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The Bioactive and Mineral Compounds in Birch Sap Collected in Different Types of Habitats

Authors:

Abstract

Birch sap is used as a traditional drink and in traditional medicine in many countries in the northern hemisphere. However, there are scarce data on the antioxidant properties, nutrients and the mineral content of birch saps. In this study, the above-mentioned properties were analyzed in two different birch species Betula pendula Roth (silver birch) and Betula pubescens Ehrh. (downy birch) in various areas (suburban, traffic and industrial). The current study evidenced significant differences between the antioxidant, nutrition and mineral content depending on the type of habitat, not on species. It was shown that higher antioxidant properties, sugar and protein content were detected for silver birch sap from industrial area, which may be due to the response of plants to environmental stress. Moreover, heavy metals presenting in soil were not detected or detected at low concentrations in the sap. Birch sap can be used as a valuable natural beverage, which is especially important nowadays, when there is a pressure to minimize the use synthetic and artificial food ingredients.
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THE BIOACTIVE AND MINERAL COMPOUNDS IN BIRCH SAP COLLECTED /.../ D. GRABEK-LEJKO ET AL.
Introduction
In the olden days, the sap of spring trees was fre-
quently used in traditional medicine in forested areas of
northern hemisphere. In Europe, the main source of tree
sap was birches: Betula pendula Roth. (silver birch), Bet-
ula pubescens Ehrh. (downy birch) (Jones 2011, Svanberg
et al. 2012). Birch sap was known as valuable antidote
against scurvy, kidney, stomach and liver diseases, for
gall stones, skin diseases and as a nutritional drink. It was
used also in veterinary and as a cosmetic product – hair
conditioner. Nowadays, the birch sap has become more
and more popular as natural probiotic, after fermenta-
tion (Semjonovs et al. 2014). Its tapping is carried out
in Russia, Belarus, Ukraine, Latvia, Estonia and also in
Korea, Japan and China at large scales (Svanberg et al.
2012, Kūka et al. 2013). The best time for the birch sap
harvesting depends on geographical location, climate and
weather course. In central Europe it is late March and ear-
ly April, with later start toward the north. Generally, birch
tree can secrete sap from two to four weeks and its yield
depends on birch species (Kallio and Ahtonen 1989, Jiang
et al. 2001, Peev et al. 2010). Birch sap is a transparent
The Bioactive and Mineral Compounds in Birch Sap
Collected in Different Types of Habitats
DOROTA GRABEK-LEJKO1*, IDALIA KASPRZYK2, GRZEGORZ ZAGUŁA3,
AND CZESŁAW PUCHALSKI3
1University of Rzeszów, Department of Biotechnology and Microbiology, Zelwerowicza 4 St., 35-601 Rzeszów,
Poland
2University of Rzeszów, Department of Environmental Biology, Zelwerowicza 4 St. 35-601 Rzeszów, Poland
3University of Rzeszów, Department of Bioenergy Technology, Zelwerowicza 4 St. 35-601 Rzeszów, Poland
*Correspondence author: dorobek@o2.pl; phone: 0048 17 7855438.
Grabek-Lejko, D.*, Kasprzyk, I., Zaguła, G. and Puchalski, Cz. 2017. The Bioactive and Mineral Compounds in
Birch Sap Collected in Different Types of Habitats. Baltic Fo restry 23(1).
Abstract
Birch sap is used as a traditional drink and in traditional medicine in many countries in the northern hemisphere. However,
there are scarce data on the antioxidant properties, nutrients and the mineral content of birch saps. In this study, the above-mentioned
properties were analyzed in two different birch species Betula pendula Roth (silver birch) and Betula pubescens Ehrh. (downy birch)
in various areas (suburban, trafc and industrial). The current study evidenced signicant differences between the antioxidant, nutri-
tion and mineral content depending on the type of habitat, not on species. It was shown that higher antioxidant properties, sugar and
protein content were detected for silver birch sap from industrial area, which may be due to the response of plants to environmental
stress. Moreover, heavy metals presenting in soil were not detected or detected at low concentrations in the sap. Birch sap can be
used as a valuable natural beverage, which is especially important nowadays, when there is a pressure to minimize the use synthetic
and articial food ingredients.
Keywords: Antioxidants, Betula pendula, Betula pubescens, birch sap, minerals, nutrients, heavy metals.
or a slightly opalescent uid. It tastes similar to water and
is slightly sweetish (Peev et al. 2010). It contains many
bioactive compounds. The total amino acid concentration
ranges from 100–500 mg.L-1. Among free amino acids
glutamine, citrulline, glutamic acid, isoleucine, valine and
asparagine are the most often detected. They represent
92–96 % of the total amino acid content. Their concentra-
tions change during ow season (Kallio et al. 1985, Kallio
and Ahtonen 1989). In Japan, the maximum of the total
amino acid content of silver birch was above 50 mg.L-1
and reached this value at the end of the ow season (Jiang
et al. 2001, Jeong et al. 2012).
The total sugar content oscillates from 1% in Finland
and 2.5-2.6% in Poland. The dominant carbohydrates are
glucose and fructose. Their concentrations range between
2-5 g L -1 in equal proportions each of them representing
over 80% of total sugar. The content of sucrose is three to
ten time less than fructose or glucose content (Kallio et al.
1985, Kallio and Ahtonen 1987, Kūka et al. 2013, Łuczaj
et al. 2014).
Birch sap also contains valuable minerals. Calcium
and potassium occur in the highest concentrations. In Lat-
vian silver birch sap, the mean content of Ca ranged from
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41 to 150 mg L-1 and K from 41 to 142 mg L-1 (Kūka et
al. 2013, Vincēviča-Gaile 2014). In many samples, Zn,
Mg, Mn, Cu, Cd, Fe and Na were detected (Jeong et al.
2012, Kūka et al. 2013, Vincēviča-Gaile 2014, Bilek et al.
2015a). In Polish samples, the contents of these minerals
were lower and the variability between individual trees
was much higher (Bilek et al. 2015a).
The problem of the chemical composition of tree sap
was frequently investigated in the 80s and 90s of the 20th
century. Much less attention has been paid to the bioactive
properties (Klinger et al. 1989). Lee et al. (2009) observed
a weak inhibitory effect on microbial growth, as well as
phagocytosis-inuencing, antiphlogistic and antipyretic
activities. The question of impact of the type of habitat
on the nutrient and mineral content was also very rarely
investigated (Vincēviča-Gaile 2014). Due to the increas-
ing use of birch sap, an exact knowledge of its properties
seems to be justied.
