In a post last February, I described how to use Google Book Search as a kind of electronic index to On Food & Cooking. And I mentioned that Google engineers were working on a search box for this site that would take you directly to the snippets. Well, they've done it, and it works wonderfully! Find the search box in the right-hand column on this page, type in your word(s) and hit search, and on the resulting page look at the fourth box down along the right edge.
It will give you snippets around the term, and page references. The entire text isn't viewable on Google Books, so you'll probably have to go back to your hard copy to see all the appearances of the term. And the search index may not be complete. But it's much more complete than the book's printed index.