Production and Characterization of Nutritious
Peanut Butter Enhanced with Orange Fleshed
Sweet Potato by Naveen
Puppala in Novel Techniques in Nutrition and Food Science_journal of food technology
Abstract
Peanuts worldwide are popular for their nutritional quality and commercial potential. Their consumption
in Uganda is high and second after common beans thus making them a suitable food for fortification to
fight the increasing vitamin A deficiency in the country. Consumption of orange fleshed sweet potato
(OFSP) is equally high in the country and this too offers potential to fortify peanut butter for increased
intake of vitamin A. The objective of this study was to investigate the potential of producing a nutritious
peanut butter, with high shelf-life. An OFSP ratios of 0% (Control), 5% (Treatment 1), 10% (Treatment
2) and 15% (Treatment 3) were mixed with peanut butter. The product was assessed for proximate
composition using AOAC methods and sensory qualities. The shelf-life of product was also established by
determining the fat quality, beta-carotene retention and microbial quality. Fortifying peanut butter with
OFSP significantly increased the protein content from 20.47 to 27.76%, fat from 30.8 to 32.4%, sugars
from 2.96 to 25.51% and, beta-carotene from 244 to 1388μg 100g-1. In all treatments, the control had the
lowest amount of nutrient, while OFSP that was fortified with 15% peanut butter had the highest levels
of the nutrient. When OFSP was fortified with 10 and 15% peanut butter it resulted in higher retention
of β-carotene between 400 to 600μg 100-1g which could meet the daily World Health Organization
(WHO) recommendations of 350 to 500μg 100-1g. After storing the product for five months, OFSP that
was fortified with 10 and 15% peanut butter had good fat quality as reflected by the low acid value (AV)
below 0.9mg KOH-1 and peroxide value (PV) below 4mEq kg-1 respectively. There was a strong negative
correlation (r=0.049; p˂0.05) between peroxide formation and the amount of β-carotene in the peanut
butter. All peanut butter samples were free of dangerous levels of microbes. The peanut butter treated
with OFSP had acceptable sensory score of 6-7 on the scale of 1 to 9. The results suggest that peanut
butter fortified at 15% OFSP had greater shelf-life and meet the vitamin A requirements of school going
children.
Keywords: Peanut butter; OFSP; β-carotene; Fat quality
Introduction
Peanuts (Arachis hypogaea L) are popular worldwide because
of their value as plant protein source (23-35%) and fat (45-52%) [1].
The peanuts possess high nutritional and commercial value due to the
presence of fatty acids, protein, carbohydrates, minerals and vitamins
[2,3]. Globally, peanut consumption is relatively high and is consumed
either as roasted, cooked or as peanut butter [4]. In Uganda, peanuts
rank second with annual production of 210,000 tons in shell after common
beans (Phaseolus vulgaris; FAO, 2017). Peanuts are potential food
source for fortification since they are consumed widely in Uganda in
various forms as sauce, peanut butter and paste. In Uganda increasing
prevalence of vitamin A deficiency amongst children and pregnant women
has been reported at a rate of 19% to 20% respectively [5]. This
situation along with limited access to nutritious foods adversely
affects the wellbeing of children and adults. Consumption of peanut
butter fortified with vitamin A is considered as a way to reduce vitamin
A deficiency [6,7].
Peanut butter is a semi-perishable product with prolonged shelf life
due to its low moisture content [8]. Peanut products in storage are
exposed to ambient conditions, with exposure to sunlight. The heat
accumulated during storage and accelerates rancidity [8-10]. The rancid
peanut butter is unfit for consumption because of off flavors [11,12].
The β-carotene is a powerful antioxidant that provide protection against
oxidative processes in food systems [13,14]. The antioxidant activity
of β-carotene is attributed to their polyene frameworks [15]. Orange
Fleshed Sweet Potato (OFSP), one of the major sources of beta-carotene
is widely grown and consumed in Uganda [16]. In the year 1995,
researchers recognized the potential of OFSP varieties to address
widespread vitamin A deficiency in Sub Saharan Africa using integrated
agriculture-nutrition approach [17]. Use of OFSP is a rich plant-based
source of β-carotene, which the body converts into vitamin A [17].
Through the multi-partner initiative, OFSP was launched in Uganda headed
by Harvest-Plus. Various Non-Government Organizations (NGO), Volunteer
Efforts for Development Concerns (VEDCO), Farming for Food and
Development Program-Eastern Uganda (FFDP-EU) and National Agricultural
Research Organization (NARO) have since disseminated OFSP in Uganda to
create awareness and have released varieties such as Ejumula, Vita, and
Kabodeamong others; and value addition for increased consumption [18].
Research has shown that OFSP has the potential to improve the vitamin A
status of individuals [19,20]. Study by Jaarsveld et al. (2005) showed
that, there was a 10% significant improvement in Vitamin A that liver
stores amongst the school children who were fed on OFSP. Product
diversity can be a driver to its increased consumption especially
amongst the children. This study therefore aimed at production of a
shelf stable, high nutritious OFSP-fortified peanut butter product that
could be used by school-going children.
Materials and Methods
Materials
Twenty kilograms of peanut (Valencia variety) were obtained from the
National Semi-Arid Resources Research Institute, Soroti, Uganda.
Triglyceride stabilizer was purchased from Dansico Company, United
States of America (USA). Two hundred (200)kg of Orange fleshed sweet
potato roots (Kabode variety) were purchased from VEDCO Uganda at
maturity age of 4 months when roots have attained dark orange color and
expected to contain highest β-carotene content. Chemicals and reagents
used in laboratory analysis were obtained from Westford laboratory,
Kampala, Uganda.
