Biomedical Engineering Reference
In-Depth Information
content of kvass varies and is influenced by the choice of ingredients, the mixture
of microorganisms, the duration and temperature of fermentation, as well as by
consumer preference. It can even be considered that kvass is spoiled if it contains
more than 1% of ethanol [
31,
32
] .
Before the nineteenth century, kvass production was limited only to private
homes. Rye bread was soaked in water and spontaneously fermented with yeast and
lactic acid bacteria. Several days of fermentation resulted in an alcohol concentra-
tion lower than 1.5 vol-%. Berries, fruits, herbs or honey can be added either before
or after fermentation to adjust the flavour. Because of the high sugar and low alco-
hol concentration, and the absence of pasteurisation, kvass was only enjoyed for
short periods of time and could not be stored [
31
] .
In the nineteenth century, most kvass producers specialised in particular raw
materials, leading to new flavours, such as apple, pear and peppermint kvass.
At the same time the growing urbanisation and industrialisation made homemade
kvass increasingly rare. In the 1960s, the success of the Coca-Cola Company
inspired the Russian government to assign chemists in Moscow the task of devel-
oping an economical method for kvass production. In the early years of industrial
production, the final product was filled and sold directly in large containers, which
were commonly situated on trailers on street corners and in market places. Now
the vast majority of kvass is sold in 1-3-l plastic bottles, which can be stored for
4-6 weeks [
31
] .
11.10
Sourish Shchi
Sourish shchi is a Russian beverage with a low level of alcohol (below 2.5 vol-%).
It was popular in Russia during the eighteenth and nineteenth centuries, but it is still
in production. The origin of this beverage is most likely linked to the appearance of
champagne in Russia as it required champagne bottles and a second fermentation.
The six components usually involved in the preparation of sourish shchi (shchi is
old Russian and means “six”) were three kinds of malt: barley, rye, wheat; one kind
of flour: wheat or rye; buckwheat and honey [
34
] .
In the beginning of the process, malted and unmalted grains are mashed sepa-
rately using hot water and then the two fractions are combined to produce a wort
(Fig.
11.4
). Fermentation starts spontaneously through the naturally occurring
microbes found on grains, in the vessels and in the air. The wort is allowed to stand
in a warm place for 12-24 h. Once the wort begins to ferment, there follows one or
more inoculations with a “special sour” culture (from the sediment of the vessel
from the previous fermentation). For example, Dankovtsev et al. [
34
] used
S. cerevisiae
,
S. uvarum
(
carlsbergensis
) and
S. minor
yeasts, as well as
L. brevis
as starter cul-
tures. The majority of the spontaneous sour inoculum in the experiments of
Dankovtsev et al. [
34
] consisted of wild and cultured yeast, such as the previously
mentioned starter strains, as well as
Saccharomyces oviformis
, and strains from the
genera
Torula
and
Candida
. The bacteria were identified as lactobacilli.
