Having discussed the different styles of baijiu and the basic fundamentals of fermentation, I’d like to turn our attention to the actual business of making baijiu. Every brand has its own tricks, but one popular method in southwestern China is what’s called continuous fermentation, or sour mash. If this sounds vaguely familiar to American readers, it’s because we love sour mash in the States – it has a long, proud history with Bourbon and Tennessee whiskey.
When you are making grain alcohol you combine mashed grains with a fermenting agent (yeast in the West, qu in China, and then the fermenting agent converts sugars to alcohol. The alcoholic liquid is then heated until it vaporizes, the vapor is collected in a receptacle and then it’s cooled back into a liquid with much higher alcohol content – the process known as distillation.
Sour mash is the process by which a previously fermented batch of grain mash (or simply “mash”) is reincorporated into a fresh mash. The sour mash process is not dissimilar from the process of making sourdough bread, where a piece of the previous loaf starter is reused in the next. The thinking behind sour mash is that it not only creates a better tasting drink, but it also ensures a degree of continuity between batches.
Two of the best known practitioners of sour mash in the baijiu world are Luzhou Laojiao 泸州老窖 and Maotai 茅台, but their techniques vary.
Luzhou uses a technique they call “thousand-year mash” that ferments the grain in a 4:1 ratio of old to new mash. After distillation the mash is put back into the baijiu fermentation pits (more on these later), where residual liquid will be allowed to soak into the soil.
Maotai starts off its process with a fresh mash that is immediately distilled after a month-long fermentation. The resulting distilled liquor is mixed with the used mash and allowed to ferment a second time. Then more raw materials are added at a 1:1 mash to sour mash ratio, the combination is fermented, distilled and mixed with more raw materials. And so on until eight fermentations have taken place, and the resulting liquor is aged for 3 to 20 years in barrels.
Though its still widely practiced in the United States, I have heard that advances in modern distillation methods have made sour mash of negligible importance in whiskey making. Baijiu may be another story, because its production uses fermentation and distillation methods that have changed little over hundreds, perhaps thousands, of years. It’s a fascinating topic (to me at least), but I’ve rambled on enough for one post, so baijiu distillation methods will be covered in the next “baijiu basics” installment.