the use of purple yam (dioscorea trifida) as a health-promoting ingredient in bread making
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Jou
rn
al of R
esearch
in
Biology
The use of purple yam (Dioscorea trifida) as a health-promoting
ingredient in bread making
Keywords: Purple yam (Dioscorea trifida); antioxidant activity; health-promoting food; Amazon region.
ABSTRACT: The use of purple yam (Dioscorea trifida) was evaluated as possible health-promoting ingredient in bread making in the state of Amazonas, Brazil. The centesimal composition, energy, and antioxidant activity of purple yam and its incorporated bread formulations (0%, 10%, 15% and 20%) were determined. An acceptance test and microbiological analysis of the formulations 10%, 15% and 20% were also performed. Except for lipids, the centesimal composition and caloric values revealed no statistically significant differences. An addition of purple yam in natura up to 20%, instead of wheat flour in ordinary bread (0%), can be made with no effect on the diet’s energy. The free radical scavenging, 2.2-diphenyl-1-picryl-hydrazyl (DPPH) and lipid per oxidation (LPO) methods revealed that the greater the percentage of purple yam being added into the breads the higher the antioxidant activity detected. The acceptance test applied to compare the three formulations of purple yam breads revealed a significant difference only in the attribute colour. Purple yam breads showed no preferable differences. Results highlight the feasibility of purple yam bread as a health-promoting food in the Amazon region.
747-758 | JRB | 2013 | Vol 3 | No 1
This Open Access article is governed by the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which gives permission for unrestricted use, non-commercial, distribution and reproduction in all medium, provided the original work is properly cited.
www.jresearchbiology.com
Journal of Research in Biology
An International Open Access
Research Journal
Authors:
Teixeira AP1,
Oliveira IMA1, Lima ES1
and Matsuura T2.
Institution:
1. Faculdade de Ciências
Farmacêuticas (FCF),
Universidade Federal do
Amazonas (UFAM), Rua
Alexandre Amorim, 330,
Aparecida, CEP: 69010-330,
Manaus, AM, Brasil.
2. Instituto de Ciências
Biológicas (ICB),
Universidade Federal do
Amazonas (UFAM), Av.
General Rodrigo Octávio
Jordão Ramos, 3000,
Campus Universitário,
Coroado I CEP: 69077-000,
Manaus, AM, Brasil.
Corresponding author:
Antonia Paiva Teixeira.
Email:
nietapt@yahoo.com.br
Web Address: http://www.jresearchbiology.com
document/ RA0306.pdf.
Dates: Received: 15 Nov 2012 Accepted: 27 Nov 2012 Published: 09 Jan 2013
Article Citation: Teixeira AP, Oliveira IMA, Lima ES and Matsuura T.
The use of purple yam (Dioscorea trifida) as a health-promoting ingredient in bread making. Journal of Research in Biology (2013) 3(1): 747-758.
Journal of Research in Biology An International Open Access Research Journal
Original Research
INTRODUCTION
Yams belong to the family Dioscoreaceae, genus
Dioscorea (Pedralli, 1988; 1997; Pedralli et al., 2002;
Pedralli, 2004). This family is made up by 6 to 9 genera
comprising over 600 species distributed throughout the
World’s tropical, subtropical and temperate regions
(Barroso et al., 1974; Pedralli, 1988; 1997; Melo
Filho et al., 2000; Pedralli et al., 2002; Pedralli, 2004).
The yams (Dioscorea spp.) yield tubers, which are very
important as staple, nutritional and healthy food, and are
still used as an ingredient in traditional Chinese herbal
medicine. They show a worldwide distribution, and are
found in many tropical countries, in South-Eastern Asia
and Western Africa, where the species were introduced
by cultivators (Rasper and Coursey, 1967; Akanbi et al.,
1996; Omonigho and Ikenebomeh, 2000; Lin et al.,
2005). They can also be found in some American
countries, particularly in Brazil, where one can find them
in all regions, from the Amazon down to the Southern
part of the country (Chu and Figueiredo-Ribeiro, 1991;
Pedralli, 1997; 2004).
