Organic birch sap is delivered to the enterprises in the containers to which it is
being poured during the gathering. Birch sap is gathered to glass jars, with a capacity
not more than 10 dm3, or juice receivers, made of polymeric materials approved for
food contact by the Ministry of Health. Then the juice is merged into wooden barrels
with a capacity of 50 dm3, 100 dm3, 150 dm3, 200 dm3, metal churns for milk and
dairy products, and food tank trucks. Juice pouring is conducted using filters of two-
layered buttercloth or synthetic filtering fabrics.
Treatment of juice receivers, containers and auxiliary materials is carried out in
accordance with the standards [6].
The juice received for processing is sent to heat exchangers, vacuum machines or
cookers for pasteurization at a temperature of (80 ± 2)°С during (10 ± 1) minutes.
Fermentation is carried out in containers filled with juice up to the lid to prevent
mold and film yeast contamination. The starter culture of one of Lactobacillus casei
ssp. alactosus strains grown during a full day on sterile birch sap at a temperature of
(25 ± 1)°С is prepared to initiate lactic fermentation. Seed material is added in the
amount of 3% of the juice's volume. The juice is stored at room temperature in
hermetically sealed containers, to avoid the ingress of alien microorganisms, and
relative humidity of 75%.
Upon achievement of a total juice acidity of 0.3-0.6%, it can be transferred for
processing within three months.
Before transfer, the juice is filtered through two-layered buttercloth or filter cloth
and then fed for centrifugation using separators and afterwards filtered through filter
presses.
Filtration through filter presses is carried out at a pressure of 40 ... 160 kPa through
a filter carton of T grade. The first cloudy portion is collected separately and after
setting, it is filtered for a second time.
The technological scheme of fermented birch sap production is provided at Figure
5, and the process and hardware scheme is shown at Figure 6.
Determination of rational process parameters for birch sap fermentation. It
is necessary to investigate the regularities of fermentation process's kinetics to
determine the duration (τ) of birch sap fermentation, in which it is possible to provide
the necessary titrated acidity of birch sap based on lactic acid accumulation, depending
on initial concentration of sugars c
0
.
It is known that the fermentation process kinetics depends on many factors. Initial
concentration of sugar c
0
and fermentation process's duration τ are the most important
among them. It is desirable to conduct the fermentation process without heating the
juice, at room temperature, to reduce energy consumption.
From the literature [7] it is known that the kinetics of most biochemical processes
has a significant nonlinearity in duration, and can be described by various mathematical
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