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The Federal University of Technology, Akure, Nigeria
JoST 2011
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Centre for Research and Development (CERAD)
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Microbial and sensory qualities of plantain flour
and its reconstituted dumpling (amala) as influenced
by blanching temperatures and duration
E
OLUWALANA, I. B.*, OLUWAMUKOMI, M. O., FAGBEMI, T. N. and
OLUWAFEMI, G. I.
Department of Food Science and Technology,
The Federal University of Technology, Akure, Ondo State. Nigeria.
1
ABSTRACT: The effect of blanching conditions on the microbiological quality of flour produced from
plantain (Musa AAB) and sensory qualities of reconstituted plantain flour (dumpling or amala) w ere
investigated. Results show ed that vary ing the blanching temperature and time had considerable
effects on the microbial quality of the plantain flour. The total viable counts of samples of unripe
plantain pulp blanched at 60 oC for 5 minutes (UPB60 – 5 ), unripe plantain pulp blanched at 60 oC for
10 minutes (UPB60 – 10 ) and unripe plantain pulp blanched at 80 oC for 5 minutes (UPB80 – 5) w ere the
same (2.0 cfu/gx 103). Whereas, extending the duration of blanching at 60 oC to 15 minutes (UPB60 – 15)
and dipping the samples in hot water at 80 and 100 oC for 10 and 15minutes (UPB80 – 10, UPB80 – 15,
UPB100 – 10 and UPB100 – 15) reduced the total viable count significantly. The control unblanched sample
(UPUBCO) had the highest total viable count of 3.0 cfu/g x 103. Coliform w as not found in any of the
blanched samples. Mould and yeast grow th were also higher in the control and samples blanched at a
low er temperature of 60 oC for 5 and 10 minutes compared to the other samples treated at higher
temperatures and longer duration. For the sensory quality evaluation, the samples blanched at 60 oC
for 10 and 15 minutes w ere rated best for taste, colour and tex ture. Amala produced with plantain
slices blanched at 60OC for 5 min had a similarly preferred tex ture but w as less acceptable in terms of
c o l o ur a nd t a s t e . T he P a ne l i s t s do w ng r a de d pr o du c t s f r o m pl a nt a i n s l i c e s di ppe d i n ho t w a t e r a t
temperatures above 80OC for more than 10 minutes particularly in terms of colour, taste and tex ture.
Keyw ords: Plantain, Blanching, Sensory attributes, Microbial quality.
JoST. 2011. 2(2): 70-73.
Accepted for Publication, August 1, 2011
I NT R O D UC T I O N
Plantain, the edible fruit of the genus Musa, is
one of the major crops of the humid lowland
tropical areas, whose production in Nigeria has
gained considerable importance in recent years.
Ogazi (1982) reported that over 80% is harvested
during the period of September to February and
that there is much wastage at this time as some
of the products do not store for a long period.
Plantain is a remarkable example of a neglected
food crop because the proportion of research
r e s o u r c e s a l l o c a t e d t o i t fa l l s fa r f r o m o t h e r
s t a r c h y f r u i t s . T h e f r u i t r i p e n s u s u a l l y a ft e r
harvest to soft sweet fruits of high sugar and
l o w a c i d c o n t e n t . O n e o f t h e r e a s o n s fo r t h e
neglect of plantain by researchers is its close
relationship to banana which has received more
attention earlier and the common but erroneous
belief that plantain and banana are similar in
physiological pattern (Wilson, 1986).
Plantain is known to have an advantage over
other starchy staple foods like yam, cassava and
cocoyam where labour is an important factor of
production as a result of its high energy returns
per unit of labour. Plantain is widely consumed
* Corresp on den c e t o: Dr. Olu wa la n a , I. B . ; i olu wa lan a 2 0 02 @ yah oo. com;
Journal of Sustainable Technology, Vol. 2, No. 2 (November 2011), ISSN: 2251-0680
Pp 7 0
Microbial and sensory qualities of plantain flour
by the whole pop ulation and many different
dishes from a wide range of cultural groups are
prepared from it (Stover and Simmonds, 1987).
It is important to study the quality of the plantain
flour to determine its suitability for use in the
production of a thick traditional dumpling called
“ A m a l a ” wh i c h i s p o p u l a r i n s o u t h we s t e r n
Nigeria among the Yorubas. Amala is prepared
by reconstituting two parts of the flours with
about one part of boiling water which is mixed
thoroughly with a wooden spatula over a heating
medium (Ogazi, 1998).
The objective of this work was to produce and
examine the micro bio logical quality of flo ur
produced from blanched plantain as well as the
sensory qualities of the reconstituted plantain
flour known as Amala.
