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Assessment of the Potential Use of Young Barley Shoots and Leaves for the Production of Green Juices

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It is possible to use the aboveground parts of barley, which are cultivated as a forecrop. They are often simply composted or dried for bedding. It is worth trying other more effective methods of processing aboveground biomass. The aim of this study was to preliminary investigate the possibility of using young barley leaves and shoots for the production of green juice with potential health properties. The material was collected at days 7, 14, 21, and 28 after plant emergence. The length and strength of the shoots were measured and the pressing yield was calculated. The pH value and the content of protein, chlorides, and reducing sugars were also determined. The juice was additionally subjected to pasteurisation and freezing, and changes in pH and chlorophyll content occurring during storage were determined. The pressing yield of young barley leaves and shoots was estimated to be between 69% and 73%. The product was characterised by a high content of total protein (34.45%–51.81%d.w.) and chlorophylls (6.62 mg·g−1). The chlorophyll content declined during barley juice storage. Pasteurisation of the juice from young barley leaves does not induce statistically significant changes in the pH of the juice, but reduces the chlorophyll content. Our results revealed that the most effective way to preserve the green juice is by freezing. This process does not induce changes in juice acidity and only slightly reduces the chlorophyll content during storage of the product.
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sustainability
Article
Assessment of the Potential Use of Young Barley
Shoots and Leaves for the Production of Green Juices
Agata Blicharz-Kania 1, Dariusz Andrejko 1, Franciszek Kluza 1, Leszek Rydzak 1,* and
Zbigniew Kobus 2
1Department of Biological Bases of Food and Feed Technologies, University of Life Sciences in Lublin,
20-612 Lublin, Poland
2Department of Technology Fundamentals, University of Life Sciences in Lublin, 20-612 Lublin, Poland
*Correspondence: leszek.rydzak@up.lublin.pl; Tel.: 81-531-9650
Received: 9 June 2019; Accepted: 19 July 2019; Published: 21 July 2019


Abstract:
It is possible to use the aboveground parts of barley, which are cultivated as a forecrop.
They are often simply composted or dried for bedding. It is worth trying other more eective
methods of processing aboveground biomass. The aim of this study was to preliminary investigate
the possibility of using young barley leaves and shoots for the production of green juice with potential
health properties. The material was collected at days 7, 14, 21, and 28 after plant emergence. The
length and strength of the shoots were measured and the pressing yield was calculated. The pH
value and the content of protein, chlorides, and reducing sugars were also determined. The juice was
additionally subjected to pasteurisation and freezing, and changes in pH and chlorophyll content
occurring during storage were determined. The pressing yield of young barley leaves and shoots
was estimated to be between 69% and 73%. The product was characterised by a high content of
total protein (34.45%–51.81%
d.w.
) and chlorophylls (6.62 mg
·
g
1
). The chlorophyll content declined
during barley juice storage. Pasteurisation of the juice from young barley leaves does not induce
statistically significant changes in the pH of the juice, but reduces the chlorophyll content. Our results
revealed that the most eective way to preserve the green juice is by freezing. This process does not
induce changes in juice acidity and only slightly reduces the chlorophyll content during storage of
the product.
Keywords: juice; barley; pressing; protein; chlorophylls; green food
1. Introduction
In order to improve the soil quality and protect it from weeds and, consequently, obtain a better
crop of the cultivated plant, producers often use forecrop cultivation. Depending on what kind of
plant will be grown, an appropriate forecrop will be selected. For cereals, the best options are root
crops (mainly potatoes), legumes, or rapeseed. However, when growing vegetables, such as tomatoes,
carrots, or white cabbage, it is better to use a cereal forecrop, and rye, wheat, or barley can be used [
1
].
These cereals can be used via two techniques. The first method involves ploughing whole plants and
using them as a fertilizer. Plants that are a forecrop can also be cut. Then, only roots and postharvest
residues are ploughed. In the case of the latter method, it is possible to continue using the green parts
of the plants, which are often simply composted or dried for bedding.
Recently, products from young barley leaves and shoots have gained popularity. They are
available in a variety of forms, i.e., juice, tablets, or powder. Young parts of plants are a source
of phenolic acids and many vitamins, e.g., C, E, and B group vitamins. Additionally, barley grass
contains substantial amounts of carotenoids, folic acid, calcium, iron, magnesium, potassium, zinc,
and copper. Importantly, products obtained from cereal leaves and shoots can be used as supplements
Sustainability 2019,11, 3960; doi:10.3390/su11143960 www.mdpi.com/journal/sustainability
Sustainability 2019,11, 3960 2 of 11
in a high-protein diet. Barley grass contains approximately 30% of protein in dry matter [
2
4
]. The
chemical index of nutritional value (Chemical Score, CS) is 41.44% (Methionine) [
5
]. Barley shoots and
leaves are also a source of chlorides. Naturally occurring chlorides exert a beneficial eect on organism
function. Chloride ions participate in the regulation of water, as well as electrolyte metabolism and
maintaining acid–base balance [6].
One of the most important active compounds in “green food” is chlorophyll. Seed plants contain
type A and B chlorophylls, which dier according to the type of substituent on the second pyrrole ring.
