the loss of dry soluble substances on the fifth day in amount of 34%, and that with 2%
concentration has an increase of these losses up to 39% due to sugar to acid conversion.
Figure 2. Dynamics of dry soluble substances' losses in the process of
fermentation
Consequently, sugar should be added in to freshly-gathered birch sap to activate
lactic fermentation with its small amount.
Influence of temperature on fermentation time and birch sap's transparency
It is known that both high and low temperatures effect the development of
bacteria. However, they can survive at low temperatures (up to freezing), when the
elevated ones (after 45°С) lead to a lethal reaction [5].
Some authors believe that homofermentative mesophilic lactobacilli reach their
most active development at a temperature of about 30°С, while others consider that
optimal temperature is 16...18°С [5].
Figure 3 shows a direct correlation of temperature influence on fermentation time
of birch sap.
Figure 3. Influence of temperature on fermentation time of birch sap
y = -0,0014x
2
-0,1094x + 1,172
R² = 0,9693
y = 0,0443x
2
-0,4677x + 2,538
R² = 0,995
0
0,5
1
1,5
2
2,5
1
2
3
4
5
D
ry
s
u
b
st
an
ce
s,%
Fermentation period, full days
Losses of dry substances after application of sugar in 1% concentration
Losses of dry substances after application of sugar in 2% concentration
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