Research Article
Patience Chisa Obinna-Echem
Patience Chisa Obinna-Echem
Corresponding Author
Food Science and Technology, Rivers State
University, Nkpolu-Oroworukwo, Port Harcourt, Nigeria
E mail: patience.obinna-echem@ust.edu.ng; Tel: +234 90 9400 0342.
Godstime Uchechi Thomas
Godstime Uchechi Thomas
Food Science and Technology, Rivers State
University, Nkpolu-Oroworukwo, Port Harcourt, Nigeria
Abstract
This study assessed the physicochemical and sensory
properties of roasted skinned and unskinned groundnuts sold in River State
University campus and its environment. Samples were obtained from three
locations: University’s back gate, main gate and shopping complex with sample
codes BSG, MSG and SSG respectively, for the skinned samples and BUG, MUG and
SUG for the unskinned samples. Standard analytical methods were used for the
analysis. The physicochemical properties of the skinned and unskinned samples
ranged respectively, from 6.49 - 6.64 and 6.48 – 6.58 for pH; 0.04 – 0.07 and
0.06 – 0. 09 %lactic acid for titratable acidity (TTA); 1.17 – 2.55 and 1.12 –
2.08% for moisture; 0.28 – 0.47 and 0.53 – 0.99% for free fatty acid (FFA) and;
11.90 – 19.50 and 10.20 – 14.00 mEq for peroxide value (PV). The assessors’ degree of likeness for the appearance,
aroma, taste (sweetness), freshness, crunchiness and overall acceptability of
the roasted skinned groundnut samples ranged from 6.20 – 7.10, 5.65 –
6.10, 5.35 – 6.20, 5.45 – 5.70, 5.75 – 6.45 and 6.00 – 6.15 respectively, while
the values for the unskinned samples ranged from 5.15 – 5.80, 5.65 – 5.85, 5.65
– 6.10, 4.85 – 5.85, 5.90 – 6.50, and 5.55 – 5.88 respectively, pH, TTA,
moisture, FFA and PV of the samples are within satisfactory limits and the
third quartile sensory results reveal degree of likeness from like slightly to
like very much, implying that the roasted groundnut whether peeled or unpeeled
were of good quality for consumption.
Abstract Keywords
Roasted skinned and unskinned groundnuts, pH, Peroxide
value, Free fatty acid, moisture content, sensory properties.
1. Introduction
Groundnut (Arachis
hypogaea L.), commonly known as peanut, is a tropical legume grown for its
edible seeds and consumed in different parts of the world. In West Africa,
Nigeria is the largest groundnut producing country accounting for 51% of
production in the region. Groundnuts are utilized in various forms. It can be
consumed directly after boiling or roasting with or without the shell (epicarp)
[1-2], crushed for oil extraction for home
and industrial uses, cooking, soap production, and body cream [3], and the cake afterwards consumed as snack. It
is also used in production of peanut butter, mixed with other spices for snack
foods, used as flour for incorporation into different food formulations etc. [1-2, 4]. Groundnut roasted or boiled with or
without the shell and the seed coat skinned or unskinned is sold in public
places such as markets, offices, schools, motor parks, restaurants,
supermarkets and also hawked along express way in both rural and urban areas
especially in southern Nigeria. Nutritionally, roasted groundnut contain high
levels of protein (31.45-33.17%) and fat (47.3-49.15%) with low levels of
moisture (2.02 -2.17%), ash (4.04 – 4.13%, carbohydrate (6.63-7.87%) and crude
fibre (5.47-6.56%) [5]. Low
moisture content is desirable in roasted groundnuts. It prevents the formation
of secondary, volatile compounds, such as aldehydes and ketones, which cause
groundnut off-flavor while high water content will encourage microbial growth,
chemical reactions (oxidation) and sensory changes leading to decline in
product quality and acceptability. The off-flavour in roasted groundnut is also
attributed to the role of water activity during storage of fresh produce.
Groundnut is a good source of lipid (47%) [6] and
the lipid content is high in polyunsaturated fatty acids: Oleic acid (C18:1) in
the range of 44.78-82.17%, Linoleic acid (C18:2) ranging from 2.85-33.92% with
small amount of saturated fatty acid such as Palmitic acid (C16:0) in the range
of 5.31-11.49 [7]. Susceptibility of
groundnut to oxidation is attributable to the lipid content which can lead to
decrease in nutritional and product quality. Hydrolysis of the lipid molecules
in groundnut releases the free fatty acids. Free fatty acid is an indication of
lipase efficacy that can catalyze oxidative decay of oils by enzymatic and or
chemical hydrolysis to form off volatile components [8].
