Where would one go to locate reputable scientific studies on different subjects?

When I type a controversial subject in to a search engine, the first things that pop up are pages after pages of hysterical blogs. For example, I’m trying to find some information on what preservatives fast foods would use in their food that isn’t found in the same foods we buy in the grocery store. My common sense tells me that the big chains wouldn’t have any more need for preservatives than I do. I’m thinking that they go through their food much faster than I do in my household. Hamburger meat, for example, can sit in my freezer for a month or so before I use it and that is the only form of preservation I use or need. I don’t see any reason why it would be any different for the fast food chains. Being overstocked and having unused food sitting around for too long would result in a loss of profits.

However, those are just my thoughts and I need to find some reputable evidence to either back me up or show me that I’m wrong.

How do I bypass the hysteria and get to the valid studies and results?

(Yes, Snopes is the first place I usually look, but I’m not finding anything there.)