How do I consume Google API JSON data specifically Google Product

I am having issues parsing the data I receive back from a Query for products in Google Product . If I run a query similar to...

curl --header "Authorization:GoogleLogin Auth=<AuthKey>" --header "Content-Type:application/atom+xml" https://content.googleapis.com/content/v1/8076653/items/products/generic?alt=json

This I receive a JSON(ish?) document, similar to the following 

{
  "version":"1.0",
  "encoding":"UTF-8",
  "feed":{
  ...
  }
}

but when I run the following

res.on('end', function() {
  console.log(res.body.feed);
  mainRes.send(res.body);
});

The console shows undefined.

Should be...

res.on('end', function() {
  console.log(JSON.parse(res.body).feed);
  mainRes.send(res.body);
});