However, these pigments are unstable. Many factors, e.g., UV radiation or pH and temperature changes,
cause chlorophyll degradation in food products. Chlorophylls are a valuable source of magnesium;
they can also improve metabolism and eliminate unpleasant mouth odours. Additionally, they have
antibacterial and anti-inflammatory properties, remove toxins from the liver and blood [
7
11
], and
even act as a haemoglobin substitute [12].
The consumption of green juices has therapeutic properties: it exerts an antidiabetic eect, regulates
blood pressure, strengthens immunity, protects the liver, and has anti-acne and antidepressant activities.
It also improves the function of the digestive tract and prevents hypoxia, cardiovascular diseases,
fatigue, and constipation. Additionally, it alleviates atopic dermatitis and has anti-inflammatory,
antioxidant, and anticancer eects [
4
]. Kubatka et al. [
13
] have demonstrated positive changes in
tumour cells in rats treated with juice from young barley leaves. A significantly more pronounced
eect of the therapeutic treatment was observed in a study group receiving a diet supplemented with
the juice. It has also been confirmed that supplementation of the diet with barley leaf powder can
relieve the clinical symptoms of diabetes [
14
]. Additionally, barley grass contains substantial amounts
of dietary fibre (mainly an insoluble fraction), which has a positive eect on metabolism through
regulating the appetite and, thus preventing the development of overweight. Son et al. [
3
] recommend
enrichment of the diets of young children using valuable nutrients from young barley leaves.
Products from young barley leaves have been used in East Asia for a long time. Currently, they
are available in supermarkets, as well as online, in the United States and many European countries.
The increase in consumer awareness has contributed to an appreciation of the health benefits of
“green food” [
8
]. A number of products based on young cereal leaves are recommended as dietary
supplements and, hence, are currently being manufactured to be purchased in pharmacies.
There is a paucity of scientific publications confirming the health-promoting properties of the
juice from young barley leaves. There are also no preliminary investigations describing the impact of
production and processing on the quality of green juices. Furthermore, the relationship between the
date of raw material harvesting and the pressing process, as well as the content of nutrients—including
proteins—in the juice, has not yet been analysed. Another unexplored area is the changes occurring
in the chlorophyll content of barley juice, depending on the thermal treatment. Knowledge of these
relationships has great practical significance as it provides information on methods for the acquisition
of a product with a high nutritional value and, at the same time, ensures the longest possible growth
period for the plant (and, thus, the greatest mass of roots to be used as forecrop).
The aim of this work was to preliminary examine the eciency of the process of pressing green
juice from young barley leaves and shoots and to determine the chemical composition of the product
obtained. An additional goal of the research was to compare the eect of preservation methods like
pasteurization and freezing on the chlorophyll content and pH of barley juice.
2. Materials and Methods
2.1. Research Material
Barley grain cv. Kangoo was used for the investigations. The seeds, weighing 5 kg, were sown
under laboratory conditions (Figure 1). No fertilisation was applied during the cultivation. The
material was collected at days 7, 14, 21, and 28 after plant emergence. The crop area was divided into
four parts, and these four parts were then divided again into 12 smaller ones. Three parts from the
Sustainability 2019,11, 3960 3 of 11
whole field were chosen at random for each series of investigation (dierent harvest time: 7, 14, 21,
and 28 days). Each sample of shoots and leaves of young barley for juice production weighed 200 g.
Sustainability 2019, 11, x FOR PEER REVIEW 3 of 12
whole field were chosen at random for each series of investigation (different harvest time: 7, 14, 21,
and 28 days). Each sample of shoots and leaves of young barley for juice production weighed 200 g.
Figure 1. Cultivation of barley.
2.2. Measurement of Physical Properties
Samples without mechanical damage were selected for determination of the length and
strength of the barley. The length of five barley shoots was measured with the use of a calliper to the
nearest 0.01 mm. The shoot strength was determined by applying a uniaxial tensile test to the leaves.
The test was carried out using a Zwick/Roell Z0.5 materials testing machine (Zwick.Roell AG,
BT1-FR0.5TN.D14, Ulm, Germany) equipped with a measuring head at a maximum force of 50 N
(travel speed = 50 mm·min1). Tensile strength was applied to the material until rupture. TestXpert II
software (Zwick/Roell AG, Ulm, Germany) was used to assess the force required for destruction of
the barley grass.
2.3. Pressing
The juice was squeezed from barley grass (with a weight of 200 g for each repetition) using a
press designed for pressing green plant leaves, i.e., Manual Juicer BL-30 (BioChef, Byron Bay, NS,
Australia).
The pressing efficiency was calculated using the following equation:
𝑊
(%) = 𝑀
𝑀
∙ 100 (1)
where:
Wj—pressing yield, %;
Mj—mass of juice after pressing, kg;
Mi—mass of input material, kg.
2.4. Preserving Juice
The juice obtained in the first harvest term (at seven days after plant emergence) was
additionally subjected to pasteurisation for 10 min at 75°C and freezing. Immediately after the
thermal treatment, the product was cooled (in a blast chiller–freezer) to 3°C. The other batch of juice
was blast-frozen to a temperature of 18°C. The material was stored under appropriate conditions,
i.e., 4°C in the case of the unprocessed (UJ) and pasteurised (PJ) juice and 18°C in the case of the
frozen juice (FJ). The study material was analysed after three (UJ and PJ) and seven (UJ, PJ, and FJ)
storage days.
