regression equations, it is possible to predict by what day and at which concentration
the juice will have had the preferred acidity.
Table 2 Dynamics of lactic-acid accumulation
Sugar
concentration, %
Titrated acidity, %, after fermentation (full days)
1
2
3
4
5
0,1
0,02
0,05
0,07
0,1
0,22
0,2
0,02
0,08
0,10
0,21
0,34
0,3
0,02
0,11
0,14
0,3
0,47
0,4
0,02
0,24
0,27
0,36
0,62
0,5
0,02
0,17
0,19
0,4
0,7
0,6
0,02
0,20
0,22
0,47
0,8
0,7
0,02
0,22
0,25
0,5
0,93
0,8
0,02
0,25
0,28
0,62
1,1
0,9
0,02
0,28
0,32
0,7
1,3
1,0
0,02
0,37
0,46
0,82
1,5
Figure 1. Dynamics of lactic acid accumulation (according to the content of
titrated acidity) depending on the concentration of sugar in the substrate
The concentration of titrated acids on lactic basis was varying throughout the
fermentation period, which proceeded in a straight-line correlation, which was
confirmed by the correlation coefficients: R2 = 0.98 and 0.99 and by losses of dry
substances (Figure 1).
As it is depicted at Figure 2, fermentation activity of lactobacilli on the first and
second days is much higher than that in subsequent days. This is evidenced by a
decrease in the concentration of dry soluble substances due to sugars' metabolisation.
Dry substances make up 70.4%, and on the 5th day there is only 58% of their initial
content. With increasing sugar concentration in the substrate, the activity of lactic-acid
bacteria also increases. In such a way, the substrate with 1% sugar concentration has
y = -0,0002x
2
+ 0,0302x + 0,0207
R² = 0,9992
y = 0,0048x
2
+ 0,0753x + 0,1773
R² = 0,9826
0
0,2
0,4
0,6
0,8
1
1,2
1,4
1,6
1,8
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1
1
T
it
ra
te
d
a
ci
d
it
y
,
%
Sugar concentration in the juice, %
2 days
5 days
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