Question

What are the different methods of preservation?

a) Collect the wrappers of frozen and canned food items and milk.
b) Find about the preservatives present in these food items.
c) List the various preservatives and methods of their preservation.

Answer 1

Clue - Lists of some food and likely preservatives used.

Packed Food                                            Preservatives

Tomato sauce                                 -          Sodium Benzoate

Sorbets                                           -          Citric acid

Jams                                                -         Citric Acid/ Sorbates / Benzoates

Cheese, Bread, Baked products, Pickles   -      Sodium/ Calcium Propionate or Sorbates

Carbonated drinks, Fruit juices                  –      Benzoates

Sorbates include calcium/sodium/potassium salt of Sorbic acid and inhibit yeast and mold but they may be less effective on bacteria.

Sodium/Calcium Propionate prevent growth of mold but they are not effective on yeast or bacteria

Sodium Benzoate is used in preservation of acidic foods to prevent food from molding and also in beverages like fruit juices and soft drinks. 

Citric acid is used as a food preservative and is a natural acid found in lemons, limes, plums, grapefruit, oranges. They are extracted by adding calcium oxide which results in calcium citrate.