Figure 1. Cultivation of barley.
2.2. Measurement of Physical Properties
Samples without mechanical damage were selected for determination of the length and strength of
the barley. The length of five barley shoots was measured with the use of a calliper to the nearest 0.01 mm.
The shoot strength was determined by applying a uniaxial tensile test to the leaves. The test was carried
out using a Zwick/Roell Z0.5 materials testing machine (Zwick.Roell AG, BT1-FR0.5TN.D14, Ulm,
Germany) equipped with a measuring head at a maximum force of 50 N (travel speed =50 mm
·
min
1
).
Tensile strength was applied to the material until rupture. TestXpert II software (Zwick/Roell AG, Ulm,
Germany) was used to assess the force required for destruction of the barley grass.
2.3. Pressing
The juice was squeezed from barley grass (with a weight of 200 g for each repetition) using a press
designed for pressing green plant leaves, i.e., Manual Juicer BL-30 (BioChef, Byron Bay, NS, Australia).
The pressing eciency was calculated using the following equation:
Wj(%)=Mj
Mi
·100 (1)
where:
Wj—pressing yield, %;
Mj—mass of juice after pressing, kg;
Mi—mass of input material, kg.
2.4. Preserving Juice
The juice obtained in the first harvest term (at seven days after plant emergence) was additionally
subjected to pasteurisation for 10 min at 75
C and freezing. Immediately after the thermal treatment,
the product was cooled (in a blast chiller–freezer) to 3
C. The other batch of juice was blast-frozen to a
temperature of
18
C. The material was stored under appropriate conditions, i.e., 4
C in the case
of the unprocessed (UJ) and pasteurised (PJ) juice and
18
C in the case of the frozen juice (FJ). The
study material was analysed after three (UJ and PJ) and seven (UJ, PJ, and FJ) storage days.
Sustainability 2019,11, 3960 4 of 11
2.5. Determination of pH
Juice samples were placed in 50 mL beakers and the pH was recorded with a pH meter (model
780, Metrohm AG, Herisau Switzerland).
2.6. Measurement of Total Protein Content
The determinations were carried out using the Kjeldahl method and a Foss Kjeltec 8400 automatic
distiller (Foss Anatytical AB, Högan
¨а
s, Sweden). The total protein content was calculated using a
6.25 conversion factor.
2.7. Determination of the Chloride Content
The chloride content was determined with the Mohr method using a TitraLab AT1000 Series
automatic titrator (HACH Company, Willst¨аtterstraße, Germany). The solution was titrated with a
0.1 N silver nitrate solution. The chloride content was given as g in 100 gf.j. (of fresh juice).
2.8. Determination of the Content of Reducing Sugars
The Lane–Eynon method was used to determine the content of reducing sugars. The material was
extracted and deproteinised. The content of reducing sugars was determined in the obtained liquid by
direct hot titration of a specific copper salt with the analysed sugar solution (against methylene blue as
an indicator of the end of the reaction) [15,16].
2.9. Determination of Dry Matter Content
The moisture content of the research material was measured by drying 3 g of juice at 105
C for 3
h. The measurements were carried out in triplicate.
2.10. Measurement of Chlorophyll Content
The juice was analysed for the content of chlorophylls A and B. The pigments were extracted
with methyl alcohol. The chlorophyll content was measured using a UV–vis Helios Omega 3
spectrophotometer (Thermo Scientific, England). The measurement consisted of the determination of
the absorbance (A) at dierent wavelengths (
λ
): 650 and 665 nm [
17
]. Next, the content of chlorophylls
A and B and the total chlorophyll content were calculated with Equations (2)–(4):
Chlorophyll A content (Cchl(a)):
Cchl(a) =16.5·A(665) 8.3·A(650) (2)
Chlorophyll B content (Cchl(b)):
Cchl(b) =33.8·A(650) 12.5·A(665) (3)
Total chlorophyll content (C):
C=4.0·A(665) +25.5·A(650) (4)
where:
A(650) =absorbance at a 650 nm wavelength;
A(665) =absorbance at a 665 nm wavelength.
The chlorophyll content was calculated in mg·g1, taking into account the sample weight.
2.11. Statistical Analysis
The data were analysed statistically. A significance level of
α
=0.05 was assumed for inference. The
analysis was carried out using ANOVA (StatSoft Polska, Poland) with post hoc tests for homogeneous
Sustainability 2019,11, 3960 5 of 11
groups based on Tukey’s test. These groups comprised means between which no statistically significant
dierence was found at the assumed significance level, α.
The determinations were carried out in triplicate, except for leaf length and strength tests, which
were repeated five times.
3. Results and Discussion
3.1. Characterisation of the Physical Traits of the Raw Material
Changes in the length of the barley shoots relative to the harvest date are shown in Table 1.
Table 1. Properties of the raw material relative to the harvest time of barley leaf harvesting.
Harvest Time (Day) 7 14 21 28 p-Value
Length of leaves (mm) 9.08 ±1.14 a15.48 ±1.26 b17.58 ±1.44 bc 19.53 ±1.35 c<0.0001
Strength of leaves (N) 3.75 ±0.25 a3.27 ±0.45 ab 3.20 ±0.39 ab 3.01 ±0.69 b0.0144
a,b,c,d
Means in the same line denoted by dierent letters were significantly dierent. The results are expressed as
mean ±SD (n=5).
