Clean the quinces, peel and put them in a blender. Turn it on for 2-3 seconds, then off, and repeat this process until the quinces turn to pieces but don't let them turn to a puree.
Bring the water to a boil on the stove and pour in the quinces. Leave them to boil on low heat and stir periodically. Once they reach the necessary jam consistency, pour in the citric acid, stir and take it off the heat. Leave it to rest for 5-10 min. and distribute into hot jars. Flip them over to vacuum seal the caps.
Notes: I got about 6 full jars of quince jam. It was amazing, I've never made it by blending the fruits to pieces before but it worked out. I boiled it on a medium heat setting on the stove.