I have made Japanese style Marron Glace. One kg of chestnuts were boild for short time once. The hard shell was peeled. This process was a bit laborious. Then they were boiled "6 times" in order to get rid of the bitter taste. Soda was not used. They were then sweetened with sugar. Bitter inner skin was much preserved. But it won't taste bitter any longer. Rich bodied taste with elegant sweetness. Canned could be stored for several weeks.