Mineral Properties and Dietary Value of Raw and Processed Stinging Nettle (Urtica dioica L.)

Abstract

Stinging nettle (Urtica dioica L.) has a long history of usage and is currently receiving attention as a source of fiber and alternative medicine. In many cultures, nettle is also eaten as a leafy vegetable. In this study, we focused on nettle yield (edible portion) and processing effects on nutritive and dietary properties. Actively growing shoots were harvested from field plots and leaves separated from stems. Leaf portions (200 g) were washed and processed by blanching (1 min at 96–98°C) or cooking (7 min at 98-99°C) with or without salt (5 g·). Samples were cooled immediately after cooking and kept in frozen storage before analysis. Proximate composition, mineral, amino acid, and vitamin contents were determined, and nutritive value was estimated based on 100 g serving portions in a 2000 calorie diet. Results show that processed nettle can supply 90%–100% of vitamin A (including vitamin A as β-carotene) and is a good source of dietary calcium, iron, and protein. We recommend fresh or processed nettle as a high-protein, low-calorie source of essential nutrients, minerals, and vitamins particularly in vegetarian, diabetic, or other specialized diets.

Full text

Hindawi Publishing Corporation
International Journal of Food Science
Volume , Article ID , pages
http://dx.doi.org/.//
Research Article
Mineral Properties and Dietary Value of Raw and Processed
Stinging Nettle (Urtica dioica L.)
Laban K. Rutto,1Yixiang Xu,2Elizabeth Ramirez,3and Michael Brandt1
1Alternative Crops Program, Agriculture Research Station, Virginia State University, Petersburg, VA 23806, USA
2Food Processing and Engineering Program, Agriculture Research Station, Virginia State University, Petersburg, VA 23806, USA
3College of Agriculture and Life Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
Correspondence should be addressed to Laban K. Rutto; lrutto@vsu.edu
Received  February ; Accepted  April 
Academic Editor: Fernanda Fonseca
Copyright ©  Laban K. Rutto et al. is is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Stinging nettle (Urtica dioica L.) has a long history of usage and is currently receiving attention as a source of ber and alternative
medicine. In many cultures, nettle is also eaten as a leafy vegetable. In this study, we focused on nettle yield (edible portion) and
processing eects on nutritive and dietary properties. Actively growing shoots were harvested from eld plots and leaves separated
from stems. Leaf portions ( g) were washed and processed by blanching ( min at –∘C) or cooking ( min at -∘C)
with or without salt ( g⋅L−1). Samples were cooled immediately aer cooking and kept in frozen storage before analysis. Proximate
composition, mineral, amino acid, and vitamin contents were determined, and nutritive value was estimated based on  g serving
portions in a  calorie diet. Results show that processed nettle can supply %–% of vitamin A (including vitamin A as 𝛽-
carotene) and is a good source of dietary calcium, iron, and protein. We recommend fresh or processed nettle as a high-protein,
low-calorie source of essential nutrients, minerals, and vitamins particularly in vegetarian, diabetic, or other specialized diets.
1. Introduction
Stinging nettle (Urtica dioica L.)hasalonghistoryasone
among plants foraged from the wild and eaten as a vegetable
[,]. Although not fully domesticated, the species remains
popular even in the current era for food and medicine as
reported, for example, in Nepal [] and Poland [].
Despite U. dioic a being recognized as an edible and highly
nutritious vegetable, research attention has focused more on
its value as a source of alternative medicine and ber. Clinical
trials have conrmed the eectiveness of nettle root and
saw palmetto (Serenoa repens (Bart.) Small) fruit extracts
in the treatment of benign prostatic hyperplasia []. Dried
nettle leaf preparations are also known to alleviate symptoms
associated with allergic rhinitis [], and a technology for
granulating lipophilic leaf extracts for medicine has been
developed []. A recent report from ongoing work in Italy
conrms the potential of U. dioica as a sustainable source of
textile ber [].
ere are a number of reports that address the role of U.
dioica in human nutrition. Fatty acid and carotenoid content
in leaf, stem, root, and seed samples have been measured
[], and the properties of phenolic compounds in leaves,
stalks, and bers have been reported []. Furthermore, the
quality and safety [] and microbiological properties []
of sucuk, a Turkish dry-fermented sausage, incorporating
dried U. di oic a leaf have been studied, and the capacity
of nettle extracts to improve oxidative stability in brined
anchovies has been reported []. In the Basque region of
Spain, young shoots are reportedly eaten raw or included in
omelets []. In terms of postharvest processing for long-term
storage,microwavedryingatWwasfoundtobethebest
method for preservation of leaf color, energy consumption,
and processing time []. Mineral content []andtracemetal
concentrations [] in nettle leaf tea made by infusion or
decoction have also been determined.