Purple yam (Dioscorea trifida) is an American
native species, which was domesticated by Amerindians,
with the cultivar distribution possibly pointing out its
domestication in Brazilian and Guyana border areas,
followed by dissemination throughout the Caribbean
islands (Pedralli, 1988; Pedralli et al., 2002; Pedralli,
2004). D. trifida shows a wide distribution in Central and
South America, from the Caribbean to Peru. In Brazil it
is found all the way from the Amazon right down to the
Southern region. The species is associated to forest
environments-Amazonian highland tropical rainforests,
Coastal Atlantic Forest in Southeastern Brazil and,
mesophytic (seasonable) and gallery forests (Pedralli,
1997).
Here in the Amazonian region, purple yam
(D. trifida) may be consumed in the following ways:
baked, boiled, mashed, as ingredients for soups and meat
stews, and in the formulation of flour for making cakes,
pies and porridges. Nevertheless, this species has
undergone little scientific investigation, so little is known
about its management techniques, genetic improvement,
nutritional potential, industrial use, storage procedures,
characterization, uses as natural dye, as well as its use as
a health-promoting ingredient, among others.
By and large, the bread consumed throughout the
world is made mostly of wheat flour, salt and yeast.
Many other ingredients, have been incorporated into
bread formulation, so as to increase its diversity and
product appeals (Hsu et al., 2004).
A few studies have highlighted the great
potential of purple yam in bread making. In this case,
yam flour may replace part of the wheat flour, improving
bread quality, as well as adding economical advantages
to it (Abramo, 1990; Hurtado et al., 1997; Litvin et al.,
1998; Omonigho and Ikenebomeh, 2000; Ratti, 2001).
Hsu et al., (2004) demonstrated the presence
of antioxidants in the flour of purple yam
(Dioscorea purpurea), in five formulations of breads
prepared with this tuber’s flour, with excellent
acceptance in Taiwan supermarkets. Contado et al.,
(2009) showed yam (Dioscorea spp.) mucilage-based
loaf to present good public acceptance as to flavor,
aroma and texture with sensory attributes, demonstrating
the use of this tuber to be feasible as improvers in bread
making.
The following aspects motivated the use of
purple yam (Dioscorea trifida) in natura as a bread
manufacturing health-promoting ingredient, in the
present work: 1) its significant world consumption,
presenting a considerable, expanding tillage alternative
(Rasper and Coursey, 1967; Abramo, 1990; IITA, 2007);
2) although, as yet incipient, an increase on the
production of this tuber in the State of Amazonas, Brazil,
especially in Caapiranga and Careiro Castanho
municipalities is being observed. According to the
Instituto de Desenvolvimento Agropecuário do Estado
do Amazonas (IDAM) in 2008, 110 families of the
Teixeira et al., 2013
748 Journal of Research in Biology (2013) 3(1): 747-758
Caapiranga municipality yielded 2,475 tonnes in an area
of 165 ha; and 3) the presence of antioxidants in purple
yam, which increases the nutritional capacity in breads
made from this tuber (Hsu et al., 2004).
The main aim of the present study was to
evaluate the potential of purple yam yield in the State of
Amazonas, Brazil as a health-promoting ingredient in
bread making. On this context, it determined the
centesimal composition, caloric value, and antioxidant
properties of purple yam as well as of breads made from
this tuber in natura. Then, it undertook an organoleptic
characteristic assessment of the breads, following tasters’
panel acceptance criteria. This purple yam species is, for
the very first time, being used in the Amazonian region,
as a feasible alternative for bread making.
MATERIALS AND METHODS
Species identification and purple yam tuber
(Dioscorea trifida) collection
Identification of the species Dioscorea trifida
was accomplished by comparisons with a voucher
herbarium specimen (Exsicata number 1353) deposited
at the National Research Institute of Amazonia (INPA)
Herbarium. It is very common to find the purple yam
(D. trifida) exhibiting several color hues of its flesh
(edible portion), in Amazonas State Townships. The
types most easily identified are: roxinho (light purple
flesh); roxo (mid purple flesh); roxão (dark purple flesh);
branco (white flesh); and misto (white-purple flesh)
(Figure 1).
Purple yam samples were collected at two
Amazonas Townships: Caapiranga and Careiro
Castanho. Due to the seasonality and availability of these
tubers in the region, the centesimal composition analyses
of yams and breads were performed with Caapiranga
samples. Yam and bread antioxidant and bread sensory
and microbiological analyses were carried out with
Careiro Castanho samples.
