The global food supply chain generally delivers products that are safe to drink and eat, but every so often there are some stories about unscrupulous distributors who try to sell knockoff items that aren't exactly what they say they are. The infamous 2008 scandal
in China is probably the scariest example where melamine was added to infant formula to make it look like the milk had a higher protein content. Less dangerous tricks involve deceptive food labeling practices, and it can be extremely difficult to detect food fraud when it's not so egregious. Here are just a few links on identifying authentic foods.
If you'd like to read more awesome and interesting stuff, check out this unrelated (but not entirely random!) Techdirt post