This can cause rancidity and affect the sensory quality of the product
in terms of color, texture, and other physiological properties [9]. Peroxide value is another quality index for
oil seed like groundnut. Peroxide values express the reactive oxygen content in
terms of milliequivalents (meg) of free iodine per kilogramme of fat [10]. They are indicators of the ability to resist
lipolytic and oxidative deterioration when stored [6].
Products with low peroxide value (< 10 mEg/kg) are considered fresh
and of good quality, while high peroxide value would mean a weak resistance to
reactive forms of oxygen and a signal of deterioration [11-12]
and between 20 - 40 mEg/kg rancid, taste becomes noticeable. Lipid
oxidation reactions will lead to the formation of aliphatic aldehydes, ketones
and alcohols [13]. Aldehydes are key
compounds that affect the flavour of roasted groundnuts. The pleasant sensory
attributes of roasted groundnuts appreciated by consumers when eaten alone or
with other foods are flavour, aroma, colour, appearance, taste, texture in
terms of crunchiness. There are some studies on groundnut and groundnut based
snacks in different parts of the country: proximate composition of raw and
roasted varieties of groundnut [5], mycotoxin
and fungi metabolites in groundnut snack foods in Lagos [14], effect of potash on quality of fried groundnut cake
called kulikuli [15], effect of roasting on the quality of
groundnuts [16] and effect of edible coating
materials on roasted groundnut [13]. Knowledge
of the quality characteristics of roasted skinned and unskinned groundnuts from Rivers
State and the university campus is lacking. This study was therefore, aimed at
assessing the physicochemical and sensory attributes of roasted skinned and unskinned groundnuts
sold in Rivers State University and its environs.
2.
Materials and methods
2.1 Materials
Freshly packaged roasted skinned and unskinned groundnut
samples were purchased from three locations: Main gate, Back gate and Shopping
complex of the Rivers State University, Port Harcourt Rivers State, Nigeria.
The chemicals used were of analytical grade from the laboratories of the
Department of Food Science and Technology, Rivers State University, Port
Harcourt.
2.2. Method
2.2.1. Determination of the
physicochemical properties of the roasted peeled and unpeeled groundnut samples.
The physicochemical properties of the samples: Moisture, pH,
titratable acidity (TTA), peroxide value (PV) and free fatty acids (FFA) of the
roasted peeled and unpeeled groundnuts were determined following the standard
method of AOAC [17].
2.2.1.1 Moisture
content determination
The moisture
content of 5 g of the milled sample was determined gravimetrically after drying
to a constant weight in a hot air oven (Gallen Kamp, UK) at 1050C
and cooling in a desiccator.
2.2.1.2. pH and total titratable acidity
(% Lactic acid)
pH of the samples was determined using a pH meter (TS 625,
USA) after calibration using standard buffer of pH 4.0 and 7.0. The milled
sample (5 g) was homogenized with 20 ml of distilled water and then filtered
into a beaker. The pH meter probe was inserted and the reading taken.
Thereafter, 2 drops of phenolphthalein indicator was added and titrated against
standard 0.1N sodium hydroxide solution until a pale pink color persisted for
about 10-15 seconds for complete neutralization. The titratable acidity was calculated as: %TTA = (Titre X
Normality of equivalent acid X 100)/sample weight.
2.2.1.3. Peroxide value determination
To each of the powdered samples (5 g) in a conical flask and
a blank, was added 18 ml of chloroform, 12 ml of acetic acid and 0.5 ml of 2%
Potassium Iodide solution. The solution was thoroughly mixed and stored in the
dark for 30 min. Thereafter, 30 ml of distilled water and 1 ml of starch
indicator were added and slowly titrated with 0.01N Na2S2O3
until the purple color disappeared. The peroxide value was calculated as: PV =
(Titre X Normality of acid X 100)/Sample weight.
2.2.1.4 Free fatty acid determination
To 5 g of milled sample in a 200 ml conical flask with 2 ml
of phenolphthalein indicator was added 25 ml of neutralized warm ethanol and
titrated with 1 N NaOH
until the solution retained a pinkish colour
for at least 30 seconds the endpoint reading was recorded. The FFA was
calculated as: %FFA = 0.256 x Titre.
2.2.2.
Sensory evaluation
Sensory analysis was
carried out according to the method described by Obinna-Echem and Torporo, [18]. Roasted
skinned and unskinned groundnuts were evaluated for aroma,
appearance, taste, crunchiness, rancidity and overall acceptability. Twenty
untrained panelists from the
University community were used. They were staff and students of the Department of Food
Science and Technology, who are consumers of the groundnut type. The assessors evaluated the range of sensory
attributes of the samples based on a 9-point Hedonic scale, with the degree of
likeness of the product attribute expressed as: 1 = Dislike extremely, 2 =
Dislike very much, 3 = Dislike moderately, 4 = Dislike slightly, 5 = Neither
like or dislike, 6 = Like slightly, 7 = Like Moderately, 8 = Like very much and
9 = Like extremely. The panelists were asked to rinse their mouths
with water after tasting each groundnut sample.
