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Food Spoilage &Food Preservation🍒

Posted by Friend Tutor on July 24, 2020

Do You know there are lot of nutrients in various types of food such as fruits,vegetables,milk and meat products.But whether all nutrients enter our body as such as we intake?????NO

List the ways in which nutrients are lost?

  • Washing Fruits and Vegetables after cutting: we need to wash Vegetables and fruits before cutting itself,else some nutrients are washed away while washing. Vitamins C and E are mostly lost after cutting.
  • Cooking the Vegetables in excess water also leads to loss of nutrients.Because due to excessive heat nutrients are lost in the water used for cooking.we through the excess water in vegetables once we cook.
  • Cooking the vegetables for longer time leads to loss of nutrients.
  • Improper storage of food also leads to loss of nutrients. Ex: Cut fruits and vegetables gets dried out  fast when not stored properly.  

2.What is Food Spoilage?

Improper storage of food leads to growth of microorganisms(Germs,Pathogens).These germs release poisonous substances called toxins,which ultimately leads to Food Spoilage

3.How do we know that food is spoiled?

  • Change in texture(shape of food)
  • Change in Odor(unpleasant smell)
  • Change in taste(unpleasant flavor)
  • Change in Colour of food.

4.What are effects of eating a spoiled food?

  • Eating a spoiled food causes food poisoning. we may experience the following symptoms.
  • Loss of appetite(No feeling to eat)
  • Diarrhoea (watery stools)
  • Nausea(sensation to vomit)
  • Vomiting

5.What are Microorganisms? What is their role in food spoilage?

  • Microorganisms also called as germs or pathogens,which are present everywhere.They are not visible to naked eyes. 
  • They can only be viewed under Microscope(Instrument used to magnify the microbes)
  • Under certain conditions,they grow on food and release toxins leading to food spoilage.
  • Some ex: of microbes are bacteria,virus,fungi
  • Examples for spoilage caused by microbes
  • Milk spoiling is caused by Lactobacillus bacteria.
  • Mould growth in bread caused by yeast.
Growth of microbes in Bread

6.Under what conditions do microbes grows?

  • Medium(Food)                                              
  • Warmth(Heat)                                                                                                     
  • Oxygen 
  • Moisture.

Now let us see the ways to preserve the growth of micro organisms by following various techniques

1. What is Preservation?

Preservation is protecting the food  either by preventing or inhibiting the growth of microorganisms.This can be achieved by various techniques such as long term preservation and short term preservation of foods.Ex: Drying,Freezing etc.

2.Why do we need preservation techniques? 

  • To inhibit the growth of the microorganisms.
  • To maintain nutritional value!(safe to consume), Texture, Color and Flavour.
  • To prevent Oxidation of foods leading to unpleasant smell and taste.
  • Note: Oxidation means lipids in fats react with oxygen in the food giving unpleasant odour and taste.
  • After cutting Apple the colour changes is an example for oxidation of food.

3. How these preservation techniques work?

Microbes grow only under certain conditions.They require Oxygen,Warmth,Moisture and Medium. If any one condition is absent, then microbes cannot survive.

4.Where are these preservation techniques used?

Preservation techniques are mainly used in Food Processing industries,Food packing industries. 

5.What are the types of preservation?  

There are two main types of preservation.Short term Preservation and Long term Preservation

Various methods of Food Preservation

Short term
Long term

This method is
used for protecting
food against microbes
only for a short period.
This method is used for
protecting food
against microbes for a 
longer period. 
Using this techniques 
food can be stored
for few days.
Using this technique food 
is stored for years.

Short term 
Preservation includes
Freezing and Pasteurisation.
Long term Preservation 
includes Drying,Canning,
Vacuum  Packing and 
adding preservatives.
Examples for food stored
by this method are Milk,
Meat, Fish,Chicken etc.
Example for food stored
by this method are
Pickles,Nuts,Dried Fish, Jam
Major Differences between Short and Long term

 Long term Food Preservation


 It is the oldest 
method of preservation. 
moisture content 
from the food is 
completely removed by
exposing it to heat or
 by sunlight.
Fish, Fruits(Apple,
Apricots, Grapes)
 Canning Foods are stored in sterile*  containers. These bottles are used for packing foods.Fruit juices and Sauces etc

 Vacuum packing
Plastic bags are stored with foods.Before sealing the bags, 
air is completely removed from
the bag. Microbial growth is 
inhibited when there is no air.
 Meat, Nuts etc.

 Adding Preservatives
It is also an older method of preservation.Preservatives are 
certain substances 
that inhibit the growth of 
Salt = Fish Sugars= Sugar syrups
Oil = Pickles
Vinegar = Jam,. Readymixes

NOTE:*Sterilization is the process in which bottle or containers are boiled at higher temperature.This method either kills or weakens the growth of microbes in the bottles. 
Short term preservation: 

This includes Freezing and Pasteurisation. Freezing: When foods are stored in lower temperatures, it inhibit the growth of micro organisms. Eg: Fruits and vegetables, meat etc.

Pasteurisation method is used in Dairy industry. It is used to store milk. Pasteurisation is the process in which milk is boiled at higher temperature followed by immediate cooling. 

Advantages of Food Preservation:

  • Germs do not grow easily in the preserved food.
  • Preserved food are safe to eat.
  • Preserved foods can be transported to various parts of the world from site of production.
  • We can store some fruits and vegetables by preservation techniques and enjoy during off season.
  • Preservation in some cases it gives us new food products. Eg: Wine and Raisins from Grapes.

Disadvantages of Food Preservation:

  • Excess oil,sugars and salt in preserved food not good for health.
  • Some preservation techniques lead to loss of nutrients.
  • There is variation in taste,and they taste bland when compared to fresh food.
  • Improper storage of preserved food promote the growth of microbes.
  • Preservation can be done only for certain types of foods.

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