On iPhone, the search box is at the bottom of the Kitchen tab; tap ✕ beside it to clear it. On an iPhone Duo that’s open and turned sideways, it’s in the row with Everything, Recipes and Pantry. On iPad, tap the search button (a magnifying glass) at the top right. Search looks at names, brands, tags, ingredients, directions, summaries, sources and notes (with just one or two letters, only names, brands and notes).
As you type, matching tags and ingredients appear under Add as a filter. Tap one to filter by it instead.
Type the numbers of a barcode to find the pantry item with that barcode.
To leave notes out of a search, turn off Search Notes Too in the filters, under Options.