2.3 Statistical analysis
Data obtained were
subjected to statistical analysis using Minitab (Release 18.1) Statistical
Software English (Minitab Ltd. Conventry, UK). Statistical differences and
relationships among variables were evaluated by analysis of variance under
general linear model and Turkey pairwise comparison at 95% confidence level.
Differences in the sensory attributes were established using nonparametric
Friedman test.
3. Results
and discussion
3.1. Physicochemical properties of roasted
skinned and unskinned groundnuts from different
locations in Rivers State University campus and its environment
3.1.1. Moisture content
The moisture content of the roasted skinned and unskinned
groundnuts is shown in Fig 1. Moisture content of the skinned roasted groundnuts ranged from 1.17 –
2.55% for samples BSG and SSG, respectively, while the roasted unskinned
groundnuts moisture content varied from 1.12 – 2.08%. Sample from MUG had
significantly (P<0.05) the highest moisture content and sample from BUG had
the least. The moisture content of any food is an index of its
water activity and is used as a measure of the stability and susceptibility to
microbial contamination [19]. Moisture
content of the skinned
and unskinned roasted groundnuts is in agreement with the moisture
content groundnut (1.81%) reported by Atasie et al., [6] and 2.02 – 2.17
reported by Kamuhu et al., [5]. 4 - 6.8%). Moisture content of 9.0% is recommended by the
CODEX standard for peanuts [20]. Low
moisture content is crucial for safe storage of nuts, this implies that the
roasted groundnut samples with low moisture content can be stored for a long
period of time and still retain their crunchiness which it is appreciated by
consumers. It will also prevent the formation of secondary, volatile compounds,
such as aldehydes and ketones, which cause off-flavour in groundnuts.
Figure
1.
Moisture content of roasted skinned and unskinned groundnut from Rivers State
University and its environment.
(Bars and error bars represent mean and standard
deviation of duplicate samples. Bar with the same superscript are not
significantly different at p<0.05. BSG = Back gate skinned roasted groundnut;
BUG = Back gate unskinned roasted groundnut; MSG = Main gate skinned roasted
groundnut; MUG =Main gate unskinned roasted groundnut; SSG = Shopping complex
skinned roasted groundnut; SUG = Shopping complex unskinned roasted groundnut).
3.1.2. pH and Total titratable acidity
Fig. 2, presents the pH and Total titratable acidity (TTA)
as % Lactic acid of the groundnut samples. pH of the roasted skinned
groundnuts ranged from 6.49 - 6.64 for
samples SSG and BSG, respectively. The pH of the roasted unskinned groundnuts
ranged from 6.48 – 6.58, sample SUG had significantly (P<0.05) least pH and
sample MUG had the highest. pH is a
measure of the acidity or alkalinity of a solution on a logarithm scale on
which 7 is neutral, lower values are more acid and higher values more alkaline [21]. The
pH of the roasted groundnuts was near neutral (6.48 - 6.64) and within the
range of the standard pH (6–7) for peanuts [22]. TTA
of the roasted skinned groundnuts ranged from 0.04 – 0.07 %
lactic acid for samples MSG, SSG and BSG. TTA of the roasted unskinned
groundnuts ranged from 0.06 – 0. 09 % lactic acid for sample BUG and SUG
respectively. Total titratable acidity is a function of a given
base (sodium hydroxide, NaOH) neutralizing an acid(s) (lactic, phosphoric,
etc.) in a volume of liquid, thus estimating both free hydrogen ions and
hydrogen ions that are bound to weak acids that can react with the strong base
and be neutralized [23]. The TTA of the
roasted groundnuts is low indicating little or no acid production in the
samples which is desirable for an unfermented product. There was no significant
(p<0.05) difference in the acidity of the roasted skinned or unskinned groundnut
samples. The result was comparable with the values of 0.10 - 0.14 reported for
groundnut milk by Adeiye et al., [24]. pH
and TTA impact on flavour. Tartness is attributable to acid pH due to the production
of organic acids but TTA is a better prognosticator of acids impact on flavour than pH [24].
Figure
2.
pH and total titratable acidity (% lactic acid) content of roasted skinned and unskinned groundnut
from Rivers State University and its environment.
(Bars and error bars represent mean and standard
deviation of duplicate samples. Bar with the same superscript are not
significantly different at p<0.05. BSG = Back gate skinned roasted
groundnut; BUG= Back gate unskinned roasted groundnut; MSG = Main gate skinned
roasted groundnut; MUG =Main gate unskinned roasted groundnut; SSG=Shopping
complex skinned roasted groundnut; SUG=Shopping complex unskinned roasted
groundnut).
