Although Kung Pao Chicken is known foremost for its spice, it has a vinegary edge too, thanks to the inclusion of something called "zhenjiang xiang cu." I'd love to try making it—if only I knew how to ask for this important ingredient at the Asian grocery store.

Coming to my rescue is the Asian Market Shopper app I just loaded onto my iPhone. The new $3.99 app, created by Asian culinary expert and cookbook author Andrea Nguyen, categorizes 100 of the most commonly used ingredients, from miso to curry pastes to dried kelp, by region: Southeast Asia, South Asia and East Asia. Although many Asian ingredients are available in regular supermarkets these days, Asian markets still carry a wider variety of produce, grains, spices, noodles and condiments—and they're a fun place to explore (where else would you find chestnut rice cake mochi balls?).

Each ingredient in the Asian Market Shopper app, from annatto (the heart-shaped seeds of the evergreen annatto tree, used in Filipino and Vietnamese cooking) to yellow split peas, has a photo, its English name and its Asian name—and with the tap of an icon, Nguyen speaks the ingredient's name in both languages.

You can "favorite" certain ingredients, email them to yourself or a friend, even post them to Facebook or Twitter. The app has 25 recipes (and as you'd expect, any Asian ingredients have links to their specific pages on the app). There are instructional videos too, covering how to rig a steamer, how to clean and break down a crab and other tasks that are easier to grasp when demonstrated.

And zhenjiang xiang cu, in case you're wondering, is an inky, smoky, slightly bitter vinegar made mostly of sticky rice and malt. Besides kung pao dishes, it's also used for dipping northern Chinese dumplings. Thanks to my app, I know that Golden Plum brand is the standard bearer—and I even know to watch out for imposters.