Ảnh hưởng của dòng nấm men, pH và nhiệt độ lên men đến quá trình sản xuất rượu vang sim

J. Sci. & Devel., Vol. 12, No. 1: 89-97 
Tạp chí Khoa học và Phát triển 2014, tập 12, số 1: 89-97 
www.hua.edu.vn 
89 
EFFECTS OF YEAST STRAINS, pH AND FERMENTATION TEMPERATURE ON WINE 
MADE FROM Rhodomyrtus tomentosa FRUIT (MANG DEN, KONTUM PROVINCE) 
Nguyễn Minh Thủy, Nguyễn Phú Cường, Nguyễn Thị Mỹ Tuyền, Đinh Công Dinh 
Can Tho University 
Email: nmthuy@ctu.edu.vn 
Received date: 24.10.2013 Accepted date: 24.02.2014 
ABSTRACT 
The effects of yeast strains, fermentation temperature and pH on quality of Rhodomyrtus tomentosa wine were 
examined. At ambient temperature (28±2oC), the fermentation was induced by inoculation with Saccharomyces 
cerevisiae strains isolated, purified and screened from sugar palm (Borassus flabellifer) and pineapple juice in 
comparison with commercial yeast (initial populations of yeast raging from 104107 cells/ml). The medium was 
adjusted before fermentation to five different pH values (3.44.2). The effect of fermentation temperature (20 and 
28±2°C) on strain population was also studied. The resulting wines were chemically analyzed. Pure cultures of 
Saccharomyces cerevisiae isolated from sugar palm significantly yielded in ethanol production higher than other 
strains in the fermentation at 28±2°C.. Yeast strains performed better at low temperatures with high alcohol yield. At 
20±2°C, the fermentation was dominated by the growth of S. cerevisiae in Rhodomyrtus tomentosa juice with 
maximum ethanol concentrations (13.43%Vol.) The methanol and SO2 concentrations met the Vietnamese Standards 
(QCVN 6-3 2010/BYT). In addition, the total acid, ester and aldehyde concentration were also low. 
Keywords: Alcohol quality, pH, Rhodomyrtus tomentosa fruit, Saccharomyces cerevisae, temperature. 
Ảnh hưởng của dòng nấm men, pH và nhiệt độ lên men 
đến quá trình sản xuất rượu vang sim 
TÓM TẮT 
Rượu vang sim rừng Măng Đen (vang đỏ) được lên men từ trái sim chín tím đỏ với nấm men phân lập và thuần 
chủng. Ảnh hưởng của dòng nấm men, nhiệt độ lên men và pH đến chất lượng rượu vang sim đã được nghiên cứu. 
Quá trình lên men ở nhiệt độ phòng (28±2oC) sử dụng nấm men Saccharomyces cerevisiae được phân lập, tuyển 
chọn từ nước thốt nốt và nước khóm so sánh với nấm men thương mại (mật số nấm men dao dộng trong khoảng 
104107 tế bào/ml). Dịch lên men được điều chỉnh ở 5 mức độ pH khác nhau (3,44,2). Ảnh hưởng của nhiệt độ (20 
và 28±2°C) đến quá trình lên men cũng được nghiên cứu. Các phân tích hóa học trên rượu vang thành phẩm đã 
được thực hiện. 
Dòng nấm men thuần chủng phân lập từ nước thốt nốt thể hiện khả năng sinh ethanol vượt trội so với các dòng 
nấm men khác (nấm men phân lập từ nước khóm và nấm thương mại) khi lên men ở nhiệt độ 28±2°C, pH 3,6 và mật 
số nấm men 106 tế bào/ml (với nồng độ ethanol thu được từ 11,85 và 12,35%v/v). Hàm lượng ethanol thu được cao 
hơn khi lên men ở nhiệt độ thấp. Ở 20±2°C, nấm men S. cerevisiae thể hiện khả năng lên men tốt hơn trong nước 
sim và nồng độ ethanol thu được tối đa (13,43% v/v). Các chỉ tiêu hóa học của rượu vang như hàm lượng methanol 
và SO2 đạt yêu cầu Quy chuẩn Việt Nam (QCVN 6-3 2010/BYT). Ngoài ra, hàm lượng acid tổng số, ester và 
aldehyde trong rượu cũng ở mức thấp. 
Từ khóa: Chất lượng, nhiệt độ, pH, Saccharomyces cerevisae, trái sim. 