Preparation of OFSP peanut butter
Peanut butter was produced following [21], with some modifications to
suit the available technology. Peanut kernels were selected, cleaned
using a 2-step wise cleaning method; 1) dry cleaning where sorting is
done, and 2) wet cleaning where the kernels were washed to remove dust
on the surfaces. The peanut kernels were then roasted in the electrical
oven (Model: GU-6) for 25 minutes at a temperature of 140 °C, then
cooled for 5 minutes and test was removed to ease sorting of seeds by
color to reduce the incidences of aflatoxin infection [22]. Peanuts that
passed sorting, were ground using a blade grinder (Capacitor Start
Motor; type: YC112M-2; HP 248A) till a smooth peanut butter was formed.
The OFSP flour was added to the smooth peanut butter in ratios of 0%
(C0), 5% (Treatment 1), 10% (Treatment 2) and 15% (Treatment 3). Varying
ratios were used to increase the concentration of β-carotene and
putting into consideration the effect of solids on the quality of peanut
butter [23]. The OFSP flour was chosen over OFSP pulp because of the
deteriorative effect that pulp can impose on the product due to high
moisture content. Mixing was done using a dough mixer (Type: 94/R10; No.
21602) for 15 minutes to achieve uniform and consistence mixture, and
0.7% of triglyceride stabilizer was added. The OFSP peanut butter and
control sample were packed in food grade plastic jars.
Chemical analyses
The samples packaged in food grade containers were delivered to
Makerere University chemistry laboratory for proximate analysis
(Moisture content, protein, fat, sucrose, fiber and beta-carotene), and
shelf stability (acid value, peroxide value, β-carotene retention and
microbial quality) studies.
Moisture
About 3g of each sample was weighted in the dry dishes and weight
recorded. The dishes with the sample were put in the oven and dried for
about 6 hours at temperature of 95 °C. The dishes were then cooled in a
desiccator and weights recorded and percent moisture determined,
Protein
Crude protein content of samples was determined using the standard
Kjeldahl method [24]. About 0.2g of each sample was digested using 5ml
concentrated Sulphur acid and Kjeldahl tablets as catalysts. The sample
solution was heated slowly for the first 6 minutes, heated rapidly after
stabilization for 2 hours then left to cool. The digest was
quantitatively transferred to a 50ml volumetric flask and made to volume
with distilled water, then shaken to homogenize the solution. The
sample distillate was prepared by pipetting 10ml aliquots of the digest
in a Markham still (Foss, Tecator, Britain), 20 ml of 40% sodium
hydroxide was introduced into the distillation chamber and distillation
was allowed to proceed for about 4 minutes. The distillate was collected
into the conical flask containing 10 ml boric acid (4%) and mixed
indicators (bromocresol green and methyl red); the end point was marked
by color change back to the original brown color. The blank titer was
subtracted from the sample titer and the total crude protein determined
using the equation below:
Note: (Titre X NHCL/1000 = No. of mole NH3)
Dietary fiber
Dietary fiber was determined on the basis of Acid Detergent Fibre
(ADF) standard method [24]. One gram of each sample was weighed and
mixed in 100ml of acid detergent fiber (28ml concentrated Sulphur acid
and 20g cetyltrimethylammonium ammonium Bromide) solution. The solution
was boiled for 1 hour on the fiber analyzer (Labconco Corporation,
Kansascity, Missouri 64132. Serial No. 246719) and then filtered through
a pre-weighed glass sintered crucible. The crucible was dried in the
oven for 30 minutes and cooled in the desiccator before weighing. The
fiber was determined using the formula below:
Fat
About 3g of sample was weighed into a thimble in triplicates. The
thimbles and their contents were placed into 50ml of petroleum ether
(PE) in a beaker assembled in the Soxhlet system. The fat in the sample
was extracted using PE, by boiling at 115 °C for 20 minutes and then
rinsed for 45 minutes. The beakers were transferred to the oven to
evaporate off the PE and other water-soluble material for 30 minutes at
90 ᵒC. The beakers were cooled in the desiccator to room temperature and
weights taken.
Sugar
Total sugars were determined by hot water extraction method (AOAC,
2002). One gram of each sample of peanut butter was accurately weighed
into 250ml beakers to which 1ml lead acetate was added followed by 70ml
of hot water. The beakers with the contents were then placed on a hot
water bath at 80 °C and heated for 1 hour. To the cooled sample
solution, half a spatula of sodium bicarbonate was added to precipitate
all the excess lead acetate. The sample was then transferred to 100ml
volumetric flask quantitatively and shaken to mix well. A portion of the
sample was poured into test tubes and centrifuged at 700rpm for 5
minutes.
Five (5) ml of the clear solution of the sample, 1 ml of concentrated
Sulphur acid and 20ml of distilled water were added to 100ml conical
flasks and then heated to boiling for 10 minutes. The cooled solution
was neutralized with sodium bicarbonate and transferred quantitatively
to 50ml volumetric flask and made to volume with distilled water and
mixed. To develop the color, 1ml of sample was added followed by 1ml of
phenol (5%) and 5ml of concentrated sulphuric acid to a clean test tube
and mixed well. The absorbance of the solution was read off at 470nm.
β-carotene
Following Rodriguez et al. [18], three (3)g of peanut butter was
weighed in the mortar. Using 50ml of cold acetone, the sample was ground
to extract the carotenoids. Experiment was repeated until the sample
was colorless, and then mixture was filtered through a funnel. About
30ml of petroleum ether where added to filtrate. To remove the acetone
residue, the mixture was washed in a 500ml separator funnel using 300ml
of distilled water, this was repeated three times. Petroleum ether (PE)
phase was collected in a 50ml volumetric flask through a funnel
containing 15g anhydrous sodium sulfate to remove residual water.
Absorbance of beta-carotene was read at 450nm using a spectrophotometry.
Shelf stability of OFSP peanut butter under different conditions
The peanut butter with added OFSP and control sample were stored on
shelf under ambient conditions that reflected the retail environment of
peanut butter and then analyzed for quality changes over a period of 5
months. Fat quality (acid value and peroxide value), β-carotene
retention and microbial quality (microorganisms of interest were E. coli, S.aureus, yeasts and moulds)was determined every after a month.