Purple yam bread elaboration
On account of the probability of getting breads
with higher antioxidant concentration (Hsu et al., 2004),
roxão (dark purple flesh) type samples were used in the
present study (Figure 1C). Yams in natura, for replacing
wheat flour, were washed, peeled, weighed, ground
in the liquidizer together with yeast, oil and water.
Then, this mixture was added to the previously mixed
dry ingredients (wheat flour, powdered milk, sugar and
salt). Bread manufacturing formulations can be seen at
(Table 1). Homogenization (30 min.), dough underwent
initial fermentation (60 min.), intermediate time for
Teixeira et al ., 2013
Journal of Research in Biology (2013) 3(1): 747-758 749
B A
C D E
Figure 1. Flesh color varieties of the kinds of purple yam (Dioscorea trifida)
commonly found in fairs and markets of Manaus-AM. A) roxinho (light-purple
flesh); B) roxo (mid-purple flesh); C) roxão (dark purple flesh);
D) branco (white flesh); and E) misto (white-purple flesh).
bread shaping (25 min.), final fermentation (60 min.),
time for baking (30 min.) are followed for making yam
bread. After being prepared the breads were cooled to
room temperature and packed in polyethylene bags
displaying the product’s labeling.
Centesimal composition analyses of purple yam and
its incorporated breads
Centesimal composition analyses of purple yam
(Dioscorea trifida), and purple yam incorporated breads
in four formulations: 0%, 10%, 15% and 20%, were done
in triplicate. Moisture, ashes, lipid, proteins and crude
fiber contents were determined according to procedures
described by the Instituto Adolfo Lutz-IAL (2008).
Carbohydrate and caloric values were determined
according to the method of (AOAC, 2005).
Findings obtained on the bread formulation
centesimal composition analyses were subjected to
Teixeira et al., 2013
750 Journal of Research in Biology (2013) 3(1): 747-758
Table 1. Purple yam (D. trifida) incorporated
bread formulations.
Ingredients Type of bread*
0% 10% 15% 20%
Wheat flour (g) 500 450 425 400
Purple yam (g) 0 50 75 100
Sugar (g) 10 10 10 10
Salt (g) 5 5 5 5
Yeast (g) 10 10 10 10
Milk powder (g) 10 10 10 10
Oil (g) 10 10 10 10
Water (mL) 250 250 250 250
Total (g) † 545 545 545 545
*Percentage of wheat flour replaced by purple yam. †Total amount of ingredients used for preparing the
breads.
Parameters Yam
(D. spp.)* Yam
(D. alata)** Purple Yam (D.trifida)***
Moisture (%) 72.60 73.70 76.43 ± 0.50
Lipid (%) 0.20 0.10 1.13 ± 0.69 Protein (%) 2.00 2.30 1.83 ± 0.13
Crude Fiber (%)
0.60 7.30 1.80 ± 0.05
Ash (%) 0.90 0.90 0.78 ± 0.02 Carbohydrate
(%) 24.30 23.00 18.04 ± 0.66
Caloric value (Kcal/100g)
100.00 96.00 89.64 ± 4.52
Table 2. Yam centesimal composition.