Effects of yeast strains, pH and fermentation temperature on wine made from Rhodomyrtus tomentosa fruit (Mang 
Den, Kontum province) 
90 
1. INTRODUCTION 
Rhodomyrtus tomentosa (Ait.) Hassk, 
commonly known as rose-myrtle, mainly 
distributes in South-East Asian countries, 
especially Southern parts of Vietnam, China, 
Japan, Thailand, Philippines, and Malaysia 
(Saising et al., 2011). In Vietnam, the 
Rhodomyrtus tomentosa grows on the highland 
and mountains regions. Especially, there are 
over 700 hectares of the Rhodomyrtus 
tomentosa growing in Mang Den, Kon Plong 
district, Kontum province. The Rhodomyrtus 
tomentosa fruit is sweet and slightly sour. The 
main pigments which are responsible for 
Rhodomyrtus tomentosa color are anthocyanin 
compounds (Tung et al., 2009) including 
hydrolysable tannins, flavones, triterpenes and 
steroids (Hui et al., 1976). 
Red wine has long been thought to be heart 
healthy. The alcohol and certain substances in 
red wine called antioxidants may help prevent 
heart disease. Resveratrol might be a key 
ingredient in red wine that helps prevent 
damage to blood vessels, reduces "bad" 
cholesterol and prevents blood clots. The 
Rhodomyrtus tomentosa fruit from Phu Quoc 
Island was also reported to be used for red wine 
fermentation (Thuy, 2010). However, study on 
using isolated yeast for Rhodomyrtus tomentosa 
wine fermentation to improve wine quality has 
not been conducted. Moreover, maintaining 
Rhodomyrtus tomentosa wine color is still a 
problem. Red wine quality is affected by 
complex interactions involving yeast strain, 
must condition and winemaking technology 
(Torija et al., 2002). Some factors, such as 
Saccharomyces cerevisiae species, different 
sources of yeast temperature, and pH of the 
must strongly affect fermentation and wine 
quality (Fleet and Heard, 1993; Ribéreau-
Gayon et al., 2000). Therefore, the objectives of 
this study were to determine whether the pH of 
must effects on the Rhodomyrtus tomentosa 
wine quality, especially wine color, and to select 
high activity yeast strains, yeast population as 
well as fermentation temperature to improve 
the Rhodomyrtus tomentosa wine quality. 
2. MATERIALS AND METHODS 
2.1. Materials 
2.1.1. Yeast strains 
Three yeast strains (isolated from palm 
juice, pineapple juice, and commercial yeast) 
were used for this investigation. The isolated 
strains that were selected from palm juice and 
pineapple juice with highest fermentation 
capacity were identified as Saccharomyces 
cerevisiae (Thuy et al., 2011a; Thanh et al., 
2013). A mixture of isolated yeast strains 
including isolates from palm juice and from 
pineapple juice was also applied for wine 
fermetation. Commercial yeast (Saf-instant, 
France) as commercial S. cerevisiae was bought 
from CEMACO company. 
Yeast culture and propagation: Pure 
culture of each strain wase propagated to obtain 
the required fresh yeast (106cell/ml). Yeast cells 
were cultured in nutritional medium (20% of 
potato, 2% glucose , 0,2% (NH4)2SO4, 0,2% 
KH2PO4 in 100 ml distilled water) which was 
sterilled for 15 minutes at 121oC. Then, the 
cultured medium was incubated at 30oC for 1 
days in shaker (140 rpm). 
2.1.2. Rhodomyrtus tomentosa fruits 
The Rhodomyrtus tomentosa fruits were 
harvested from Mang Den village, Kom Tum 
province and transported to laboratory of 
Department of Food Technology, Can Tho 
University. 
2.2. Methods 
2.2.1. Wine fermetation 
The fruits were selected, and, washed with 
water and drained before crushing with warm 
water (45oC). The fruit paste was treated with 
pectinase (0.075% of Pectinex Ultra SPL, China) 
for 30 minutes. The fruit juice, afterwards, was 
extracted and filtered by hydraulic press. 
