Queso fresco is a popular Mexican cheese that is typically un-pasteurized. This means it has not been heated to kill off any bacteria, making it more perishable than other cheeses. As such, it has a shorter shelf life and should be stored in the refrigerator for up to two weeks after opening. The freshness of queso fresco makes it an ideal topping for tacos or burritos, but because of its lack of pasteurization, pregnant women and people with compromised immune systems are advised against consuming it.