Fat quality
Acid value (AV): Acid value of treatments and
control sample was determined [24] by weighing 3g of each sample into
100ml conical flask. Solvent mixture (50ml; neutral 95% ethanol: diethyl
ether, v/v) with phenolphthalein were added to the sample in the flask.
The mixture was allowed to stand for 20 minutes shaking at an interval
of 3 minutes to ensure that the free fatty acids in the sample dissolve
into the solvent. The supernatant was decanted off and was titrated with
standard sodium hydroxide solution to the pink endpoint (the pink color
persisting for at least 10 seconds). The acid value was expressed as
percentage.
Where;
V is the number of ml of NaOH solution used
N is the exact normality, and
M is the mass in g of the sample
Peroxide Value (PV)
The Peroxide value was determined [24] by weighing 5g of sample into a
beaker and mixed thoroughly in a 30ml mixture of 3:2 glacial acetic
acid and chloroform solution by vigorous shaking. Saturated potassium
iodide solution (0.5ml) was added to the mixture, as a result of which
iodine was liberated due to reaction with the peroxide. This was then
titrated against a standard solution of sodium thiosulphate, using
starch solution as indicator. The procedure was repeated to determine
the titration value for a blank sample. PV was calculated as below:
Where;
S=Titration value of the sample (ml)
B=Titration value of the blank sample (ml)
N= Normality of the Sodium Thiosulphate solution= 0.01N
Sample Weight=5gm
Microbial Analysis
Staphylococcus auerus
Ten (10) grams of peanut butter sample was added into sterile bottles
having 90ml peptone water. After thoroughly mixing, the sample was
serially diluted up to 10-6. Twenty ml Baird parker agar (BPA) was
poured on Petri-dishes and left to set at room temperature. After
complete solidification, the plates were inverted to avoid dripping of
condensed water on solidified agar. Duplicate samples (0.1ml) of
dilutions 10-1 and 10-2 were surface spread on the solidified plated
petri-dishes using sterile glass rod. The plates were incubated at 37 °C
for 3 days. Enumeration was done considering spreaders and clusters as a
single colony (ISO 21527-2)
Yeasts and moulds
Yeasts and moulds count were made by adding 10g of peanut butter
sample into sterile bottles having 90ml peptone water. After thoroughly
mixing, the sample was serially diluted up to 10-6. Acidified agar
(15-20ml) was poured on Petri dishes and left to set at room
temperature. After complete solidification, the plates were inverted to
avoid dripping of condensed water onto the solidified agar. Duplicate
samples (0.1ml) of 10-1 and 10-2 dilutions were surface spread on the
solidified plated petri-dishes using sterile glass rod. The plates were
incubated at 30 °C for 3 days in upright position because yeasts and
molds grow upwards. Enumeration was done considering spreading colonies
and clusters as a single colony (ISO 21527-2)
Coliforms (E-coli)
Ten grams of peanut butter sample were added into sterile test
bottles having 90ml peptone water. After thoroughly mixing, the sample
was serially diluted up to 10-6. Dilutions of 10-1 and 10-2 were taken
in duplicate samples (1ml) and pour plated using 20ml of violet red bile
agar. After thoroughly mixing, the plated sample was allowed to
solidify and then incubated at 37 °C for 24 hours. Counts were made
considering the purplish red colonies as coliform colonies and clusters
as single colonies (ISO 4832).
Assessing acceptability of OFSP peanut butter
Fifty (50) consumer panelists were recruited from the School of Food
Technology, Nutrition and Bioengineering, Makerere University. The
panelists were briefed before the start of session. Four samples from
the five treatment combinations were presented to each panelist. Samples
were evaluated in the order of appearance on the ballot. Panelists were
asked to place a spoonful of peanut butter on plain bread to evaluate
the spread ability and consistency. They were also asked to rinse their
mouths with water between samples. The samples were evaluated and ranked
by the panelists for color, flavor, spread ability, consistency and
overall acceptability using 9-point Hedonic Scale, where 1=dislike
extremely, and 9=like extremely [25].
Data analysis
Data for sensory evaluation was analyzed using SPSS [26]. Data on
proximate analysis and keeping quality of the peanut butter sample were
tabulated and means subjected to ANOVA using Genstat 13th Edition). The means were separated using LSD (P≤0.05) to determine significant differences.
Result and Discussion
Although the moisture content of the control (C0) was significantly
lower than the treatment samples (P< 0.05), the moisture content of
the latter did not differ significantly implying that increased amount
of OFSP have no influence on the moisture content of the fortified
peanut butter. The moisture content of the control sample was 1.89%
which is in agreement with findings of McDaniel et al., 2012 who
reported that peanuts have moisture content between 1.4 to 2%. Fiber
content increased significantly (P<0.05) with an increase in the
ratio of added OFSP flour to peanut butter. The control sample had the
least fiber content, followed by treatment 1, 2, and 3. The increase in
the fiber content of the samples with increased ratio of OFSP could be
due to relatively high fiber content of OFSP which is reported to be in
the range of 1.8 to 3% [27].
The results showed that addition of OFSP to peanut butter does not
significantly affect the fat content of the peanut butter (Table 1). The
fat content of the control and treatments ranged between 30.83 to
32.45% though there was no significant difference among the samples. The
control sample (32.45%) and treatment 1 (32.53%) had the highest fat
content while treatment 3 (30.83%) had the least amount. The findings
also show that, the amount of fat decreased with increasing ratio of
OFSP flour added to the peanut butter. The current study showed that the
fat content of the peanut butter was between 32-30%, this is in
agreement with the findings of [28] who also reported peanut butter fat
content of 32% in the peanut butter. However, others reported higher fat
content between 49 to 51% [29-31]. This variation in fat content could
be due to differences in agro-ecology and varietal differences [21].