This research was aimed to evaluate antioxidant
properties, nutrient and mineral content of fresh sap of
two birch species B. pendula Roth. and B. pubescens
Ehrh. The goal of this study was to verify the prelimi-
nary hypothesis that the type of habitats (like soils with
heavy metals content) and birch species affect the above-
mentioned properties. The purpose of this study was also
to evaluate whether birch sap, so popular lately, can be a
valuable natural beverage.
Materials and Methods
Sample collection
The study was conducted in three sites that differed
in terms of the type of habitats: industrial area (steel mill,
Ostrowiec), high trafc area (Rzeszów) and suburban area
(Zalesie). Birch sap was collected from 4-5 randomly
chosen individuals of B. pendula and B. pubescens. Soil
samples were taken from one soil layer (0-20 cm) close the
trees from which sap were harvested. The sampling was
carried out at the end of March and the beginning of April
2015. At a height of 30 cm of the trunk, small 8 mm diam-
eter holes were drilled, then, a plastic pipe (15 cm long and
8 mm in diameter) was put into the hole. Underneath each
pipe, a sterile plastic tube was placed (volume of 50 mL).
The tubes were closed after collecting the sap and then l-
tered with 0.45 µm lters and frozen at -80 oC till analysis.
Chemical analysis
Antioxidant activities
Antioxidant activities were determined by two meth-
ods: FRAP and ABTS. For ABTS determination, method
of Re et al. (1996) was used. The results were expressed
as µmoles of Trolox per 1L of birch sap.
A manual assay of ferric reducing/antioxidant power
(FRAP) was used based upon the methodology of Benzie
and Strain (1999). A standard Trolox solution was used
for the calibration curve and the results were expressed as
µmoles of Trolox equivalent per 1L of birch sap.
Total polyphenol content was measured using the
Folin-Ciocalteu colorimetric method (Singleton and Ros-
si 1965). The results were expressed as mg of gallic acid
equivalents (GAE) per 1L of birch sap.
Microbiological assay with Enterococcus hirae
ATCC™ 8043 was used for folic acid determination ac-
cording to Difco™ & BBL™ Manual, 2nd Edition. E. hi-
rae was added to the medium used for this analysis (Folic
Acid Assay Medium - FAAM). E. hirae cannot grow on
FAAM without addition of external folic acid. The addi-
tion of folic acid in specied increasing concentrations
gives a growth response that can be measured turbidi-
metrically. Briey, night culture of E. hirae (previously
washed tree times in order to remove all residues of folic
acid from the medium) was used for inoculation of FAAM
medium with increasing concentrations of folic acid (0-10
ng/10 ml for calibration curve) or with different concen-
trations of analyzed birch saps. After 24 h incubation at
37 oC, bacterial growth was determined turbidimetrically
at OD 660 nm. Concentration of folic acid was calculated
from the calibration curve.
Nutrients determination
Sugars (glucose, fructose, sucrose) were determined
reectometrically according to the appropriate manuals
of Merck Reectoquant®. Results were expressed as g of
sugar per 1L of birch sap. Proteins were determined ac-
cording to the Lowry method (Lowry et al. 1951). For the
calibration curve, bovine serum albumin was used. Re-
sults were expressed as mg of protein in 1L of birch sap.
Total calories were calculated as a sum of calories from
sugars and proteins, where proteins possess 4 kcal g-1 and
sugars 3.8 kcal g-1.
Minerals detection
Mineral elements were analyzed by an inducted cou-
pled plasma optical emission spectrometer (ICP-OES),
ThermoiCAP Dual 6500 (USA). Each time, the dilution
of 1 mL volume of birch sap lled up the tube to 10 mL
with deionised water was performed. For each of the ele-
ments, 3-point calibration curves were created. Selection
of appropriate length measuring line has been validated
by method of standard additions in amount of 10 ppb to
100 ppb give the recovery on selected lines above 98.5%
for each of the elements.
Soil samples were heated at 100 oC till constant
weight. Then 0.2 g of soil samples were lled up with
6 mL of 40 % HCl + 2 mL of HNO3. Microwave miner-
alization procedure with Milstone Ethos One Microwave
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Digestion System was used. After mineralization, samples
were lled up to 50 mL with demi water and used for min-
eral elements detection. Mineral elements were analyzed
with the aid of inducted coupled plasma optical emission
spectrometer (ICP-OES), ThermoiCAP Dual 6500 (USA).
Results were expressed as g per kg of dry soil sample.
Data analysis
The comparison of the means of the analyzed pa-
rameters of two species was tested by the parametric Stu-
dent’s T-test. ANOVA or Kruskall-Wallis test (nonpara-
metric) with appropriate post-hoc tests (Tukeya or Dunna
respectively) were applied to compare the means from
three sites. The type of statistical test was chosen after
analysis of the data distribution using Shapiro-Wilk test.
The statistical hypotheses were tested with α ≤ 0.05.
Results
Antioxidant activities
The in vitro antioxidant effect of the investigated
extracts was evaluated by the ABTS assay as a capabil-
ity of ABTS∙+ - compound possessing and antiradical ac-
tivity to scavenge free radicals and by the FRAP assay
as a capability of antioxidants to reduce Fe(III) to Fe(II)
(Liaudanskas et al. 2014). The results obtained from the
study of the antioxidant properties are given in Table 1.
It was shown that birch saps from Ostrowiec contained
the highest levels of antioxidants in comparison with saps
from Zalesie and Rzeszow. Antioxidant activities were
higher by about 45-80% for the FRAP and 54-64% for the
ABTS methods. Analysis of the variance allowed us to
prove that there are statistically signicant differences in
antioxidant activities between different localities of silver
birch trees. Antioxidant properties detected by FRAP and
ABTS methods are different between saps from the indus-
trial area (Ostrowiec) and the trafc area (Rzeszow), and
also between the industrial region (Ostrowiec) and the
suburban region (Zalesie). There are slightly but not sig-
nicant differences in antioxidant activities between saps
from Zalesie and Rzeszów (Table 1). Antioxidant proper-
ties were higher for silver birch sap, but the differences
were not statistically signicant.
Phenolic compounds
The total phenolic content of the birch saps was
estimated by using the Folin-Ciocalteu reagent. Table 1
summarizes that average concentration of total pheno-
lic compounds in birch saps varied widely ranging from
35.41 mg GAE.L-1 for silver birch from Zalesie to 55.15
mg GAE.L-1 for silver birch sap from Ostrowiec. When
comparing the concentration of phenolic compounds de-
pending on the locality, where sap was taken, there have
been revealed statistically signicant differences between
the industrial region Ostrowiec and the suburban re-
gion – Zalesie, which are in correlation with antioxidant
activities (Table 1). Authors did not detect statistically
signicant differences in phenolic compounds concentra-
tion between the birch species.
