| Abstract | Batat (Ipomoea batatas L.) je višegodišnja tropska vrsta iznimno velike nutritivne vrijednosti
korijena i lista. Pripada u skupinu funkcionalne hrane zbog značajne količine specijaliziranih
biljnih metabolita, antioksidativnih spojeva (vitamina, polifenola, karotenoida) i sadržaja
esencijalnih minerala, dijetalnih vlakana, uz niski glikemijski indeks korijena. Sastav i
koncentracija specijaliziranih biljnih metabolita su promjenjivi, zbog utjecaja genotipa,
ekoloških uvjeta uzgoja i gnojidbe, što predstavlja problem u proizvodnji povrća kao
funkcionalne hrane, od koje se očekuje ujednačena hranidbena i zdravstvena vrijednost. S
obzirom na povećan interes za proizvodnjom batata stabilne antioksidacijske aktivnosti te
malobrojne rezultate o toj problematici, uočena je potreba istraživanja utjecaja sorte i
rastuće gnojidbe posebice kalijem na komponente prinosa, udio polifenola i antioksidacijsku
aktivnost korijena i lista batata, u cilju dobivanja smjernica tehnologije uzgoja batata
povećanih nutritivnih vrijednosti i ujednačene kvalitete. S tim ciljem je u SZ Hrvatskoj na
Pokusno-pokaznom polju u Varaždinu, provedeno dvogodišnje istraživanje, radi utvrđivanja
smjernica tehnologije uzgoja batata veće funkcionalne vrijednosti. Tijekom 2008. i 2009.
godine postavljeni su istovjetni dvofaktorijalni poljski pokusi po metodi slučajnog bloknog
rasporeda u četiri ponavljanja. Prvi faktor je sorta u dvije razine (ʹBatʹ i ʹBoniatoʹ), i drugi
gnojidba dušikom i kalijem u tri razine (kontrolna gnojidba odnos N i K 1:1, druga razina
odnos N i K 1:2,5 i treća odnos N i K 1:5). Tijekom istraživanja s obzirom na sortu i rastuću
gnojidbu dušikom i kalijem ostvareni su u obje godine veći prinosi korijena m-2 (ʹBatʹ 2,78
do 4,67 kg i ʹBoniatoʹ 2,70 do 4,92 kg) i lista (ʹBatʹ 1,82 do 3,73 kg i ʹBoniatoʹ 3,68 do 5,33
kg) veći postotak K u korijenu (ʹBatʹ 1,49 do 2,34 % i ʹBoniatoʹ 1,20 do 1,81%) i listu (ʹBatʹ
2,22 do 3,20 % i ʹBoniatoʹ 2,72 do 3,68 %), veći postotak N u korijenu (ʹBatʹ 1,49 do 1,80 %
i ʹBoniatoʹ 1,55 do 1,83 %) i listu (ʹBatʹ 3,16 do 3,73 % i ʹBoniatoʹ 3,04 do 3,38 %),veći udio
krupnije frakcije korijena (ʹBatʹ 17,29 do 19,86% i ʹBoniatoʹ 9,61 do 17,79 %), veći udio
ukupnih polifenola korijena sorte ʹBatʹ (3,75 do 16,08 mg GAE g-1 st) i ORAC vrijednosti
korijena (ʹBatʹ 15,10 do 73,03 µmol TE g-1 st) i veći udio flavonoida u listu (ʹBatʹ 8,27 do
11,58 mg g-1 ST i ʹBoniatoʹ 9,59 do 20,61 mg g-1 ST), dok je udio ukupnih polifenola u listu
(ʹBatʹ 49,68 do 50,25 i ʹBoniatoʹ 51,77 do 53,31 mg g-1 ST) i ORAC vrijednosti (ʹBatʹ 402,50
do 422,17 µmol TE g-1 ST i ʹBoniatoʹ 439,90 do 474,96 µmol TE g-1 ST) bio veći u drugoj
godini istraživanja. Obje sorte su uz veću razinu gnojidbe dale veće prinose korijena i lista,
veći udio N, sirovih proteina, K, dok je udio ukupnih polifenola i antioksidacijska aktivnost
bila značajno veća u listu u odnosu na korijen kod obje razine gnojidbe. |
| Abstract (english) | Sweet potato (lat. Ipomoea batatas) is a vegetable species of extremely high nutritional
value of roots and leaves. It belongs to a group of functional foods because of the significant
amount of specialized herbal metabolites, antioxidants (vitamins, polyphenols, carotenoids)
and the content of essential minerals, dietary fibres, with low glycaemic root index.
Polyphenol compounds include a large group of specialized plant metabolites that
contribute to better organoleptic and nutritional components of vegetables and fruits.
