Which protein is identified as the primary foam former in beer?

The primary foam former in beer is indeed Protein Z. This protein plays a critical role in stabilizing the foam produced during the brewing process. When beer is poured, the proteins interact with the carbon dioxide that is released, leading to the formation of bubbles. Protein Z helps to stabilize these bubbles and contributes significantly to the beer's overall head retention.

In brewing, a stable and persistent foam is considered desirable, as it enhances the sensory experience of the beer, retaining aromas and presenting a visually appealing beverage. The foam stability is influenced by various factors, including the type of proteins present in the beer, their concentrations, and their molecular characteristics.

The other proteins listed do not serve the primary role in foam formation and stabilization as Protein Z does. Therefore, Protein Z's unique properties and function in creating a stable head of foam make it the correct answer for this question.