However, nettle is consumed primarily as a fresh veg-
etable whereby it is added to soups, cooked as a pot herb, or

International Journal of Food Science
used as a vegetable complement in dishes. In this sense, more
work needs to be done on nutritive value of fresh nettle, and
thefateofmineralsandbioactivecompoundsinprocessed
products. is information is essential because the capacity
of fresh nettle to irritate bare skin may discourage potential
consumers and postharvest processing methods that make it
safe to handle, while maintaining nutritive value will benet
the development of U. dioic a as a specialty vegetable.
In this study, we report dietary values, mineral properties,
and other quality attributes of raw, blanched, and cooked
stinging nettle.
2. Materials and Methods
2.1. Plant Materials. Plant samples were obtained from eld
plots planted as a part of an ongoing agronomic study on
U. dioica at Randolph Farm (.∘N; .∘W), Virginia State
University (VSU). Samples from fall and spring growth were
collected in October  and May , respectively, by
harvesting actively growing shoots (20 ± 2cm) before the
onset of owering. Individual shoots were clipped with a
pairofshearsandconsolidatedinventedplasticbagsbefore
transfer to a demonstration kitchen located at the VSU Farm
Pavilion for further processing.
2.2. Sample Processing. In the kitchen, the shoots were
washed, and twelve 200 ± 5g units were weighed before
separating leaves and tender shoot tips from the woody
stem. e edible portion (leaves and tender shoot tips) was
weighed,andmeanyieldwasdeterminedbypresenting
the weight of edible portion as a percentage of total unit
mass. Treatments, each replicated three times, were applied
as follows: raw samples were packaged and frozen without
further processing, blanched samples were immersed in
boiling water (-∘C)formin,andcookedsampleswere
boiled (–∘C) with or without salt ( g⋅L−1 H2O) for
 min. Both blanched and cooked samples were cooled to ∘C
with shaved ice immediately aer treatment. All samples were
kept in frozen storage (−∘C) before analysis. Samples for
proximate composition analysis were submitted frozen, while
those for fatty and amino acid analysis were freeze-dried and
ground to a ne powder before analysis.
2.3. Proximate Analysis. All analysis was done according to
the Association of Analytical Chemists (AOAC) methods
(AOAC, ). Moisture content was determined by drying
samples to constant weight using a convection oven. Nitrogen
(N) content was measured using a CN analyzer (LECO ,
LECO Corp., St. Joseph, MI), and protein content was derived
by multiplying N values with .. Total fat was determined
by gas chromatography (Agilent , Agilent Technologies,
Santa Clara, CA, USA) aer extraction of saponiable and
unsaponiable fractions, and ash content was measured by
ignition at ∘C to constant weight. Carbohydrate content
and calorie values were calculated by dierence. Total dietary
ber was determined following methods described by the
American Association of Cereal Chemists (AACCI method
-.).
2.4. Vitamin and Mineral Analysis. Total vitamin A and vita-
min A as 𝛽-carotene were determined by colorimetry aer
alkaline digestion followed by extraction with hexane. Vita-
min C was extracted in acid and sample content determined
by titration. For mineral analysis, samples were subjected to
wet digestion before calcium, iron, and sodium content was
determined using an ICP spectrometer (AOAC, ).
2.5. Amino Acid Analysis. For amino acid analysis, a ground
subsample of nettle tissue was hydrolyzed with  M HCl at
∘C for  hr as previously described []. Acid hydrolyzed
amino acids were derivatized with phenyl isothiocyanate
(Acros Organics, Geel, Belgium) and separated using a 
Alliance HPLC equipped with a -cm Pico-Tag column, 
UV/Vis detector, and Empower soware (all from Waters
Corp., Milford, MA) using previously described conditions
[]. Amino acid concentrations are expressed in g/ g of
nettle leaf.
2.6. Fatty Acid Analysis. Fattyacidmethylesters(FAMEs)
were prepared by treating raw and processed samples with
ethyl chloride and absolute methanol as described []. Fatty
acid methyl esters were analyzed by gas chromatography
using an Agilent  N GC system (Agilent Technologies),
equipped with a HP-INNOWax column ( m ×. mm
I.D. ×. 𝜇m lm thickness) and ame ionization detector.