*(Montaldo, 1977), **(TACO 2006), ***Present study Bre
ad
M
ois
ture
(%
) L
ipid
(%
) P
rote
in (
%)
Cru
de
Fib
er
(%)
Ash
(%
) C
arb
oh
yd
rate
(%
) C
alo
ric
va
lue
(kca
l/100 g
)
0%
29.7
9 ±
2.0
4a
4.4
9 ±
0.1
2ab
11.6
2 ±
0.8
1a
1.9
5 ±
0.0
8a
1.1
8 ±
0.2
8a
50.9
5 ±
2.7
9a
290.7
3 ±
7.5
6a
10%
31.0
3 ±
0.8
3a
4.2
4 ±
0,0
4a
10.6
7 ±
0,4
1a
1.9
1 ±
0,1
0a
1.4
1 ±
0.0
3a
53.4
1 ±
4.0
7a
294.4
5 ±
15.6
3 a
15%
32.6
5 ±
1.3
0a
4.8
7 ±
0.3
7ab
9.8
2 ±
1,2
4a
1.8
4 ±
0.0
7a
1.3
8 ±
0.0
7a
49.4
5 ±
2.2
6a
280.6
4 ±
3.9
5a
20%
35.0
9 ±
5.6
2a
4.7
4 ±
0.1
0b
10.0
6 ±
2,1
2a
2.3
4 ±
0.3
7a
1.2
0 ±
0.0
5a
53.4
3 ±
3.1
3a
269.1
7 ±
21.8
2a
P
0.0
752
0.0
370
0
.2699
0.1
438
0.0
683
0.2
587
0
.0862
Tab
le 3
. C
ente
sim
al
com
po
siti
on
an
d c
alo
ric
va
lue
mea
n a
nd
sta
nd
ard
dev
iati
on
on
acc
ou
nt
of
the
dry
mate
ria
l (e
xce
pt
for
the
mois
ture
con
ten
t) o
f th
e fo
ur
an
aly
zed
pu
rple
ya
m i
nco
rpo
rate
d b
read
fo
rmu
lati
on
s (0
%,
10
%,
15%
an
d 2
0%
). P
rob
ab
ilit
y (
P)
valu
es c
alc
ula
ted
fro
m K
rusk
al-
Wa
llis
AN
OV
A f
oll
ow
ed
by
post
hoc
test
s are
sh
ow
n.
Valu
es e
xh
ibit
ing
dif
fere
nt
lett
ers
in
th
e sa
me
colu
mn
in
dic
ate
sta
tist
icall
y s
ign
ific
an
t d
iffe
ren
ces
(P
<0.0
5).
statistical analysis through the statistical software
package (Statsoft STATISTICA 8.0 2007). Given to the
number of sampled observations (n=3), Kruskal-Wallis
ANOVA and post hoc tests were applied as a
non-parametric alternative to Fisher ANOVA, for
independent data, in the comparison among the bread
formulations.
Findings showing significance level of (P<0.05)
were considered as statistically significant.
Preparation of purple yam and its incorporated
breads methanolic extract
Samples of purple yam (Dioscorea trifida),
were peeled and ground with the aid of a knife. They
were then dehydrated in a laboratory oven at 60°C for
24 h. Purple yam incorporated breads of four
formulations: 0%, 10%, 15%, and 20%, were cut into
1 cm thick slices, and dehydrated in a laboratory oven at
40°C for 24 h (Hsu et al., 2004). Dehydrated yams and
breads were ground with pestle and mortar, weighed at
0.125, 0.25, 0.5 and 1.00 g (40, 80, 160 and 330 mg/mL,
respectively). They were placed into small test tubes
added with 5 mL of methanol and left in a rotary shaker
for 24 h. The material was centrifuged at 2,500 RPM
for 10 min so as to obtain the supernatant (methanolic
extract). The antioxidant activity of the samples was
determined by the free radical scavenging, 2.2-diphenyl-
1-picryl-hydrazyl (DPPH) and lipid peroxidation (LPO)
methods. The latter method evaluates the inhibition of
free radicals generated during the linoleic acid
peroxidation, and is based on spectrophotometric
measurements of discoloration (oxidation) of ß-carotene,
induced by linoleic acid oxidative degradation products
(Marco, 1968; Miller, 1971; Duarte-Almeida et al.,
2006).
Antioxidant activity determination through free
radicals scavenging methods (DPPH) in purple yam
and its incorporated breads
DPPH method, following the methodologies
described by Shimada et al., (1992) and Hsu et al.,
(2004), with some modifications, where 2 mg of DPPH
were dissolved into 15 mL of methanol, and applied so
as to determine the antioxidant activity of samples of
purple yam and its incorporated breads in the four
aforementioned formulations. A micro plate bearing
96 well was used. Thirty microliters (30 µL) of the
methanolic extract, plus 170 µL of methanol (used as the
blank) were placed in the wells. The reading was
performed on an Elisa reader (DXL 800-BECKMAN
COULTER) at a wavelength of 492 nm, using triplicate
samples. Then, 100 µL of the DPPH solution were
added, and the material was stored in a dark place for
30 min, and the reading was repeated as soon as this time
was over. Two hundred microliters (200 µL) of methanol
added to 100 µl of the DPPH solution were used as
the control. Thirty microliters (30 µL) of quercetin
(10 µg/mL), 170 µL of methanol and 100 µl of the
DPPH solution, were used as the standard. The following
formula was used so as to calculate the antioxidant
activity percentage
Antioxidant activity determination through the lipid
peroxidation (LPO) method in purple yam and its
incorporated breads
The determination of the antioxidant activity of
the samples through the LPO method was carried out
according to the method reported by Duarte-Almeida
et al., (2006), based on the methodology originally
described by Marco (1968), and later modified by Miller
(1971). The reactive mixture was prepared in
an Erlenmeyer flask, containing 50 µL of linoleic acid,
200 µL of tween 80 (emulsifying agent), 150 µL of
ß-carotene solution at 2 mg/mL in chloroform, and
500 µL of chloroform. The mixture was then subjected to
evaporation in nitrogen till there was no more
chloroform left. Later, the mixture of 25 mL of
previously oxygen saturated water was added, and during
Teixeira et al., 2013
Journal of Research in Biology (2013) 3(1): 747-758 751
A sample - A blank
% AA = 100 - x 100
A control
a period of 30 min it was homogenized through vigorous
shaking.