3.1.3. Free fatty acid
Free fatty acid (%) of the roasted skinned and unskinned groundnuts is presented in Table 1. The FFA of the roasted skinned groundnuts ranged from 0.28 – 0.47% for samples BSG and MSG, respectively, while that of the roasted unskinned groundnuts ranged from 0.53 – 0.99%. Sample from BUG had significantly (P<0.05) least value while sample from MUG had the highest value. Free fatty acid is an indication of lipase efficacy that can catalyze oxidative decay of oils by enzymatic and or chemical hydrolysis to form off volatile components [8] that can affect the sensory quality of the product. The free fatty acid content of the groundnut samples (0.28 - 0.99%) are within the acceptable CODEX standard of 1.0% for peanuts [20], implying that there was no hydrolytic retrogression or oxidative rancidity of the samples to levels that would impair the sensory attributes of the roasted groundnut, though the levels in the unpeeled samples were significantly (p<0.05) higher. FFA was employed to verify the quality and edibility of the oils of which groundnut is an excellent oil seed and the result indicated that the roasted groundnuts whether skinned or unskinned for sale were good for consumption.
Table
1.
Free fatty acid and Peroxide value of
roasted skinned and unskinned
groundnuts from in Rivers State University campus and its
environment
Sample |
Free Fatty Acid (%) |
Peroxide Value (mEq O2/Kg) |
BPG |
0.28d±0.03 |
10.20d±0.28 |
BUG |
0.53bc±0.03 |
15.90d±0.14 |
MPG |
0.47c±0.05 |
11.90cd±0.14 |
MUG |
0.99a±0.03 |
15.00b±1.41 |
SPG |
0.39cd±0.01 |
14.00bc±0.00 |
SUG |
0.67b±0.05 |
19.50a±0.70 |
Values are means ± standard deviation of duplicate
determinations. Means within a column with different superscripts are
significantly different at (p<0.05).
(BSG=Back gate skinned roasted groundnut; BUG=
Back gate unskinned roasted groundnut; MSG=Main gate skinned roasted
groundnut; MUG=Main gate unskinned roasted groundnut; SSG=Shopping complex
skinned roasted groundnut; SUG=Shopping complex unskinned roasted groundnut). |
|
3.1.4. Peroxide value
Peroxide values of the roasted skinned and unskinned
groundnuts are shown in Table 1. The roasted skinned groundnuts had peroxide values in the
range of 10.20 – 14.00 mEq O2/Kg, sample SSG had significantly
(P<0.05) highest peroxide value and sample BSG had the least. Peroxide value
of the roasted unskinned groundnuts varied from 11.90 – 19.50 mEq O2/Kg
respectively, for samples MSG and SUG. Fatty
acid composition of peanut and peanut products makes them susceptible to rancid
and off-flavours through lipid oxidation [26]. The
peroxide values of the roasted skinned
and unskinned groundnuts samples were within the range of peroxide
value of different varieties of peanut crude oil (2.87 – 15.38 mEq O2/Kg)
[27], except for sample SUG with a peroxide
value of 19.50 mEq
O2/Kg which may be due to the high proportion
of unsaturated fatty acids (85.76%) in this sample compared to the others. The
values are within the Codex Alimentarius acceptable peroxide values of 10–15 mEq O2/Kg
[28], except for sample SUG. At higher
peroxide value, the groundnut would have a rancid flavour, due to lipolytic and
oxidative reactions [6]. The high peroxide
value (19.50 mEq O2/Kg)
of unskinned roasted
groundnut from sample SUG could imply an onset of rancidity though the sample
at the point of purchase was freshly
packaged.
3.2.
Sensory properties of roasted peeled and unpeeled groundnuts from different locations in Rivers
State University campus and its environment
The mean of the
assessors’ degrees of likeness of the sensory attributes (appearance, aroma,
taste - sweetness, freshness, crunchiness and overall acceptability) of the
roasted skinned and unskinned groundnuts
are shown in Fig. 3. Other relevant information from the analyzed sensory data such
as the first and third quartile, interquartile ranges, mode and frequency of
mode are shown in Table 2.