Specialized secondary herbal metabolites are compounds synthesized in plants as
secondary metabolic products in the interaction of plants with agro-environmental
conditions. Specialized metabolites differ according to the chemical structure and their
function in the organism. In food, specialized metabolites are most often defined as natural
non-nutritional food ingredients, which have health-beneficial effects if consumed in
adequate quantities. Moreover, antioxidants play an important role in human nutrition due
to the strong function of protecting the body and boosting the immune system. By
consuming foods rich in antioxidants, we help the body fight against various diseases
caused by free radicals. The composition and concentration of specialized plant metabolites
are variable due to the influence of genotypes, ecological conditions of cultivation and
fertilization, which presents a problem in the production of vegetables as a functional food,
which is expected to have a consistent nutritional and health value. The functional value of
food is found in products that, besides basic nutritional value, have a positive effect on
human health, preventing and reducing the risk of developing certain diseases. Due to the
content of specialized metabolites, sweet potato is classified into functional foods because
besides being a good source of minerals and vitamins, it supplies the body with important
antioxidants. Antioxidants are produced in the cells or are introduced into our body through
food intake, and function in several ways: they prevent the formation of new free radicals in
the body, they destroy the radicals created in the body, or repair damage in the cells created
by the action of free radicals. Oxidative stress implies a shift of balance in cellular oxidationreduction
reactions in the direction of oxidation. Oxidative stress causes excessive
formation of free radicals of oxygen, resulting in the loss of balance in creating free radicals
and the inability of a cell to disintegrate them, and causing changes related to cell damage.
The root and leaf consumption of sweet potatoes is associated with various positive
physiological effects on health, such as antioxidant activity, ant mutagenicity, anti
cancerogenicity, antimicrobial activity, and antidiabetic effect. Functional values of the
sweet potato prompted producers to commercially breed sweet potato, as a new vegetable
crop in Croatia. Due to the increased interest in the production of sweet potato with stable
antioxidant activity and a small number of results on this problem, the need to investigate
cultivar influence and growing fertilization, especially potassium on yield components,
polyphenol concentrations and antioxidant activity of its root and leaf, has been recognized.
With this aim, a two-year research was conducted in the Experimental-demonstration field
in Varazdin to determine the guidelines for the breeding technology of equally balanced but
nutritional and functional values of the sweet potato. During 2008 and 2009, identical twofactor
polymorphisms were set up according to the method of randomized complete block
design with four repetitions. The first factor is the variety in two steps, and the second
fertilization with nitrogen and potassium in three steps. Two types of fertilization (ʹBatʹ and
ʹBoniatoʹ) and two increased fertilization levels (500 and 1000 kg ha-1 NPK 7:14:21) were
carried out with the addition of potassium salt K2SO4 to achieve a ratio of N:K 1:2.5 and 1:
5t. As a control variant, a lower fertilization level was used with the ratio N:K 1:1 with 250
kg ha-1 NPK 15:15:15. Transplant production with a lump of substrate in polystyrene
containers was organized in the protected area of the Department of Vegetable Crops of
the Faculty of Agriculture. Planting was carried out in mid-May, with 2 plants per m2 on
raised bed covered with PE film, or 40 plants per basic parcel of 20 m2. Sweet potato
transplants were planted manually on a 1.2 m spacing distance and a 0.4 m line spacing,
enabling 2 plants per square meter. Fertilization was performed prior to machine shaping
and setting of PE film. Temperatures and rainfall were monitored daily on CDA devices.
