One of the food additions is aspartate which is also mentioned in the link below. In http://www.cf.ac.uk/biosi/staff/jacob/teaching/sensory/taste.html
it is written that bacon really hits our umami receptors because it is a rich source of amino acids.
Glutamate is present in a variety of protein-rich foods, and particularly abundant in aged cheese.
http://www.vivo.colostate.edu/hbooks/pathphys/digestion/pregastric/taste.html
Believe it or not, our first encounter with Umami is as a baby. Baby formulas and mother's milk are loaded with Umami, but it doesn't stop there. Umami can also be detected in many normal every day foods we eat such as ripe tomatoes, parmesan cheese, cured ham, mushrooms, meat, fish, wine and beer. So if we encounter Umami every day why is it so elusive to define? One reason is that we can not buy it in bulk like sugar or salt. (For those who think MSG is Umami, read on, you're only partially correct). Also, it has a strange name; the taste itself is rather subtle; and it actually interacts with the four other tastes.
http://winegeeks.com/articles/115/umami___taste_receptor_tactile_sensation_and_flavor_intensifier/