A number of additives are commonly added in our food items. The most common additives, probably, are the preservatives. These are additives that will ensure a longer life for the food item. Color additives are another major class of additives and impart certain specific color to the food items.
The most common way for the companies to inform the customers about the additives used in food items are by mentioning them on product label. In fact, as per the FDA (Food and Drug Administration) rules, companies are required to mention all the contents (including the additives) on the product label. The contents are listed in order of their quantity, with the most dominant content first, etc. The additives and many minor ingredients can be clubbed together and mentioned as a class.
Thus, a customer need to only look at the product label to get an idea of the additives that are in the food item.
Hope this helps.