First cut the bitter gourd in thin circles.
Now in a pan boil the water.
Put bitter gourd in this boiling water for 2 minutes.
Mix the salt in water.
After 2 minutes drain out the bitter gourd.
Wash the bitter gourd in cold water.
After some dry keep it in a polythene bag.
Put this polythene bag in refrigerator freezer section.
You can use these bitter gourd pieces as you use fresh bitter gourd.