Peaks were identied against retention times for a known
FAMEandquantiedbytheaidofheptadecanoicacid(:)
included as an internal standard. e concentration of each
fatty acid is presented as a percentage of total saponiable oil
in sample.
2.7. Statistical Analysis. One-way analysis of variance
(ANOVA) using the Analyst function in SAS (version .
for Windows, SAS Institute, Cary, NC) was performed to
compare the eects of blanching and cooking on stinging
nettle quality and nutritive value. Treatments were treated as
independent variables, and data for fall  and spring 
were analyzed separately. Tukey’s HSD (𝑃 < 0.05)wasused
to separate treatment means within season.
3. Results and Discussion
3.1. Yield of Edible Portion in U. dioica. Actively growing
stinging nettle shoots are ideally harvested before owering
for consumption as a potherb or spinach alternative. Leaves
on stems were found to be tender enough for use as a
vegetable up to  cm from the growing point, but stems
become woody about cm away from the growing point
necessitating destemming aer harvest to separate the tender
tip (approx.  cm and leaves) from the woody stem. Our
resultsshowthatthewoodystemportionaccountsfor%–
% of total biomass with edible portion comprising of %
or more of harvested material (Tabl e  ). Yield (edible portion)
washigherinfallthaninspringsamplesbecauseofseasonal
dierences in U. dioi ca growth characteristics. Consistent
with published observations [], U. dioica displays two
distinct phenological stages when grown in south-central

International Journal of Food Science 
T : Edible portion (leaf) yield as a percentage of total biomass
in stinging nettle (Urtica dioica L.) harvested from eld plots in the
fall of  and spring of . Actively growing shoots ( ±cm)
were harvested and processed by de-stemming.
Season Shoot wt. (g) Stem wt. (g) Leaf wt. (g) Loss (%)
Fall   ±.a ±.  ±.  ±.
Spring   ±.  ±.     ±.  ±.
aMean (𝑛=3)±standard deviation.
Virginia: reproductive growth up to late spring, limited
development during summer, and mostly vegetative growth
in the fall.
3.2. Eect of Blanching and Boiling on Proximate Composition,
Vitamin, and Mineral Content in U. dioica. Aer draining,
there was not much dierence in moisture content between
raw and processed samples in the fall of , while there was
slightly more moisture in processed samples in the spring
of , likely due to dierences in draining time. ere
was a slight reduction in crude protein, ash, and fat aer
blanching or cooking in both fall and spring samples. In
both cases, the most signicant reductions were observed
with longer exposure to heat and also to salt. e same
applies to dietary ber, carbohydrate content, and calorie
value. Samples harvested in the spring contained signicantly
higher values for all parameters measured and showed higher
decline aer processing (Ta b l e ). Preparation and cooking
generally result in deterioration of vegetable quality. For
example, cooking signicantly reduces ash, carbohydrate
content, and caloric value in Cocoyam (Colocasia esculenta)
leaves [], while chopping amaranth (Amaranthus sp.) leaves
before cooking can result in increased loss of vitamins and
minerals []. Our results show that vitamin A, calcium,
and iron contents in U. dio ica leaf are similarly aected by
cooking. Sodium content was low and was not aected by
cooking,butthesaltaddedtocookingwaterinoneofthe
treatments signicantly (𝑃 < 0.05) increased sodium content
in drained samples (Ta b l e  ). Salt addition for seasoning or
preservation has been reported to aect vegetable quality
through dilution of minerals and other chemical changes
[]. Cooking led to changes in the fatty acid prole of U.
dioica with more saturated fat being converted into mono-
unsaturated and polyunsaturated forms (Tabl e  )orlostinto
solution. Saponiable oil content in raw and processed U.
dioica samples (.%–.% in the spring; .%–.% in the
spring) was comparable to that in wild asparagus (Asparagus
acutifolius)andblackbryony(Tamus communis), edible wild
greens common to Mediterranean diets [].
3.3. Eect of Cooking on Fatty and Amino Acid Composition
in U. dioica Tissue Samples. Data on individual amino and
fatty acid content in stinging nettle shows that the species
can supply signicant quantities of oleic (:), linoleic (:),
and 𝛼-linoleic (:) acids and is a good source of unsaturated
fatty acids. Considerable amounts of palmitic acid (:), a
saturated fatty acid, were found in the leaf (Tab l e  ;Figure ).
ere were no signicant dierences in fatty acid content
between samples collected from fall and spring growth.