MATERIALS AND METHODS
Mature green and healthy plantain (Musa, AAB
g r o u p ) b u n ch e s wer e o b ta i ne d f r o m th e
International Institute of Tropical Agriculture
(IITA), Oyo Road, Ibadan. All reagents used
were of analytical grade.
Preparation of Plantain Flour
T he fruits which were hard and green were
subsequently defingered, washed, hand-peeled
and manually sliced into cylindrical pieces of
2mm thickness. Blanching was carried out on
the sliced samples in hot water at 60oC, 80oC and
100oC. For each temperature chosen, the timing
was varied for 5, 10 and 15 minutes and dried in
t h e a i r o v e n a t 6 5 oC f o r 2 4 h r s , w h i l e t h e
unblanched samples (Control) were also dried
using the air oven at the same temperature and
time as recommended by Baiyeri and Ortiz (2000).
The dehydrated pieces were milled in a hammer
mill to prod u c e f l o u r w h i c h p a s s e d th ro u g h a
1 5 0 �m s c re e n . T h e p l a n ta i n f l o u r o b ta i n e d w a s
p a c k a g e d i n p o l y e th y l e n e b a g s l a b e l e d a n d
s to re d a t ro o m te m p e ra tu re f o r f u rth e r a n a l y s i s .
T h e f l o u rs w e re c o d e d a s f o l l o w s : U P B 60-5 =
Unripe plantain blanched at 60oC for 5 minutes;
UPB60-10 = Unripe plantain blanched at 60oC for
10 minutes; UPB60-15 = Unripe plantain blanched
at 60oC for 15 minutes; UPB80-5 = Unripe plantain
b lanched at 8 0 oC fo r 5 minutes; UP B 80-10 =
Unripe plantain blanched at 80oC for 10 minutes;
UPB80-15 = Unripe plantain blanched at 80oC for
15 minutes; UPB100-5 = Unripe plantain dipped
in hot water at 100oC for 5 minutes, UPB100-10 =
Unripe plantain dipped in hot water at 100oC for
10 minutes, UPB100-15 = Unripe plantain dipped
in hot water at 100oC for 15 minutes and UPUBc
= Unripe and un-blanched plantain (Control).
Microbiological examination
The samples were evaluated for microbiological
e xa mi na t i o n a s d e s c r i b e d b y A n d e r so n a n d
Hollorook (1980). Plantain flours were examined
for viable count of Bacteria, Coliform, Yeast and
Moulds using Nutrient Agar (NA), MacConkey
Agar (MCA) and Potato Dextrose Agar (PDA)
respectively. The pour plate method was used
t o e n u me r a t e t h e t o t a l n u mb e r o f v i a b l e
micro o rgani sms in the p lantain fl o ur. Serial
dilution was done using normal saline diluted to
10-3 dilution and 1ml of 10-3 dilution was added
into each sterile Petri dish. Molten Plate Count
Agar (MPCA) was added into the plates, agitated
and allowed to solidify and incubated at 37oC
for 48hrs. The number of colonies counted on
t h e p l a t e s t a k e n i n t o c o n s i d e r a t i o n wi t h t h e
dilution factor.
The presence of coliform was determined by
inoculating plantain flour samples on MCA and
incubating at 37 oC for 18 hrs. The presence of
y e a s t s a n d mo u l d s we r e e n u me r a t e d b y
inoculating the serial dilution of plantain flour
samples on PDA. The plates were incubated at
25oC for 3 days as recommended by Harrigan
and McCance (1976).
Sensory evaluation
A total of 10 semi–trained panelists drawn from
the Department of Food Science and Technology,
F e d e r a l U n i v e r s i t y o f Te c h n o l o g y A k u r e
a sse sse d t he se nso r y q ual i ty of the
r e c o nst it ute d p la nt a in f lo u r “a ma l a ” . T he
Journal of Sustainable Technology, Vol. 2, No. 2 (November 2011), ISSN: 2251-0680
Pp 7 1
Microbial and sensory qualities of plantain flour
Statistics Analysis
All the experiments were conducted in triplicates
a n d t h e me a n ± s t a n d a r d d e v i a t i o n we r e
repo rted. Data were subjected to analysis of
variance (ANOVA) and means sep arated b y
D u n c a n M u l t i p l e R a n g e Te s t ( D M RT ) a t a
significance level of Pd” 0.05
sensory quality of amala made from each flour
sample was measured on a standard nine-point
Hedonic scale. The panelists rated the amala
samples for colour, taste and texture on a scale
varying from 1 = dislike extremely to 9 = like
extremely (Larmond, 1982).
RESULTS AND DISCUSSION
The microbiological evaluation of the plantain
flour and sensory attributes of the reconstituted
flour ‘amala’ samples are presented in Table 1.