Table 2. Relevant analyzed sensory data of roasted skinned and unskinned groundnuts from the Rivers State University campus and its environment
Attributes |
Samples |
Mean |
StDev |
Minimum |
Q1 |
Median |
Q3 |
Maximum |
Mode |
N for Mode |
Appearance |
BPG |
7.10 |
1.45 |
4 |
6.25 |
7.5 |
8 |
9 |
8 |
8 |
BUG |
5.15 |
1.57 |
2 |
4 |
5.5 |
6.75 |
7 |
4, 6, 7 |
5 |
|
MPG |
6.20 |
1.15 |
4 |
5 |
6 |
7 |
8 |
6 |
6 |
|
MUG |
5.80 |
1.54 |
3 |
4.25 |
6 |
7 |
9 |
6, 7 |
5 |
|
SPG |
6.85 |
1.27 |
3 |
6 |
7 |
8 |
9 |
7 |
7 |
|
SUG |
5.75 |
2.07 |
1 |
4 |
6.5 |
7 |
9 |
7 |
7 |
|
Friedman Test Pvalue: Not Adjusted
for ties =0.002; Adjusted for ties = 0.001 |
||||||||||
Aroma |
BPG |
6.10 |
1.97 |
2 |
4.25 |
7 |
8 |
9 |
7, 8 |
5 |
BUG |
5.65 |
1.60 |
3 |
4 |
6 |
7 |
8 |
4 |
6 |
|
MPG |
5.65 |
1.27 |
4 |
4.25 |
6 |
6 |
8 |
6 |
8 |
|
MUG |
5.80 |
1.47 |
3 |
5 |
6 |
7 |
8 |
6 |
6 |
|
SPG |
6.00 |
1.81 |
3 |
4 |
6.5 |
7 |
9 |
7 |
6 |
|
SUG |
5.85 |
1.98 |
2 |
5 |
6 |
7 |
9 |
5 |
5 |
|
Friedman Test Pvalue: Not Adjusted
for ties =0.881; Adjusted for ties = 0.858 |
||||||||||
Taste |
BPG |
5.35 |
2.32 |
2 |
4 |
5.5 |
7 |
9 |
4 |
5 |
BUG |
5.75 |
1.71 |
3 |
4.25 |
6 |
7 |
8 |
7 |
6 |
|
MPG |
6.2 |
1.58 |
4 |
5.25 |
6 |
7.75 |
9 |
6 |
9 |
|
MUG |
6.1 |
1.29 |
4 |
5 |
6 |
6.75 |
9 |
6 |
8 |
|
SPG |
6.05 |
1.82 |
3 |
4.25 |
6 |
8 |
9 |
6, 8 |
5 |
|
SUG |
5.65 |
2.39 |
1 |
4.25 |
6 |
7.75 |
9 |
6 |
8 |
|
Friedman Test Pvalue: Not Adjusted
for ties =0.918; Adjusted for ties = 0.907 |
||||||||||
Freshness |
BPG |
5.70 |
1.66 |
3 |
4 |
5.5 |
7.75 |
8 |
4, 8 |
5 |
BUG |
5.30 |
1.69 |
2 |
4 |
5 |
6.75 |
9 |
5 |
5 |
|
MPG |
5.50 |
1.79 |
2 |
4 |
5.5 |
6 |
9 |
4, 6 |
6 |
|
MUG |
4.85 |
1.73 |
1 |
4 |
5 |
6 |
8 |
5 |
8 |
|
SPG |
5.45 |
1.4 |
2 |
4.25 |
6 |
6 |
7 |
6 |
9 |
|
SUG |
5.85 |
1.63 |
2 |
5 |
6 |
7 |
9 |
7 |
6 |
|
Friedman Test Pvalue: Not Adjusted
for ties =0.523; Adjusted for ties = 0.451 |
||||||||||
Crunchiness |
BPG |
5.75 |
2.2 |
1 |
4.25 |
6 |
8 |
9 |
8 |
5 |
BUG |
5.90 |
2.27 |
2 |
4 |
6 |
7.75 |
9 |
6 |
6 |
|
MPG |
6.45 |
1.79 |
1 |
6 |
6.5 |
7.75 |
9 |
6 |
7 |
|
MUG |
6.50 |
1.47 |
3 |
6 |
6 |
7.75 |
9 |
6 |
7 |
|
SPG |
6.40 |
1.96 |
2 |
5.25 |
6 |
8 |
9 |
6 |
6 |
|
SUG |
6.30 |
1.98 |
1 |
5 |
6 |
8 |
9 |
6, 8 |
5 |
|
Friedman Test Pvalue: Not Adjusted
for ties =0.748; Adjusted for ties = 0.705 |
||||||||||
Overall Acceptability |
BPG |
6.00 |
1.53 |
3.6 |
4.85 |
6 |
7.4 |
8.2 |
5 |
3 |
BUG |
5.55 |
1.46 |
2.6 |
4.25 |
5.7 |
6.6 |
8.2 |
6.6 |
3 |
|
MPG |
6.00 |
0.86 |
4.6 |
5.4 |
6 |
6.9 |
7.4 |
5.4, 7 |
3 |
|
MUG |
5.81 |
1.00 |
4.2 |
5.2 |
5.7 |
6.35 |
8.4 |
4.6, 5.2, 5.4, 5.6 |
2 |
|
SPG |
6.15 |
1.11 |
3.8 |
5.45 |
6.1 |
7 |
7.8 |
5.6 |
3 |
|
SUG |
5.88 |
1.54 |
1.4 |
4.95 |
5.7 |
7.2 |
7.8 |
5.6, 7.8 |
3 |
|
Friedman Test Pvalue: Not Adjusted for ties =0.784; Adjusted for
ties = 0.779 |
Sensory evaluation is a scientific method that
evokes, measures, analyzes and interprets responses to products as perceived
through the senses of sight, smell, touch, taste, and sound [29]. The skills of the assessors in the
interpretation of their perception of the attributes and translating same to
the mean degree of likeness scale is very crucial for a reliable result. For
the roasted skinned groundnut samples, the degree of likeness of the
appearance, aroma, taste, freshness against rancidity, crunchiness and overall
acceptability ranged respectively, from 6.20–7.10, 5.65 – 6.10, 5.35– 6.20,
5.45 –5.70, 5.75–6.45 and 6.00–6.15, which is within the scale of neither like
nor dislike to like moderately. The third quartile values for the appearance,
aroma, taste (sweetness), freshness, crunchiness and overall acceptability as
