Some sour fruits are lemons, limes and kumquats. These fruits are known as citrus fruits, which are acidic fruits with juicy pulp, stippled rinds and high amounts of vitamin C.
Kumquats are small, orange grape-size fruit that are native to China. They have a sweet skin and very sour pulp. Kumquats can be eaten whole with the skin and are a great source of fiber.
Lemons are a very sour yellow fruit. Lemons are typically used in cooking and are rarely eaten out of hand. Varieties of lemons include Meyer, Eureka and Lisbon.
Limes are green fruit that are similar to lemons, but more acidic and contain less Vitamin C. There are several varieties of limes, such as kaffir, Persian and key.
Other examples of sour fruits include the grapefruit, Seville orange and tangelo.