I have to say that I was a little bit incredulous when I first considered the using the itemprop attribute to markup ingredients for a recipe for search engines to detect. Who would want a clumsy list of recipes compiled by a search engine when they typed “Recipes with Sriracha,” rather than a human written article or blog post with hand-selected recipes that are representative of the way Sriracha can be put to use. In fact, the first results that pop-up on that google search are exactly that. This probably suits a more direct query like the above; however, I realized that the real value of marking up ingredients allowed to perform Boolean searches for recipes by ingredient.
One of the most interesting implementations of this is http://www.supercook.com/ This site returns recipes with most closely match the ingredients that you have on hand. Not only that, when I sampled the recipes that where returned the ingredients were all marked up semantically. So it seems there is a real tangible benefit to taking the time to think about the metadata encoding on your webpage.