shown in Table 2 were respectively in the range of 7.00 – 8.00, 6.00 – 8.00,
7.00 – 8.00, 6.00 - 7.75, 7.75 – 8.00 and 6.90 – 7.40. It showed that 75% of
the assessors’ degree of likeness for the attributes was that of like
moderately to like very much. For the roasted unskinned
groundnut samples, the degree of likeness of the appearance, aroma, taste
(sweetness), freshness, crunchiness and overall acceptability ranged
respectively, from 5.15 – 5.80, 5.65 – 5.85, 5.65 – 6.10, 4.85 – 5.85, 5.90 –
6.50 and 5.55 – 5.88. These mean values
are in the scale of neither like nor dislike. The third quartile values were
6.75 – 7.00, 7.00, 6.75 – 7.75, 6.00 - 6.75, 7.75 – 8.00 and 6.35 – 7.20
respectively, for the appearance, aroma, taste (sweetness), freshness,
crunchiness and overall acceptability. It showed that 75% of the assessors’
degree of likeness for the attributes was that of like slightly to like
moderately. The result revealed that the assessors’ degree of likeness for the unskinned roasted groundnuts was significantly (p<0.05) lower than those of
the skinned roasted groundnuts. This could be due to the already exposed
appearance of the skinned ones against the unskinned and
the unskinned ones required the assessors’ efforts in skinning
before assessment and consumption. The degree of likeness of the freshness of
the samp-les confirms the physicochemical result that the samples had not gone
rancid.
Figure
3.
Box plot of Assessors’ degrees of likeness of sensory attributes of roasted skinned and unskinned groundnut
from Rivers State University and its environment.
Bars and error bars represent mean and standard
deviation of duplicate samples. Bar with the same superscript are not
significantly different at p<0.05. (BSG=Back gate skinned roasted groundnut;
BUG = Back gate unskinned roasted groundnut; MSG = Main gate skinned roasted
groundnut; MUG=Main gate unskinned roasted groundnut; SSG=Shopping complex
skinned roasted groundnut; SUG=Shopping complex unskinned roasted groundnut).
4.
Conclusions
The pH of the samples
is near neutral with low TTA which showed that there was no biochemical
reaction for the production of organic acids in the sample. Moisture, FFA and PV of the roasted skinned and unskinned groundnut
samples were within the CODEX standard for peanuts. The assessors’ degree of likeness for
the sensory
attributes: appearance, aroma, taste (sweetness), freshness, crunchiness and
overall acceptability of the roasted skinned groundnut samples was within the
scale of neither like nor dislike to like moderately (5.35 - 7.10) for the
skinned samples and dislike slightly to like slightly (4.85 - 6.50) for the unskinned samples. The
third quartile sensory results revealed that the degree of likeness by 75% of
the assessors was that of like moderately to like very much. This implies that
the roasted groundnut samples whether skinned or unskinned were of good quality and liked to
varying degrees by the consumers. It will be important to ascertain the
microbiological quality of the ready to eat roasted groundnuts as
microbiologically unsafe foods may look, smell and taste good.
Acknowledgements
The authors appreciate the technical assistance of
Dr. Owuno Friday of the Analytical Laboratory in the Department of Food Science
and Technology.
Funding
Not
Applicable
Availability
of data and materials
All data will be made available on request according
to the journal policy.
Conflicts
of interest
Authors have declared that no competing interests
exist.
References
1.
Akinnibosun, F. I.; Osawaru, E. E.
Quality assessment of peeled and unpeeled roasted groundnut (Arachis hypogaea
L.) Sold in Benin City, Nigeria. Int. Res. J. N. Appl. Sci. 2015, 2(3), 18-32.
