What roles do food additives play in the colour and flavour of food and in the preservation of some food items?
Citric acid is a common and natural additive that is used to retain color of foods (like putting lemon juice on apples to prevent them from browning), it also adds a bitterness that can enhance the flavors of some foods. They will also do a cure for corned beef using potassium nitrate for the bright red color because otherwise, when it's cooked in liquid, it can turn a most unpleasant gray color that wouldn't be attractive to look at. It's about marketing, you eat with your eyes first so if a product doesn't appeal to you visually you probably wouldn't buy it to eat.
Additives in food can increase the nutrition value e.g. added fiber, Vitamin C, Vitamin D etc. Obviously additives are used to preserve foods making them last longer and also to change or enhance the color of foods. I've heard that some supermarkets use additives to keep the outside of fresh meat looking red or pink so it looks fresh longer than it should.