The reactive mixture showed to be clear with
absorbency ranging from 0.6 to 0.7 at a wavelength of
492 nm. A 96 well bearing micro plate was used. Two
hundred forty microliters (240 µL) of the reactive
mixture and 10 µL of the methanolic extract samples
were placed in the wells. Ten microliters (10 µL) of
methanol and an equal volume of butylhydroxytoluene
(BHT) at a concentration of 40 µg/mL were used as
control and standard, respectively. The micro plate was
incubated at 50ºC to speed up the oxidation reactions and
start β-carotene discoloration. Discoloration slope
readings of samples, control and BHT (in triplicate) were
performed readily, in an Elisa reader at a wavelength of
492 nm every 15 min for 135 min. The following
formula was used so as to calculate the oxidation
inhibition percentage:
Sensory analysis of purple yam incorporated breads
The acceptance test of purple yam in natura
incorporated breads counted with the participation of 78
non-trained volunteer judges. Each one of them was
provided with an answering card bearing a 9 point
hedonic scale (9-like extremely to 1-dislike extremely),
adapted from Stone et al., (1993) and Silva et al., (2005).
The judges were provided with three purple yam
incorporated bread samples, produced from three
formulations (10%, 15% and 20%) (Table 1). Samples
were served in white, disposable plastic plates; encoded
with three randomly chosen numbers. Samples were
evaluated according to their sensory qualities: global
feel, aroma, flavor, color and texture. Judges were
advised to always rinse their mouth with water before
testing the next sample.
The findings obtained on the acceptance test
were submitted to statistical analysis through statistical
software package (Statsoft STATISTICA 8.0 2007). The
Shapiro-Wilk test rejected the frequency distribution
normality of the three tested bread formulations, in all
their sensory attributes. However, the Levene test
accepted the homocedasticity (homogeneity of variances)
among the formulations for all sensory attributes. As
frequency distribution normality and variance
homogeneity are basic assumptions made for the
application of parametric tests, such as Fisher’s
ANOVA, and as these assumptions were not attended to,
the Friedman ANOVA followed by post hoc tests were
applied as a non-parametric alternative for paired data in
bread comparisons. Findings presenting significance
level of (P<0.05) were considered as statistically
significant.
Microbiological analysis of purple yam breads
Following the recommendation of the
Brazilian National Health Surveillance Agency
(in Portuguese, Agência Nacional de Vigilância
Sanitária, ANVISA), based on Ruling Number 12 (RDC,
2001), we carried out the microbiological analysis so as
to verify Coliforms and Salmonella in samples of the
three purple yam bread formulation samples through the
membrane filtration method (APHA, 2001).
RESULTS AND DISCUSSION
Centesimal composition and caloric value of purple
yam
Moisture (76.43±0.50), protein (1.83±0.13) and
ash (0.78±0.02) contents, as well as the caloric value
(89.64±4.52) of purple yam (D. trifida) samples analyzed
in the present study (Table 2) show to be near
those presented by Montaldo (1991) for yam
(Dioscorea spp.) and those found in the Brazilian
Food Composition Table TACO (2006), for the yam
(D. alata). Lipid content (1.13±0.69) stayed well above
that presented by Montaldo (1991) and TACO (2006).
