1. EFFECT OF FOOD PROCESSING ON
NUTRIENT CONTENT OF FOOD
&
FOOD SPOILAGE
By:
AYUSHI JAIN
2010BT04
2. FOOD 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”
3. AIM
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)
6. Effect 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
7. Heat 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
8. Cooking
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
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.
12. Microwave 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.
13. Pasteurisation
• 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
15. Concentration
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.
16. Salting
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.
17. Blanching
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
18. Losses 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.
19. Sulphites
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.
20. Freezing
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 -
18°C to prevent their rapid deterioration. If this
temperature is not maintained then some
nutrient losses will occur, which are not
regained by refreezing.
21.
22.
23. Canning
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.
26. Dehydration
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.
28. Cutting, 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.
31. How 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.
34. Food Spoilage
Loss or damage of original nutritional value,
texture and flavour of the food making it harmful
to people and unsuitable to eat.
36. Natural decay in Food
a) 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.
40. Fungal 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
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
25°C and 30°C.
Extreme heat destroys all yeasts and most are
destroyed at temperatures above 60°C.
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 20°C and 40°C.
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 70°C.
They also like a slightly acid medium and this is
why they attack citrus and the surface of jams.
45. Bacterial 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 116°C (240°F) in a pressure canner.
Eating spoiled food caused by bacteria can
cause food poisoning.
47. Effect 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.