The largest gain in the length of barley shoots was noted within seven days after emergence. In
the following days, the rate of shoot growth declined. There were no statistically significant dierences
in the length of shoots between the material harvested at day 21 and day 28 after emergence. The
length of shoots collected on day 21 and day 28 was 17.58 and 19.53 cm, respectively. The height of the
plants was characteristic of unfertilised crops [1820].
The strength of the barley shoots decreased over time. However, there were only significant
changes in the tensile strength of the shoots in the material collected on day 28 of growth (in comparison
to the material collected on day 7). Changes in the strength of cereal shoots are associated with the
chemical composition, which is modified during plant growth [18].
3.2. The Pressing Eciency
The eect of the harvest date on the pressing yield is shown in Figure 2.
Sustainability 2019, 11, x FOR P EER REVIEW 5 of 12
The determinations were carried out in triplicate, except for leaf length and strength tests,
which were repeated five times.
3. Results and Discussion
3.1. Characterisation of the Physical Traits of the Raw Material
Changes in the length of the barley shoots relative to the harvest date are shown in Table 1.
The largest gain in the length of barley shoots was noted within seven days after emergence. In
the following days, the rate of shoot growth declined. There were no statistically significant
differences in the length of shoots between the material harvested at day 21 and day 28 after
emergence. The length of shoots collected on day 21 and day 28 was 17.58 and 19.53 cm, respectively.
The height of the plants was characteristic of unfertilised crops [1820].
The strength of the barley shoots decreased over time. However, there were only significant
changes in the tensile strength of the shoots in the material collected on day 28 of growth (in
comparison to the material collected on day 7). Changes in the strength of cereal shoots are
associated with the chemical composition, which is modified during plant growth [18].
Table 1. Properties of the raw material relative to the harvest time of barley leaf harvesting.
Harvest time (day)
7
21
28
p-value
Length of leaves (mm)
9.08 ± 1.14 a
17.58 ± 1.44 bc
19.53 ± 1.35 c
<0.0001
Strength of leaves (N)
3.75 ± 0.25 a
3.20 ± 0.39 ab
3.01 ± 0.69 b
0.0144
a,b,c,d Means in the same line denoted by different letters were significantly different. The results are
expressed as mean ± SD (n = 5).
3.2. The Pressing Efficiency
The effect of the harvest date on the pressing yield is shown in Figure 2.
714 21 28
Harvest time (day)
67
68
69
70
71
72
73
74
75
Pressing efficiency (%)
bb
c
a
p = 0.0004
Figur e 2. Pressing yield of the barley shoot and leaf juice relative to the harvest date.
The pressing yield ranged from 69.04% to 73.26%. It was obtained from 137 to 146 mL of juice
(depending on the time of harvest). The highest value was noted during the processing of material
harvested on cultivation day 21. The longer period of cultivation was associated with a statistically
Figure 2. Pressing yield of the barley shoot and leaf juice relative to the harvest date.
Sustainability 2019,11, 3960 6 of 11
The pressing yield ranged from 69.04% to 73.26%. It was obtained from 137 to 146 mL of
juice (depending on the time of harvest). The highest value was noted during the processing of
material harvested on cultivation day 21. The longer period of cultivation was associated with a
statistically significant drop in the pressing yield. The pressing yield of barley leaves collected on
day 28 was estimated at 69.4%. These results are consistent with data obtained by other authors.
Paulíˇckováet al. [2]
reported a pressing yield of 68% in a study that involved the extraction of juice
from barley shoots. The decline in the pressing yield accompanying the longer harvesting period is
probably caused by changes in the chemical composition, which lead to an increase in the fibre content.
3.3. Juice Acidity
Irrespective of the harvest date, the juice from the leaves and shoots of young barley had an acidic
reaction (changes in pH are shown in Figure 3), shown by the significant decrease in pH values over
time. The pH of the products pressed from leaves and shoots collected on day 7–28 ranged from 5.71
to 5.95. These values are similar to the pH of vegetable juices such as carrot or beetroot juice [2123].
Sustainability 2019, 11, x FOR P EER REVIEW 6 of 12
significant drop in the pressing yield. The pressing yield of barley leaves collected on day 28 was
estimated at 69.4%. These results are consistent with data obtained by other authors. Paulíčková et
al. [2] reported a pressing yield of 68% in a study that involved the extraction of juice from barley
shoots. The decline in the pressing yield accompanying the longer harvesting period is probably
caused by changes in the chemical composition, which lead to an increase in the fibre content.
3.3. Juice Acidity
Irrespective of the harvest date, the juice from the leaves and shoots of young barley had an
acidic reaction (changes in pH are shown in Figure 3), shown by the significant decrease in pH
values over time. The pH of the products pressed from leaves and shoots collected on day 728
ranged from 5.71 to 5.95. These values are similar to the pH of vegetable juices such as carrot or
beetroot juice [2123].
714 21 28
Harvest time (day)
5,5
5,6
5,7
5,8
5,9
6,0
pH (-)
a
b
c
d
p < 0.0001
Figur e 3. Impact of barley shoot harvesting time on juice pH.