Sucrose and citric acid were added to serve as 
additives to the must [total soluble solid content 
(TSS) 23oBrix with the corresponding sugar 
content of 219 g/l and five different pH values 
Nguyễn Minh Thủy, Nguyễn Phú Cường, Nguyễn Thị Mỹ Tuyền, Đinh Công Dinh 
91 
Figure 1. Fermentation system 
Note: : Primary fermentation tank;  and : Secondary fermentation tank : Exhaust valve; : Pressure gauge; 
: Gas exhaust valve; : Controlling temperature system 
from 3.4 to 4.2], followed by the addition of 
Sodium metabisulfite (120 mg/L) for 2 hours to 
inhibit bacterial growth. For primary 
fermentation, the yeast cultures (from palm 
juice, pineapple juice, and mixture of both 
isolates (from palm juice and pineapple juice) 
and commercial yeast were inoculated into the 
must with different populations 
(104107cells/ml). The fermentation process was 
conducted by using the fermentation tanks 
shown in figure 1. The effect of temperature on 
fermentation efficiency was investigated by 
performing primary fermentation at two 
temperatures, including ambient temperature 
28±2oC and controlled temperature (20±2oC). 
Secondary fermentation process was followed 
for 3 months before transferring final wine 
product to bottles. 
2.2.2. Temperature mornitoring 
During the primary fermentation step, 
temperature was kept track by using 
thermosensor connectingd to the computer and 
using Logger Lite Software version 4.0. 
2.2.3. Quality analysis 
Aliquot samples were taken after primay 
fermentation for analysis of alcohol content 
(%Vol.), total soluble solid content (Brix degree), 
residual sugar (g/l), titratable acidity (mg/l), 
methanol (g/l of 100% ethanol), aldehyde (mg/l), 
sulfite (mg/l), ester (mg/l), and tannin content (g/l) 
using assays as described by Mai et al. (2009). 
Absorbance: The absorbance (A) of red wine 
was measured at 550nm by a UV-Vis 
spectrophotometer model U-2800A (Hitachi 
High Technologies America, Inc) to evaluate 
color difference. The absorbance was calculated 
by the equation: 
x
I
IA o 
 log
where A is the absorbance, Io and I are the 
light intensity before and after transmission 
through the cuvet,  is the wave length of the 
light (at 700 nm). 
Total anthocyanin measurement: The total 
anthocyanin content was determined according 
to the spectrophotometric pH-differential 
method (Lee et al., 2005). The total anthocyanin 
content was calculated as cyanidin-3-glucoside 
equivalents as the following equation: 
L)(mg
mLε
VDFMA=C /10
3
where A is the absorbance, MW is the 
molecular weight of cyanidin-3-glucoside (449.2 
Da), DF is the dilution factor, V is the final 
Effects of yeast strains, pH and fermentation temperature on wine made from Rhodomyrtus tomentosa fruit (Mang 
Den, Kontum province) 
92 
volume (mL), 103 is the factor for conversion 
from g to mg, ε is the cyanindin-3-glucoside 
molar absorbance (26,900), L is the cell path 
length (1 cm), and m is the sample weight (g). 
2.2.4. Sensory analysis 
Sensory analysis was done on color, taste 
and odor of the wine. The sensory evaluations 
were carried out by a panel of 10 fixed 
panellists. For QDA analysis, each panel was 
requested to evaluate the wine quality for 
various attributes using 5-point hedonic scale (0 
= unacceptable, 1 = moderately unacceptable, 2 
= neither good nor bad, 3 = moderately good, 
4 = good). 
2.3 Data analysis 
Significant differences between mean of 
parameters were determined by ANOVA and 
the Multiple Range Test at 95% confidence 
interval by using Statgraphic software (version 
15.2.11). 
3. RESULTS AND DISCUSSIONS 
3.1. Effect of pH on Rhodomyrtus 
tomentosa wine quality 
3.1.1. Physicochemical properties 
Several factors affecting to yeast 
fermentation rate such as temperature, pH and 
nutritional compounds of the must (Torija et al., 
2003). The quality of Rhodomyrtus tomentosa 
wine which were fermented from different pH 
media were shown in table 1. A similar alcohol 
content (11,6%) was obtained in all the samples 
in which pH was initially adjusted from 3.6 to 
4.2, while a significantly lower ethanol content 
was shown in the sample of low initial pH 
medium (pH value of 3.4). Samples with low 
initial pH media, corresponding to high acid 
content, indicated high anthocyanin and tannin 
content in the final product and vice versa. The 
anthocyanin content of Rhodomyrtus tomentosa 
wine was in range of 11.2 to 16.1 mg/l and 
tannin content varied from 0.47 to 0.66g/l, 
depending on pH value. According to Roobha et 
al. (2011) the intensity and stability of the 
anthocyanin pigments is dependent on various 
factors including concentration of the pigments, 
pH, temperature, light intensity and so on. The 
concentrations of anthocyanin and tannin are 
responsible for the colour of Rhodomyrtus 
tomentosa wine. As a consequence, high 
anthocyanin and tannin contents, resulting in 
higher absorbance value (0.71 and 0.51 at 550 
nm) were observed when using low initial pH 
media (pH value of 3.4 to 3.6). Figure 2 showed 
a deep-red color of Rhodomyrtus tomentosa 
wine samples which had pH value of 3.4 or 3.6 
whereas by stepwise pH increase until 4.2, 
the color gradually changed toward slight 
reddish color. 