Crude fiber content (1.80±0.05) is above the value
observed by Montaldo (1991), and well below that
Teixeira et al., 2013
752 Journal of Research in Biology (2013) 3(1): 747-758
A2 sample - A1 sample
% I = 100 - x 100
A2 control - A1 control
presented in TACO (2006). The high fiber content
presented by TACO (2006) might be due to the
enzymatic gravimetric method employed in the analyses.
That method warrants a higher precision for determining
the dietary fiber as compared to the acid digestion
methodology used in the present study as well as
by Montaldo (1991). Total carbohydrate content
(18.04±0.66) is well below Montaldo (1991) and TACO
(2006) values. The remaining differences in centesimal
composition values presented by Montaldo (1991) and in
the present study might be related to the different soil
types being employed on planting the tubers and/or to the
different species being utilized. Nevertheless, the
different values presented in TACO (2006) may be
related to the different yam species being analyzed.
Centesimal composition and caloric value of purple
yam incorporated breads
Based on data from Kruskal-Wallis (ANOVA)
followed by post hoc tests (Table 3), it may be asserted
that, except for the lipids (P<0.05), all other centesimal
composition and caloric values of the four purple yam
incorporated bread formulations (0%, 10%, 15% and
20%) showed to be statistically similar (P>0.05). That is,
replacing wheat flour by purple yam in natura in up to
20% neither modifies bread centesimal composition nor
caloric value. As for lipid, statistically significant
difference was only observed for 10% and 20%
formulations; this negligible 0.5% difference may be
neglected in technological applications.
Purple yam incorporated breads centesimal
composition and caloric value were compared to those of
ordinary bread loaf (OBL) (Anton et al., 2006) and
whole bread loaf (WBL) (TACO, 2006) (Table 4). One
notices, a high fiber content (6.90%) in the whole bread
loaf (WBL) (TACO, 2006), relative to the remaining
breads. It can be highlighted that in whole bread
composition, we have the presence of grain-composed
whole flour, almost wholly made up of bran, germ and
endosperm (FDA, 2006). By and large, all other values
show to be approximate. All differences found may be
related to formulations employed in the preparation of
those breads.
Antioxidant activity determination through the free
radical scavenging method (DPPH) in purple yam
and its incorporated breads
Antioxidant activity (% AA) of the methanolic
extract pertaining to purple yam (Dioscorea trifida)
Teixeira et al ., 2013
Journal of Research in Biology (2013) 3(1): 747-758 753
Bread Moisture
(%)
Lipid
(%)
Protein
(%)
Crude Fiber
(%)
Ash
(%)
Carbohydrate
(%)
Caloric value
(kcal/100 g)
0% 29.79 4.49 11.62 1.95 1.18 50.95 290.73
10% 31.03 4.24 10.67 1.91 1.41 53.41 294.45
15% 32.65 4.87 9.82 1.84 1.38 49.45 280.64
20% 35.09 4.74 10.06 2.34 1.20 53.43 269.17
OBL 34.46 1.93 9.42 2.57 2.09 52.10 247.50
WBL 34.70 3.70 9.40 6.90 2.30 49.90 253.00
Table 4. Centesimal composition and caloric value of ordinary bread loaf (OBL) (Anton et al., 2006),
whole bread loaf (WBL) (TACO, 2006) and purple yam (D. trifida) incorporated breads at 0%, 10%,
15% and 20% (present study).
0
10
20
30
40
50
60
70
80
90
100
40 80 160 330
Concentration (mg/mL)
An
tio
xid
an
t acti
vit
y (
%)
Purple yam
0% Bread
10% Bread
15% Bread
20% Bread
Quercetin
Figure 2. Antioxidant activity expressed by free
radical scavenging percentage, of samples of purple
yam (Dioscorea trifida) and its incorporated bread
extracts in four formulations: 0%, 10%, 15% and
20%, as determined by DPPH method. The quercetin
was used as standard control. Bars indicate standard
deviation.
samples in the concentrations of 330, 160, 80 and
40 mg/mL, as determined by the DPPH method, were
higher than 70%, reaching a maximum of 88.13±0.12.