The pH values of the juice from young barley leaves did not change significantly during storage
(Figure 4). The statistical analysis only revealed significant differences in the pH value in the case of
juice refrigerated for seven days. The pasteurisation and freezing processes did not change this
parameter significantly. Juice acidity has an important effect on pigments and other ingredients (e.g.,
chlorophyll, carotenoids, anthocyanins, myoglobin, etc.) responsible for the colour of fruits,
vegetables, and meat [21,2426].
Figure 3. Impact of barley shoot harvesting time on juice pH.
The pH values of the juice from young barley leaves did not change significantly during storage
(Figure 4). The statistical analysis only revealed significant dierences in the pH value in the case
of juice refrigerated for seven days. The pasteurisation and freezing processes did not change this
parameter significantly. Juice acidity has an important eect on pigments and other ingredients (e.g.,
chlorophyll, carotenoids, anthocyanins, myoglobin, etc.) responsible for the colour of fruits, vegetables,
and meat [21,2426].
Sustainability 2019,11, 3960 7 of 11
Sustainability 2019, 11, x FOR P EER R EVIEW 7 of 12
CP UJ 3rd day UJ 7th day PJ 3 rd day PJ 7th day FJ 7th day
Type of juice
5,5
5,6
5,7
5,8
5,9
6,0
6,1
pH (-)
a
bb
a
a
a
p < 0.0001
Figure 4. Impact of the conditions and length of storage on barley juice pH. (CPcontrol probe for
fresh juice, UJunprocessed juice, PJpasteurised juice, FJfrozen juice; 3rd dayafter three
storage days, 7th dayafter seven storage days).
3.4. Total Protein Content
Protein content was expressed as a percentage of dry matter, which was 4.71% on average.
Changes in the protein content of the analysed juices are shown in Figure 5. The total protein content
in the juice increased along with the barley harvest date. The differences in the protein content
between the harvest dates were statistically significant. The highest protein content, i.e., 51%, was
determined in samples collected on day 21. The statistical analysis revealed that the content of this
component in the juice produced after the next harvest (day 28) was significantly lower (42.68%). As
demonstrated by Paulíčkoet al. [2], the total amino acid content in juice from barley leaves and
shoots decreased over time. The highest protein content recorded for the Malz cultivar (collected in
phase IDC 29) was 30.44%d.m. However, it should be noted that the authors collected the raw
material at a later stage of barley growth. Therefore, these results may explain the lower protein
content in the juice from barley leaves and shoots harvested on day 28 of growth (in comparison
with the material obtained on day 21).
Figure 4.
Impact of the conditions and length of storage on barley juice pH. (CP—control probe for
fresh juice, UJ—unprocessed juice, PJ—pasteurised juice, FJ—frozen juice; 3rd day—after three storage
days, 7th day—after seven storage days).
3.4. Total Protein Content
Protein content was expressed as a percentage of dry matter, which was 4.71% on average.
Changes in the protein content of the analysed juices are shown in Figure 5. The total protein content in
the juice increased along with the barley harvest date. The dierences in the protein content between
the harvest dates were statistically significant. The highest protein content, i.e., 51%, was determined
in samples collected on day 21. The statistical analysis revealed that the content of this component in
the juice produced after the next harvest (day 28) was significantly lower (42.68%). As demonstrated
by Paul
í
ˇckov
á
et al. [
2
], the total amino acid content in juice from barley leaves and shoots decreased
over time. The highest protein content recorded for the Malz cultivar (collected in phase I—DC 29) was
30.44%
d.m.
However, it should be noted that the authors collected the raw material at a later stage of
barley growth. Therefore, these results may explain the lower protein content in the juice from barley
leaves and shoots harvested on day 28 of growth (in comparison with the material obtained on day 21).
Sustainability 2019, 11, x FOR P EER R EVIEW 8 of 12
714 21 28
Harvest time (day)
32
34
36
38
40
42
44
46
48
50
52
54
Protein(%d.m. )
d
b
a
c
p < 0.0001
Figur e 5. Changes in the protein content in barley shoot juice relative to the harvest date.
3.5. Chloride Content
The changes in chloride content in the analysed juices are shown in Figure 6. The chloride
content in the juices was positively correlated with the length of barley growth. The statistical
analysis demonstrated statistically significant differences in this parameter between the harvest
dates. The chloride content ranged from 0.021 to 0.117 g·100 g f.j. 1 for juice pressed from barley leaves
and shoots collected on days 728. The increase in the chloride content was clearly correlated with a
decrease in the pH of the juice. Park et al. [27] also showed that the amount of chlorides in the
aboveground parts of plants may depend on the type of fertilization used.
714 21 28
Harvest time (day)
0,00
0,02
0,04
0,06
0,08
0,10
0,12
0,14
Chloride s (g·100 gf.j.-1)
d
c
b
a
p < 0.0001
Figure 5. Changes in the protein content in barley shoot juice relative to the harvest date.
Sustainability 2019,11, 3960 8 of 11
3.5. Chloride Content
The changes in chloride content in the analysed juices are shown in Figure 6. The chloride
content in the juices was positively correlated with the length of barley growth. The statistical analysis
demonstrated statistically significant dierences in this parameter between the harvest dates. The
chloride content ranged from 0.021 to 0.117 g
·
100 g
f.j. 1
for juice pressed from barley leaves and shoots
collected on days 7–28. The increase in the chloride content was clearly correlated with a decrease in
the pH of the juice. Park et al. [
27
] also showed that the amount of chlorides in the aboveground parts
of plants may depend on the type of fertilization used.