Folic acid concentration
Folic acid is one of the vitamins, which also possess
antioxidant activities. The highest values were obtained
from silver birch sap from Ostrowiec, and values subse-
quently decreased in the following order: silver birch
Zalesie < silver birch – Rzeszow < downy birch (Table 1).
Nutrients
Among sugars, which were analyzed, the lowest glu-
cose and fructose concentrations were detected for downy
birch sap and the highest ones for silver birch sap from Os-
trowiec. Differences between glucose concentrations are
from 36% to 55%, and for fructose concentrations from
24% to 60%. The concentration of sucrose is also the low-
est for the downy birch sap. Saps from silver birch trees lo-
calized in Rzeszow and Ostrowiec were the same in terms
of the sucrose content and the highest sucrose concen-
tration was detected for sap from Zalesie. However, it is
worth to state that the standard deviation in these samples
is very high. On the other hand, the highest protein con-
centration was detected for silver birch sap but differences
between the protein concentrations are quite low, around
6 – 12% (Table 1). Comparing the saps of the two birch
species, it can be stated that statistically signicant dif-
ferences were detected only in the content of glucose and
sucrose (Student’s T-test; p = 0.0014; Table 1). Birch sap is
a low-calorie diet beverage. Calorie content of silver birch
sap from suburban and industrial sites was in the range
from 29.95 to 47.68 kcal L-1, respectively, and the average
calorie content for downy birch sap is 39.45 kcal.L-1.
Minerals in the birch sap
Of all the investigated minerals, calcium presented
the highest content especially in the trafc area, where its
concentration was signicantly higher than at the other
sites (above 75%). In the industrial and suburban areas, its
concentrations were similar oscillating around 165 mg per
litre. Also, a quite high potassium content was noted. Its
concentrations ranged on average from 100 to 180 mg L-1.
Authors stated signicant differences in the potassium
concentration at sites with the lowest content in the sub-
urban area. Concentrations of manganese and zinc in sil-
ver birch sap were similar and on average ranged from 2
to 4 mg L-1. It was stated that concentrations of certain
microelements depended on the habitats. Mean concentra-
tion of sodium was the highest in the industrial area, and
of iron and phosphorus in the trafc one. Copper concen-
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trations differed at each of the habitats (Table 2). Silver
and downy birches differed in phosphorus and iron con-
tent, which were higher for the latter species (Student’s
T-test; 0.046, p = 0.0049 respectively; Table 2). In downy
birch sap, sodium was not detected. Concentrations of
cadmium, chromium, lead, nickel and aluminium were
below their levels of determination.
Species Sites
FRAP
Trolox
(µmoles.L-1)
ABTS
Trolox (µmoles.L-1)
Phenolic
compounds
Gallic acid (mg.L-1)
Folic acid
(µg.L-1)
Mean ± SD
Z 41.10±18.89a313.03±67.95a35.41±19.82a5.79±2.49ab
B. pendula Ra49.45±8.38a305.92±60.18a40.39±9.91ab 4.39±1.04a
O 71.95±15.51b481.36±73.83b55.15±15.89b7.10±2.43b
B. pubescens Rb40.00±14.62 294.32±46.44 38.13±7.26 3.93±1.83
Species Sites Glucose (g.L-1) Fructose (g.L-1) Sucrose (g.L-1) Proteins (g.L-1)
Mean ± SD
Z 5.23±3.47 5.36±2.95 0.63±0.71 0.272±0.105
B. pendula Ra4.72±2.09 4.82±1.82 0.28±0.12 0.272±0.117
O 5.38±1.11 6.23±3.11 0.28±0.19 0.287±0.130
B. pubescens Rb3.46±0.61 3.88±0.38 0.014±0.023* 0.307±0.073
Species Sites Ca (mg.L-1) K (mg.L-1) Mg (mg.L-1)
Mean ± SD
Z 169.270±68.987a107.366±58.401a18.635±11.538a
B. pendula Ra212.767±16.238b174.569±53.820b25.307±4.6107a
O 162.587±29.356a179.136±60.641b31.196±12.646b
B. pubescens Rb217.874±67.501 149.087±43.746 24.9627±6.642
Species Sites Zn (mg.L-1) P (mg.L-1) Na (mg.L-1)
Mean ± SD
Z 2.967±0.995a 7.008±2.054a0.266±0.359a
B. pendula Ra4.115±1.72a 23.522±7.447b 0.158±0.279a
O 3.243±0.775 a 19.916±6.124b 1.974±1.689b
B. pubescens Rb4.498±1.608 a 34.992±8.44* nd
Species Sites Cu (µg.L-1) Fe (mg.L-1) Mn (mg.L-1)
Mean ± SD
Z 0.048±0.019a0.198±0.042a 2.955±2.363
B. pendula Ra0.099±0.015b0.249±0.049b4.092±6.977
O 0.138±0.021c0.203±0.034a1.929±1.910
B. pubescens Rb0.089±0.020 0.304±0.089* 7.923±3.61
Table 2. Mean concentrations of chosen minerals for Zalesie (Z), Rzeszów (Ra – B. pendula ,Rb – B. pubescens) and Ostrowiec (O)
Notes: (a, b and c mark statistically signicant differences between the sites according to ANOVA or Kruskal-Wallis tests and post
hoc tests, α≤ 0.05;
* the statistically signicant differences between species according to Student’s t-test (with α ≤ 0.05).
Table 1. Mean concentrations of chosen parameters of antioxidants and nutrients for Zalesie (Z), Rzeszów (Ra – B. pendula ,Rb – B. pubescens)
and Ostrowiec (O)
Notes: (a, b and c mark statistically signicant differences between the sites according to ANOVA or Kruskal-Wallis tests and post
hoc tests, α ≤ 0.05;
* the differences between species according to Student’s t-test with α ≤ 0.05;
nd stands for “not detected”.
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Minerals in soil
It can be stated that soil samples from Ostrowiec dif-
fers from soil samples from other places containing high-
er concentrations of some elements. They are richer in Ca,
Zn, P, Ca, Cu, Fe and Na (Table 3). Among heavy metals,
Pb, Cd and Cr concentrations are higher in soil from Os-
trowiec too. Ni and Al concentrations are similar in all
types of soils varying from 0.01 to 0.024 and from 4.1 to
6.38 g kg- 1, respectively. Pb concentration is 5-11 times
higher than in soils from the trafc area, and more than
30 times higher than in soil from the suburban area. Cd
concentration is 20 times higher than in suburban area and
one soil from the trafc area was around 10 times higher
than in the soil from other trafc area. Cr concentration
is 1.5 times higher than in the trafc area, and 3.5 times
higher than in the suburban area. Heavy metals (HM) like
Ni, Pb, Cd, Cr, Al and Zn were determined in all analysed
soil samples. But it can be stated that in most cases HM
concentrations in soil from the industrial area (Ostrowiec)
were higher than from ones of the other localities.