3.1.2. Sensory evaluation 
Sensory quality of final wine was also 
evaluated in three attribute parameters (odor, 
color and taste). Odor average scores from the 
panel ranged from 2.6 to 2.9 (“quite good” to 
“good”) for all the wine samples (Figure 3). 
Table 1. Effect of pH on the quality of Rhodomyrtus tomentosa wine 
(after 18 days of fermentation at ambient temperature) 
pH Ethanol (% Vol.) Tritratable acidity (mg/l) Anthocyanin (mg/l) Tannin (g/l) 
Absorbance at 550 
nm 
3.4 10.94b* 6616a 16.11a 0.65a 0.71a 
3.6 11.65a 4680b 14.61a 0.66a 0.56b 
3.8 11.61a 4520b 12.75b 0.43bc 0.46c 
4.0 11.6a 4120c 11.81b 0.40c 0.40d 
4.2 11.67a 4000c 11.18b 0.47b 0.37d 
Note: Mean of triplicates values in the same column with similar superscript letters are not significantly different (P > 0.05). 
Nguyễn Minh Thủy, Nguyễn Phú Cường, Nguyễn Thị Mỹ Tuyền, Đinh Công Dinh 
93 
(a) (b) (c) (d) (e) 
Figure 2. Colour of Rhodomyrtus tomentosa wine 
with different initial pH value (a) pH 3.4, (b) pH 3.6, (c) pH 3.8, (d) pH 4.0, (e) pH 4.2 
0
1
2
3
4
Color
OdorTaste
pH 3.4
pH 3.6
pH 3.8
pH 4.0
pH 4.2
Figure 3. Sensory evaluation of Rhodomyrtus tomentosa wine 
with different initial pH value 
Increase in pH value resulted in a decrease 
in color acceptance. At pH 3.4 to 3.6, the wine 
has the most favorite color, however, the taste 
represented low score (2.4) while good taste is 
noticed for wine fermented in pH 3.6. In 
general, at pH value of 3.6, the Rhodomyrtus 
tomentosa wine has good quality with high 
ethanol content, high concentration of 
anthocyanin and tannin, leading to favorable 
flavor and color. 
3.2. Effect of different yeast strains and 
their population on Rhodomyrtus 
tomentosa wine quality 
3.2.1. Ethanol content 
The effect of different yeast strains and 
their populations on ethanol content was 
observed. By using isolated yeast from palm 
juice, the must had the highest fermentation 
and achieved highest ethanol content 
(approximate 12.08 % Vol.) after 18 days. The 
mean of ethanol yields by isolates from 
pineapple juice, isolate mixtures and 
commercial yeast in wine showed a lower levels 
(around 10.8% Vol.) (Table 2). 
Different yeast cell populations for each 
type of yeast strain were also inoculated for 
wine fermentation. After 18 days, the primary 
fermetation (at ambient temperature) of all 
samples stopped and the quality of these wine 
products were determined. The statistical 
results showed that high alcohol yield reached 
similar maximal levels (11.85 and 12.18% Vol.) 
by using yeast populations of 106 to 107 cells/ml 
in the initial media while for the samples using 
Effects of yeast strains, pH and fermentation temperature on wine made from Rhodomyrtus tomentosa fruit (Mang 
Den, Kontum province) 
94 
Table 2. Alcohol degree (% Vol.) of Rhodomyrtus tomentosa wine using different yeast 
strains and their population (after 18 days of fermentation at ambient temperature) 
Yeast strains 
Yeast cell population (cell/ml) 
Means 
104 105 106 107 
Isolates from pineapple juice 10.77 10.77 11.63 12.16 11.33b 
Isolates from palm juice 11.60 11.90 12.52 12.28 12.08a 
Mixture of isolates 10.87 11.17 11.6 12.63 11.57b 
Commercial yeast 10.80 11.10 11.66 11.67 11.31b 
Means 11.01b 11.24b 11.85a 12.18a 
Note: Values in the same column or row with similar superscript letters are not significantly different (P > 0.05). 
lower initial yeast populations of 104 and 105 
cells/ml showed less alcohol contents in wine 
(11.01 and 11.24% Vol., respectively). It could be 
explained by the consuming nutrients in the 
fermentation environment to increase biomass 
of yeast cell that caused sugar content loss and 
low alcohol content in the final product. 