Similarly blanching and cooking with or without salt did
not aect fatty acid content within season except for a
general trend showing an increase in unsaturated fatty acid
content and a corresponding decrease in the concentration of
saturated fatty acids (Table ). Similarly, high levels of linoleic
and 𝛼-linoleic acids in young and mature leaves and the
presence of relatively high concentrations of the same oils in
U. dioica seed, stem, and roots portions have been reported
[], with the seed containing up to % saponiable oil.
In terms of omega- fatty acid content, U. dio ica compares
favorably with frozen spinach (Spinacia oleracea L.) pre-
treated by steaming, blanching, or autoclaving []. Relative
to other commonly consumed wild plants, it contains a hig her
concentration of omega- fatty acids than borage (Borago
ocinalis), and about the same level as water-blinks (Montia
fontana)[], watercress (Rorippa nasturtium-aquaticum),
sheepsorrel(Rumex acetosella), and sorrel (Rumex induratus)
[]. However, carbohydrate content (including total sugars)
was signicantly lower in raw and processed U. dioica (.%–
.%) than in the four species above reported to constitute
.%–.% total carbohydrates []. ese results show
that processing by blanching and cooking has a minimal
impact on U. dioi ca fatty acid composition, implying that it
can be a good source of essential fatty acids when eaten as a
leafy vegetable.
With regard to individual amino acids, tissue content
was similarly not aected by season. Our results show
that U. dioica can supply considerable amounts of essential
amino acids including threonine, valine, isoleucine, leucine,
phenylalanine, and lysine, along with lower concentrations
of histidine and methionine (Table ;Figure ). Amino acid
content was largely unchanged in the spring as compared
with fall growth though asparagine, glutamine, leucine, and
histidine levels were generally lower in samples from spring
growth. ere were slight to signicant increases in amino
acid content aer blanching or cooking in fall samples,
but no similar observation was made for samples collected
in the spring (Tab l e ). ere may be dierences between
and within species in response to postharvest handling and
processing conditions. In one study, a signicant increase in
amino acid content was recorded aer cooking relative to
raw spinach [], while the opposite was true for cooked and
frozen versus raw Brussels sprouts [].
Data from this experiment show that both raw and
cooked U. dioica can be important sources of dietary protein.
e species can supply higher concentrations of essential
amino acids than Brussels sprouts []andhasabetter
amino acid prole than most other leafy vegetables. Although
similar to S. oleracea in terms of total amino acid content,
U. dioica contains higher levels of all essential amino acids
exceptleucineandlysine.Someofthepublishedrecipes
incorporating U. dioica leaf our in bread, pasta, and noodle
dough suggest that it can be used as a protein-rich supplement
in starchy diets associated with poor and undernourished
populations. is is because on a dry weight basis, U. dioica
leaf is better than almond (dry) and is comparable to com-
mon bean (Phaseolus vulgaris)andchicken(Gallus gallus)
asasourceofessentialaminoacids[]. e agronomic

International Journal of Food Science
T : Proximate composition, vitamins, minerals, and fatty acid prole of rawand processed stinging nettle (Urtica dioica L.) shoots harvested from eld plots in the fall of  and spring
of .