Discussion
Nowadays, there is a tremendous resurgence in the
interest and use of natural healthy products, foods, me-
dicinal plants etc. According to the World Health Orga-
nization (WHO), as many as 80 % of the world’s people
depend on traditional medicine for their primary health-
care needs (WHO 1993, Škrovánková et al. 2012). The
number of consumers interested in healthy food continues
to grow, which corresponds with an increasing number
of health-food and specialty stores, in which different
healthy products are available (Briskin 2000). Birch sap
is an example of such a product that is becoming more and
more popular in Poland. It is available in special healthy
food stores but lately also in supermarkets, the advertising
campaign was extended in the popular media, and more-
over, there are more and more distributors and producers
of this product.
The present study quantitatively determined the con-
centration of bioactive and nutrition compounds as well
as mineral substances in saps obtained from two species
of birch trees, B. pendula (silver birch) and B. pubescens
(downy birch). We have attempted to nd out if there are
any differences in these parameters depending on the
birch species and localities (between the trafc, suburban
and industrial areas).
According to these studies, authors can easily detect
that antioxidant properties of saps from the industrial re-
gion are signicantly higher than those from the trafc
and suburban areas both for FRAP and ABTS methods,
respectively. It is known that different stress factors, en-
Sites Ca (g.kg-1) K (g.kg-1) Mg (g.kg-1) Zn (g.kg-1) P (g.kg-1)
Mean ± SD
Z 1.234±0.014a0.801±0.014a1.318±0.014a0.026±0.001a0.246±0.003a
Ra4.842±0.066b3.609±0.029b3.418±0.014b0.0797±0.000b0.607±0.014b
O 12.284±0.014c1.220±0.014c2.635±0.043c0.806±0.014c8.091±0.052c
Rb1.600±0.054d2.309±0.052d2.510±0.025d0.056±0.001d0.632±0.014b
Sites Na (g.kg-1) Cu (g.kg-1) Fe (g.kg-1) Mn (g.kg-1) S (g.kg-1)
Mean ± SD
Z 0 0.007±0.000a7.404±0.052a0.2696±0.001a0.059±0.001a
Ra0.097±0.003a0.023±0.003b17.229±0.076b0.382±0.014b0.287±0.001b
O 0.088±0.004b0.063±0.001c22.463±0.413c0.479±0.009c0.812±0.014c
Rb0.041±0.004c0.035±0.001d13.238±0.090d0.338±0.013d0.158±0.001d
Sites Ni (g.kg-1) Pb (g.kg-1) Cd (g.kg-1) Cr (g.kg-1) Al (g.kg-1)
Mean ± SD
Z 0.010±0.000a0.004±0.000a0.00009±0.000a0.015±0.001a4.100±0.025a
Ra0.024±0.001b0.029±0.001b0.0002±0.052b0.037±0.000b6.375±0.025b
O 0.016±0.001c0.138±0.001c0.00193±0.000c0.053±0.001c5.350±0.025c
Rb0.018±0001c0.012±0.000d0.00008±0.000a0.030±0.001d6.300±0.05b
Table 3. Mean concentration of chosen minerals in soil from Zalesie (Z), Rzeszów (Ra – B. pendula ,Rb – B. pubescens) and Ostrowiec (O)
Notes: (a, b and c mark statistically signicant differences between the sites according to ANOVA or Kruskal-Wallis tests and post
hoc tests with α ≤ 0.05;
* the statistically signicant differences between species according to Student’s t-test with α ≤ 0.05.
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vironmental pollution etc. causing oxidative stress are
connected with reactive oxygen species (ROS) formation.
Living organisms like plants possess several antioxidative
defense systems to scavenge toxic-free radicals in order
to protect themselves from the oxidant stress (Zeneli et al.
2013). It was reported that the tolerance of plants for oxi-
dative stressing conditions may be explained by the en-
hanced activity of antioxidative enzymes preventing cell
and tissue damage (Shi et al. 2006). Higher antioxidant
properties of saps from the industrial region may have re-
ected higher environmental stressing conditions in com-
parison with saps from other sites (Krishnaveni 2013).
Moreover, it was reported that antioxidant properties may
depend on the species or even individuals. Some plants,
growing near cement factory and exposed to cement dust
pollution, exhibited higher antioxidant properties than
control plants, but other species have a lower defense
system against cement dust pollution and lower antioxi-
dant potential than appropriate control plants (Mutlu et al.
2009). Therefore, higher antioxidant capacities of birch
sap from the industrial area can be explained as a high tol-
erance of birch to environmental pollution, manifested by
an increased content of antioxidants protecting the plant
against different environmental stresses. Therefore, in
theory, variations in antioxidant responses throughout the
life cycle occur, making the plant more or less susceptible
to seasonal variations in diverse environmental stressors.
Variations in the levels of antioxidants may also oc-
cur during the aging of the plant (Ferreira and Domingos
2012). The authors chose the trees randomly so this can
be an explanation for large differences in maximum and
minimum values of these parameters at one location. It is
difcult to compare results obtained in our study to oth-
ers because there is little information about antioxidants
in birch saps or researchers used different methods to es-
timate the antioxidant capacity with different standards,
incubation time and concentrations. Kūka et al. (2013) de-
tected the antioxidant concentration of Latvian birch saps
at 0.35 mg L-1 of quercetin equivalent.
It is known that the concentrations of phenolic com-
pounds in many plants are strictly correlated with their an-
tioxidant properties (Piluzza and Bullitta 2011, Jeong et al.
2013). Observed differences between the phenolic content
in analyzed saps showed that phenolic compounds were
important antioxidant components. Concentration of folic
acid along with antioxidant properties (Joshi et al. 2001)
is much higher in saps from the industrial region, which
means that in all methods used for antioxidant detection,
authors observed statistically signicant difference in their
concentration in saps from the industrial region compared
with saps from the trafc and suburban areas.
The formation and level of antioxidants may be sea-
sonality marked in response to changes in the environ-
mental conditions. This is plausible because the seasonal-
ity is reected in solar irradiation, photoperiod, tempera-
ture, relative humidity and actions of other meteorologi-
cal factors. Some authors also observed that antioxidants
concentration can be a response to the meteorological
characteristics of each season of the year (Ferreira and
Domingos 2012). The differences in the antioxidant con-
centration between localities can be explained by some
differences in the course of weather in 2015 during ow
season in different regions of Poland as well as the micro-
climate (Meteoblue Weather 2016).