However, according to Nagodawithana et al. 
(1974), the higher the initial yeast count (8.108 
cells/ ml), the greater the rate of cell death 
occurred even though the nutrients and oxygen 
were not apparently limiting. The above results 
suggested that it might be possible to get a high 
ethanol yield by selecting an initial yeast count 
from 106 to 107cell/ml. This result was in 
agreement with previous finding (Thuy et al., 
2011b) that the S. cerevisiae (isolated from 
palm juice) performed better than commercial 
yeast in fermentation plam juice wine and 
obtained highest alcohol content of 13.67% Vol. 
3.2.2. Residual sugar content 
Rhodomyrtus tomentosa wine which was 
fermented with the Saccharomyces cerevisiae 
isolated from palm juice, has low residual sugar 
content (4.43g/l) and significant differences from 
the wine using other yeast strains (Table 3). 
Moreover, higher yeast cell populations led to 
higher sugar consumption during fermentation 
process and as a consequence the lower residual 
sugar content in the final product was obtained. 
Rhodomyrtus tomentosa wine which used cell 
populations of 106 to 107 cells/ml has lower 
residual sugar content (5.5 and 3.43 g/l, 
respectively) compared to the sample fermented 
from yeast population of 104 and 105 cells/ml 
(around 6.5 - 6.8 g/l of residual sugar). 
3.3. Effect of fermentation temperature on 
Rhodomyrtus tomentosa wine quality 
Temperature affects not only the 
fermentation rate and length of fermentation 
but also the yeast metabolism, which determins 
the chemical compositions and flavor of the 
wine. The quality parameters of Rhodomytus 
tomentosa wine which were fermented at two 
different temperatures were determined. 
Table 3. Residual sugar content (g/l) of Rhodomyrtus tomentosa wine using different yeast 
strains and their population (after 18 days of fermentation at ambient temperature) 
Yeast strains 
Yeast cell population (cell/ml) 
Means 
104 105 106 107 
Isolated from pineapple juice 6.86 6.81 6.04 3.58 5.82a* 
Isolated from palm juice 5.52 5.57 4.04 2.59 4.43b 
Mix of isolated yeast 7.49 7.10 5.79 3.23 5.82a 
Commercial yeast 7.26 6.46 6.49 4.32 6.13a 
Means 6.78a 6.49a 5.50b 3.43c 
Note: Mean of triplicates values in the same column or row with similar superscript letters are not significantly different (P > 0.05). 
Nguyễn Minh Thủy, Nguyễn Phú Cường, Nguyễn Thị Mỹ Tuyền, Đinh Công Dinh 
95 
3.3.1. Ethanol content, residual sugar 
content and total fermentation days 
Controlling fermentation temperature is 
very important for high quality wine production 
(Zamora, 2009). In this study, different 
temperature [ambient temperature (28 2oC) 
and controlled temperature (20 2oC)] were 
applied for primary fermentation periods. The 
fermentation time, TSS and ethanol content of 
Rhodomyrtus tomentosa wine which were 
fermented at different temperatures are shown 
in table 4. At controlled temperature (20 2oC), 
the fermentation took place longer but 
produced good wine product with higher ethanol 
content (13.43% Vol.) and low residual sugar 
content. These results are in the line with 
previous study of Torija et al. (2002) which 
reported that at low temperature, fermentation 
started slowly, but consumed faster all the 
sugars because the high biomass of yeast was 
maintained throughout the process, as a result 
the high ethanol yield was obtained at lower 
fermentation temperature. 
In contrast, a shorter time of fermentation was 
observed at ambient temperature (28 2oC). In fact, 
this result agreed with previous reports 
(Nagodawithana et al., 1974; Casey et al., 1984) 
that illustrated a shorter fermentation period, 
lower ethanol content and high sugar content 
product was obtained throughout high temperature 
fermentation. These results have been explained in 
literatures as a decrease of yeast viability due to a 
greater accumulation intracellular ethanol at 
higher temperatures that produce cell toxicity, 
alter the structure of the membrane, and decrease 
its functionality (Lucero et al., 2000). 
3.3.2. Methanol 
Methanol content in Rhodomytus 
tomentosa wine was not effected by different 
fermentation temperature. The methanol 
content obtained from the wine fermented at 
ambient temperature and low temperature took 
account of 0.163 and 0.153 g/l ethanol 100% 
(Table 5), respectively. The result of Gnekow & 
Ough (1976) also indicated that a temperature 
difference between 60 and 70oF made little 
difference in the methanol content of the wine. 