OFSP flour is devoid of fat 0.41% [32] and this could explain why there
was decrease in fat content of treatments with high ratio of OFSP flour.
Table 1: Proximate analysis for peanut butter samples.
Values are means±standard deviations. Means followed by the same letter in the same column are not significantly
different (p>0.05).
Note: Control (0% OFSP), treatment 1 (5% OFSP flour), treatment 2 (10%OFSP flour) and treatment 3 (15% OFSP flour).
The sugar and β-carotene contents in the study significantly
increased with increasing addition of OFSP flour in peanut butter,
implying that the more OFSP flour used, the more sugar and β-carotene
content of the peanut butter. The control sample had the least content
of sugar and β-carotene of 2.96% and 244µg100g-1 respectively
while Treatment 3 had the highest levels, over eight times and five
times of sugar (25.51%) and beta-carotene (1388µg100g-1)
respectively. The results also show that treatment 2 had higher sugar
and β-carotene content than Treatment 1, and both treatments had
significantly greater sugar and β-carotene than control. The sugar
content of the peanut butter was 2.96% which was in agreement with the
literature as stated by Settaluri et al. [2]. Sweet potatoes have a
relatively high sugar content, and this explains why increase in its
concentration led to significantly increased percentage of sugars.
According to study done by King et al. [33], he reported that peanuts
contain around 3µg/100g β-carotene, while [34] reported β-carotene
content in peanuts of 15.23µg/100g and Pattee et al. [35] reported
β-carotene of 60µg/100g. All the findings are in contrary to the results
of the current study, and this natural variation may be explained by
the geographical and varietal differences. On addition of OFSP to peanut
butter, beta-carotene increased to values that could meet the World
Health Organization [36] daily recommended in takes of 350 to 500µg100g-1 for children between 5 and 16 years.
The protein content significantly ranged from 20.47 to 27.76%, with
control having the highest protein content (27.76%), followed by
treatment 1 (25.79%), then treatment 2 (24.36%) and lastly treatment 3
(20.47%). The results reflect that, as substitution ratio of OFSP
increased, the protein content of peanut butter reduced significantly.
The results obtained in the study are in agreement with what was
reported by Shakerardekani et al. [30]; Riveros et al. [31] and Singh et
al. [37], who reported protein content in peanut butter in the range of
22 to 30%. According to Low et al., 2010, OFSP has a low protein value
of 0.016% and this could explain why there was significant decrease in
protein content of product with increased substitution ratio of OFSP.
Fat quality
Fat quality is very important as far as storage of peanut butter is
concerned because it affects peanut butter shelf life due to oil
susceptibility to rancidity [30,31]. Rancidity is often used as an
indicator of the stability and edibility of oils [38-40].
Acid value (AV)
Changes in the AV of control (C0), Treatment 1 (5% OFSP), Treatment 2
(10% OFSP), and Treatment 3 (15% OFSP) (Figure 1) showed a gradual
increase as the OFSP ratios and storage time increased. Acid Value in 5th
month of storage increased significantly in all samples, with control
(C0) showing 109% increase followed by 91% in treatment 1, 81% in
treatment 2, and 76% in treatment 3. By the fifth month, AV of control
and treatment 1 had increased to 1.08 milli-grams of potassium hydroxide
per gram of fat (mgKOHg-1) and 1.004 mg KOHg-1respectively. Treatment 2 and treatment 3 were still below 1mgKOHg-1. Kirk et al. [40] stated that when acid value is in the range of 1 to 1.5mgKOHg-1, rancidity is detected by sensory tests.
Figure 1: Changes in AV concentration of the OFSP peanut butter and control sample with storage time.
Line labeled ** shows the limit beyond which acidity of oils can start to affect sensory properties. Control sample
(C0), Treatment 1(5% OFSP), Treatment 2 (10% OFSP) and Treatment 3 (15% OFSP).
The AV represents the amount of the free fatty acids present in food
sample and is determined by measuring the number of milligrams of
potassium hydroxide required to neutralize the free fatty acids in 1g of
the sample. The AV also shows the extent to which the glycerides in the
oil have been decomposed by lipase [40]. Thus, every increase in the
potassium hydroxide shows the presence of more free fatty acids and also
indicates lipase activity on fats [41]. The free fatty acids increase
with storage time as described by Bendini et al. [38]. The increase is
triggered by exposure of lipase and other lipolytic materials to
atmospheric oxygen after peanut crushing [42]. Light and heat also
accelerate the breakdown and decomposition of fats to free fatty acids
[43]. Since the peanut butter samples were stored at ambient conditions,
there was a possibility of exposure to elevated temperatures and light
conditions during storage, which could have led to increased formation
of free fatty acids.
Peroxide value (PV) of OFSP peanut butter samples
From the first to the third month of storage, the treatment 2 and 3
did not register any peroxide unlike treatment 1which recorded some
peroxides. The control sample (C0) had peroxides formed in the second
month of storage. During the fourth and fifth month of storage, all the
samples had registered some levels of peroxides but with C0 registering
significantly high increase to a value of 19.62meqkg-1 (Figure
2). The results also show that, treatments with low OFSP ratio had high
rate of increase in the peroxide value. At peroxide value of 10meqkg-1,
oxidation reactions are initiated, and rancid flavors may start to be
noticed. The results however showed that, for the first four months of
storage PV was not high to cause rancidity unlike in the fifth month
where the PV for C0 significantly increased above the limit.
Figure 2: Changes in PV with storage time for the different peanut butter with added OFSP and control sample.
Line labeled** indicates the induction period beyond which peroxide formation accelerates rapidly and
development of off flavors. Control sample (C0), Treatment 1 (5% OFSP), Treatment 2(10% OFSP) and Treatment
3 (15% OFSP).