Fall  Spring 
Raw Blanched Cooked Cooked + salt Raw Blanched Cooked Cooked + salt
Proximate analysis
Moisture (%) . ±.a. ±.a. ±.a. ±.a. ±.c. ±.b. ±.b. ±.a
Protein (%) . ±.a. ±.ab . ±.a. ±.b. ±.a. ±.b. ±.b. ±.c
Fat (%) . ±.a. ±.b. ±.b. ±.b. ±.a. ±.a. ±.a. ±.b
Ash (%) . ±.a. ±.ab . ±.b. ±.b. ±.a. ±.b. ±.c. ±.c
Fiber, total dietary (%) . ±.a. ±.b. ±.c. ±.bc . ±.a. ±.b. ±.b. ±.c
Carbohydrates, total (%) . ±.a. ±.ab . ±.b. ±.b. ±.a. ±.b. ±.b. ±.c
Other carbohydrates (%) . ±.ab . ±.a. ±.b. ±.a. ±.a. ±.b. ±.b. ±.c
Calories, total (kcal/ g) . ±.a. ±.a. ±.a. ±.b. ±.a. ±.b. ±.c. ±.d
Calories from fat (kcal/ g) . ±.a. ±.ab . ±.bc . ±.c. ±.a. ±.ab . ±.b. ±.c
Vitamins and minerals
Vitamin A, total (IU/ g)  ±a ±a ±b ±b ±a ±bc  ±c ±b
Vitamin A, as 𝛽-carotene (IU/ g)  ±a ±b ±b ±c ±a ±b ±b ±c
Vitamin C (mg/ g) . ±.a. ±.b. ±.b. ±.b. ±.a. ±.a. ±.a. ±.a
Calcium (mg/ g)  ±c ±a ±ab  ±bc  ±a ±b ±b ±c
Iron (mg/ g) . ±.c. ±.b. ±.a. ±.a. ±.a. ±.b. ±.b. ±.c
Sodium (mg/ g) . ±.b. ±.b. ±.b. ±.a. ±.b. ±.b. ±.b. ±.a
Fatty acid prole
Saturated fat (%) . ±.a. ±.b23.6 ± 4.1c. ±.d. ±.a. ±.bc . ±.b. ±.c
Monounsaturated (%) . ±.c. ±.a. ±.a. ±.b.  ±.a. ±.b. ±.b. ±.c
Polyunsaturated (%) . ±.c. ±.b. ±.c. ±.a. ±.d. ±.b. ±.c. ±.a
Cholesterol (mg/ g) . ±.a. ±.a. ±.a. ±.a. ±.a. ±.a. ±.a. ±.a
aMean (𝑛=3)±standard deviation. Values within a year followed by dierent letters are signicantly dierent at 𝑃 < 0.05 (Tukey’s HSD).

International Journal of Food Science 
T:Fattyacidcontent
ain raw and processed stinging nettle (Urtica dioica L.) shoots harvested from eld plots in the fall of  and spring of .
Total fat (%) Fatty acidb(% of total fat)
: : : : : : : : : : :
Fall 
Raw 3.15 ± 0.12c17.06 ± 0.05a2.54 ± 0.04b1.86 ± 0.01a2.18 ± 0.01c23.30 ± 0.20a49.55 ± 0.10d0.83 ± 0.01a0.03 ± 0.01a1.37 ± 0.02a0.06 ± 0.01b1.23 ± 0.03a
Blanched 4.72 ± 0.05ab 14.91 ± 0.12b2.54 ± 0.02b1.41 ± 0.02c2.23 ± 0.02b21.58 ± 0.20b54.42 ± 0.37c0.67 ± 0.01c0.06 ± 0.01a1.11 ± 0.01c0.09 ± 0.02ab 0.98 ± 0.01b
Cooked 4.65 ± 0.10b14.83 ± 0.09b2.45 ± 0.02c1.60 ± 0.01b1.91 ± 0.03d20.96 ± 0.10c55.48 ± 0.20b0.69 ± 0.01b0.03 ± 0.01a1.13 ± 0.01b0.05 ± 0.01b0.88 ± 0.01d
Cooked + salt 4.78 ± 0.14a14.22 ± 0.11c2.62 ± 0.01a1.35 ± 0.01d2.54 ± 0.01a19.67 ± 0.2d56.70 ± 0.34a0.67 ± 0.01bc 0.05± 0.01a1.13 ± 0.01b0.14 ± 0.01a0.91 ± 0.01c
Spring 
Raw . ±.d. ±.a. ±.b. ±.a. ±.a. ±.a. ±.d. ±.a. ±.a. ±.a. ±.a. ±.a
Blanched .±.b. ±.b. ±.d. ±.c. ±.a. ±.b. ±.c. ±.b. ±.c. ±.b. ±.b. ±.d
Cooked . ±.a. ±.d. ±.a. ±.c. ±.c. ±.c. ±.a. ±.c. ±.b. ±.b. ±.b. ±.c
Cooked + salt 3.58 ± 0.06c14.29 ± 0.05c. ±.c1.67 ± 0.03b. ±.b. ±.d. ±.b. ±.b. ±.d. ±.b. ±.c. ±.b
aMethylated samples were analyzed for total fatty acid content using gas chromatography.
bPalmitic acid (:); palmitoleic acid (:); stearic acid (:); oleic acid (:); linoleic acid (:); 𝛼-linoleic acid (:); gadoleic acid (:); behenic acid (:); erucic acid (:); lignoceric acid (:).
cMean (𝑛=3)±standard deviation. Column values followed by dierent letters within season are signicantly dierent at 𝑃 < 0.05 (Tukey’s HSD).