3.3.3. Titratable acidity 
Titratable acid content of the wine 
fermented at low temperatures (5736 mg/l) was 
significantly different and higher than that at 
ambient temperature (4920 mg/l) (Table 5). 
According to Zamora (2009), the delay or 
fermentation can produce a greater amount of 
acetic acid. Thus, Rhodomyrtus tomentosa wine 
fermented at low temperatures may contain 
high amount of acetic acid which was, produced 
during long fermentation period. 
Table 4. Effect of fermentation temperature on ethanol content, 
residual sugar content of Rhodomyrtus tomentosa wine and total fermentation days 
Fermentation temperature Ethanol content (%Vol.) Residual sugar content (g/l) Total fermentation days 
Ambient temperature (28 2oC) 12.52a 6.9a 18 
Controlled temperature (20 2oC) 13.43b 4.6b 32 
Note: Mean of triplicates values in the same column with similar superscript letters are not significantly different (P > 0.05). 
Table 5. Quality parameters of Rhodomyrtus tomentosa wine after primary fermentation 
period (30 days at low temperature and 18 days at ambient temperature) 
Fermentation temperature Methanol (g/l 100% ethanol) 
Titratable acidity 
(mg/l) 
Ester 
(mg/l) 
Aldehyde 
(mg/l) 
SO2 
(mg/l) 
Ambient temperature (28 2oC) 0.163a 4920b 2200b 473.73a 29.01a 
Controlled temperature 
(20 2oC) 0.153
a 5736a 2769a 271.33b 24.75a 
Note: Mean of triplicates values in the same column with similar superscript letters are not significantly different (P > 0.05). 
Effects of yeast strains, pH and fermentation temperature on wine made from Rhodomyrtus tomentosa fruit (Mang 
Den, Kontum province) 
96 
Ester, aldehyde, and sulfite content 
In order to evaluate the effect of temperature 
on the production of secondary metabolites, the 
concentration of ester, aldehyde, and sulfite 
content were recorded. Low temperature is 
considered as an extra cellular stress, this could 
explain a higher ester production such as 
increasing floral (fatty acid ethyl esters) and fruity 
(fusel alcohol acetates) yeast aromas and 
maintained a high level of varietal aromas 
(terpens) (Beltran et al., 2008). The statistical 
analysis illustrated that the concentrations of 
ester were higher in wine fermented at low 
temperature (2769 mg/l) than that at ambient 
temperature (2200 mg/l) (Table 5). 
Acetaldehyde contributes positive effect on 
the aroma of wines (Etievant, 1991). However, a 
beyond threshold of acetaldehyde was described 
as creating bad smell (Jackson, 1994). Aldehyde 
content in the Rhodomyrtus tomentosa wine 
fermenting under controlled temperatures 
(271.33 mg/l) was lower than at ambient 
temperature (473.73 mg/l) (Table 5). 
Sulfur compounds evolution during 
fermentation was not effected by temperature of 
environment. Sulfite concentration in wine 
fermented at ambient and under controlled 
temperature has similar level and not 
significantly different among them (29.01 and 
24.15 mg/l, respectively) (Table 5). 
The sulfite and metathol content in the 
Rhodomyrtus tomentosa wine derived from 
fermentation process at both temperatures met 
the requirement of Vietnamese standard for red 
wine (QCVN 6-3 2010/BYT). However, 
controlled temperature at 20 2oC is 
recommended for fermentation Rhodomyrtus 
tomentosa wine to obtain not only high ethanol 
content but also greater flavor of the final 
product. 
4. CONCLUSION 
Yeast s isolated from palm juice showed 
greater ethanol yield than isolates from 
pineapple juice, mixture of both isolated yeasts 
and commercial yeast during fermentation 
Rhodomyrtus tomentosa wine. At pH 3.6 and 
inoculation with yeast populations of 106 
cells/ml, the ethanol concentration produced 
ranged between 11.85 and 12.52% Vol. In 
addition, the wine obtained in these conditions 
had favorable colour. 
Low temperature fermentation (20 2oC) 
took longer time and produced high ethanol 
content (13.43% Vol.). The chemical criteria of 
wine such as methanol and sulfite 
concentrations met Vietnamese standards for 
red wine (QCVN 6-3 2010/BYT). Moreover, the 
total acid, ester and aldehyde contents were 
kept at low levels. 
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