What grains can be used to enhance a beer's head due to their protein content?

Wheat is commonly used in brewing to enhance a beer's head due to its higher protein content compared to other cereal grains. The proteins in wheat contribute to the formation and stability of the foam, which is crucial for the visual appeal and sensory experience of the beer. When wheat is included in the grain bill, it can help produce a thick, long-lasting head, making it a popular choice for various beer styles, especially wheat beers like Hefeweizens and Witbiers.

Barley is also used in brewing and contains proteins that can form foam, but wheat typically has a superior capacity for head retention due to its specific protein composition. Rice and corn, on the other hand, are adjuncts that primarily serve as fermentable sugars and do not offer the same level of protein enhancement necessary for head stability. Thus, when considering grains specifically for enhancing a beer's head, wheat stands out as the preferred choice.