Thirty-sixty days after planting, leaves and stems were counted on each plot, and the length
of the stem and leaf area index was measured, while the total yield of leaf mass and root
was weighed at the end of the vegetation. After the roots’ transport and storage, individual
weighing of each root was performed, in order to calculate the share of individual root
fractions and the influence of variety and fertilization on root size and marketable yield. The
reference root and leaf sample were analyzed on the content of dry weigh, nitrogen,
phosphorus and potassium at the Faculty of Agriculture, while total and individual
polyphenols and antioxidant activity were analyzed at the Faculty of Food Technology at
the Department of Biochemical Engineering. During the study, the validity of varieties was
affirmed, along with fertilizers and their interaction on the amount of dry weigh in the leaf in
both research years (ʹBatʹ 5.97 to 7.34 %, ʹBoniatoʹ 5.81 to 7.29 %), on raw protein in the
leaf (ʹBatʹ 18.43 to 23.34 %, ʹBoniatoʹ 18.81 to 21.13 %), the total amount of N in the leaf
(ʹBatʹ 2.95 to 3.74 %, ʹBoniatoʹ 3.04 to 3.38 %), (ʹBatʹ 0.22 to 0.33 %, ʹBoniatoʹ 0.21 to 0.34
%), quantity of K in the leaf (ʹBatʹ 2.22 to 3.20 %, ʹBoniatoʹ 2.23 to 3.68 %). The values of
the antioxidant activity of the leaf and total polyphenols of the ʹBatʹ variety were growing
(80.07 to 121.27 μmol Trolox g-1 DW, that is 14.38 to 23.17 mg GAE g-1 DW in 2008 and
396.87 to 422 , 2 μmol TE g-1 DW, or 48.52 to 50.25 mg GAE g-1 DW in 2009) and the
ʹBoniatoʹ variety values were falling (in 2008, 126 to 104 μmol TE g-1 DW, ie 22,03 to 20,58
mg GAE g-1 DW and increased in 2009 to 396.38 to 474.96 μmol TE g-1 DW, that is 50.02
to 53.31 mg GAE g-1 DW). There were higher values of individual and total flavonoids in the
leaf (ʹBatʹ 8.27 to 11.58 mg g-1 DW and ʹBoniatoʹ 9.56 to 20.61 mg g-1 DW). In the roots,
bigger amounts of dry weigh were found in both research years (ʹBatʹ 14.50 to 25.28 %,
ʹBoniatoʹ 16.15 to 23.64 %), as well as raw protein in the root (ʹBatʹ 9.18 to 11.25 %, ʹBoniatoʹ
8.56 to 11.44 %), the total amount of N in the root (ʹBatʹ 1.47 to 1.80 %, ʹBoniatoʹ 1.37 to
1.83 %), the amount of P in the root (ʹBatʹ 0.15 to 0.28 %, ʹBoniatoʹ 0.19 to 0.27 %), the
amount of K in the root (ʹBatʹ 1.49 to 2.34 %, ʹBoniatoʹ 1.18 to 1.81 %). The values of the
antioxidant activity of root and total polyphenols of the Bat variety were growing (9.26 to
17.40 μmol TE g-1 fw, that is 2.30 to 4.32 mg GAE g-1 fw in 2008 and 48.73 to 61,56 μmol
TE g-1 fw, or 13.03 to 16.08 mg GAE g-1 fw in 2009). The values of the ʹBoniatoʹ variety were
falling (30.69 to 20.34 μmol TE g-1 fw, or 7.62 to 5.05 mg GAE g-1 fw in 2008, and in 2009
51.00 to 48.08 μmol TE g-1 fw, while polyphenols were growing 11.88 to 13.02 mg GAE g-1
fw). During the study, varying impact of variety and fertilization and their interaction with
morphological properties (length of stem, number of stems, leaf counts and leaf area index)
was determined, with ʹBoniatoʹ variety having significantly higher values compared to the
ʹBatʹ variety. The length of stem thirty days after planting (ʹBatʹ 27.68 to 29.90 cm, ʹBoniatoʹ
30.00 to 31.88 cm), number of stems (ʹBatʹ 1.57 to 1.80, ʹBoniatoʹ 1.63 to 1.80 ), number of
leaves (ʹBatʹ 21.93 to 25.78, ʹBoniatoʹ 28.88 to 40.45), leaf area index (ʹBatʹ 200.40 to 235.63
cm2, ʹBoniato ʹ263.93 to 369.73 cm2). The length of stem sixty days after planting was (ʹBatʹ
50.93 to 61.45 cm, ʹBoniatoʹ 59.83 to 63.78 cm), number of stems (ʹBatʹ 12.80 to 15.38,
ʹBoniatoʹ 15.40 to 18.28), number of leaves (ʹBatʹ 219.30 to 255.25, ʹBoniatoʹ 313.93 to
369.00), leaf area index (ʹBatʹ 2004.40 to 2330.70 cm2, ʹBoniatoʹ 2869.25 to 3305.95 cm2).
In both years, variety and fertilization interactions provided higher root yields per m2 (ʹBatʹ
2,78 to 4,67 kg and ʹBoniatoʹ 2,70 to 4,92 kg) and leaves (ʹBatʹ 1,82 to 3,73 kg and ʹBoniatoʹ
3,68 to 5,33 kg), a higher share of a larger root fraction (ʹBatʹ 17.29 to 19.86 % and ʹBoniatoʹ
9.61 to 17.79 %) and a higher share of the total marketable root (ʹBatʹ 89.78 to 91,12 % and
ʹBoniatoʹ 83.77 to 87.68 % in 2008 and in 2009 ʹBatʹ 78.1 to 86.57 % and ʹBoniatoʹ 87.80 to
90.95 %). Higher level of fertilization in both varieties gave higher roots and leaf yields,
higher percentage of dry weigh and crude protein, higher amounts of N, P and K, and bigger
quantities of larger roots fractions. Total and individual polyphenols and antioxidant activity
were variable (higher in ʹBatʹ variety and slightly lower in ʹBoniatoʹ variety), but significantly
higher in the leaf of both varieties compared to the root. |