This plainly shows this species to exert DPPH radical
scavenging activity (Figure 2). This same figure reveals
purple yam incorporated breads prepared in 10%, 15%
and 20% formulations, to also present a certain
antioxidant activity, reaching 43.32±1.18; 48.13±1.17
and 53.71±1.01 maximum percentile values,
respectively. Those findings are above the values
presented by Hsu et al., (2004) (20-40% approximately),
who used breads of several formulations prepared with
flour from the purple yam tuber (Dioscorea purpurea)
representing the one with the widest variety in Taiwan,
for substituting part of the wheat flour. Bread prepared
with no purple yam at all (0%) showed certain
antioxidant activity, as well, probably due to Maillard
reaction products, where, some hot processed foods,
present free radical scavenging activity (Kim et al.,
2007; Jing and Kitts, 2000; Hsu et al., 2004; Michalska
et al., 2008). Corroborating data from Hsu et al., (2004),
it was confirmed that the antioxidant activity rose as the
percentage of purple yam substituting wheat flour
increased. The high free radical scavenging activity
observed by Hsu et al., (2004) in flour of Taiwan purple
yam (D. purpurea), was also detected in the Amazonian
region’s purple yam (D. trifida).
Antioxidant activity determination through the lipid
per oxidation (LPO) method in purple yam and its
incorporated breads
Discoloration slope (Figure 3) and free radical
inhibition activity (Figure 4) determined through the
LPO method confirmed the antioxidant activity (% I) in
purple yam (55.80±4.85) and its breads from the three
formulations (10%, 15% and 20%), with the values of
46.16±4.90; 48.20±3.72 and 49.13±2.79, respectively.
Teixeira et al., 2013
754 Journal of Research in Biology (2013) 3(1): 747-758
Tests Bread% Color Aroma Flavor Texture Overall impression
Shapiro-Wilk P 10 0.0009 < 0.0001 0.0023 0.0044 0.0001
15 < 0.0001 0.0009 0.0008 0.0019 < 0.0001
20 < 0.0001 0.0001 0.0002 0.0090 0.0005
Levene P 0.0519 0.5580 0.2306 0.8415 0.5184
Table 5. Probability (P) values calculated from Shapiro-Wilk and Levene tests for evaluating frequency
normality and homogeneity of variances, respectively, of the data obtained in the sensory analysis of the
three tested purple yam incorporated bread formulations.
Values were considered statistically significant at (P< 0.05).
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0 15 30 45 60 75 90 105 120 135
Time (min)
Ab
s 4
92
Blank
Purple yam
0% Bread
10% Bread
15% Bread
20% Bread
BHT
Figure 3. Discoloration slope of purple yam
(Dioscorea trifida) and its incorporated bread
extracts in four formulations: 0%, 10%, 15%, 20%,
blank and BHT, as determined through the LPO
method.
0
10
20
30
40
50
60
70
80
90
Purple yam 0% Bread 10% Bread 15% Bread 20% Bread BHT
Inh
ibit
ion
(%
)
Figure 4. Inhibition percentage of free radicals of
purple yam (Dioscorea trifida) and its incorporated
bread extracts in four formulations: 0%, 10%, 15%,
20%, and BHT as determined by LPO method. Bars
indicate the standard deviations.
As it was observed by the DPPH method, the
antioxidant activity rose as the percentage of purple yam
substituting wheat flour in the breads increased.
Moreover, bread with no addition of purple yam (0%)
presented some antioxidant ability which might have
resulted from the development of Maillard reaction
products (Kim et al., 2007; Jing and Kitts, 2000; Hsu
et al., 2004; Michalska et al., 2008). Anthocyanins might
be partly responsible for the antioxidant activities
detected in the purple yam (D. trifida) and its
incorporated breads analyzed in the present study, since
these pigments were detected in purple yams, D. alata
(Rasper and Coursey, 1967) and D. trifida L.
(Carreno-Diaz and Grau, 1977; Escudero et al., 2010).
In fact, polyphenols and anthocyanins, usually detected
in plants, might be the active components for this
antioxidant activity in yams (Hou et al., 2001; Hsu et al.,
2004).
Sensory analysis of purple yam incorporated breads
Table 5 shows the rejection of the frequency
distribution normality of the three tested purple yam
incorporated bread formulations (10%, 15% e 20%)
through the Shapiro-Wilk test, and the acceptance of the
homocedasticity among the formulations through the
Levene test on all sensory attributes evaluated in the
acceptance test (i.e. statistically significant values at
(P <0.05).
