Rice wines, are fermented alcoholic beverages produced from cereals, with wheat koji or XIAO QU as saccharifying and fermenting agents. The raw materials used for rice wines were chestnut, millet ( Setaria italica), broomcorn millet ( Panicum miliaceum) mainly in the North, and rice (especially glutinous rice) mainly in the South in ancient times.
Rice: Because the political, cultural and economic center was transfered from the North to the South since Song Dynasty, and the distilled spirits had developed from the the time of South Song Dynasty and spreaded rapidly in the North, the production of rice wines in the North decreased gradually, and was only limited in several Provinces in the South ( Jiangsu Province, Zhejiang Province, Jiangxi Province, Fujian Province), and the output of rice wines in the South surpassed that in the North. These situation has been lasted up to now. In the South, rice is a pricipal crop, accordingly, rice became the most important raw material for rice wines.
Rice, including glutinous rice, long- grained nonglutinous rice, black rice are used mainly in the South. It has been considered that polished glutinous rice is the most suitable to rice wine brewing.
Millet: It is mainly used in the Northern part of China. Its varieties include: chestnut, broomcorn millet ( Panicum miliaceum).
Maize: Historically speaking, it was rarely used for rice wines making. From 1970's, scientists have developed a process using maize as principal materials. after solving the major problems in pretreating the maize, the large scale production of so called "Maize Wine" in North China gained greatly successful.
Highland barley: In Xizang and Qinghai Provinces, the Highland barley is principal raw material for making QINGKE JIU ( a fermented alcoholic beverage similar to HUANG JIU).
Wheat: It is not the principle raw material but is used for making wheat koji that acts as saccharifying and fermenting agents.
Water consisting about 80% in rice wine is one of the important materials. For thousands of years, the quality of water used in brewing has been considered as a major factors in determining rice wines quality. Brewmasters like to take water from underground sources, spring water or the water in central area of lakes or rivers where the water was protected from pollution by the geological structure. Older established rice wine brewing centres that have become famous for a particular type of rice wine were often associated with water supplies with a special composition that was presumably beneficial to the type of rice wine being produced. For example, brewing water used for Shaoxin Rice Wines has been taken from the central area of Jian Hu lake. The hardness of brewing water had better be in the range of 2-6, and pH be around 7.The water for rice wine brewing needs to be colorless, tasteless and odorless, containing traces of iron, calcium, and other minerals. Water with a low iron content is ideal for rice wine brewing.
3.3.2 Pretreatment of Raw Materials
In contrast to the use of malt and corn for beer brewing and spirit production, in the process of rice wine brewing, the rice grains are to be polished before they are used. The main purpose of polishing is to remove protein, lipids and minerals contained more than necessary in the germ and surface parts of the rice grain, which are considered undesirable to rice wines brewing in so much quantity. In general, rice used for rice wine brewing is polished to remove about 10% of its weight. Crude fat and ash contents decrease most rapidly, while the protein content decrease gradually.
22.214.171.124 Polishing of Rice
The next step in the rice wine brewing process is to wash the polished rice chosen specially. Usually the rice should be washed repeatedly until the drained water become clear. During washing, the grains are subjected to a kind of polishing caused mainly from collision of the grains in water. This process removes some of the surface parts fo the grains (1 to 2 % of the total grain weight) . During washing, the grains absorb water up to 9 to 17 % of their weights.
126.96.36.199 Washing and Steeping of rice
Washed rice grains are steeped in water immediately. After this procedure the grains absorb water to about 25 to 30 % of their weights, which promotes penetration of heat into the grains during steaming.
The factors affecting the steeping of rice include:
Hardness of water: usually, steeping with soft water favours penetrating of water into the grains.
Temperature of the steeping water: with increasing temperature of the water, the time needed is shortened.
The varieties of the rice grains: glutinous rice absorbs water more quickly than long-shaped rice.
Traditionally, the rice grains are steeped in vats. As the large scale production, pits constructed with concrete or tanks made by steel plates are used. Transportation of the rice grains is undertaken by using mechnical devices or hydraulic power.
