Algerian mustard sauce

I received a question via email regarding Algerian mustard sauce and why Algerians add prepared mustard like Maille to salad dressings. We have a traditional mustard sauce based on ground mustard and verjuice or vinegar. I know that it goes back to Moorish Andalusia, possibly older than that. Refer to mustard (sinab).

"Mustard: Sinab was simply mustard as we know it, ground mustard seed made into a condiment with grape juice or vinegar; it was common in Andalusian cooking but not known in the Levant, where mustard was always a spice, never a condiment."

I don't know if mixing mustard sauce into salad dressings is a French influence. Industrially prepared mustard sauces such as Maille are obviously a French influence in Algeria.

So, we had an older simpler homemade mustard sauce and easily accepted a more convenient, ready made substitute in the form of Maille. And, non we don't have Grey Poupon.