RESULTS AND DISCUSSION
A strain of yeast designated NP01 was isolated from the
Thai traditional alcoholic beverage ou. NP01 yeast was
found to be the fermentation yeast with globose or
subglobose cells. Pseudohyphae were not observed
during cultivation. D-Glucose, D-galactose, maltose, and
sucrose were fermented, while lactose and trehalose
were not. According to these and other characteristics, the
isolated yeast was identified as a strain of the genus Scerevisiae. The isolated yeast S. cerevisiae NP01 was
available for ethanol fermentation.
The fermentation curves of the mashes made from the
two yeasts and black rice grains are shown in Figure 3.
The characteristics of alcoholic beverages, designated as
black rice wine, made from the two yeasts and black rice
grains, are shown in Table 1. The total amount of the CO2
output was 11.4 to 12.0 g, and the ethanol concentration
of the black rice wine was from 12.4 to 13.1% (v/v). The
amount of total phenolic compounds of black rice wine
made from the uncooked black rice grains was higher
than that of the beverage made from cooked black rice
grains. The anthocyanin content of black rice wine made
from cooked and uncooked black rice grains with NP01
yeast was 52 and 118 μg/ml, respectively. The
anthocyanin content of the black rice wine made from
cooked and uncooked black rice grains with W-4 yeast
was 57 and 131 μg/ml, respectively.
The black rice wine made from the two yeasts and the
black rice grains was red in color; moreover, the one
made from the uncooked black rice grains was brilliant red
in color, just like red wine. The Hunter a values of the
black rice wines made from the cooked and uncooked
black rice grains with NP01 yeast were 2.65 and 6.89
(Table 2), respectively, and those of the black rice wines
made from the cooked and uncooked black rice grains
with W-4 yeast were 3.23 and 9.23, respectively. The
Hunter, values of the beverages made with W-4 yeast
were higher than those of the beverages made with NP01
yeast. The Hunter b values of the beverages made from
the cooked and uncooked black rice grains with the two
yeasts ranged from 4.22 to 4.72. The Hunter L value of
the black rice wine made from the uncooked black rice
grains was lower than that of beverages made from the
cooked black rice grains.
The absorption spectra of the black rice wine made from
NP01 yeast and black rice grains are shown in Figure 4The absorption spectra of the black rice wine made from
W-4 yeast and black rice grains are shown in Figure 4.
The resulting rice wine made from the cooked and
uncooked black rice grains showed absorbance at 520
nm. The absorbance of the rice wine made from the
uncooked black rice grains was strong and relative to that
of the rice wine made from cooked black rice grains. Part
of the anthocyanin might have been decomposed duringthe cooking process because the rice wine made from the
uncooked black rice grains showed typical peak of
anthocyanin at 520 nm.
The antioxidative activity of the black rice wine was
determined. The DPPH radical scavenging activity of the
rice wine made from the uncooked black rice grains was
higher than that of the rice wine made from the cooked
black rice grains (Figure 5A). The lipid peroxidation of the
alcoholic beverages was also determined. The inhibitory
activity of the lipid peroxidation of the rice wine made from
the uncooked black rice grains was higher than that of the
rice wine made from the cooked black rice grains (Figure
5B). The antioxidative activity of various rice wines made
from black rice was similar (Koguchi et al., 2010)