The various seed mashes used for rice wine brewing can be classfied into three types according to the preparation processes: "Traditional seed mash" ("LING FANG Jiu Mu" in Chinese pronunciation) , "Pure Cultured Seed Mash" and Active Instant Dried Yeast (AIDY).
Polished rice ↓ Steeping in hot and acidified liquid ↓ Steaming ↓ Spreading the steamed rice to cool it to a room temperature ↓ Mixed with Jiu Qu, acidified liquid, young mash or dried seed mash ↓ Fermentation for about 7 days ↓ Seed mash ready for rice wine brewingSo the seed mash preparation process had no considerable difference with main mash fermentation process.
Fresh water Polished rice │ ↓ ├────────→ Socking │ ↓ │ Steaming │ ↓ ├───────→ Cooling the steamed rice │ ↓ by drenching fresh water through it │ Mixed with Xiao Qu ← Xiao Qu │ ↓ │ Sacchrafication │ ↓ └──────→ Mixed with wheat Jiu Qu and water ← wheat Jiu Qu ↓ Fermentation ↓ Stirring ↓ Secondary fermentation ↓ Seed mash
|ingredients||weight ( kg)|
|Wheat Jiu Qu||19.5|
|Xiao Qu||0.187~0.25||( major microbes are Rhizopus spp. and yeasts)|
|Water (including the water||230|
|absorbed in the cource of steeping|
Saccharification and fermentation of the seed mash lasts about 7 days, then the young seed mash is poured into jars with narrow neck for secondary fermentation. Much ethanol is produced after 20- 30 days (or may be three months ). Usually the ethanol content of the seed mash can reached up to 15%. The chemical compositions of the seed mash is given in table 1 below.
|Ethanol (v/v, %)||15.44|
|Total acids ( g/100 ml)||0.3799|
|Sugar ( g/100 ml, glucose)||0.3936|
|Starch ( g/100 ml)||4.42|
The instant seed mash is inoculated with yeast pure cultures instead of traditional Jiu Qu ( wheat Jiu Qu and XIAO QU) , so the possibility of infection caused by inaseptic operation by using XIAO QU is greatly reduced. Also, to adjust the pH of the seed mash to around 4.0-4.5, the lactic acid is added into the seed mash instead of adding acidified steeping water in which some unwanted microorganisms may exsit.
In current practice, a large yeast inoculum is prepared from the nutrient agar slant by a stepwise propagation of the yeast in successively larger volumes until an adequate inoculum is available to inoculate a plant fermenter. The basic ingredients for preparation of instant seed mash are similar to that of traditional seed mash, but water content may be higher than that of traditional seed mash. In order to suppress the proliferation of indigenous lactic acid bacteriua, lactic acid is added to the mash to regulate the pH of the mash to about 4.0, which favorate the yeast proliferation. Usually, a 1- 2 % (v/v) yeast inoculum is used, and the initial temperature of the mash is set at 26-30 ℃ according to the weather. When the temperature of the mash reaches above 31-32 ℃, stir the mash with pressed air. The cultivation time lasts about 1-2 days.
Another method of pure culture of yeast is currently used in rice wine breweries. Glucoamylse is added to the mash ( the ingredients are almost the same as those in the traditional seed mash but diluted with much water), then raise the temperature of the mash to 55- 60℃. Glucoamylase converts the geletinized starch in order to reduce sugar which is easily used by yeast culture. At this high temperature, wild yeasts and bacteria are destroied, so pure yeast cultures grow well.