2.
Kayode,
F. O.; Oguntona, C. R. B.; Elemo, G. N.; Bankole, A. O.; Erukainure, O. L. Chemical
properties and microbial quality of peanut (Arachis hypogaea) snacks in Lagos
metropolis. Ferment. Technol. Bioeng. 2011, 1, 77–87.
3.
Lawan,
I.;
Ali, M. A.;
Abubakar, M. S.; Muhammad, A.I. An
Overview of Groundnut Oil Extraction Technologies. Conference Paper · September
2015
Proceedings of Second International
Interdisciplinary Conference On Global Initiatives for Integrated Development
(IICGIID 2015 Chukwuemeka Odumegwu University, Igbariam Campus Nigeria) Sept.
2–5, 2015
4.
Tapiwa,
R.S.; Yu-Xiang, M.; Zhao, Q.; Hua-Min, L.; Xue-De, W. Technical aspects of
peanut butter production processes: Roasting and grinding processes review. J.
Food Process. Preserv. 2022, 46(4), e16430.
5.
Kamuhu, R.; Mugendi, B.; Kimiywe, J.;
Njagi, E. Proximate analysis of raw and roasted groundnut (Arachis hypogaea L.): Red Valencia and manikanta varieties. Int. J.
Food Sci. Nutri. 2019, 4(4), 191-194
6.
Atasie, V. N.; Akinhanmi, T. F.; Ojiodu,
C. C. Proximate analysis and physico-chemical properties of groundnut (Arachis hypogaea L) Pakistan J. Nutri.
2009, 8(2), 194–197.
7.
Indiarto,
R.; Rezaharsamto, B. The physical, chemical and microbiological properties of
peanuts during storage: A Review. Int. J. Sci. Technol. Res. 2020, 9(3), 1909–1913.
8.
Gulluoglu, L.; Bakal, H.; Onat, B.;
El-Sabagh, A.; Arioglu, H. Characterization of peanut (Arachis hypogaea L.) seed oil and fatty acids composition under
different growing season under Mediterranean environment. J. Exp. Biol. Agric.
Sci. 2016, 4(5S), 564–571.
9.
Opio,
P.; Photchanachai, S. “Modified atmosphere influences aflatoxin B1
contamination and quality of peanut (Arachis
hypogaea L.) kernels cv. Khon Kaen 84 -8,” J. Stored Prod. Res. 2018, 78,
67–73,
10.
Low, L. Kim.; Ng, C. S. Analysis of
oils: Determination of peroxide value Book Section Publisher Marine Fisheries
Research Department, Southeast Asian, http://hdl.handle.net/1834/41021.
Accessed 03/01/2023 07:43:27. Fisheries Development Center.
11.
Mohammed, M. I.; Hamza, Z. U.
Physicochemical properties of oil extracts from Sesamum Indicum L. seeds grown
in Jigawa state Nigeria. J. Appl. Sci. Environ. Manag. 2008, 12(2), 99–101.
12.
Adebayo, S. E.; Orhevba, B. A,; Adeoye,
P. A.; Musa, J. J.; Fase, O.J. Solvent extraction and characterization of oil
from African star apple (Chrysophyllum
albidum) seeds. Acad. Res. Int. 2012, 3(2), 178.
13.
Riveros, C. G.; Mestrallet, M. G.;
Quiroga, P. R.; Nepote, V.; Grosso, N. R. Preserving sensory attributes of
roasted peanuts using edible coatings Int. J. Food Sci. Technol. 2013, 48,
850–859.
14.
Kayode,
O.F.; Sulyok, M.; Fapohunda, S.O., Ezekiel, C.N.; Krska, R.; Oguntona, C.R.B.
Mycotoxins and fungal metabolites in groundnut- and maize-based snacks from
Nigeria, Food Additives & Contaminants: Part B: Surveillance, 2013, 6:4,
294-300, DOI: 10.1080/19393210.2013.823626.
15.
Balogun,
M. A.; Karim, O. R.; Akintayo, O. A.; Oyeyinka, A. T.; Kolawole, F.L.; Okereke,
E. E.
Effect of potash addition on groundnut
oil yield and quality of kulikuli (fried groundnut cake)
Agrosearch, 2020, 20(1), 23-33.
16.
Bagheri,
H.; Kashaninejad, M.; Ziaiifar, A. M.; Aalami M. Textural, color and sensory
attributes of peanut kernels as affected by infrared roasting method Info.
Process. Agric. 2019, 255-264.
17.
AOAC. Official Methods of Analysis of the
Association of Analytical Chemists. 19th ed. Washington, DC, USA. 2012.
18.
Obinna-Echem, P. C., Torporo, C.N.