Sustainability 2019, 11, x FOR P EER REVIEW 8 of 12
714 21 28
Harvest time (day)
32
34
36
38
40
42
44
46
48
50
52
54
Protein(%d.m.)
d
b
a
c
p < 0.0001
Figur e 5. Changes in the protein content in barley shoot juice relative to the harvest date.
3.5. Chloride Content
The changes in chloride content in the analysed juices are shown in Figure 6. The chloride
content in the juices was positively correlated with the length of barley growth. The statistical
analysis demonstrated statistically significant differences in this parameter between the harvest
dates. The chloride content ranged from 0.021 to 0.117 g·100 g f.j. 1 for juice pressed from barley leaves
and shoots collected on days 728. The increase in the chloride content was clearly correlated with a
decrease in the pH of the juice. Park et al. [27] also showed that the amount of chlorides in the
aboveground parts of plants may depend on the type of fertilization used.
714 21 28
Harvest time (day)
0,00
0,02
0,04
0,06
0,08
0,10
0,12
0,14
Chloride s (g·100 gf.j.-1)
d
c
b
a
p < 0.0001
Figure 6. Changes in the chloride content in barley shoot juice relative to the harvest date.
3.6. Content of Reducing Sugars
Changes in the content of reducing sugars are shown in Figure 7. Their highest content was
determined in the juice from barley leaves and shoots collected on day 21 of growth (
8.20 g·100 gd.m. 1
).
The dierences in the value of this parameter between products obtained from shoots collected on
days 14 and 28 were not statistically significant. The statistical analysis confirmed the lower content of
reducing sugars only for juice made from raw material collected on day 7. The study conducted by
Paul
í
ˇckov
á
et al. [
2
] showed that the content of simple sugars varied, depending on the plant growth
phase. Other factors that significantly determined the changes in the analysed parameter include
the conditions of the soil and the variety of barley. Paul
í
ˇckov
á
et al. [
2
] demonstrated that the sugar
content in most barley varieties steadily decreased throughout the growing season.
Sustainability 2019,11, 3960 9 of 11
Sustainability 2019, 11, x FOR P EER REVIEW 9 of 12
Figur e 6. Changes in the chloride content in barley shoot juice relative to the harvest date.
3.6. Content of Reducing Sugars
Changes in the content of reducing sugars are shown in Figure 7. Their highest content was
determined in the juice from barley leaves and shoots collected on day 21 of growth (8.20 g·100 gd.m.
1). The differences in the value of this parameter between products obtained from shoots collected
on days 14 and 28 were not statistically significant. The statistical analysis confirmed the lower
content of reducing sugars only for juice made from raw material collected on day 7. The study
conducted by Paulíčková et al. [2] showed that the content of simple sugars varied, depending on
the plant growth phase. Other factors that significantly determined the changes in the analysed
parameter include the conditions of the soil and the variety of barley. Paulíčková et al. [2]
demonstrated that the sugar content in most barley varieties steadily decreased throughout the
growing season.
714 21 28
Harvest time (day)
7,0
7,2
7,4
7,6
7,8
8,0
8,2
8,4
Reducing sugars (g·100 gd.m.-1)
b
a
ab a
p = 0.0170
Figure 7. Changes in the content of reducing sugars in barley shoot juice, depending on the harvest
date.
3.7. Chlorophyll Content
The chlorophyll content in the barley juice and the impact of the thermal treatment methods on
changes in this parameter are shown in Table 2. The content of chlorophyll A and B and the total
chlorophyll content changed significantly during storage. The highest determined content of total
chlorophylls, i.e., 6.62 mg/g, was found in fresh juice. The chlorophyll contents in fresh raw material
obtained by other authors ranged from 10.15 to 19.62 mg/g [28,29]. After seven days of storage, the
total chlorophyll content was reduced by 37.9% (UJ), 42.12% (PJ), and 2.43% (FJ), in comparison with
the untreated juice. It can thus be concluded from the present investigations that chlorophyll A is
more sensitive to heat than chlorophyll B. Similar findings were reported by Weemaes et al. [30],
who analysed the kinetics of chlorophyll degradation in thermally treated broccoli juice.
The process of freezing had the lowest effect on changes in the content of chlorophyll A and
total chlorophylls. By contrast, in the case of chlorophyll B, the least significant changes were noted
for the unpasteurised product refrigerated for one day and in the case of the frozen juice stored for
seven days. Paulíčková et al. [2] also confirmed the significant effect of thermal treatment of barley
leaf juice (freezing, drying, and freeze-drying) on changes in the nutrient content. The analysis of
Figure 7.
Changes in the content of reducing sugars in barley shoot juice, depending on the harvest date.
3.7. Chlorophyll Content
The chlorophyll content in the barley juice and the impact of the thermal treatment methods on
changes in this parameter are shown in Table 2. The content of chlorophyll A and B and the total
chlorophyll content changed significantly during storage. The highest determined content of total
chlorophylls, i.e., 6.62 mg/g, was found in fresh juice. The chlorophyll contents in fresh raw material
obtained by other authors ranged from 10.15 to 19.62 mg/g [
28
,
29
]. After seven days of storage, the
total chlorophyll content was reduced by 37.9% (UJ), 42.12% (PJ), and 2.43% (FJ), in comparison with
the untreated juice. It can thus be concluded from the present investigations that chlorophyll A is
more sensitive to heat than chlorophyll B. Similar findings were reported by Weemaes et al. [
30
], who
analysed the kinetics of chlorophyll degradation in thermally treated broccoli juice.