Friedman ANOVA followed by post hoc tests
applied for comparing the three purple yam incorporated
bread formulations revealed a significant difference
(P<0.05), only for the colour attribute (Table 6). The
bread at 20% presented a better evaluation regarding the
remaining ones, probably due to the higher purple yam
concentration, which gives the final product a more
attractive kind of color. It was observed that the larger
the purple yam amount being added to the bread the
higher the mean score obtained (values ranging from
6.15 to 6.97).
Choosing a determined food should depend
Teixeira et al ., 2013
Journal of Research in Biology (2013) 3(1): 747-758 755
Bre
ad
Colo
r A
rom
a
Fla
vo
r
Textu
re
Over
all
im
pre
ssio
n
Mea
n
Med
ian
M
ean
M
edia
n
Mea
n
Med
ian
M
ean
M
edia
n
Mea
n
Med
ian
10%
6.1
5 ±
1.4
6ª
6
6.7
1 ±
1.2
2ª
6
6.2
8 ±
1.4
4ª
6
6.0
3 ±
1.5
0ª
6
6.5
4 ±
1.2
3ª
6
15%
6.2
9 ±
1.3
0ab
6
6.5
1 ±
1.3
4ª
6
6.4
4 ±
1.2
2ª
6
5.9
4 ±
1.6
7ª
6
6.5
9 ±
1.1
4ª
6
20%
6.9
7 ±
1.5
5b
7
6.6
8 ±
1.2
0ª
6,5
6.4
1 ±
1.4
3ª
6
6.2
2 ±
1.6
1ª
6
6.8
8 ±
1.3
3ª
7
P
0.0
001
0.6
285
0.9
641
0.5
264
0.0
608
Tab
le 6
. S
enso
ry e
va
luati
on
res
ult
s of
the
thre
e p
urp
le y
am
in
corp
ora
ted
bre
ad
fo
rmu
lati
on
s. P
rob
ab
ilit
y (
P)
valu
e w
as
ob
tain
ed t
hro
ugh
Fri
edm
an
AN
OV
A f
oll
ow
ed b
y p
ost
hoc
test
.
Valu
es e
xh
ibit
ing d
iffe
ren
t le
tters
in
th
e sa
me
colu
mn
poin
t ou
t st
ati
stic
all
y s
ign
ific
an
t d
iffe
ren
ces
(P<
0.0
5).
mainly on its nutritional value. Nevertheless, color,
aroma and texture are the factors usually guiding the
consumer’s preference rate. Of these three factors, color
interferes the most on the product’s preference (Bobbio
and Bobbio, 2001).
Given that there were no preferential differences
among the other sensory attributes, the three breads
evaluated can be considered approved.
Microbiological analysis
Considering that the microbiological analysis
was negative for Coliforms and Salmonella (Table 7), the
purple yam incorporated breads may be considered
proper for human consumption, as long as they have
been properly handled.
CONCLUSIONS
Through such findings, one concludes that any
of the purple yam incorporated breads tested in the
present study (10%, 15% and 20%), can substitute
ordinary bread (0%), with no effect on the diet’s caloric
value, since their centesimal compositions are similar.
Due to the presence of antioxidants in purple yam
incorporated bread, and to their ability to fight free
radicals, those breads can be considered as
health-promoting food. Furthermore, these findings point
out the feasibility of the consumption of purple yam
incorporated bread, as an alternative in the local bread
making industry, and an incentive to a larger production
of this tuber in the Amazonian region.
ACKNOWLEDGEMENTS
The authors are indebted to the Fundação de
Amparo à Pesquisa do Estado do Amazonas (FAPEAM)
for the master scholarship granted to Antonia Paiva
Teixeira. To Dr. Antonio José Inhamuns da Silva and
MSc. Cynthia Tereza Corrêa da Silva of Universidade
Federal do Amazonas (UFAM) for kindly having
allowed to carry out the centesimal composition analyses
in their laboratories. To MSc. Antonio Fábio Lopes de
Sousa, Arleilson de Sousa Lima and Ana Cláudia dos
Santos for their invaluable aid in undertaking of the
laboratory analyses. To Misters Claudio Adriano
Cardoso Amanajás and Francisco de Oliveira Batista for
their logistical support in the collection of purple yam
samples.
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