What spice do chinese restaurants use in their hot mustard sauce?!

Question:

What spice do chinese restaurants use in their hot mustard sauce?

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I live in Germany, and the grocery store close to use doesn
Answers: if I am not mistaken it has a small amount of horseradish in the mustard. The vinagar is probably a Hot pepper infused type. Combine Coleman's dry mustard, wine vinegar, and a tiny dash of salt into a paste. To increase the heat, add a touch of red pepper! Really it's just mustard powder and water:

This article really explains it:
Chinese Cuisine: What Makes Hot Mustard Hot?
http://chinesefood.about.com/library/blc... wa

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