Rice-steeping times varies from 1 day to 20 days. In traditional processes, rice-steeping time lasts 13-20 days. The purpose of steeping rice for such a long time is for the rice not only to absorb enough water, but also to obtain acidified rice-steeping liquid derived from lactic souring of rice-steeping water.
The acidified rice-steeping liquid is useful in the traditional brewing pracess. Traditionally, in some workshops, the step of rice -steeping lasted 10-25 days, until the rice- steeping water becomes souring, or acidifing owing to the lactic acid fermentation of soluble substrates in the rice-steeping water by lactic acid bacteria.
The functions of acidified rice-steeping liquid include:
(1) The acidfied rice-steeping liquid creates an environment in the fermenting mash, inhibitory to bacterial spore germination and to the growth of vegetative bacterial cells;
(2) The acidfied rice-steeping liquid provides amino acids and vitamines for the yeast growth;
(3) The acidfied rice-steeping liquid can improve the flavour of rice wines.
When the acidified rice-steeping liquid being permented inside of the rice, the steeping liquid is drawn out from a special filter which is like a bamboo basket with a conical bottom inserted into the rice -steeping vats.
After the acidified liquid being collected, the acidified liquid is evaporated to remove the extra water. The concentrated liquid is used to mix with the cooled steamed rice as acidifing liquid for mash. Because the pH of the steeping liquid is lower, after mixing with the steamed rice, the pH of the mash (fermentation medium of rice wine) is accordingly reduced to a suitable range favourable for yeast growth.
Historically, there were alternative methods of achieving the same result. Two kinds of acidfied liquid may also be used: the diluted vinegar solution and the broth made from wheat flour which was fermented spotanously to become to soured liquid, after several day's incubation at a suitable temperature. This used to be a common process for making high quality acidfied liquid in Song Dynasty.
Now the common practice is to use lactic acid instead of acidfied rice-steeping liquid.
The purpose of steaming of rice is to gelatinize the starch contained in rice kernel by the effect of water vapor penerated into it. During the cource of steaming, the crystal structure of rice starch is destroyed and becomes to α-type, which favours the growth of mycelial mold. The gelatinized starch is easily hydrolyzed by amylase or glucoamylase. At the same time, the commonly quoted reason for rice steaming is to sterilize the raw materials.
188.8.131.52 Steaming of Rice
In traditional processes, the drained rice is transfered to the side of a steamer. First a master fills the cauldron two- thirds full of water. When the water in the cauldron starts boiling, the master scoops the soacked rice into the steamer gradually. A layer of rice should be spread to cover all the surface of the bamboo grid. When the steam begins to rise through the first layer of rice, a second layer of rice is spreaded onto the first one. This operation repeated until the steamer is almost full. The steamer is covered with a lid. Measuring from this time, the rice being steamed lasts for 20 minutes, during which, some water or acidified liquid is poured to the steamed rice. In this way, the steamed rice becomes softer.
The standard procedures for traditional steaming process for long -shaped non- glutinous rice is summurized as, "steaming twice", "drenching with water twice" and "covering twice with lid".
During the period of 1960's and 1970's, various continuos steamers have been developed. The "Horizontal Steamer" and "Vertical Steamer" are widely used, with the latter being proved more acceptable.
There are two basic operating methods for cooling the steamed rice, that is, (1) cooling the rice by air after spreading it on bamboo mats, and (2) cooling the rice by flowing cold water through the hot rice (drenching).
184.108.40.206 Cooling of the Steamed Rice
When using the first method, after being steamed, the rice is spread evenly on a bamboo mat to be cooled. Using a wooden spade, the master turns over the rice, breaking up large clumps by whacking them with the spade's flat blade. The temperature of the rice should lowered down within a suitable range according to the environmental temeprature. For example, in summer, the rice should be cooled as low as possible.
By using the second method, the steamed rice is scooped into a bamboo bascket or a wooden tub with a screen mounted beneath the bottom. Cold water is poured into the rice layer, and the drained water ( now becomes hot) is collected and poured into the rice again. It is important to keep the rice cooled evenly. The rice temperature control is the same as described before.
Both methods mentioned above are characterized by high- laboured intensity and time comsuming. In a lager scale production with continuos steamers, the air-blower is used to cool the steamed rice.