Table 2.
Changes in the chlorophyll content in juice from young barley leaves during storage in various
conditions (p<0.0001).
Type of Heat
Treatment/Ti-Me of Storage
Fresh
(Control Probe)
Unprocessed (UJ) Pasteurised (PJ) Frozen (FJ)
3rd Day 7th Day 3rd Day 7th Day
Chlorophyll A (mg·g1)4.80 ±0.01 a4.15 ±0.02c2.99 ±0.01 e3.80 ±0.00 d
2.83
±
0.015
f4.66 ±0.01 b
Chlorophyll B (mg·g1)1.53 ±0.00 a
1.51
±
0.00
bc 0.85 ±0.01 d1.50 ±0.00 c0.83 ±0.00 e1.51 ±0.00 b
Total chlorophylls (mg·g1)6.62 ±0.01 a6.02 ±0.04 c4.11 ±0.04 e5.72 ±0.02 d
3.83
±
0.007
f6.46 ±0.04 b
a,b,c,d,e,f
Means in the same line denoted by dierent letters were significantly dierent. The results are expressed as
mean ±SD (n=3).
The process of freezing had the lowest eect on changes in the content of chlorophyll A and total
chlorophylls. By contrast, in the case of chlorophyll B, the least significant changes were noted for the
unpasteurised product refrigerated for one day and in the case of the frozen juice stored for seven
days. Paul
í
ˇckov
á
et al. [
2
] also confirmed the significant eect of thermal treatment of barley leaf juice
(freezing, drying, and freeze-drying) on changes in the nutrient content. The analysis of their results
also allows for the conclusion that freezing exerts the weakest eect on the quality of the product.
Koca et al. [25]
demonstrated a faster rate of degradation of chlorophylls at a lower pH value (from 5.5
to 7.5). Hence, the significantly lower chlorophyll content of juice stored for seven days may be caused
by, e.g., changes in the pH of the product.
Sustainability 2019,11, 3960 10 of 11
4. Conclusions
The present investigations confirm the potential benefits of consuming green juice from young
barley shoots and leaves as part of a daily diet. The product obtained from the material harvested after
7, 14, 21, and 28 days of growth contains many valuable nutrients, e.g., a high level of total protein
(with CS =41.44 Meth). Additionally, high pressing yields of approximately 70% can be achieved.
The study has demonstrated that barley leaves and shoots harvested on day 21 of plant growth
are the best raw material for the production of juice. The process of pressing material collected at this
time exhibits the highest eciency, and the juice contains the highest levels of protein and reducing
sugars, as well as a high chloride content.
The most eective way to preserve the juice from young barley leaves is freezing. This process
does not induce changes in juice acidity and only slightly reduces the content of chlorophylls A and B
during storage of the product. Pasteurisation of the juice significantly reduces the chlorophyll content,
but does not induce statistically significant changes in the pH of the juice.
The reported results are a preliminary study on the topic. However, it is necessary to continue
research to determine the impact of other factors (e.g., barley varieties, growing conditions) on the
quality of juices from young barley shoots and leaves. It is also possible scale-up the experiment using
a higher number of samples, filed conditions, etc.
In addition, this way of using shoots and leaves of young barley will have economic importance.
The costs of obtaining raw materials for juice production will be reduced. The use of shoots and
leaves of young barley, which is grown as a forecrop, for the production of green juices, may have a
beneficial eect on the development of sustainable crop production. This will allow more ecient use
of the plants.
Author Contributions:
Conceptualization, A.B.-K., D.A., F.K. and L.R.; methodology, A.B.-K. and D.A.; formal
analysis, A.B.-K. and F.K.; investigation, A.B.-K. and L.R.; data curation, A.B.-K. and L.R.; writing—original draft
preparation, A.B.-K. and Z.K.; writing—review and editing, D.A.; visualization, A.B.-K.; supervision, D.A.
Funding: This research received no external funding.
Conflicts of Interest: The authors declare no conflicts of interest.
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2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access
article distributed under the terms and conditions of the Creative Commons Attribution
(CC BY) license (http://creativecommons.org/licenses/by/4.0/).
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Barley grass powder is the best functional food that provides nutrition and eliminates toxins from cells in human beings; however, its functional ingredients have played an important role as health benefit. In order to better cognize the preventive and therapeutic role of barley grass for chronic diseases, we carried out the systematic strategies for functional ingredients of barley grass, based on the comprehensive databases, especially the PubMed, Baidu, ISI Web of Science, and CNKI, between 2008 and 2017. Barley grass is rich in functional ingredients, such as gamma-aminobutyric acid (GABA), flavonoids, saponarin, lutonarin, superoxide dismutase (SOD), K, Ca, Se, tryptophan, chlorophyll, vitamins (A, B1, C, and E), dietary fiber, polysaccharide, alkaloid, metallothioneins, and polyphenols. Barley grass promotes sleep; has antidiabetic effect; regulates blood pressure; enhances immunity; protects liver; has anti-acne/detoxifying and antidepressant effects; improves gastrointestinal function; has anticancer, anti-inflammatory, antioxidant, hypolipidemic, and antigout effects; reduces hyperuricemia; prevents hypoxia, cardiovascular diseases, fatigue, and constipation; alleviates atopic dermatitis; is a calcium supplement; improves cognition; and so on. These results support that barley grass may be one of the best functional foods for preventive chronic diseases and the best raw material of modern diet structure in promoting the development of large health industry and further reveal that GABA, flavonoids, SOD, K-Ca, vitamins, and tryptophan mechanism of barley grass have preventive and therapeutic role for chronic diseases. This paper can be used as a scientific evidence for developing functional foods and novel drugs for barley grass for preventive chronic diseases.
