The concept of a proprietary white blend is the same as a Red Blend, whereby the term ‘proprietary blend’ holds no legal implications. The name will generally be found on a wine that doesn’t declare the exact blend and proportion of grapes. Essentially, you can liken this term to ‘Bordeaux-blend’, or ‘Port-blend’. In the USA some producers list their wines using the term ‘Meritage’, denoting to the fact that they are members of the Meritage Association.
Joseph Phelps Insignia is another example of a proprietary blend; this Cabernet-based wine does not state the names of the grapes on the label and therefore creates a terminology within itself.