Nutritional characteristics of kale populations from the Herzegovina region

Abstract

Kale is vegetable crop with high biological, nutritional and health values. Due to the high consumption of kale
in Herzegovina region, where the large number of local populations are traditionally cultivated, chemical
analyzes of leaf material have been carried out. To set up the field trial, the seed obtained from isolated selffertilized
inflorescence of collected original kale populations is used. Leaves were sampled in five harvests on
five representative plants of each population. Analytical methods have been determined the dry matter content,
ash, fat, protein, total and natural sugars and cellulose. Statistical analysis of the data showed that there are
significant differences in certain researched quality characteristics between self fertilized generations in
compare to original populations. The results certainly contribute to a better knowledge of the nutritional
properties of our native species of vegetables.

Full text

Works of the Faculty of Agriculture and Food Sciences, University of Sarajevo
Vol. LXI, No. 66/1
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NUTRITIONAL CHARACTERISTICS OF KALE POPULATIONS FROM THE HERZEGOVINA
REGION
Elma Sefo
1
, Zdravko Matotan1, Zrinka Knezović1, Anita Ivanković1, Katica Arar1
Scientific paper
Summary
Kale is vegetable crop with high biological, nutritional and health values. Due to the high consumption of kale
in Herzegovina region, where the large number of local populations are traditionally cultivated, chemical
analyzes of leaf material have been carried out. To set up the field trial, the seed obtained from isolated self-
fertilized inflorescence of collected original kale populations is used. Leaves were sampled in five harvests on
five representative plants of each population. Analytical methods have been determined the dry matter content,
ash, fat, protein, total and natural sugars and cellulose. Statistical analysis of the data showed that there are
significant differences in certain researched quality characteristics between self fertilized generations in
compare to original populations. The results certainly contribute to a better knowledge of the nutritional
properties of our native species of vegetables.
Key words: kale, nutritional characteristics, original populations, self fertilized generations
INTRODUCTION
Kale is considered as one of the highest-quality brassicas in terms of chemical composition. Younger and more
tender leaves of kale are used for human consumption and older leaves as fodder crop (Cartea et al., 2002).
Kale has a long tradition of cultivation and has an important place in the diet of the population in the northern
parts of Turkey (Ayaz et al., 2006), on the Pyrenean Peninsula (Velasco et al., 2007), southeast of the USA
(Olson and Freeman, 2007), and insular and coastal parts of Croatia (Batelja et al., 2009). Based on the
levels of protein and calcium in leaf, this vegetable with the common name Galega kale was assumed to be a
substitute of milk in the poorest rural areas of Portugal (Monteiro and Rosa, 2008). Vilar et al. (2008)
selected two kale landraces with the highest vegetable yield and the best nutritional qualities for human
consumption, which were significantly better than the best commercial varieties. Compared to other types of
vegetables, kale has a higher content of beta carotene and lutein (USDA, 2002). Kale leaves are rich in amino
acids (Lisiewska et al., 2008). In the Herzegovina region, kale is certainly the best known brassica with many
local populations and is an indispensable part of the traditional gastronomy. Previously described Herzegovinian
kale populations showed a high variability in individual morphological and agronomic traits (Sefo et al., 2011;
Knezovic et al., 2013).
MATERIALS AND METHODS
A field trial was carried out by the method of complete random design at the Jasenica site near Mostar. Seeds of
sixteen kale populations originating from different parts of the Herzegovina region were used as the material.
Seeds of the populations are the progeny obtained from isolated self-fertilised inflorescences of the original
populations collected in the previous year at the Buna site, where an analysis of morphological and agronomic
properties was carried out. Fifteen plants of each population in the phase of 4-5 true leaves were transplanted at
the inter-row spacing and inter-plant spacing within the row of 60 cm. Five harvests were carried out on five
representative plants of each population. One most typical leaf was saved from each representative plant from
each harvest, of which an average sample of five leaves was made for each plant. The following nutritional and
chemical properties were analyzed on samples of plant material using the analytical methods: the content of dry
matter (by drying in a thermostat at the temperature of 105°C), ash (by burning in a muffle furnace at the
temperature of 600°C), proteins (using the Kjeldahl method), total and natural sugars (Luff-Schoorl method), fat
(Weibull-Stoldt method) and cellulose (Gravimetric method). T-test was used to evaluate the significance of
1
Faculty of Agriculture and Food Technology University of Mostar, Bosnia and Herzegovina
Correspondence: Elma Sefo, Biskupa Čule bb 88000 Mostar, Bosnia and Herzegovina, e-mail: elma.sefo@sve-mo.ba

