Fruit Jams and pickles for that matter have many corrosive compounds.(including weaker organic acids)Plastic containers are basically modified petroleum products, which are reactive towards these acids. So when you keep Jams or pickles in plastic containers , they tend to corrode the plastics , forming harmful inedible products. Glass on the other hand , doesn't get corroded by these weak acids and is hence a more suitable option. Views · View Upvotes.