Analyzing the sugar concentration, authors observed
that the saps contained mainly fructose and glucose, how-
ever, sucrose was also found in lower amounts. Sugar pro-
portions were similar to those found in northern Europe
and in Poland (Kūka et al. 2013, Łuczaj et al. 2014). Sug-
ar, protein and mineral concentrations obtained by other
authors were shown in Table 4.
These results are also similar to those detected by
Korean researchers for white birch sap (Jeong et al.
2012). They detected that its sugar content varied from
3.6 to 4.3 g L-1 and from 4.9 to 6.6 g L-1 for glucose and
fructose, respectively. In results presented in this paper,
glucose concentration was slightly higher for silver birch
sap from Zalesie and Ostrowiec. Polish silver birch sap
contains more glucose and fructose than birch sap pro-
duced in Lithuania and in Finland (Kūka et al. 2013). Glu-
cose and fructose concentrations in downy birch sap is
approximately 30 % lower than in saps from Polish and
Table 4. Concentration of sugars, proteins and selected minerals in birch saps
Parameter Object Analytical results Reference
Glucose (g·L-1)
B. pendula 3.6 to 4.3 Jeong et al. (2012)
B. pendula 9.3±3.9 Łuczaj et al. (2014)
B. pendula 3.55-4.96 Bilek et al. (2015b)
B. pendula 4.46±0.04 Kûka et al. (2013)
B. pubescens 1.99-3.016 Bilek et al. (2015b)
B. pubescens 9.6±2.9 Łuczaj et al. (2014)
B. platyphylla var. japonica 2.5 Jeong et al. (2013)
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Fructose (g·L-1)
B. pendula 4.9 to 6.6 Jeong et al. (2012)
B. pendula 5.39±0.05 Kûka et al. (2013)
B. pendula 12.1±4.9 Łuczaj et al. (2014)
B. pendula 4.03-4.77 Bilek et al. (2015b)
B. pubescens 13.5±3.3 Łuczaj et al. (2014)
B. pubescens 1.83-2.77 Bilek et al. (2015b)
B. platyphylla var. japonica 3.3 Jeong et al. (2013)
Sucrose (g·L-1)
B. pendula 0.07 Jeong et al. (2013)
B. pendula 0-1.509 Bilek et al. (2015b)
B. pendula 0.58±0.01 Kûka et al. (2013)
B. pendula 3.2±2.4 Łuczaj et al. (2014)
B. pubescens 3.1±1.4 Łuczaj et al. (2014)
Protein (mg·L-1)
B. pendula 127±2 Kûka et al. (2013)
B. platyphylla var. japonica 15-35 Jiang et al. (2001)
B. verrucosa 15-28 Jiang et al. (2001)
Ca (mg.L-1)
B. pendula 41.0-53.3 Kûka et al. (2013)
B.pendula 5.52 -17.28 Bilek et al. (2015)
B. pubescens 15.12±4.74 Bilek et al. (2015)
B. platyphylla var. japonica 25.82±0.12 Jeong et al. (2013)
Betula sp. 42 – 150 Vincēviča-Gaile (2014)
Cu (mg.L-1)
B. pendula 0.15-0.39 Bilek et al. (2015)
B. pendula 0-0.04 Kûka et al. (2013)
B. pubescens 0.48±0.42 Bilek et al. (2015)
B. platyphylla var. japonica 0.82±0.10 Jeong et al. (2013)
Betula sp. 0.02-0.03 Vincēviča-Gaile (2014)
Fe (mg.L-1)
B. pendula 0-0.1 Kûka et al. (2013)
B. platyphylla var. japonica 0.61±0.09 Jeong et al. (2013)
Betula sp. 0.05-0.11 Vincēviča-Gaile (2014)
K (mg.L-1)
B. pendula 10.56-23.76 Bilek et al. (2015)
B. pendula 41.1-66.4 Kûka et al. (2013)
B. pubescens 18.08±18.85 Bilek et al. (2015)
B. platyphylla var. japonica 30.10±4.81 eong et al. (2013)
Betula sp. 54 – 142 Vincēviča-Gaile (2014)
Mg (mg.L-1)
B. pendula 4.42-14.36 Bilek et al. (2015)
B. pubescens 13.82±5.55 Bilek et al. (2015)
B. platyphylla var. japonica 11.90±0.15 Jeong et al. (2013)
Betula sp. 0 Vincēviča-Gaile (2014)
Mn (mg.L-1)
B. pendula 0.5-0.52 Kûka et al. (2013)
B. platyphylla var. japonica 2.36±0.02 Jeong et al. (2013)
Betula sp. 0.11-6.16 Vincēviča-Gaile (2014)
Na (mg.L-1)
B. pendula 0.56-0.59 Bilek et al. (2015)
B. pubescens 0.55±0.62 Bilek et al. (2015)
B. platyphylla var. japonica 7.51±0.36 Jeong et al. (2013)
Betula sp.0Vincēviča-Gaile (2014)
Ni (mg.L-1)B. pendula 0-0.03 Kûka et al. (2013)
Betula sp. 0.02-0.16 Vincēviča-Gaile (2014)
Zn (mg.L-1)
B. pendula 0.88-1.85 Bilek et al. (2015)
B. pubescens 1.29±0.17 Bilek et al. (2015)
B. platyphylla var. japonica 3.82±0.47 Jeong et al. (2013)
Betula sp. 0.9-4.96 Vincēviča-Gaile (2014)
P (mg.L-1)Betula sp.3 - 41 Vincēviča-Gaile (2014)
S (mg.L-1)Betula sp. 5 – 12 Vincēviča-Gaile (2014)
Cr (mg.L-1)Betula sp. 0.02 Vincēviča-Gaile (2014)
Co (mg.L-1)Betula sp. 0.05 Vincēviča-Gaile (2014)
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Latvian silver birch (Table 4). In contrast to these results,
Łuczaj et al. (2014) did not detect signicant differences
in sugar concentrations between silver birch and downy
birch saps. It can be explained by the fact that the amount
of sugars in tree saps depends on many parameters. The
tree sap sugar concentrations can be affected by the time
of day, stage of ow cycle (beginning/end of the ow),
tree size, age and soil fertility, basal area of ray issue and
weather conditions in the year, or even shifts in gas con-
tents in the atmosphere.
Sucrose concentration in white birch sap detected by
Jeong et al. (2013) was 0.07 g L-1. For these sap, sucrose
concentration was at least four times higher than for sil-
ver birch sap localized in Rzeszow and Ostrowiec, and al-
most ten times higher than for sap from Zalesie. However,
authors observed a great variability between individuals.
On the other hand, sucrose concentration for downy birch
was ve times lower than those detected by Jeong et al.