PV is an indicator of the initial stages of oxidative change in food
[44]. This method utilizes the principle of ferric ion complexion where
hydrogen peroxide (ROOH) is reduced with Fe2+ leading to formation of Fe3+ complexes
[41]. The concentration of peroxides as represented by the PV is useful
in assessing the extent to which spoilage has advanced. The report by
Azhar et al. [45] indicated that PV increased with storage time which is
in agreement with the current study which showed that PVs of the
samples increased with increasing storage time. Mailer et al. [46] also
claimed that more oxidation occurs in lipids with prolonged time of
storage. When the concentration of peroxides reaches an induction point
(10mEq/kg), complex chemical changes occur, and volatile products are
formed that are mainly the rancid taste and odour [38]. In the current
study, the PV for the different samples was between 2.5-19mEq/kg of fat
with C0 (19mEq/kg) having the highest and Treatment 3 the least PV
(2.5mEq/kg). Therefore, the OFSP peanut butter had not yet attained the
values necessary to produce the rancid flavors during the five months of
storage.
The presence of carotenoids in OFSP can inhibit the formation of
peroxides. Amongst the carotenoids, β-carotene has a higher potent for
peroxides, which involves formation of hydrogen radical abstraction
(ROO-CAR) complex, thus inhibiting utilization of the free radicals by
oxygen [15]. This may explain the reduced rates of peroxide formation in
samples with OFSP flour. Furthermore, peanuts have naturally occurring
phytochemicals like tocopherols and polyphenolics; these also play a
role in slowing or preventing lipid oxidation due to their
anti-oxidative nature [41,47].
Relationship of PV and AV with OFSP levels and storage time
Table 2: Correlation of PV with independent variable AV, storage time and OFSP ratio.
R2=68.9; Values with * have a significant positive or negative relationship at P≤0.05
There was no linear relationship between AV and OFSP ratio (r=
-0.1847, P≥0.05) (Table 2). However, a strong positive relationship
between AV and time of storage (r=0.8955, P≤0.05) was detected. PV was
significantly negatively (r=-0.4971) and positively (r=0.5852)
associated with OFSP ratio and storage time, respectively (Table2). The
correlations further show that AV significantly affected PV positively
(r= 0.758). The negative relationship between PV and OFSP indicates that
OFSP was resisting the formation of peroxides. This may be because
β-carotene contained in OFSP reacts with fat radical to form a stable
radical which does not quickly react with oxygen [48]. Antioxidants
terminate the free radical intermediates, by being oxidized themselves,
thus acting as reducing agents [48,49].
β-carotene retention of treatment samples with storage time
In all the samples, β-carotene significantly reduced as the storage
time increased (Figure 3). The control sample (C0) had the least
β-carotene which also significantly kept on reducing with storage time.
Treatment 3 with highest level of β-carotene (1388.2µg/100g) in the 1st month of storage and it had reduced to 580.6µg/100g in the 5th
month. The results further show that, the reduction in β-carotene was
proportion to the amount present in the samples. Treatment 2 and 3 which
had high values, also registered a significantly high loss with
storage. However, at the end of the fifth month of storage, treatment 2
and 3 still had considerably high β-carotene levels compared to
treatment 1 and control (C0).
Figure 3: Changes in β-carotene with storage time for the different peanut butter with added OFSP and control
sample.
Control sample (C0), Treatment 1: (5% OFSP flour), Treatment 2: (10%OFSP flour) and Treatment 3: (15% OFSP
flour).
The losses in β-carotene over time may be due to exposure of peanut
butter samples to light during storage as β-carotene is sensitive to
heat and light [50]. The processing procedures and time also expose
β-carotene to oxygen which may further influence the losses as noted by
Bechoff et al. [51] and Wheatley [52]. In addition, the difficulty in
complete extraction of the carotenoids during analysis may have
introduced variability in the results obtained as it was also noted by
Bengtsson et al. [16]. Despite the fact that there was significant loss
in β-carotene during storage, the quantities retained by the Treatments 2
and 3 were high compared to the control sample. Thus, peanut butter
fortified with 10% and 15% OFSP can contribute some level of β-carotene o
the daily β-carotene requirements.
Relationship between β-carotene with storage time, OFSP ratio and PV units
Results in Table 3 show that β-carotene was significantly correlated
with storage time, OFSP flour and PV value while both storage time and
PV were negatively correlated (r=-0.5483 and; r=-0.5852) with the
β-carotene retention, respectively. On the other hand, there was a
strong positive correlation observed between OFSP ratio and the
β-carotene (r=0.7547, P≤0.05). The literature indicates that a decrease
in β-carotene during storage is natural [51]. This was also reflected in
the study as a strong negative correlation was noted between
beta-carotene and storage time (r=0.5483, P≤0.05). The decrease in
β-carotene can be addressed by increasing the amount added to the food.
The current study showed that β-carotene content correlates positively
with the amount of OFSP flour added in the sample (r=0.7547, P≤0.05)
indicating that an increase in the OFSP flour increased positively the
level of β-carotene. These findings agree with Bechoff et al. [12] and
Bengtsson et al. [16] who reported that more OFSP flour added in foods
increases the β-carotene content.
Table 3: Correlation of B-carotene with other independent variables.
R2=89.2; values with *have a significant positive or negative relationship (P≤0.05)
Among other factors that influence β-carotene content, is oxidation.
Since β-carotene plays an anti-oxidative role, the increasing PVs of the
peanut butter samples negatively affected the retention of β-carotene
as it is expected that β-carotene is used up in the process of
inhibition of peroxide formation. β-carotene binds with the free
radicals and blocks oxygen uptake during oxidation and it is depleted as
it binds with the free radicals [37]. This phenomenon explains why
β-carotene correlates negatively with the PV and may also explain why
treatments with high OFSP registered lower values of PV since β-carotene
inhibited the formation of peroxides
Changes in microbial quality of OFSP peanut butter during storage.
