3.4. Research on the production of new-type rice wine with uncooked
materials
Winemaking with uncooked materials has occurred at different
times throughout history. Research on winemaking by this method
was first reported as early as the 1950s. By the early 1970s many
researchers competed with each other in studying winemaking
with uncooked materials against the general background of ‘‘global
energy crisis”, but most of them concluded that ‘‘this method is
infeasible”, which postponed its development. The method was
not applied in the rice wine brewing industry until ten years ago
roughly, and since then it has begun to occupy a place in the
market economy (He, Xiao, Wu, & Zhang, 2007; Lu, 2001).
The methods of winemaking with uncooked materials can be
further divided into two specific techniques as well, the solidand
liquid-state methods. The brewing of CRW mostly adopts the
liquid-state method, that is, after adding water and starter into
the raw material rice, the crude starch is directly put through
saccharification, alcoholization and acidification for trilateral
fermentation without immersion or cooking anymore. The advantages
of this method include low investment cost, cleaner and
more sanitary production, easy operation, energy conservation
with emission reduction, high wine yield, significant economic
benefits, among other benefits (Bely, Sablayrolles, & Barre, 1990;
Krishnan, Nghiem, & Davison, 1999; Zou, Liang, & Ma, 2005).
Since the beginning of this century, this method has been gradually
applied in industrial production presenting a distinct trend of
dramatic development. Yue, Chen, and Huang (2003) expounded
the whole course of the brewing of corn wine by the liquid method,
demonstrated its feasibility and provided the saccharifying
fermentation conditions. According to the study, adopting the ageing
by high and low-temperature intervals increased the utilization
rate of raw materials and significantly shortened the wine-making
time. Hou and Wang (2004) studied the technique and conditions
of the brewing of glutinous rice wine with uncooked materials and
found that when 3% wheat starter and 6% uncooked material
starter were added to the raw materials for fermentation at about
26 C, a new type of rice wine with low sugar content and alcohol
content could be obtained. Shi, Zhao, Wang, and Chen (2013)
added the root of kudzu vine into glutinous rice to brew rice wine
with uncooked materials, and determined the conditions for brewing
new-type nutritional CRW with uncooked materials.
However, in recent years, research on the technique of brewing
rice wine with uncooked materials is rarely seen globally, leading
to a lack of technological parameters like starter selection and
enzyme addition, as well as starter dose, enzymolysis degree,
liquid-to-solid ratio, fermentation temperature and time, etc. If
the technique can be improved to solve these problems: poor wine
stability, long fermentation period, susceptibility of finished wine
to rancidity and so forth, the method of brewing new-type rice
wine can be expected to step onto a promising pathway.
4. Optimization of rice wine fermentation
According to traditional methods, the fermentation of CRW is
generally realized through adding yeasts into cooked rice for
saccharifying fermentation, and 2–3 days later with saccharification
mash formed successfully, the starter is added into the jar
for secondary fermentation. This fermentation not only imposes
high requirements on the added yeasts and strains, but also is
extremely sensitive to temperature (susceptible to rancidity in
the case of high-temperature fermentation in the summer) and
requires a very long fermentation period (20–30 days). All of these
factors are unfavorable for the expansion of production scale. Thus,
many researchers have made numerous efforts to improve the
immobilized fermentation mode of traditional techniques, and to
explore new fermentation techniques, including optimal selection
of strains, continuous fermentation by immobilized complex
yeasts or non-starter holoenzyme fermentation.