International Journal of Food Science
T : Amino acid content in raw and processed stinging nettle (Urtica dioica L.) shoots harvested from eld plots in the fall of  and spring of .
Amino acid (g/ g) Fall  Spring 
Raw Blanched Cooked Cooked + salt Raw Blanched Cooked Cooked + salt
Isoleucine . ±.b. ±.ab . ±.a. ±.a. ±.a. ±.a. ±.a. ±.a
Leucine . ±.b. ±.ab . ±.a. ±.a. ±.a. ±.a. ±.a. ±.a
Lysine . ±.a. ±.a. ±.a. ±.a. ±.a. ±.a. ±.a. ±.a
Methionine . ±.a. ±.a. ±.a. ±.a. ±.a. ±.a. ±.a. ±.a
Tyrosine . ±.b. ±.ab . ±.ab . ±.a. ±.a. ±.a. ±.a. ±.a
Phenylalanine . ±.b. ±.ab . ±.a. ±.a. ±.a. ±.a. ±.a. ±.a
reonine . ±.a. ±.a. ±.a. ±.a. ±.a. ±.a. ±.a. ±.a
Valine . ±.b. ±.ab . ±.a. ±.a. ±.a. ±.a. ±.a. ±.a
Histidine . ±.b. ±.ab . ±.ab . ±.a. ±.a. ±.a. ±.a. ±.a
Total essential amino acids . ±.b. ±.ab . ±.a. ±.a. ±.a. ±.a. ±.a. ±.a
Arginine . ±.b. ±.ab . ±.a. ±.a. ±.a. ±.a. ±.a. ±.a
Aspartic acid + asparagine . ±.a. ±.a. ±.a. ±.a. ±.a. ±.a. ±.a. ±.a
Glutamic acid + glutamine . ±.a. ±.a. ±.a. ±.a. ±.a. ±.a. ±.a. ±.a
Serine . ±.b. ±.ab . ±.ab . ±.a. ±.a. ±.a. ±.a. ±.a
Proline . ±.b. ±.ab . ±.ab . ±.a. ±.a. ±.a. ±.a. ±.a
Glycine . ±.b. ±.ab . ±.ab . ±.a. ±.a. ±.a. ±.a. ±.a
Alanine . ±.b. ±.ab . ±.ab . ±.a. ±.a. ±.a. ±.a. ±.a
Total amino acids . ±.b. ±.ab . ±.ab . ±.a. ±.a. ±.a. ±.a. ±.a
Dry matter (g/  g edible portion) . . . . . . . .
aMean (𝑛=3)±standard deviation. Row values followed by dierent letters within season are signicantly dierent at 𝑃 < 0.05 (Tukey’s HSD).

International Journal of Food Science 
1.5 2 32.5 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5
1.1
0.9
0.7
0.5
0.3
0.1
Retention time (min)
Absorbance units (AU)
Glu +Gln −1.731
Asp +Asn − 1.568
Ser − 2.985 Gly − 3.147
His − 3.257
Arg −3.556
r − 3.722 Ala − 3.837
Pro −3.949
Tyr − 5.069
Val − 5.484
Met − 5.616
Cys2 − 2.785
Ile −6.539 Leu −6.665
Phe − 7.317
Lys − 8.136
Nleu − 6.917
(a)
0 2 4 6 8 1012141618
0
300
600
900
Retention time (min)
Peak area (pA)
16:0−5.677
16:1 − 6.282 17:0−6.917
18:0 − 8.134
18:1 − 8.444
18:2−9.119
18:3 − 10.062
20:0 − 10.868
20:1 − 11.179
22:0 − 13.571
20:1 − 14.254
24:0 − 16.449
(b)
F : Representative chromatograms showing peaks and retention times for dierent amino (a) and fatty (b) acids in raw and processed
stinging nettle (Urtica dioica L.) leaf samples.
F : Suggested food labeling information for raw and processed stinging nettle (Urtica dioica L.).
properties of U. dioi ca including perennial growth, quick
response to fertilization, and high biomass yield make it an
excellent candidate for low-cost mass production for such a
purpose.
