Join Date: Jul 2002
Location: Outside the box
"malt" refers to grains that have been turned into sugar, ready to be brewed. If you have grains they go through a malting process, turning starch into sugar. Then the sugar is fermented, making alcohol. The the alcohol is made into vinegar, you can buy "mother of vinegar" to turn alcohol into vinegar.
The "malt" bit really is distinguishing the vinegar as being one made from grain, corn (maize), barley, rye, wheat etc. It could just as easily be called grain vinegar, like some vodkas might be referred to as a "grain spirit". It distinguished it from wine or cider vinegars.
Grain is a very cheap way to make alcohol, so I would expect most distilled vinegar is made from grains, and hence can be called malt vinegar. You could also get "white vinegar" made from wine, cider, anything really, if you made rhubarb wine it can be turned into white vinegar.
I have never seen undistilled vinegar on sale in supermarkets. Some chippers make their own vinegars, which can be undistilled. Some will blend their brewed vinegar with distilled vinegars.
Most brown vinegars in supermarkets will be distilled white vinegar with colour added, and maybe some unfermented malt to sweeten and colour it. This is similar to what white & brown rum are, unfermented molasses is added back to the distilled white rum to produce brown rum. "Proper" brown vinegar would get its colour from being aged, just like whiskey, distilled whiskey is a clear liquid.
Some asian shops can sell acetic acid cheap enough. But IME clear distilled vinegar made from malted grains is very common.