Quality Changes of Naturally Fermented Kvass During Production

Abstract

Commercially available beverages sold as kvass are kvass drinks and malt extract drinks, made by diluting grain extract concentrates with water and adding colourings, different flavours and artificial sweeteners. Kvass quality parameters are defined by the Regulation No 926/2010 Quality and classification requirements for kvass and kvass (malt) beverage of the Cabinet of Ministers of the Republic of Latvia Naturally fermented kvass is made from rye bread rusks without additional additives. The aim of this research was to assess the quality changes of naturally fermented kvass during production stages. Experiments were carried out at the Latvia University of Agriculture Department of Food Technology. Dry matter (refractometer, ISO 6496), active acidity (LVS EN ISO 10523:2012) and sensory properties (25 panellists; line scale ISO 4121:2003) were analysed in kvass samples during production stages. During fermentation stage of naturally fermented kvass, pH drops from 4.08 to 3.77 and in later production stages pH is between 3.82 and 3.88, pH levels do not exceed the index values of the Regulation of the Cabinet of Ministers. Relative dry matter content reduced from 5.96% to 4.94%. Sensory evaluation showed that the intensity of flavour, aroma and acidity was most pronounced in kvass sample C (total production time 156 h), however, colour was most pronounced in kvass sample A (total production time 36 h). Longer maturation process aids in the formation of more robust flavour as well as yeast and protein residue.

Full text

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Ivo Lidums, Daina Karklina, Asnate Kirse
Department of Food Technology, Faculty of Food Technology, Latvia University of Agriculture, Liela Street 2, Jelgava, Latvia,
e-mail: ivo@riela.lv
Abstract
Commercially available beverages sold as kvass are kvass drinks and malt extract drinks, made by diluting grain extract concentrates
with water and adding colourings, different flavours and artificial sweeteners. Kvass quality parameters are defined by the Regulation
No 926/2010 Quality and classification requirements for kvass and kvass (malt) beverage of the Cabinet of Ministers of the Republic
of Latvia Naturally fermented kvass is made from rye bread rusks without additional additives. The aim of this research was to assess
the quality changes of naturally fermented kvass during production stages. Experiments were carried out at the Latvia University of
Agriculture Department of Food Technology. Dry matter (refractometer, ISO 6496), active acidity (LVS EN ISO 10523:2012) and
sensory properties (25 panellists; line scale ISO 4121:2003) were analysed in kvass samples during production stages. During
fermentation stage of naturally fermented kvass, pH drops from 4.08 to 3.77 and in later production stages pH is between 3.82 and
3.88, pH levels do not exceed the index values of the Regulation of the Cabinet of Ministers. Relative dry matter content reduced
from 5.96% to 4.94%. Sensory evaluation showed that the intensity of flavour, aroma and acidity was most pronounced in kvass
sample C (total production time 156 h), however, colour was most pronounced in kvass sample A (total production time 36 h).
Longer maturation process aids in the formation of more robust flavour as well as yeast and protein residue.
Keywords: kvass, dry matter, active acidity, sensory evaluation.
Introduction
Kvass is a non-alcoholic beverage that can be used
without restriction, its effects on the human body is
similar to kefir. This is due to lactic acid which is
formed by lactic acid bacteria (Costa et al., 2013).
Kvass has beneficial effects on the digestive tract (Feik
et al., 2010), furthermore energy value of naturally
fermented kvass is only 25 kcal (105 kJ) per 100 mL
(Costa et al., 2013). Kvass has thirst soothing and
diuretic properties.
Fermented bread kvass has the positive qualities of
beer, as well as minerals and vitamins. It contains more
than 30 minerals and trace elements. Kvass contains
such minerals as copper, phosphorus, potassium, zinc,
iron, and fluorine and B vitamins thiamine,
content of thiamine (B1) in naturally fermented kvass is
are no fat, cholesterol and nitrates in kvass. Most of the
beneficial substances come from the raw materials used
in naturally fermented kvass production rye bread
and malt.
Kvass is very low in sodium, so it promotes the
excretion of fluid and it can recommend instead of
other soft drinks for people who want to lower their
Commercially available beverages sold as kvass are
kvass drinks and malt extract drinks, made by diluting
grain extract concentrates with water and adding
colourings, preservatives, different flavours and
artificial sweeteners. The most commonly used
preservatives in soft drink production are benzoic acid,
Regulation No 926/2010 of Cabinet of Ministers of the
Republic of Latvia indicates that it is allowed to use
these raw materials if they comply with the
requirements set in food laws and regulations for kvass
production: spring water, drinking water, fruit juice and
puree, vegetable juice and puree, fruit juice
concentrate, sugar, kvass mash concentrate, bread
rusks, cereals, malt and grain products, raw plant
extracts, kvass concentrate, carbon dioxide,
compressed bakers' yeast or cultured yeast, honey,
sweeteners and flavourings (except in the production of
kvass), food additives.
Maximum cleanliness and hygiene conditions
associated with good manufacturing practice must be
provided during kvass production therefore stainless
Water quality affects the formation of kvass sensory
indicators. Kvass consistency is better if softer water is
used. Elevated sulphate content in the water causes
kvass to taste bitter, silicates interfere with the
fermentation process and causes sludge, chlorides lead
to unpleasantly sweet taste, iron and manganese affect
kvass colour and foaming (Hugenholtz, 2013).
Malt for kvass production is usually obtained from
spring barley, which has low levels of protein (8 11%)
and higher levels of starch which contains the
necessary sugars for fermentation. Germination of
grains activates the break down starch and proteins
during mash cooking (Sacher, 2013), thus obtaining
necessary nutrients for yeasts and lactic acid bacteria.
Rye bread rusks which are the basic raw material in
naturally fermented kvass production have a strong
flavour and sour taste. Rye bread rusks are obtained by
drying sliced or diced rye bread.
Bread yeast Saccharomyces cerevisiae is used for
kvass production; yeast cells cause intense ethanol
fermentation during anaerobic fermentation forming
alcohol and carbon dioxide. To control fermentation
and avoid formation of too much alcohol, oxygen is
supplied during this process (Birch et al., 2013).
Active lactic acid bacteria growth takes place
simultaneously with yeast cell growth during mash
fermentation; lactic acid bacteria produce lactic acid.