3.4. Labeling Information for Processed U. dioica. Results
from this study show that U. dioica retains a signicant
portion of minerals, vitamins, and essential nutrients aer
pre-treatment by blanching or cooking prior to frozen stor-
age. Processing may be the most eective approach to availing
the nutritional benets of U. dioi ca to consumers discouraged
by the stinging quality of live or fresh nettle. e nutritional
information in Figure , representing means of data from
bothspringandfallgrowth,canbeusedtolabelfrozen
raw and processed U. dioica leaf.However,lowervitaminA
and higher carbohydrate content and other data reported for

International Journal of Food Science
blanched U. di oica samples collected from the wild []show
that more work is required to evaluate the properties of U.
dioica products as aected by interactions between landrace,
environment, harvesting time, and processing conditions.
4. Conclusions
Although the usage of U. dioica as a leafy vegetable is
widespread, there is little information on processing poten-
tial, and the impact of dierent processing methods on nutri-
tive and functional value. e results presented in this report
show that U. dioi ca retains signicant amounts of minerals,
vitamins, and other functional values aer blanching or
cooking. We recommend processing and selling of U. dioi ca
leaf as a highly functional and nutritive food.
Conflict of Interests
e authors declare that they have no conict of interests.
Acknowledgments
e authors are grateful to Mr. Robert Kraemer and Mr. Lan-
don West, VSU Farm Manager and Assistant Farm Manager,
respectively, for eld support and to Dr. Ngowari Jaja for
assistance with sample preparation. is is a contribution of
Virginia State University Research Station Article No. .
References
[] A. di Tizio, J. Ł. Łuczaj, C. L. Quave, S. Redzic, and A. Pieroni,
“Traditionalfoodandherbalusesofwildplantsintheancient
South-Slavic diaspora of Mundimitar/Montemitro (Southern
Italy),” Journal of Ethnobiology and Ethnomedicine,vol.,article
, .
[] Y. Uprety, R. C. Poudel, K. K. Shreshta et al., “Diversity of use
and local knowledge of wild edible plant resources in Nepal,”
Journal of Ethnobiology and Ethnomedicine,vol.,article,
.
[] Ł. Łuczaj, A. Pieroni, J. Tard´
ıo et al., “Wild food plant use in
st century Europe: the disappearance of old traditions and the
search for new cuisines involving wild edibles,” Acta Societatis
Botanicorum Poloniae,vol.,no.,pp.–,.
[] N. Lopatkin, A. Sivkov, C. Walther et al., “Long-term ecacy
andsafetyofacombinationofsabalandurticaextractforlower
urinary tract symptoms—a placebo-controlled, double-blind,
multicenter trial,” World Journal of Urology,vol.,no.,pp.
–, .
[] P. Mittmann, “Randomized, double-blind study of freeze-dried
Urtica dioica in the treatment of allergic rhinitis,” Planta Medica,
vol.,no.,pp.–,.
[] S. A. Minina and M. G. Ozhigova, “Development of granulation
technology for lipophilic extracts,” Pharmaceutical Chemistry
Journal,vol.,no.,pp.–,.
[] L. Bacci, S. Baronti, S. Predieri, and N. di Virgilio, “Fiber yield
and quality of ber nettle (Urtica dioica L.) cultivated in Italy,”
Industrial Crops and Products,vol.,no.-,pp.–,
.
[] J.L.Guil-Guerrero,M.M.Rebolloso-Fuentes,andM.E.Torija
Isasa, “Fatty acids and carotenoids from Stinging Nettle (Ur tica
dioica L.),” JournalofFoodCompositionandAnalysis,vol.,no.
, pp. –, .
[] P. Pinelli, F. Ieri, P. Vignolini, L. Bacci, S. Baronti, and A.
Romani, “Extraction and HPLC analysis of phenolic com-
pounds in leaves, stalks, and textile bers of Urtica dioica L.,”
Journal of Agricultural and Food Chemistry,vol.,no.,pp.
–, .
[] S. Karabacak and H. Bozkurt, “Eects of Urtica dioica and
Hibiscus sabdaria on the quality and safety of sucuk (Turkish
dry-fermented sausage),” Meat Science,vol.,no.,pp.–
, .
[] G. Kaban, M. I. Aksu, and M. Kaya, “Behavior of Staphylococcus
aureus in sucuk with nettle (Urtica dioica L.),” Journal of Food
Safety, vol. , no. , pp. –, .
[] S. Turhan, I. Sagir, and H. Temiz, “Oxidative stability of
brined anchovies (Engraulis encrasicholus) with plant extracts,”
International Journal of Food Science and Technology,vol.,no.
,pp.–,.