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To enhance solubility and dispersibility of nutritional elements of barley grass for rehabilitation therapy, high-energy ball-milling was conducted to obtain nano-scale powder of barley grass. Ball-millings were performed at a temperature of <10 °C for 2, 4, 6, and 8 h respectively without N2 protection, while an additional ball-milling process was added for 8 h with N2 protection at the same temperature. After these ball-millings, properties of color, flavonoid, chlorophyll, flow ability, particle size, density, dietary fiber and hydration of barley grass powder were measured. As nano-scale powder of barley grass was obtained after 8 h, contents of flavonoid and chlorophyll without N2 protection were 3.21 g/kg and 14.23 g/kg, respectively; that with N2 protection were 5.34 g/kg and 19.64 g/kg. From start to 6 h, contents of flavonoid and chlorophyll, flowability and hydration decreased; yet bulk density and tapped density increased. Soluble dietary fiber content of nano-scale powder was elevated at 164 g/kg and TDF of nano-scale powder was 290 g/kg. Reverse trend of flowabilty and hydration occurred in nano-scale powder; and lightness and colors maintained well. Nano-scale barley grass powder manifests a fascinating performance of quality, hydration and nutritional properties. Ball-milling is a processing to make barley grass easy digestion for human body.
Article
Background: Young barley grass leaves are well-known for antioxidant substances of flavonoid and chlorophyll. However, low product quality and energy efficiency exist in dehydration of barley grass leaves. To improve energy supply and quality of barley grass, microwave heating instead of contact heat were applied for freeze drying of barley grass in pilot-scale at 1W/g, 1.5W/g and 2W/g, respectively; After drying, energy supply and quality parameters of color, moisture content, chlorophyll, flavonoids, odors of dried barley grass were determined for evaluating the feasibility of this study. Results: MFD allowed low energy supply and high contents of chlorophyll and flavonoids. Lightness value of 60.0, green value of -11.5, and energy supply of 0.61KW.h/g occurred in 1.5 W/g MFD; whereas drying time (7 hours) decreased by 42%, compared to contact heating. Maximum content of flavonoid and chlorophyll was 11.7g/kg and 12.8g/kg of barley grass. Microwave heat leads to odor change larger than that contact heat in freeze drying of barley grass. Conclusions: MFD retains chlorophyll and flavonoids, colors and odors of samples and decreases energy consumption in freeze drying barley grass.
Article
This study was conducted to investigate the proximate composition and antioxidative activities of young barley leaf(YBL). YBL powder(all w/w) was 2.98% moisture, 17.13% crude protein, 4.00% crude fat, 10.72% crude ash, and 65.17% carbohydrate. The contents of total, insoluble, and soluble dietary fiber were 36.62±2.33, 19.05±1.04, and 17.57±1.01g/100g, respectively. The essential and non-essential amino acids contained in the YBL powder accounted for 46.56% and 53.44% of the total amino acids, respectively. The major unsaturated fatty acid was linolenic acid. The ratio of polyunsaturated fatty acids to saturated fatty acids was 4.84. Only tartaric acid was detected. The contents of vitamins A, C, and E were 0.761, 398.05, and 0.936 mg%, respectively. The mineral contents of YBL powder were in the order of Na value for the DPPH radical scavenging of the YBL ethanol extract was 365.74±6.98mg/mL. The antioxidative index was high and was similar to that of t-butylated hydroxytouene. These results suggest that YBL can be recommended as a baby vegetable of high nutritional quality and antioxidative properties.
Article
This study examined the anti-diabetic effects of young barley leaf powder in rats with streptozotocin (STZ)-induced diabetes. Male Sprague-Dawley rats were divided into the non-diabetic (N) and diabetic groups, and fed the following for four weeks. The diabetic groups were further subdivided into three experimental groups: a diabetic control group (STZ), a diabetic group fed 5% barley leaf powder (STZ-BL), and a diabetic group fed 10% barley leaf powder (STZ-BH). Food and water intakes were higher in the diabetic groups than in the N group. Body weight gain was higher in the STZ-BL and STZ-BH groups compared with the STZ group, but there were no significant changes in body weight gain between the diabetic groups. The serum glucose and fructosamine levels were lower in the STZ-BL and STZ-BH groups than in the STZ group. The levels of serum insulin were higher in the STZ-BL and STZ-BH groups than in the STZ group. Serum ALT, AST and ALP activities decreased in the STZ-BL and STZ-BH groups compared with the STZ group, but there was no difference. These results indicate that dietary supplementation of barley leaf powder can attenuate clinical symptoms of diabetes in rats with STZ-induced diabetes.