Physico-Chemical and Sensory Quality of Tigernut (Cyperus Esculentus) –Coconut
(Cocos Nucifera) Milk Drink. Agri. Food Sci. Res. 2018, 5(1), 23-29. DOI:
10.20448/journal.512.2018.51.23.29.
19.
Nautiyal, Ph.D GROUNDNUT: Post-harvest
Operations National Research Centre for Groundnut (ICAR) 2002.
20.
Food
and Agriculture Organization. Standard for Peanuts CXS 200-1995. Adopted in
1995. Amended in 2019. https:/www.fao.org sh-proxy Assessed date 5/3/2023.
21.
Chapman, C. M. Chemistry 102, August 12,
2015. Rakinbiomed.com. 10/1/2023
22.
Isanga, J.; Zhang, G. Production and
evaluation of some physicochemical parameters of peanut milk yoghurt. Food Sci.
Technol. 2009, 42(6),1132‒1138.
23.
Gump, Barry H. "pH and Titratable
Acidity" Presentation. 2014. Retrieved 11/14/2017.
24.
Adeiye, O. A.; Gbadamosi, S. O.; Taiwo,
A. K. Effect of some processing factors on the characteristics of stored
groundnut milk extract. Afri. J. Food Sci. 2013, 7(6),134-142.
25.
Silva,
M. P.; Martinez, M. J.; Casini C.; Grosso, N. R. Tocopherol content, peroxide
value and sensory attributes in roasted peanuts during storage. Int.
J. Food Sci. Technol. 2010, 45, 1499–1504
26.
Zio,
S.; Tarnagda, B.; Zongo, O.; Boro, A.; Elothmani, D.; LE Meurlay, D.; Lancon
Verdier, V; Savadogo, A. Total gossypol and oxidation levels of refined cottonseeds
oils and crude peanut oils produced in Burkina Faso. Food Res. 2021, 5(6), 274
– 282.
27.
Codex Alimentarius. Norme pour les
huiles végétales portant un nom spécifique. Retrieved from Codex Alimentarius
website: https://inspection.canada.ca/DAM/DAM-food-aliments/WORKAREA/DAM-food-aliments/text-exte/codex_food_stand_named_veg_oils_1532975057193_fra.pdf.
1999.
28.
Stone, H.; sidel, H. Sensory Evaluation Practises 3rd
ed, San Diego, CA; Academic Press 2004.
1.
![](http://currentsci.com/icon/bync.png)
This work is licensed under the
Creative Commons Attribution
4.0
License (CC BY-NC 4.0).
Abstract
This study assessed the physicochemical and sensory
properties of roasted skinned and unskinned groundnuts sold in River State
University campus and its environment. Samples were obtained from three
locations: University’s back gate, main gate and shopping complex with sample
codes BSG, MSG and SSG respectively, for the skinned samples and BUG, MUG and
SUG for the unskinned samples. Standard analytical methods were used for the
analysis. The physicochemical properties of the skinned and unskinned samples
ranged respectively, from 6.49 - 6.64 and 6.48 – 6.58 for pH; 0.04 – 0.07 and
0.06 – 0. 09 %lactic acid for titratable acidity (TTA); 1.17 – 2.55 and 1.12 –
2.08% for moisture; 0.28 – 0.47 and 0.53 – 0.99% for free fatty acid (FFA) and;
11.90 – 19.50 and 10.20 – 14.00 mEq for peroxide value (PV). The assessors’ degree of likeness for the appearance,
aroma, taste (sweetness), freshness, crunchiness and overall acceptability of
the roasted skinned groundnut samples ranged from 6.20 – 7.10, 5.65 –
6.10, 5.35 – 6.20, 5.45 – 5.70, 5.75 – 6.45 and 6.00 – 6.15 respectively, while
the values for the unskinned samples ranged from 5.15 – 5.80, 5.65 – 5.85, 5.65
– 6.10, 4.85 – 5.85, 5.90 – 6.50, and 5.55 – 5.88 respectively, pH, TTA,
moisture, FFA and PV of the samples are within satisfactory limits and the
third quartile sensory results reveal degree of likeness from like slightly to
like very much, implying that the roasted groundnut whether peeled or unpeeled
were of good quality for consumption.
Abstract Keywords
Roasted skinned and unskinned groundnuts, pH, Peroxide
value, Free fatty acid, moisture content, sensory properties.
![](http://currentsci.com/icon/bync.png)
This work is licensed under the
Creative Commons Attribution
4.0
License (CC BY-NC 4.0).
![img](http://currentsci.com/images/articlesFile/1681308208.png)
![](http://currentsci.com/icon/openaccess.png)
This work is licensed under the
Creative Commons Attribution 4.0
License.(CC BY-NC 4.0).