[] G. Menendez-Baceta, L. Aceituno-Mata, J. Tard´
ıo,V.Reyes-
Garc´
ıa, and M. Pardo-de-Santayana, “Wild edible plants tra-
ditionally gathered in Gorbeialdea (Biscay, Basque Country),”
Genetic Resources and Crop Evolution,vol.,pp.–,
.
[] I. Alibas, “Energy consumption and color characteristics of net-
tle leaves during microwave, vacuum and convective drying,”
Biosystems Engineering,vol.,no.,pp.–,.
[] M. M. ¨
Ozcan, A. ¨
Unver, T. Uc¸ar, and D. Arslan, “Mineral con-
tent of some herbs and herbal teas by infusion and decoction,”
Food Chemistry,vol.,no.,pp.–,.
[] D. Kara, “Evaluation of trace metal concentrations in some
herbs and herbal teas by principal component analysis,” Food
Chemistry,vol.,no.,pp.–,.
[] D. M. Albin, J. E. Wubben, and V. M. Gabert, “Eect of
hydrolysis time on the determination of amino acids in samples
of soybean products with ion-exchange chromatography or
precolumn derivatization with phenyl isothiocyanate,” Journal
of Agricultural and Food Chemistry,vol.,no.,pp.–,
.
[] S. A. Cohen, M. Meys, and T. L. Tarvin, e Pico-Tag Method: A
Manual of Advanced Techniques for Amino Acid Analysis,Waters
Division of Millipore, Milford, Mass, USA, .
[] G. Lepage and C. C. Roy, “Improved recovery of fatty acid
through direct transesterication without prior extraction or
purication,” Journal of Lipid Research, vol. , no. , pp. –
, .
[] M. ˇ
Sr˚
utek, “Growth responses of Urtica dioica to nutrient
supply,” Canadian Journal of Botany,vol.,no.,pp.–,
.
[] M.N.Lewu,P.O.Adebola,andA.J.Afolayan,“Eectofcooking
on the proximate composition of the leaves of some accessions
of Colocasia esculenta (L.) Schott in KwaZulu-Natal province of
South Africa,” African Journal of Biotechnology,vol.,no.,pp.
–, .
[] O. M. Funke, “Evaluation of nutrient contents of amaranth
leaves prepared using dierent cooking methods,” Food and
Nutrition Sciences,vol.,pp.–,.
[] J. C. Rickman, C. M. Bruhn, and D. M. Barrett, “Nutritional
comparison of fresh, frozen, and canned fruits and vegetables
II. Vitamin A and carotenoids, vitamin E, minerals and ber,”
Journal of the Science of Food and Agriculture,vol.,no.,pp.
–, .

International Journal of Food Science 
[] D.Martins,L.Barros,A.M.Carvalho,andI.C.F.R.Ferreira,
“Nutritional and in vitro antioxidant properties of edible wild
greens in Iberian Peninsula traditional diet,” Food Chemistry,
vol. , no. , pp. –, .
[] E. Cho, J. Lee, K. Park, and S. Lee, “Eects of heat pretreatment
on lipid and pigments of freeze-dried spinach,” Journal of Food
Science,vol.,no.,pp.–,.
[] J. Tard´
ıo, M. Molina, L. Aceituno-Mata et al., “Montia fontana
L. (Portulacaceae), an interesting wild vegetable traditionally
consumed in the Iberian Peninsula,” Genetic Resources and Crop
Evolution,vol.,pp.–,.
[] C.Pereira,L.Barros,A.M.Carvalho,andI.C.F.R.Ferreira,
“Nutritional composition and bioactive properties of com-
monly consumed wild greens: potential sources for new trends
in modern diets,” Food Research International,vol.,no.,pp.
–, .
[] Z. Lisiewska, W. Kmiecik, P. Gebczynski, and L. Sobczynska,
“Aminoacidproleofrawandas-eatenproductsofspinach
(Spinacia oleracea L.),” Food Chemistry, vol. , no. , pp. –
, .
[] Z. Lisiewska, J. Słupski, R. Skocze´
n-Słupska, and W. Kmiecik,
“Content of amino acids and the quality of protein in Brussels
sprouts, both raw and prepared for consumption,” International
Journal of Refrigeration,vol.,no.,pp.–,.
[] FAO, “Amino-acid content of foods and biological data on
proteins,” FAO Food and Nutrition Series no. , Rome, Italy,
.
[] U.S. Department of Agriculture, Agricultural Research Service,
“USDA Nutrient Database for Standard Reference,” Release ,
, http://ndb.nal.usda.gov/ndb/foods/show/.