The presence of microbes such as Escherichia coli, Staphylococcus
aureus, yeasts and molds in peanut butter can be detrimental to human
health [53,54]. In the present study (Table 4), all samples tested
negative for yeasts and molds and E. coli. However, Treatments 1, 2 and 3 tested positive for presence of S. aureus and C0 tested negative (Table 3). The S. aureus ranged from 5.1*100cfu/g to 4*101cfu/g with treatment 3 recording the highest and treatment 2 had the least. The counts of S. aureus in treated peanut butter decreased with storage time.
Table 4: Changes in colony counts for microorganisms in peanut butter with OFSP and control sample during storage.
N. D= Not Detected
Note: Control sample (C0), treatment 1 (5% OFSP flour), treatment 2 (10%OFSP flour) and treatment 3 (15% OFSP flour).
aureus has several strains, and some are known for causing
food spoilage which doesn’t result into harm to the consumers but leads
to food wasting (Institute of Food Technologists and Food and Drug
Administration [55]. The production of S. aureus toxins is
favored by minimum water activity (aw) of 0.9 [56], yet the peanut
butter is known to have very low water activity of below 0.7 [56], which
does not support production of toxins.
S.aureus competes poorly in most foods with low moisture
content [56,57], and owing to the fact the samples had moisture in the
range of 1.8 to 2% which is far below the required for growth S. aureus
and toxin production. This may also explain the reduction trend of
Staphylococci numbers in the peanut butter samples with storage time.
USDA (2010) set the minimum Coliform content to be below 3.6cfu/g and all samples were free of E. coli. This indicates good hygiene since the presence of coliform (E. coli)
in peanut butter can reflect the possibility of fecal contamination as
coliforms are considered normal flora of the intestinal tract of humans
and animals [52]. The set standard for the yeasts and moulds by UNBS et
al. [58] in peanut butter is ˂103cfu/g of sample which also shows that
the peanut butter produced is safe for consumption since the results
from microbial analysis reported absence of yeasts and moulds.
Changes in sensory attributes of peanut butter with storage time
No significant changes in color were noticed in all the samples
(Table 5). Although significant changes in aroma, spread ability,
oiliness, taste, flavor and overall acceptability were noticed in
samples with storage time; the sensory scores were within desirable
range of 6 to 7and according to sensory scale 6 represents like
moderately and 7 like much (Table 5). The sensory attributes are mainly
affected by the changes in the fat quality of the peanut butter products
due to fat oxidation [7,59]. However, the effect of fat oxidation was
not noticed in the OFSP enriched peanut butter samples except in the
control (C0). In the present study, microbial testing was done prior to
sensory evaluation [60-62] and all treatments were found to be
microbiologically safe for sensory evaluation.
Table 5: Sensory changes for the control sample and peanut butter with added OFSP with storage time.
All values represent means ±SD; Values with same letter in a column are not significantly different (p≤0.05).
Control sample (C0), Treatment 1: (5% OFSP flour), Treatment 2: (10%OFSP flour) and Treatment 3: (15% OFSP flour).
Conclusion
The findings suggest that use of OFSP in the production of
peanut butter improved β-carotene content, which increases with
high substitution levels. Treatment 3 with 15% OFSP had the
highest β-carotene, highest beta-carotene retention on shelf, better
fat quality and had acceptable sensory score. Thus, it is concluded
that OFSP can be used in peanut butter to enhance its nutritional
value (vitamin A requirements) of the school-going children. There
is a need to encourage the diverse utilization of OFSP in peanut
butter production to improve the vitamin A status of school going
children. This could be one of the most possible ways of improving
OFSP utilization by incorporating it in common local products like
Oddi.
Acknowledgement
This research was supported in part by Makerere University,
Uganda; by the Office of Agriculture, Research and Policy, Bureau
of Food Security, US Agency for International Development, under
the terms of Award No. AID-ECG-A-00-07-0001 to the University
of Georgia as management entity for the US Feed the Future
Innovation Lab on Peanut Productivity and Mycotoxin Control. The
laboratory technicians of the School of Food Technology, Nutrition
and Bio-engineering (FTNB) are appreciated for the technical
support during the study.
References
- Muzoora
S, Margaret LK, Bailey H, Vuzi P (2017) Status on aflatoxin levels in
groundnuts in Uganda. The Pan African Medical Journal 27(4): 11.
- Settaluri
VS, Kandala CVK, Puppala N, Sundaram J (2012) Peanuts and their
nutritional aspects-A review. Food and Nutrition Sciences 3(12):
1644-1650.
- Sundaram
J, Kandala CV, Holser RA, Butts CL (2010) Determination of in-shell
peanut oil and fatty acid composition using near-infrared reflectance
spectroscopy. Journal of the American Oil Chemists’ Society 87(10):
1103-1114.
- Derek BJ, Michael B, Halmer P (2006) The encyclopedia of seeds: science, technology and uses. CABI publishers.
- Uganda Bureau of Statistics (UBOS) and ICF (2018) Uganda demographic
and health survey 2016. Kampala Uganda and Rockville, USA: UBOS and
ICF, Maryland, USA.
- Jan
KRL, Cole D, Loechl C, Lynam J, Andrade M (2010) Challenge theme paper
3: nutritional impact with orange-fleshed sweet potato (OFSP). Social
Sciences Working Paper 1: 73-105.
- Nambiar
PM, Florkowski WJ (2013) Peanut Paste/ butter consumption frequency in
the republic of uganda: count data model approach. Selected paper
prepared for presentation at the Southern Agricultural Economics
Association Annual Meeting (SAEA), Orlando, FL, 3-5.
- Gills
LA, Resurreccion AVA (2000) Overall acceptability and sensory profiles
of unsterilized peanut butter and peanut butter stabilized with palm
oil. Journal of Food Processing and Preservation 24(6): 495-516.
