At a higher temperature, the fermentation of a certain amount of substrate occurs
much faster than at low temperature. Therefore, depending on the production needs
one can realign the fermentation process using temperature factor.
Experiments on determination the temperature for birch sap fermentation period
provided evidences for the findings of those researchers who recommended lower
temperatures. In such a way Figure 3 displays that the fermentation period increases
by one day in case of decrease in temperature by 5°С. At the same time, lactic acid's
accumulation (according to titrated acidity) increases to 0.35-0.45%. In addition, the
juice, fermented at a temperature of 30°С and 25°С, was less attractive in appearance
(than that one fermented at lower temperatures) due to its haziness. This can be
explained by the fact that during more active (rapid) fermentation the amount of
lactobacilli increases and enzymatic reactions do not stop.
The advantages of fast lactic fermentation include only the reduction of its
duration, while the disadvantages are the deterioration of the aroma, haziness,
emergence of mucous substances and active decay of L-ascorbic acid [4].
The effect of fermentation temperature on the transparency of fermented birch sap
is shown on Figure 4.
Figure 4. Effect of fermentation temperature on the transparency
of fermented birch sap
The regression equation evidently shows that there is a direct dependence between
fermentation temperature and transparency at correlation coefficient of 0.98.
Therefore, as a rule, the quality of fermented products with high fermentation
temperature is much worse than that fermented at low temperature. This can be
explained by the fact that pH-medium changes faster under the influence of lactic acid.
Technology of fermented birch sap production. The purpose was to extend
birch sap's storage life and time of its processing by conduction a preliminary
fermentation with pure cultures of Lactobacillus casei ssp. alactosus. Therefore,
according to our studies, the technology of fermented birch sap has the following stages
[3].
10
20
30
40
50
60
70
80
90
5
10
15
20
25
30
35
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Temperature, °С
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