189
Bread kvass made from pure cultures of lactic acid
bacteria and yeasts is clearer and has increased
resilience. Yeast and lactic acid bacteria that give
refreshing taste and aroma are most commonly used.
(Dlusskaya et al., 2008) Malt extract and bread
fermentation process provides proteins, sugars, organic
acids and vitamins.
Usually, preservatives which extend shelf life are
added or kvass pasteurization is used. These processes
shorten production time and costs, and also impact
such sensory properties as taste and smell, as well as
biologically active compounds. Naturally fermented
kvass is made without preservatives and is not
pasteurized, thus saving the maximum quantity of
vitamins and minerals, as well as the flavour and
aroma.
Before the production of a new type of kvass it is
necessary to define sensory scores, which can
significantly affect consumer beverage choices.
Therefore the aim of this research was to assess the
quality changes of naturally fermented kvass during
production stages.
Materials and Methods
All analyses were completed at Microbiology Research
laboratory, laboratory of Sensory analyses and
laboratory of Bread technology at Latvia University of
Agriculture.
Kvass production
For the bread kvass production the following materials
were used: rye bread rusks (Ltd Liepkalni),
yeast Saccharomyces cerevisiae (Sp.z.o.o. Lallemand),
lactic acid bacteria Leuconostoc mesentericus (Ltd Chr.
Hansen), beet sugar (Ltd Dansukker) and dark malt
(Ltd Liepkalni).
To prepare 1 litre of kvass mash, 200 g of rye bread
rusks and 2 g dark malt were soaked in 2 litres of hot
water (78 ). Bread rusks were left to soak for
3 hours, then the water-bread rusk suspension was
filtered (300 microns) and the liquid fraction was
cooled down and used in further kvass production
stages.
of the estimated quantity of sugar were added to 1 litre
of kvass mash. The total quantity of sugar for kvass
production is 30 g; therefore 10 g of sugar were added
prior to fermentation. The fermentation of kvass mash
took 9 hours at 27
After fermentation kvass was placed in a refrigeration
. After cooling, the
yeasts were filtered (5 microns) and the remaining
sugar was added (blending). Kvass was maturated for
12 hours at 6 t was ready for drinking
(total production time 25 hours).
Afterwards kvass was filled in 0.5Ll plastic bottles and
stored for 156 h in total, in order to complete
physicochemical and sensory analysis. Technological
process of naturally fermented kvass production is
given in Figure 1. Shelf life of naturally fermented
kvass is 125 5 hours (about 5 days).
Figure 1. Technological process of naturally
fermented kvass production
Physicochemical analyses
The Regulation No 926/2010 defines such kvass
quality parameters:
1) dry matter content 3.0 to 14.0 percent by weight,
2) acidity 2.0 to 3.5, expressed as mL of 1N NaOH
per 100 mL.
Active acidity (pH) and dry matter content was
determined in kvass during 8 production stages
(Table 1). Active acidity (pH) was determined
according to the standard (AACC 02-31) and dry
matter was determined with table refractometer
according to the standard ISO 6496).
Microbiological analyses
Lactic acid bacteria were determined in kvass during
8 production stages (Table 1) according to the standard
LVS ISO 15214:1998.
Sensory analyses
Kvass samples were evaluated sensory by 25 trained
panellists (36% men and 64% women), average age
21 years.
Each panellist was served 3 samples of kvass in a
randomized serving sequence: kvass stored for 11 h
(sample A, total production time 36 h), kvass stored for
59 h (sample B, total production time 84 h), and kvass
stored for 131 h (sample C, total production time
156 h). Line scale was used to evaluate the intensity of
kvass sensory properties (aroma, flavour, acidity, and
colour) (ISO 4121:2003). Kvass samples for sensory