- Okello
KD, Kaaya AN, Bisikwa J, Were M, Oloka KH (2010) Management of
Aflatoxins in Groundnuts. A manual for Farmers, Processors, Traders and
Consumers in Uganda. aflatoxins in groundnuts (Arachis hypogea).
National Agricultural Research Organization in collaboration with
Makerere University pp. 18-21.
- Sewald M, Vries J (1990) Food product shelf life. Medallion Laboratories, Analytical Progress.
- Waheed
A, Ahmad T, Yousaf A, Zaefr IJ (2004) Effect of various levels of fat
and antioxidant on the quality of broiler rations stored at high
temperatures for different periods. Pakistan Veterinary Journal 24(2):
70-75.
- Kristott J (2000) The stability and Shelf-life of food. In: Kilcast
D, Subramanian P (Eds), Fats and Oils. Woodhead publishing. England, UK.
- Passwater RA (1996) Beta-carotene and other carotenoids: The
antioxidant family that protects against cancer and heart disease and
strengthens the immune system. Keats Inc. publishing.
- Charoensiri
R, Kongkachuichai R, Suknicom S, Sungpuag P (2009) Beta-carotene,
lycopene, and alpha-tocopherol contents of selected Thai fruits. Food
Chemistry 113: 202-207.
- Guo JJ, Hu
CH (2010) Mechanism of chain termination in lipid peroxidation by
carotenes: a theoretical study. Journal of Physics and Chemistry Biology
114(50): 16948-16958.
- Bengtsson
A, Namutebi A, Alminger LM, Swanberg L (2008) Effects of various
traditional processing methods on the all-trans- β-carotene content of
orange fleshed sweet potato. Journal of Food Composition and Analysis
21(2): 134-143.
- Jan
WL, Mwanga ROM, Andrade M, Carey E, Marie BA (2017) Tackling Vitamin, A
deficiency with biofortified sweet potato in Sub-Saharan Africa. Global
Food Security 14: 23-30.
- Amaya DBR, Mieko K (2004) Harvest plus handbook for carotenoid
analysis. (International center for tropical agriculture), Published by
Ciat. Technical Monograph Series 2.
- Awuni V, Alhassan MW, Amagloh FK (2017) Orange-fleshed sweet potato
(Ipomoea batatas) composite bread as a significant source of dietary
vitamin A. Food science & nutrition 6(1): 174-179.
- Jamil KM, Brown KH, Jamil M, Peerson JM, Keenan AH, et al. (2012)
Daily consumption of orange-fleshed sweet potato for 60 days increased
plasma b-carotene concentration but did not increase total body vitamin a
pool size in Bangladeshi women1-3. The journal of Nutrition Community
and International Nutrition 142: 1896-1902.
- Ozcan M, Serap S (2003) Physical and chemical analysis and fatty
acid composition of peanut, peanut oil and peanut butter from COM and
NC-7 cultivars. Grasas y Aceites 54(1): 12-18.
- Galvez BG, Matias RS, Yanez MM, Sanchez MF, Arroyo AG (2002) ECM
regulates MT1-MMP localization with β1 or αvβ3 integrins at distinct
cell compartments modulating its internalization and activity on human
endothelial cells. Journal of Cell Biology 159(3): 509-521.
- Palomar LS, Galvez LA, Dotollo MO, Lustre OA, Resurreccion AVA
(2006) Stabilized peanut spread with roasted cassava flour: Peanut
butter and spreads. Monograph series No.6. United States Agency for
International Development Peanut Collaborative Research Support Program,
Phillippines, USA.
- AOAC (2002) Official methods of analysis. Association of Official Analysis Chemistry, Washington DC, USA.
- Resurreccion, Anna VA (1998) Consumer sensory testing for product development, 1st [Ed], Springer publishers.
- SPSS Inc (2007) SPSS for windows, Version 16.0. Chicago, USA.
- Sanoussi AF, Adjatin A, Dansi A, Adebowale A, Sanni LO (2016) Mineral composition of ten elite sweet potato (Ipomoea batatas [L.] ) Landraces of Benin. International Journal of Current Microbiology and Applied Sciences 5(1): 103-115.
- Akhtar S, Khalid N, Ahmed I, Shehzad A, Suleria RH (2013)
Physicochemical characteristics functional properties and nutritional
benefits of peanut oil: A review critical reviews in Food Science and
Nutrition 51(12).
- Adjou ES, Dahouenon AE, Soumanou MM (2012) Investigations on the
microflora and processing effects on the nutritional quality of peanut (arachis hypogeal l). Journal of Microbiology, Biotechnology and Food Sciences 2(3): 1025-1039.
- Shakerardekani A, Karim R, Ghazali HM, Chin LN (2013) Textural,
rheological and sensory properties and oxidative stability of nut
spreads-A review. International Journal of Molecular Science 14(2):
4223-4241.
- Riveros
CG, Mestrallet MG, Nepote, V, Grosso NR (2009) Chemical composition and
sensory analysis of peanut pastes elaborated with high-oleic and
regular peanuts from Argentina. Grasas Y aceites 60(4): 388-395.
- Mills
JB, Tumhimbise GA, Jamil KM, Thakker SK, Failla ML, et al. (2009) Sweet
potato beta-carotene bioefficacy is enhanced by dietary fat and not
reduced by soluble fibre intake in Mongolian gerbils. Journal of
Nutrition 139(1): 44-50.
- King
JC, Blumberg J, Ingwersen L, Jenab M, Tucker LK (2007) Tree nuts and
peanuts as components of healthy diet. The Journal of Nutrition 138(9):
1736-1740.
- Panwar
MB, Mathur PB, Bhaasharla VV, Reddy D, Sharma KK (2013) Rapid, accurate
and routine HPLC method for large-scale screening of pro-vitamin A
carotenoids in oilseeds. Journal of Plant Biochemistry and Biotechnology
24(1): 84-92.