(2013) (Table 4). For Latvian birch, the sucrose concen-
tration was about 0.58 g L-1, which is twice higher than for
B. pendula from the industrial and trafc areas and slight-
ly lower – around 10 % – than for sap from suburban area
(Kūka et al. 2013). Statistically signicant differences in
glucose and sucrose concentrations between species are
attributed to species factors.
Protein concentrations in our saps are at least twice
higher than those detected for Lithuanian birch saps
(Kūka et al. 2013). Japanese researchers also detected a
very low protein concentration for saps from white and
silver birches at a level of 15-35 mg L-1 depending on the
harvesting time (Jiang et al. 2001) (Table 4). As Łuczaj et
al. (2014) said, relatively high values of sugars in Polish
saps suggest that Poland may be a suitable place for de-
veloping the tree sugar industry.
Birch sap contains over a dozen minerals (Harju and
Hylden 1990). In many scientic works, the authors in-
dicated that among minerals cooper reached the lowest
concentrations, whereas calcium and potassium the high-
est ones (Kūka et al. 2013, Vincēviča-Gaile 2014, Bilek
et al. 2015a) (Table 4). Harju and Hylden (1990) noted
the concentrations of manganese, phosphorus and zinc ex-
ceeded 1 mg L-1. Presented results are in accordance with
them, however, we observed the great variability among
individual trees as well as the sites. It concerned mainly
sodium, what was also detected by Bilek et al. (2015a).
Bilek et al. (2015a) compared the mineral com-
pounds of the sap with the recommended daily allowance
for adults. According to their results, one liter of silver
birch sap covers up to 40 % of daily copper requirements,
zinc up to 17 %, calcium up to 2%, magnesium up to
3-4 % and sodium up to 0.04 %. The authors obtained
different results such as about 11 %, 30 %, 18 %, 8 % and
0.05 %, respectively.
The high variability could be affected by environmen-
tal and anthropogenic factors. In polluted areas, concen-
trations of certain minerals in plants increases (Vincēviča-
Gaile, 2014). The authors noted that the highest iron and
phosphorus concentrations were in the sap harvested from
the trafc and industrial sites. High concentrations of
heavy metals (HM) may negatively affect living organ-
isms, the ecosystems and human health. HMs presented
in soils may be transported through the food chain to the
human body and have a signicant toxic effect to people
(Butkus and Baltrėnaitė 2007, Yan et al. 2012). Harju and
Hylden (1990) found increased concentrations of Pb, Zn,
Ag and Cd in birch sap collected in polymetallic damps in
south western Finland. Generally, in study areas the con-
centration of minerals was higher in soil collected near
steel mill (Ostrowiec) and the lowest ones in soil from
suburban area (Zalesie) but authors did not detect any
connection between mineral concentrations in soils and
in saps. Among HMs only a few ones were detected in
saps. These results conrm that transport of many HMs
from soil to plant is not very active (Kandziora-Ciupa et
al. 2015). Lead is characterized by poor bioavailability
and therefore it was not found in saps. Also very toxic
cadmium was not transported from soils to saps. Copper
and zinc as trace elements are essential for proper metabo-
lism, growth and development of plants, but in the high-
est concentrations are toxic (Wierzbicka 2015). Authors
noted that in soil these elements were presented but their
concentrations in the saps were low. These results are very
important for potential consumer because, regardless of
the heavy metal soil contamination, birch sap is resistant
to toxic minerals.
Conclusion
Taking into account its chemical composition, birch
sap should be considered as a low-calorie diet supple-
ment, a good substitute for water: medium and high min-
eralized, which should contain at least 150 mg per litre of
macronutrients like Ca, K and Mg. In respect of miner-
als, antioxidant and nutrient properties the downy birch
sap is just as valuable as the sap of silver birch. Varia-
tion in chemical compounds may be caused by the type
of habitats and inter-individual variability. It seems that
birch sap is quite resistant to heavy metals present in soil.
Heavy metals concentrations in soil, as well as other en-
vironmental stresses such as pollutants of trafc origin
may cause higher antioxidant activity of birch sap. When
preparing to sap harvesting, the potential soil and air pol-
lution in sampling site should be taken into account.
THE BIOACTIVE AND MINERAL COMPOUNDS IN BIRCH SAP COLLECTED /.../ D. GRABEK-LEJKO ET AL.
2017, Vol. 23, No. 1 (44)
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2016, Vol. 22, No. 2 (43)ISSN 2029-9230
THE BIOACTIVE AND MINERAL COMPOUNDS IN BIRCH SAP COLLECTED /.../ D. GRABEK-LEJKO ET AL.
Acknowledgement
The work was partly supported by Cross-border
Cooperation Programme Poland-Belarus-Ukraine 2007-
2013, IPBU.03.01.00-18-452/11-00 and by the Polish
Ministry of Science and Higher Education (No 3020/
PBU/0755/11/13/2014/2). Responsibility for the content
of this publication lies solely with the authors and can-
not,underanycircumstances,beconsideredtoreectthe
position of the European Union in any way.
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Received 19 March 2016
Accepted 30 September 2016
THE BIOACTIVE AND MINERAL COMPOUNDS IN BIRCH SAP COLLECTED /.../ D. GRABEK-LEJKO ET AL.
2017, Vol. 23, No. 1 (44)
... In the boreal and hemiboreal regions, birch sap is directly tapped from native birch species, mainly from silver birch (Betula pendula Roth) and downy birch (Betula pubescens Ehrh.) [6,[8][9][10]. According to the Global Forest Resource Assessment [11], these birch species account for 11%-16% of the total volume of forest stands in Russia and Fennoscandia, approximately 17% in Lithuania and 24%-28% in Belarus and Latvia. ...
... In boreal forests, the best time for birch sap harvesting is from the beginning of March to early April. However, birch sap harvesting starts later in northern countries (e.g., northern Russia and Finland) [3,8,[12][13][14]. The increasing air temperature in the spring influences the metabolic level of living wood cells and thus affects the osmotic pressure of the water within the wood [15]. ...
... Numerous studies have confirmed that the quantity of harvested birch sap, as well as its physical and chemical properties, mostly depend on the birch species and the dendrometric parameters and can change during the harvesting period [8,[16][17][18][19]. However, knowledge of the influence of soil on birch sap quantity and quality is scarce. ...
