Page 1 - 6-Lesson notes-Food Preservation
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SAI International School
                                             Subject- Biology, Class-VIII
                                      Topic- Microorganisms: Friend and Foe
                                            Subtopic- Food Preservation
                                                     Lesson Notes
               Why Is Food Preservation Important?
                   •  Prevents spoilage of food caused by microorganisms.
                   •  Helps extend shelf life and maintain nutritional value of food.

                   •  Prevents wastage and foodborne diseases.

               How Can Growth of Microorganisms be Restricted?
                   •  By creating conditions unsuitable for their growth
                       (e.g., removing moisture, using heat, cold, salt, acids, or preservatives)
               Methods of Food Preservation:
                       Chemical Method
                   •  Preservatives like sodium benzoate and potassium metabisulphite are added.

                   •  Used in pickles, jams, squashes.

               Adding Salt
                   •  Draws out moisture and kills microbes.
                   •  Used for fish, meat, pickles.
               Adding Sugar
                   •  High sugar content prevents microbial growth.
                   •  Used in jams, jellies, syrups.
               By Oil and Vinegar
                   •  Oil prevents contact with air; vinegar (acetic acid) kills germs.
                   •  Used in pickles and chutneys.

               Heat Treatment
                   •  Boiling kills most microorganisms.
                   •  Example: milk, water.
               Cold Treatment
                   •  Refrigeration and freezing slow down microbial activity.
                   •  Used for storing milk, vegetables, cooked food.
               Pasteurisation
                   •  Milk is heated to 70°C for 15–30 sec and cooled quickly.

                   •  Kills microbes without affecting taste.
                   •  Pasteurisation was discovered by: Louis Pasteur, a French scientist who found that
                       mild heating can kill harmful microbes.
                   •  He also contributed to the germ theory of disease.
               Proper Storage & Packing
                   •  Airtight and sealed packaging prevents contamination.
                   •  Common in tinned, canned, and vacuum-packed food.
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