190
evaluation were chosen according to organoleptic
evaluation by research funder. Table 1
Stages of kvass production process
Stage
Materials and technological
process Time, h
S0 Rye bread rusks, before soaking 0
S1 Kvass after fermentation 12
S2 Kvass after blending 13
S3 Kvass after maturation 36
S4 Kvass during storage 60
S5 Kvass during storage 84
S6 Kvass during storage 132
S7 Kvass during storage 156
Data analyses
The obtained data processing was performed with the
Microsoft Excel 13 for Windows; arithmetic mean,
standard deviation and standard error were calculated
(Arhipova et al., 1999). For data cross-comparison
ANOVA, Regression and other statistical calculation
functions were used. Both t-test and F-test were used in
order to assess the significance of changes and inter-
comparison of the obtained data. For the interpretation
of the results it is assumed that with 95%
., 2011).
Results and Discussion
The changes detected in pH during kvass production
stages are given in Figure 2.
The numerical value of pH decreased slightly during
kvass fermentation; the initial pH was 4.08 and pH
after fermentation was 3.77. During the rest stages of
kvass production pH stabilized and was around pH
3.85. Compared to the indexed values of the
Regulation No 926/2010, pH value of laboratory
produced kvass corresponded to the regulatory scale
(experimentally determined conversion factor
approximately1.8). pH value did not decrease to
interval lower limit value (2.0 mL 1 N NaOH) in any
of the controlled production stages; at the end a trend
in pH increase was observed. The increase of pH in
kvass at the end of production stages could be
explained by the formation of new substances because
yeast and lactic acid bacteria cells gradually die.
A strong, negative correlation (r=-0.92) was observed
between pH and lactic acid bacteria count changes in
kvass. Correlation is significant (p<0.05) primarily
during the first three stages of kvass production
(Lidums, 2011).
During later stages, at the onset of lactic culture
gradual degradation and stabilization of pH, correlation
is weak and negative (r= -0.11). As pH is the logarithm
of H+ ion concentration, correlation is compared to the
logarithmic values of lactic acid bacteria count. A
moderate, negative correlation (r= -0.50) was observed
using pairwise correlation calculation between pH and
the absolute number of lactic acid bacteria.
Figure 2. Changes in pH and lactic acid bacteria
count during kvass production stages
S0 rye bread rusks, before soaking, S1 kvass after
fermentation, S2 kvass after blending, S3 kvass after
maturation, S4, S5, S6, S7 kvass during storage
During kvass production stages dry matter content (%)
experienced a slight decrease at the expense of volatile
fermentation product formation (mainly alcohol). At
times a rise in dry matter content can be observed at the
expense of increased fermentative microorganism total
cell count.
Decrease in dry matter content was found after
intensive fermentation stage (S1). Relative dry matter
content changed from 5.96% to 4.94%. Decrease in the
intensity of fermentation caused sedimentation of some
substances that were not fully included in the test
sample. In later stages of kvass production significant
changes on dry matter content were not observed
(p>0.05).
The changes in indicator value were characterized by
this polynomial division:
,
where y the dry matter content (%) after a certain
time, x fermentation, h.
The process is characterized by regression R2 = 0.99.
The first right-hand number in the division (1) is a very
low figure, so it can be dropped and the calculations
performed with a linear response without significant
mistakes:
where y the dry matter content, %; x fermentation,
h; S0 initial dry matter content, %.
It should be noted that the decrease in dry matter
content affects physical as well as chemical and
biogenic elements, so for each particular set of
circumstances of kvass production stages a calculation
formula must be found. In general form is looks like
this:
3.31
5.61
6.15 5.88
5.44
5.75 5.56 5.48
4.08
3.77 3.82
3.86
3.86
3.85
3.82
3.88
3.6
3.7
3.8
3.9
4.0
4.1
4.2
3.0
4.0
5.0
6.0
7.0
S0 S1 S2 S3 S4 S5 S6 S7
Kvass production stages
lg lactic acid bacteria
cfu per g pH
cfu g
-
1
pH