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Birch sap is colourless or slightly opalescent and is traditionally drunk in spring. Currently, birch sap is becoming more important in the market sector as well as to pharmacy companies due to its biochemical composition and use in a wide variety of products. To extract good quality sap using birch resources in a sustainable way, there is a need to investigate the influence of the dendrometric parameters of birch trees and soil properties on the quantity and chemical composition of birch sap. This study is performed in five silver birch (Betula pendula Roth) forest stands growing in Histosol, Luvisol and Arenosol with different moisture and nutrient contents. The results indicated that the most productive silver birch trees for sap harvesting were taller than 28 m, had a diameter at breast height over 40 cm and a crown base height greater than 19 m. Additionally, the highest quantity of birch sap was harvested from trees growing in well-aerated mineral soils (Arenosol and Luvisol) with normal moisture content. However, the sweetest birch sap was harvested from trees growing in nutrient-rich organic (undrained peatland Histosol) and temporarily flooded mineral (Luvisol) soils.
... metabolites that were produced in the leaves during the growing season are stored in the trunk and roots [13]. The purpose of spring sap is to feed the buds that are opening by releasing nutrients that have been stored as lipids, proteins, carbohydrates, and minerals that the roots have taken up from the soil [12]. ...
... Birch sap contains oligosaccharides such as fructosyl/glucosyl-sucrose, gentiobiose, manninotriose and melibinose. Oligosaccharide levels fluctuate depending on the season and the dendrometric parameters [13]. Additionally, organic, and inorganic acids, specifically citric, succinic, phosphoric, and malic acids, are found in birch sap [21]. ...
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Species from Betula genus have been proven to have bioactive features, including anti-inflammatory, anti- carcinogenic and anti-rheumatic properties. They are either used for therapeutic or pharmacological purposes. There are a variety of types of products, from the well-known sap to tinctures or extracts, having different flavors, for a wider range of preferences. Thus, the purpose of this study was to compare the quality of liquid products produced from birch sap, from various companies and harvested naturally, in relation to the price of each product. This study required a thorough monitoring of prices over a period of several months, as well as qualitative and quantitative analyses. For the investigation of these indices, 6 types of products were used. The price rise research was conducted between November 2023 and January 2024, with 11 samples drawn from each type. All these tests reveal a link between the price of a product and its quality; thus, the more expensive products have a greater amount of sugar, which shows that the products have been preserved well.
... Harvesting and processing birch sap is a delicate and precise procedure that requires a careful understanding of the birch tree's biology and the optimal time to tap into its sap. Researchers have found that the chemical composition of birch sap depends on the type of birch habitat [8,9], the age of the birch tree, the daily sap volume, and the date of sap collection [10]. Typically, sap is harvested in early spring when the sap begins to rise and before the buds open. ...
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In this study, the qualitative changes in raw birch sap after freezing and thawing were determined. Ten-liter bottles and one-ton plastic containers with six replications were used for the freezing of birch sap and thawing of frozen sap. During and after the thawing, the physical and physical–chemical properties of the sap were measured. According to the results, as the ice melts, the concentration of acids and other soluble substances in the sap decreases, but changes in qualitative indicators indicate the beginning of fermentation processes through color changes and pH as the temperature of the melting sap becomes positive. As a result, to freeze raw sap in large-volume containers, it is necessary to develop fast thawing technology using auxiliary means—circulation, external energy sources, and mechanical ice crushing.
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The content of sugars was determined in the tree saps of six species from the Podkarpacie region. The experimental material included the silver birch sap (Betula pendula Roth.), downy birch sap (B. pubescens Ehrh.), hornbeam sap (Carpinus betulus L.), Norway maple sap (Acer platanoides L.), boxelder sap (A. negundo L.), and white willow sap (Salix alba L.). The qualitative analysis of sugars was performed using a high performance thin layer chromatography (HPTLC) method, and the quantitative analysis was carried out with the use of a high performance liquid chromatography method with light scattering detection (HPLC-ELSD). In the birch and the hornbeam saps, glucose and fructose prevailed and in the maple and willow saps: sucrose. The mean content of total sugars was as follows: 0.333 g/100 ml in the hornbeams saps; 1.109 g/100 ml in the boxelder saps; 0.897 g/100 ml in the silver birch saps; 0.672 g/100 ml in the white willow saps; 0.475 g/100 ml in the downy birch saps; and 1.083 g/100 ml in the Nowary maple saps. In the boxelder sap, the highest amount of total sugars was determined (1.214 g/100 ml), whereas in the hornbeam sap: the lowest amount of sugars (0.302 g/100 ml). The results of the silver birch analysis are the only ones that could be compared with the tree saps from the countries in Northern Europe and North America.
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There were analyzed tree saps of eight tree species: silver birch - Betula pendula, downy birch – Betula pubescens, common hornbeam - Carpinus betulus, Norway maple - Acer platanoides, sycamore maple - Acer pseudoplatanus, field maple - Acer campestre, boxelder maple - Acer negundo, and silver maple - Acer saccharinum). The contents of the following inorganic anions were determined: chlorides, nitrates (V), sulphates (VI), and phosphates (V) as well as of the following minerals: copper, zinc, calcium, magnesium, sodium, and potassium. The highest average content of chlorides (32.68 mg∙l-1) and sulphates (21.8 mg∙l-1) was determined in common hornbeam saps, whereas of magnesium (18.96 mg∙l-1) and calcium (30.52 mg∙l-1) in field maple saps. The highest average content of phosphates (114.53 mg∙l-1), copper (1.45 mg∙l-1), and nitrates (25.99 mg∙l-1) was detected in boxelder maple saps. The highest average contents of zinc (1.85 mg∙l-1) and sodium (0.59 mg∙l-1) were found in the silver birch saps. The Norway maple tree saps, in turn, were characterized by the highest average content of potassium (82.15 mg∙l-1). The results obtained were compared with the nutrition standards in force in Poland. They indicate that tree saps could be a valuable source of minerals, especially of copper and zinc, and to a lesser degree, of calcium, magnesium, and phosphorus. At the same time, it was reported that the ingredients showing a potentially adverse impact on human health, i.e. inorganic anions: nitrates(V), sulphates(VI), and sodium, present a negligible risk.
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This study was conducted to evaluate the effect combined with ultrafiltration (UF) and ultraviolet (UV) pasteurization on the qualityof white birch (Betula platyphylla var. japonica) sap during 40th day of storage at 4 and 25 °C. Some samples were treated with UF (apore size not more than 0.03μm) or UV independently and the other sample was treated with a combination of UF and UV devices.Total microbial number of control samples was 104CFU/ml. After treatment, they were 102CFU/ml in UF, 103CFU/ml in UV, and not detected in the mutually treatment of UF and UV devices. After treatment with a combination of UF and UV devices, the pH, total acidity, browning index, turbidity, and total microbial number were very stable until 40th day of storage at both 4 and 25 °C. Also in the UF, UV treatment independently, total acidity, browning index, turbidity, and total microbial number were increased lower than control, while the pH decreased during storage periods. Especially, in the UF, UV treatment independently, microbial number increased continuously, but in the combined consequences of UF and UV, those were not detected at all during 40th day of storage. Hence, combined consequences of UF and UV were considered as the effective method to improve the shelf-life of white birch sap.
