This isn't related to spaghetti sauce, but it was on the news lately the reason Coke tastes better in glass that in cans or plastic - glass does not absorb any of the flavor so it retains all of its flavor, so it really does taste different. (I always thought it was my imagination.) But I would think it would be the same for sauces. You can freeze in glass jars, I do it for my freezer jam and also for my left over broths.