Koji or “qu” production for Sauce Aroma baijiu
Step 2 : Synchronized saccharification and fermentation in stone pits
In the first step of the process, named “Xiasha stage”, only about a fith of the grains are crushed; the rest is left whole. The sorghum is washed several times in warm water to remove detritus and allow it to absorb liquid. It is then steamed for about two hours and spread on the ground to cool, being turned over with shovels throughout. A process similar to the malting process used in the production of single malt whisky. Once the sorghum has cooled to the desired temperature, “qu” is added and the grains are piled into mounds of about two meters high. Piling the mash helps saccharifying the starch while absorbing some of the microorganisms present in the surrounding air, such as fungi, thermophilic bacillus and yeasts.
Getting ready for steaming the grains and later cooling off steamed grains for adding the inoculation agent “qu”
Over the course of 4-5 days, the aerobic conditions will cause the microorganisms to multiply exponentially, causing them to become visible and white patches will eventually form over the piles of fermenting grain. The technical jargon for this development is “Aerobic Stacking Fermentation Technology”. The temperature of the mound rises to 45-50°C, and a fruity smell begins to emanate. Eventually, when the pile has achieved the required core temperature and the number of microorganisms have multiplied to the necessary level, the mash is shoveled into fermentation pits of about 14 to 25m³.
Aerobic fermentation on the ground for 4-5 days and getting ready for pit-fermentation
These pits are sealed with mud to prevent aeration and left to continue the anaerobic fermentation process. After a month, the mash is removed from the pit and mixed equally with freshly washed sorghum and finally distilled. After this first distillation, the mash is spread to cool, and fed with fresh “qu” and some of the tail distillate.
This fermentation process is repeated seven times: from piling to pit, each cycle is followed by a distillation cycle until the final distillate is ready. Each fermentation/distillation cycle lasts 30 days and is conducted in the same pit. The fermentation temperature in the pit varies from 35°C to 48°C. Before each fermentation cycle, the tail spirits are poured into the pit, to induce fermentation, to control acidity and to induce the growth of beneficial microorganism while blocking harmful ones.
This complicated process eventually yields this characteristic sauce aroma so prized by its producers. The quantity of tail liquor poured into the pits decreases gradually, from 15 liters per pit for the first cycles to 5 kgs for the 7th, with finally no liquor poured in the final round. This process, called “Spilled-Tail Liquor” is another specificity of Sauce-Aroma baijiu production.
Anaerobic fermentation in 8 cycles of 30 days each, in stone-pits sealed with mud
Step 3: Aging the distillates
Obviously, the distillates produced in each cycle has very different chemical characteristics, alcohol levels and flavors: The liquor from early cycles is harsh and sour, the middle cycles are smooth and aromatic while the last cycles are usually bitter and smoky. The spirits distilled from the grains at the top of the pit are the key component of the sauce aroma that is characteristic of this style of baijiu. The liquor resulting from the mash at the bottom of the pit is called “pit-flavor liquor”, and the one obtained from the grain in the middle is named “mellow -flavor liquor”; these various distillates are aged separately for at least three years in ceramic urns, then blended to achieve the desired flavor. The final product is typically bottled at 53% ABV.
Aging the different distillates in ceramic urns for minimum 3 years
Sterilization of the pit once a year
A little-known fact is that, every year the pits are sterilized to kill the bacteria and remove the undesired smells. To do so, each pit is burnt with 50 to 100 kgs of wood; when the temperature eventually drops, the ashes are removed, and a small amount of grains is scattered in the bottom and cleaned again. Finally, 7.5 liters of standard liquor is sprayed into each pits and 15 kgs of “qu” is added to nourish and activate the floors. Only then are the pits ready to be used for further production.
Typicity of Sauce Aroma Baijiu-style
Sauce Aroma Baijiu has an intense, complex and layered flavor that can only be achieved by blending dozens, in some cases more than a hundred aged distillates.
A series of Maillard compounds are responsible for the caramel, almond, coffee, dark chocolate and soy sauce-like aromas of this type of baijiu. Discrete earthiness, yoghurt and mushroom-like nuances and pineapple-like fruitiness are also typical.
The empty pit after cleaning, ready for a new complete cycle