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A method for the screening of antioxidant activity is reported as a decolorization assay applicable to both lipophilic and hydrophilic antioxidants, including flavonoids, hydroxycinnamates, carotenoids, and plasma antioxidants. The pre-formed radical monocation of 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS*+) is generated by oxidation of ABTS with potassium persulfate and is reduced in the presence of such hydrogen-donating antioxidants. The influences of both the concentration of antioxidant and duration of reaction on the inhibition of the radical cation absorption are taken into account when determining the antioxidant activity. This assay clearly improves the original TEAC assay (the ferryl myoglobin/ABTS assay) for the determination of antioxidant activity in a number of ways. First, the chemistry involves the direct generation of the ABTS radical monocation with no involvement of an intermediary radical. Second, it is a decolorization assay; thus the radical cation is pre-formed prior to addition of antioxidant test systems, rather than the generation of the radical taking place continually in the presence of the antioxidant. Hence the results obtained with the improved system may not always be directly comparable with those obtained using the original TEAC assay. Third, it is applicable to both aqueous and lipophilic systems.
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Birch sap is traditionally used as a refreshing beverage in the springtime in northern Europe. The aim of this study was to determine the suitability of birch sap for the growth of potentially probiotic Lactobacillus reuteri strains in order to develop a non-dairy functional beverage. All L. reuteri strains used in the study grew well in birch sap. pH values fell from an initial pH 6 to pH 4.20-3.18 characteristic for fermented products. Total acidity up to 36 T° and sufficient cell count was reached (6.79 cfu/ml). Glucose and fructose supplementation as well as their combination at a concentration of 0.5-1% did not significantly improve the growth of L. reuteri. Supplementation with 0.5-2% sucrose and a 2% glucose-fructose combination had a notable effect, although the latter had less effect than the former. Given that the viable cell count is the most important parameter of probiotic products, supplementation with sucrose was chosen as the best way to improve the substrate. The addition of sucrose stimulated biomass formation and improved acidification power, with the best results for sucrose 0.5-2%. Several other food grade supplements were evaluated to improve the growth of L. reuteri strains in 1% sucrose-supplemented birch sap. The best results were achieved using peppermint and malt extract supplements, which clearly indicate that L. reuteri growth in birch sap is limited not only by the availability of carbon but also by the availability of other growth factors present in the supplements used.
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The vegetal products harvested at spring time from the birch tree, known as spring elixirs, are the birch sap (Betulae limfa or succus) and the birch tree foliar buds (Betulae gemmae). This study was concerned in gathering information regarding the harvest process of the birch sap, organoleptic description of both the sap and foliar buds, as well as regarding diuretic and uricosuric activity (in vivo, on animal model) and the antiproliferative effect (phytobiologic test on Lepidium sativum grains). Diuretic and uricosuric activity of the birch sap is superior compared to the bud extracts and the antiproliferative activity evaluated through the inhibition of germination of Lepidium sativum grains, which can indicate a possible antitumoral activity of several dilutions of the birch sap and aqueous extract from birch foliar buds.
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This study evaluated the quality characteristics of white birch (Betula platyphylla var. japonica) sap with different collection times. The changes of browning index, turbidity, pH, total acidity, organic acid, free sugar, crude protein, crude ash, and mineral content were investigated. The browning index and turbidity increased from 0.076 to 0.222 and from 0.048 to 0.138, respectively, with increasing collection time. The pH decreased from 6.09 to 4.72, while total acidity increased with increasing collection time. Citric and malic acids were detected and malic acid increased with increasing collection time. Glucose and fructose as free sugars were detected and their contents were 0.364~0.433% and 0.497~0.664%, respectively. Crude protein and crude ash contents remarkably increased from 3.40 to 32.37 mg% and from 0.01% to 0.04%, respectively, with increasing collection time. Cu, Fe, Ca, Mg, Mn, and K were detected, and increased with increasing collection time. Particularly, K increased remarkably from 5.25 to 37.27 mg/L over time. These results indicate that the optimum processing method to improve the quality of white birch sap is necessary, because the quality of sap decreased as collection time increased, but nutritional value increased.
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Birch and maple saps contain carbohydrates and organic acids, B complex vitamins and vitamin C, tannins, flavonoids, glycosides and mineral substances. The aim of the study was to quantitatively determine the concentrations of bioactive compounds and mineral substances in Latvian birch (Betula pendula Roth.) and maple (Acer platanoides L.) saps. Electrical conductivity was determined (629 and 967 S/cm in birch and maple saps, respectively) to characterise the total amount of mineral substances. In birch and maple saps the titratable acidity (0.50 and 0.70 mmol of NaOH per litre of sap, respectively) and formol number (0.25 and 0.20 mmol NaOH per litre of sap, respectively) were determined. The protein concentration was found to be higher in maple sap (171 and 127 mg/l, respectively). The antioxidant concentration, determined using quercetin as a standard, was 0.35 mg of quercetin equivalents (QE)/l in birch sap and 0.77 mg QE/l in maple sap. In conclusion, Latvian maple sap contains more bioactive and mineral compounds than birch sap. Latvian birch sap contains up to 20% more glucose and fructose than birch sap produced in Finland, but Latvian maple sap contains 10 to 40% less sucrose than sap produced in North America.
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Pinus sylvestris L. and Betula pendula trees 29 Rapid urbanization, unregulated industrialization, growing transport in-tensity and agricultural activities have created a problem of heavy me-tal (HM) contamination worldwide. HMs are long-term contaminants with the ability to accumulate in soil and plants and have no natural way to be removed. Forests near local contamination sources have been subjected to HMs concentration measurements. Trees are HMs bioindicators capable to record HM concentrations in the environment in the past. In this paper, concentrations of HMs determined in wood trees were compared with phytotoxic, excessive, deficiency and naturally found HM concentrations in plants. Results of our investigation showed that HM concentrations in trees that grew in potentially contaminated areas did not exceed phytotoxic and excessive values of HMs found in plants. Concentrations of HMs in a wood of pines varied: Ni – 0. . The higher transfer of HMs to wood was associated with higher concentrations of HMs in tree environment (soil and nearby water bodies) and the function of some HMs as elements necessary for tree physiological processes. The values of HM transfer factors for trees were: Ni – 0.001–0.55; Cu – 0.04–0.45; Zn – 0.03–0.6; Mn – 0.001–0.75; Pb – 0.002–0.085; Cr – 0.005–0.11.