Nutritional characteristics of kale populations from the Herzegovina region
351
differences in qualitative properties between the average values of the tested initial populations and progeny
produced by self-fertilization grown at two sites.
RESULTS AND DISCUSSION
In order to contribute to the knowledge of the nutritional value of our native species Brassica oleraceae L. var.
acephala, chemical analyses of leaves were carried out. The results are also the first exact indicators of chemical
properties of Herzegovinian kale populations (Table 1).
Tab. 1. Chemical analyses of kale leaf (%)
Traits
Mean and range of 16 local populations (P1-P16)
Dry matter
11.85 (10.85-12.89)
Fat
1.65 (0.87–2.77)
Protein
20.62 (15.00–24.56)
Cellulose
13.00 (7.40–18.62)
Natural sugar
4.75 (3.45–6.88)
Total sugar
6.81 (3.98–10.18)
Ash
13.82 (12.69–14.81)
As shown in Table 1, the dry matter content was from 10.85% (P4) to 12.89% (P6) with the average of 11.85%
for all populations. The average protein content in all populations was 20.62% and the values of protein content
ranged from 15.00% (P5) to 24.56% (P12). The content of cellulose was from 7.40% (P8) to 18.62% (P6), while
the average cellulose content for all the populations was 13.00%. The ash content was from 12.69% (P11) to
14.81% (P7) with the average of 13.82% for all populations. The lowest content of total sugars was 3.98% (P4),
and the highest value was 10.18% (P12). The average content of total sugars for all populations was 6.81%.
Natural sugars were represented from 3.45% (P4) to 6.88% (P5) with the average of 4.75% for all populations.
The average content of fat was 1.65%, and the values ranged from 0.87% (P6) to 2.77% (P3). Comparison of
the results obtained before and after self-fertilization was carried out i.e. data from the Buna site, where initial
originally collected populations were grown in the previous year, and the Jasenica site, where the first
generation of progeny after self-fertilization was grown, were compared (Table 2), and the significance of
differences in qualitative properties between the average values of the populations at two locations was
evaluated by a t-test. The results of t-test (p 0.01) showed that there were significant differences in the content
of dry matter, ash, protein and total sugar (Table 3).
Lower average values of the content of protein, fat, natural and total sugars in the progeny obtained after self-
fertilization can be explained by inbreeding depression because kale is an allogamous plant, but also by climatic
conditions during the test. Similarly, significantly lower values of most of the studied agronomic and
morphological properties in relation to the plants of original populations were determined on plants of the same
populations grown from seeds produced by self-fertilization of isolated inflorescences (Sefo et al., 2011).
Tab. 2. Mean values of chemical characteristics of kale leaf in original populations and self fertilized
generations (%)
Chemical
characteristics
Dry
matter
Ash
Fat
Protein
Cellulose
Natural
sugar
Total
sugar
Original populations
10.50
12.78
1.69
22.36
12.80
5.43
13.97
Self fertilized generations
11.85
13.82
1.65
20.62
13.00
4.75
6.81
Chemical characteristics, primarily the content of dry matter, sugars and proteins, depend on climatic
conditions. The amount of proteins in brassicas increases in years with higher precipitation, while the amount of
sugars increases in dry conditions (Pavlek, 1978). Average values of the dry matter content (10.50%) were
lower in kale leaves of the original material in relation to the dry matter content (11.85%) in the progeny
produced by self-fertilization. Slightly higher average temperatures (16.1°C) and lower precipitation sum values
(1167 l/m2) were measured during the test with progeny produced by self-fertilization, which lead to an
increased content of dry matter.

E. Sefo, Z. Matotan, Z. Knezović, A. Ivanković, K. Arar
352
Tab. 3: t-test for the studied traits of the original populations of kale (the Buna site) and self fertilized
generations (the Jasenica site)
Trait
Dry
Matter
Ash
Fats
Proteins
Cellulose
Total
sugars
Natural
sugars
texp
8.18 **
3.27 **
0.47 n.s.
2.75 *
0.3 n.s.
11.35 **
1.78 n.s.
ttab 5%
2.13
2.13
2.13
2.13
2.13
2.13
2.13
ttab 1%
2.95
2.95
2.95
2.95
2.95
2.95
2.95
Sig.
0
0
0.65
0.015
0.77
0
0.09
It is the opposite with the content of proteins for which higher average values were established during the test
with originally collected populations when higher precipitation was measured (1394.8 l/m2) i lower values
average temperatures (15.2°C). Higher content of cellulose was found in all analyzed kale samples. Of all the
brassicas, kale has the highest cellulose content, followed by cauliflower and cabbage (Pavlek, 1978). Two
landraces of the acephala group had high content of protein (17.9% and 18.00%) (Vilar et al., 2008). Also, a
higher protein content in analyzed kale samples was established by Ayaz et al. (2006). According to the same
authors, the content of total sugars, defined as the sum of fructose, glucose and sucrose, was 3.961 mg 100 g-1 st.
CONCLUSIONS
High content of proteins, cellulose, natural and total sugars was found in leaves of all Herzegovinian kale
populations. Populations selected as the best are P3 with the highest fat content, P5 with the highest content of
natural sugars, P6 with the highest content of cellulose, and P12 with the highest content of proteins and total
sugars, which is considered positive in terms of nutrition quality.
Analyzing sixteen local kale populations that represent progeny produced by self-fertilization, lower mean
values in relation to parent populations were found for most properties as a result of inbreeding depression and
reduced vigor.
Selection of populations that are assessed as the best has a great practical significance for breeding procedures
in order to obtain improved varieties of kale and other brassicas.
Certainly a significant contribution of the research is in raising awareness of the nutritional and health value of
kale.
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