This question already has an answer here:
We made a mango pickle with green mangoes. Below is the typical recipe that was used:
20 small tender green mangoes 200g salt 2tsp. turmeric powder 2” asafoetida (rock type) 1 tbsp. peppercorns 3 tbsps. Mustard seeds ¼ tsp. fenutgreekseeds 2 tbsps. Mustard dal 100g red chilli powder 1 sp. Turmeric powder 500ml sesame seed oil
Preparation : Wash and wipe the mangoes thoroughly. Slit them into fours. Chop 4 or 5 mangoes into cubes. Sprinkle the salt and turmeric powder on all the mangoes, mix them well ands place in a plastic or wooden vessel. Keep heavy weight over the mangoes and leave them for 4 days. Daily, turn the mangoes gently, upside down to ensure that the natural green colour of the mangoes has changed. Drain out the grime and salt if any into a pan and boil it. Cool. Meanwhile remove the soft seeds from each of the mangoes carefully. Remove the black skin too if any. Should there be any hard seed, do not remove it. Next, heat a tablespoon of oil in a small pan, keep the flame low and toss in the asafoetida. Remove it after a minute. Repeat with peppercorns, mustard and fenugreek seeds. Cool the spices and grind fine. Do not use nay water. Heat the remaining oil in another pan and cool thoroughly. Now mix the chilli powder with mustard dal, turmeric powder and the ground spice, add salt (the mixture should be slightly salty). Mix some cooled oil into spice mixture. Stuff each mango with a small lump of the spice paste. Place all the stuffed mangoes in a wide mouthed jar. Pour the grime and the remaining heated and cooled oil.
Now 3 days later this pickle is foaming with gas. How can I prevent this from happening. What am I doing wrong. I have seen some of your posts and you seem to have a lot of experience in this area.