These scripts are to take all information from the USDA National Nutrient Database put them into a single file and then ultimately into a smaller SQLite representation. Here's the accompanying blog post
You will first have to register to get an API key. These keys are limited to 1000 requests per hour so be sure not to go over that.
ruby getFoods.rb [APIKey]
Then repeatedly call with enough time between calls to fill the JSON file. It should come out to ~ 100MB
ruby getFoods.rb [APIKey] [callCount]
Once this is done run the fillDB script which will create and fill the SQLite database. This may take a while
ruby fillDB.rb
I am not a ruby developer, I just use it to write small throwaway scripts so don't expect this to be high quality code.