The Total viable count range between 1 - 3 x 103
c fu / g wh i l e t h e u n b l a n c h e d c o n t r o l h a d t h e
highest value of 3 x 103 cfu/ g
Table 1: Microbiological Quality of plantain flour blanched at 60, 80 and 100 OC for 5, 10 and 15
minutes
Samples
UPUB60
UPUB80
UPUB100
U PU B CO
5
TVC
2. 0
cfu/gx103
Coliform
cfu/gx103
ND
Mould &
Yeast
sfu/gx103
3 .5
ND = Not Detected
10
15
5
10
2 .0
1. 0
2. 0
ND
ND
ND
ND
3. 2
1 .4
2 .4
2. 2
N o v i a b l e c o u n t s we r e d e t e c t e d o n s a m p l e s
UPB80-15 and UPB100-15 indicating that blanching
at 80 to 100 oC for 15 minutes greatly hindered
the microbial growth and thereby guaranteed
the microbial safety of the flour products. Total
viable count of sample: UPB60-5, UPB60-10, UPB80are not different from one another (2.0cfu/gx103)
5
while that of the UPB60-15, UPB80-10, UPB100-5 and
UPB100-10 which are treatments at either higher
temperatures or longer durations are 1.0, 1.5, 1.4
and 1.0 cfu/gx103 respectively. These counts are
minimal and are within safe levels and may not
c o n s t i t u t e h e a l t h h a z a r d s p r o v i d e d t he f l o u r
s amp le s a r e we ll ke p t t o p r ev e nt r e contamination and other microbial proliferation
after processing. Coliform was only found in
the Control sample (1.0cfu/gx103) indicating that
t he b l anching p ro c es s given to t he ot he r
samples were effective against Coliform. Mould
1. 5
15
5
10
15
ND
1. 4
1. 0
ND
3. 0
ND
1 .0
ND
1 .0
ND
2 .0
ND
2. 0
1. 0
4 .0
and Yeast count ranged between 1.0 to 4.0 cfu/g
x 103. The UPB60-5 had 3.5cfu/g x103 while the
h i g h e s t c o u n t wa s f o u n d i n t h e u n b l a n c h e d
Control (4.0 cfu/gx103).
The results of senso ry evaluation in Table 2
showed that UPB60 – 10 was rated best in terms
of taste which was significantly different (Pd”
0.05) from other treated samples and the Control
except sample UPB60 – 15. Sample UPB80 – 10 was
r a te d b e st in c o lo ur a nd wa s f o und to b e
significantly preferred (P d” 0.05) to samples
UPB60 – 5, UPB80-5, UPB100-5, UPB100-10 and UPB100
– 15. The texture of sample UPB60 – 5, UPB60 – 10,
UPB60 – 15 and the Control were found to be
higher and better and were significantly different
(Pd” 0.05) from samples UPB80 – 5, UPB100 – 5,
UPB100 – 10 and UPB100 – 15. This means that
dipping the plantain pulp in hot water at 100oC is
not advisable.
Journal of Sustainable Technology, Vol. 2, No. 2 (November 2011), ISSN: 2251-0680
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Microbial and sensory qualities of plantain flour
Table 2: Sensory Properties of Reconstituted Plantain Flour (Amala)
Sample
Taste
Colour
Texture
5.8b,c
6.9a,b
7.7a
UPUBCO
UPB60 – 5
6.7b
5.4b,c
7.2a
UPB60 – 10
8.7a
6.6a,b
7.5a
UPB60 – 15
8.5a
7.6a
7.4a
UPB80 – 5
4.6c
4.5c
5.2b
UPB80 – 10
6.6b
8.0a
6.9a
UPB80 – 15
6.7b
6.8a,b
7.3a
UPB100 – 5
3.4d
5.8b
4.8c
UPB100 – 10
4.6c
5.5bc
4.6c
UPB100 – 15
3.8c,d
4.6c
4.4c
Values in the same column with different letters in superscript are significantly
different at p< 0.05
CO NC LU SI O N
Blanching plantain pulp at temperatures of 60oC
t o 1 0 0 oC f o r 1 0 t o 1 5 m i n u t e s s i g n i f i c a n t l y
reduced the microbial load and could therefore
serve as a means of prolonging the shelf life of
the chips from pulp or flour produced from it.
Likewise the sensory qualities of taste, colour
and texture appear to be enhanced at blanching
at 60-80oC for 10-15 minutes. At 100oC for 1015oC, the texture of the amala from this sample is
found to be adversely affected. The temperature
range of 60-80 and blanching time of 10 minutes
is therefore found to be more suitable for the
he a t p r o c e s s i n g o f p l a n t a i n c hi p s i n o r d e r t o
produce acceptable quality flour.
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