191
where k coefficient of proportionality, determined
with control measurements.
Changes in dry matter content during kvass production
stages are given in Figure 3.
Figure 3. Changes in dry matter content (%)
during kvass production stages
Dry matter content decreased during kvass
fermentation, as most of the dry ingredients and sugar
were used for yeast and lactic acid bacteria
development.
Since in kvass production normative documents no
strict parameters have been set for acidity (affects
flavour) and dry matter (affects clarity), solely the
recommended value intervals, many versions and
combinations (market brands) of kvass quality and
sensory properties are possible.
The intensity of sensory properties of three kvass
samples with different storage (total production) times
was evaluated (Fig. 4).
Figure 4. The intensity of kvass sensory properties
The results show that the intensity of aroma was most
pronounced in kvass sample C (total production time
156 h) and the least pronounced in kvass sample
A (total production time 36 h) (p=0.0230). This is due
to the fact that further maturation happens during
storage and longer storage time aids in stronger aroma
forming. Flavour intensity was most pronounced in
sample C (p=0.0430), this is due to the fact that further
maturation happens during storage and as in the case of
aroma, longer storage time also aids in stronger flavour
forming. Kvass sample A, which was stored for the
shortest time, was rated as having the most intense
colour (p=0.008). Further maturation aid in the
formation of sludge, yeast and protein residue which
gives a hazy, muddy colour; the intensity of colour in
sample C was the least pronounced.
Samples C and B (total production time 84 h) were
rated as having the most pronounced acidity.
Because of further maturation happening during
storage, yeasts left in kvass continue to ferment
remaining sugars, resulting in increased acidity.
Conclusions
During production stages, changes in active acidity
range from pH 3.77 to pH 4.08. Relative dry matter
content reduced from 5.96% to 4.94%.
Sensory evaluation showed that the intensity of
flavour, aroma and acidity was most pronounced in
kvass sample C (total production time 156 h), however,
colour was most pronounced in kvass sample A (total
production time 36 h). Longer maturation process aids
in the formation of more robust flavour as well as yeast
and protein residue.
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y = 5E-05x2 - 0.0148x + 6.0285
4.5
5.0
5.5
6.0
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0 24 48 72 96 120 144
168
Dry matter, %
Time, h
0
2
4
6
8
10
Aroma
Flavour
Colour
Acidity
A
B
C