to keep the pieces as large as possible. - When boiling, add the raw food to the boiling
water rather than to cold water. - Use the smallest amount of water possible it is
not necessary to cover the food. Steaming is a
way of cooking with a minimum amount of water.
32- If possible use the cooking water for gravies,
sauces or soups as it is a source of
water-soluble vitamins and elements (minerals). - Cook for the minimum time necessary to make the
food palatable and safe. Once cooked, eat as soon
as possible. Do not keep the food warm for long
periods. - Do not use baking soda to help keep the green
colour of vegetables, as this increases loss of
vitamin C. - Do not use copper utensils. (Copper helps to
destroy vitamin C.)
33- Scope of Food Processing
- Food and crop processing ? largest industry in
most countries. - The small-scale food processing sector
- - is a major source of employment,- adds
value to crops by processing,- is a major source
of food in the diet,- in some cases, by export,
earns valuable foreign exchange,- provides
opportunities for import substitution,- benefits
a large number of poor people, such as farmers,
packaging suppliers and vendors.
34Food Spoilage
- Loss or damage of original nutritional value,
texture and flavour of the food making it harmful
to people and unsuitable to eat.
35Causes
- Two main causes
- Natural decay in foods
- Contamination by micro-organisms
36Natural decay in Food
- Moisture Loss
- mostly occurs in fruit and vegetables which
contain large amounts of water. - vegetable or fruit shrinks in size, becomes limp
and its skin becomes wrinkled and leathery - occurs in other foods like meat, fish, cheese,
due to evaporation of water from the surface.
37- b) Enzyme action
- Enzymes are sensitive to heat.
- active in temperatures found in a kitchen, very
slightly active at very low temperatures such as
those found in the freezer - activity of these enzymes stops when they are
heated above 70 oC. - Some enzymes remain inactive until the food is
harvested or slaughtered. Once activated, such
enzymes speed up the process of decay by breaking
down the tissues and components of the food in
the various ways such as oxidation, browning and
ripening.
38- Oxidation when food comes into contact with
oxygen) the enzymes cause the destruction of
certain nutrients e.g. vitamin c, thiamine and
carotene. - Browning Enzymes cause browning in certain foods
the moment they are exposed to air - Ripening Enzymes are involved in the process
that causes ripening in certain foods such as
fruits and vegetables.
39Microbial Action
- Mainly due to
- Fungal spoilage(yeasts and moulds)
-
- Bacterial spoilage
40Fungal Spoilage
- YEAST
- microscopic single celled plants, found in the
air and soil, and on the surface of fruit. - there are two types of yeasts true yeast
and false yeast. - True yeast ? metabolizes sugar producing alcohol
and carbon dioxide gas. This is known as
fermentation. - False yeast? grows as a dry film on a food
surface, such as on pickle brine. False yeast
occurs in foods that have a high sugar or high
acid environment.
41- Some can grow without the presence of oxygen
can cause food spoilage in syrups, fruits, fruits
juices and jam especially as they can survive
without air. - Yeast grow best at temperatures between 25C and
30C. - Extreme heat destroys all yeasts and most are
destroyed at temperatures above 60C.
42- MOULDS
- Grow in filaments forming a tough mass which is
visible as mould growth'. Moulds form spores
which, when dry, float through the air to find
suitable conditions where they can start the
growth cycle again. - Mould can cause illness, especially if the person
is allergic to molds. - Usually though, the main symptoms from eating
mouldy food will be nausea or vomiting from the
bad taste and smell of the mouldy food.
43- Moulds grow most readily in most conditions, at
temperatures between 20C and 40C. - They grow on a variety of foods, particularly
meat, cheese, fruit and bread, especially if the
food is stored in damp conditions. - Moulds may remain active at the low temperatures
of a refrigerator but they are destroyed by heat
above 70C. - They also like a slightly acid medium and this is
why they attack citrus and the surface of jams.
44Some examples of fungal spoilage
45Bacterial Spoilage
- may grow under a wide variety of conditions.
- They can be divided into spore-forming and non
spore-forming. - Bacteria generally prefer low acid foods like
vegetables and meat. - In order to destroy bacteria spores in a
relatively short period of time, low acid foods
must be processed for the appropriate length of
time at 116C (240F) in a pressure canner. - Eating spoiled food caused by bacteria can
cause food poisoning.
46Some examples of bacterial spoilage
47Effect of spoilage on various Food Commodities
- Protein food
- Undergo putrefaction. This is the situation
where protein foods rot, and produce very bad
smell - Fats and oils
- Undergo rancidity. This is the condition where
food containing fats and oils begin to smell and
tasted bad when they are old.
48- Carbohydrates
- Cooked cereals become marshy and slimy when
affected by micro-organisms. This condition is
known as serenasis. - Flour products smell and taste unpleasant
when they are spoilt. They are described as being
stale. - Fruits and vegetables
- They rot, ferment and decay.
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