- Pattee
HE, Pierson JL, Young CT, Giesbrecht FG (1982) Change in roasted peanut
flavor and other quality factors with seed size and storage time.
Journal of Food Science 47(2): 455-456.
- WHO/FAO (2004) Vitamin and mineral requirements in human nutrition (second edition).
- Singh B, Singh U (1991) Peanut as a source of protein for human foods. Plants for Human Nutrition 41(2): 165-177.
- Bendini
A, Cerretani L, Salvador MD, Fregapane G, Lercker G (2010) Stability of
the sensory quality of virgin olive oil during storage. An overview.
Italian Food and Beverage Technology pp. 5-18.
- Akusu
MO, Achinewhu SC, Mitchell J (2000) Quality attributes and storage
stability of locally and mechanically extracted crude palm oils in
selected communities in rivers and Bayelsa states, Nigeria. Plant Foods
for Human Nutrition 55(2): 119-126.
- Kirk RS, Sawyer R (1991) Pearson’s Composition and Analysis of Foods. In: Food (Food adulteration and inspection) Analysis. (9th edn), Longman Scientific and Technical, Harlow, UK.
- Shahidi F, Zhong Y (2005) Bailey’s Industrial Oil and Fat Products.
In: Shahidi F (Ed.), Lipid Oxidation: Measurement Methods. (6th edn), John Wiley and Sons Inc, St. John’s, Canada, Volume 6.
- Haas, MJ (2001) Lypolytic Microoganisms, Enzymatic lipid hydrolysis
(lipolysis). In: Downes FP, Ito K (Eds.), Compendium of methods of the
microbiological examination of foods. (4th edn), American public health association, Washington, US, pp. 175.
- Ahn
DU, Ajuyah A, Wolfe FH, Sim JS (1993) Oxygen availability affects
prooxidant catalyzed lipid oxidation of cooked turkey patties. Journal
of Food Science 58(2): 278-291.
- Auezova
L, Saliba C, Moussa EH, Hosry LE, Yammine S, et al. (2012) A
methodological approach to study almond oil stability in relation to
alpha-tocopherol supplementation. Journal of Food and Nutrition Sciences
3(12): 1710-1715.
- Azhar KF, Nisa K (2006) Lipids and their oxidation in seafood. Journal of Chemical Society of Pakistan 28(3): 298-305.
- Mailer RJ, Graham K, Ayton J (2012) The effect of storage in
collapsible containers on olive oil quality. Australian Government,
Rural Industries Research and Development Corporation. Publication No.
12/008. Project No. PRJ-006488.
- Maestri DM, Nepote V, Lamarque AL, Zygadlo JA (2006) Natural
products as antioxidants. In: Imperato F (Ed). Phytochemistry: advances
in research, pp. 105-135.
- Aluyor
EO, Jesu MO (2008) The use of antioxidants in vegetable oils- A review.
African Journal of Biotechnology 7(25): 4836-4842.
- Ling
LT, Palanisamy UD, Cheng MH (2010) Prooxidant/antioxidant ratio
(ProAntidex) as a better index of net free radical scavenging potential.
Molecules 15: 7884-7892.
- Boon
CS, McClements DJ, Weiss J, Decker EA (2010) Factors influencing the
chemical stability of carotenoids in foods. Critical Reviews in Food
Science and Nutrition 50(6): 515-53.
- Bechoff A,
Poulaert M, Tomlins KI, Westby A, Menya G, et al. (2011) Retention and
Bioaccessibility of Beta-carotene in blended foods containing
orange-fleshed sweet potato flour. Journal of Agricultural and Food
Chemistry 59: 10373-10380.
- Wheatley C, Loechl C (2008) A critical review of sweet potato
processing research conducted by CIP and partners in Sub-Saharan Africa.
Social Science Working Paper No. 2008-4. The International Potato
Center (CIP). Lima, Peru.
- Odu
NN, Okonko IO (2012) Bacteriology quality of traditionally processed
peanut butter sold in Port Harcourt metropolis, Rivers State, Nigeria.
Researcher 4(6): 15-21.
- United
States Department of Agriculture (USDA) (2010) USDA commodity
requirements. PP12, Peanut Products for Use in Domestic Programs.
- Institute of Food Technologists and Food and Drug Administration
(IFT/FDA) (2003) Evaluation and definition of potentially hazardous
foods: Comprehensive reviews in food science and food safety. NSF
International Volume 2.
- Behling RG, Eifert J, Erickson MC, Gurtler JB, Kornacki JL, et al.
(2010) Selected pathogens of concern to industrial food processors:
infectious, toxigenic, toxico-infectious, selected emerging pathogenic
bacteria. In: Kornacki JL (Ed), Principles of microbiological
troubleshooting in the industrial food processing environment, Food
microbiology and food Safety. Behling food safety associates, Springer
Science + Business Media publishers, Madison, Wisconsin, USA.
- FDA (2010) Water activity (aw) in foods. Inspections, Compliance, Enforcement, and Crimininal Investigations.
- https://members.wto.org/crnattachments/2013/tbt/UGA/13_4341_00_e.pdf
- Ogunwolu
SO, Ogunjobi MAK (2010) Nutritional and sensory evaluation of cashew
nut butter produced from Nigeria cashew. Journal of Food Technology
8(1): 14-17.
- Kilcast D, Subramaniam, P (2000) The stability and shelf-life of food. In: (2nd edn), Leatherhead Food Research Association. Woodhead publishing ltd, Cambridge, England.
- Food and Drug Administration (2012) Foodborne pathogenic microorganisms and natural toxins. In: Bad bug book. (2nd edn), Center for Food Safety and Applied Nurtition, USA, pp. 89-92.
- Okello
DK, Biruma M, Deom MC (2010) Overview of groundnuts research in Uganda:
Past, present and future. African Journal of Biotechnology 9(39):
6448-6459.
For more articles in journal of food technology
