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Mathematical Modelling and Applications
2020; 5(4): 214-220
http://www.sciencepublishinggroup.com/j/mma
doi: 10.11648/j.mma.20200504.12
ISSN: 2575-1786 (Print); ISSN: 2575-1794 (Online)
Modeling the Rate of Vitamin C Loss in Five Different Fruits
During Storage
Timothy Marhiere Akpomie
1, *
, Musa Safiyanu Tanko
1
, Umar Faruk Hassan
2
1
Department of Chemistry, Faculty of Science, Federal University of Lafia, Lafia, Nigeria
2
Department of Chemistry, Faculty of Science, Abubakar Tafawa Balewa University Bauchi, Bauchi, Nigeria
Email address:
*
Corresponding author
To cite this article:
Timothy Marhiere Akpomie, Musa Safiyanu Tanko, Umar Faruk Hassan. Modeling the Rate of Vitamin C Loss in Five Different Fruits
During Storage. Mathematical Modelling and Applications. Vol. 5, No. 4, 2020, pp. 214-220. doi: 10.11648/j.mma.20200504.12
Received: November 8, 2020; Accepted: November 18, 2020; Published: December 25, 2020
Abstract:
Vitamin C, also known as ascorbic acid, in five different fruit samples of orange, mango, watermelon, pawpaw
and pineapple were determined with the view of developing suitable mathematical models for subsequent estimation of the
vitamin in the fruits after several days of storage at temperatures of 4 and 29 (±1°C) respectively prior to consumption. The
iodometric titration was used to evaluate the vitamin C content of the fruit samples alongside their pH values. Measurements
were done on the 1
st
, 4
th
, 8
th
, 12
th
and 15
th
day of storage. The results obtained were then fed into a Minitab 18 Statistical
Computer programme for model development. The developed model was quadratic in nature and was of the form y=c±at±bt
2
.
For the orange sample, the model at 29°C was Vit. C=15.48 – 0.2814 t - 0.0042 t
2
, while at 4°C, the model was Vit. C=15.34 –
0.135 t – 0.0099 t
2
. Other models were; mango: Vit. C=8.113- 0.3962 t + 0.0077 t
2
& Vit. C=8.050 – 0.229 t – 0.0011t
2
,
watermelon: Vit. C=5.793 – 0.573 t + 0.0203 t
2
& Vit. C=5.338 – 0.175 t + 0.003 t
2
, pawpaw: Vit. C=8.534 – 0.227 t - 0.0069
t
2
& Vit. C=8.804 –0.291 t – 0.0009 t
2
and pineapple: Vit. C=6.459 – 0.673 t + 0.0282 t
2
& Vit. C=5.937 – 0.069 t – 0.0044 t
2
.
All models were found to be highly correlated (r
2
=86.90 – 100.00%) at 95% confidence level. Simulation using the respective
models at 29 and 4°C respectively indicated that the initial concentrations of orange (15.45±1.04), mango (7.82±1.76),
watermelon (6.05±0.94), pawpaw (5.48±0.94) and pineapple (8.35±1.09 mg/100 cm
3
) would respectively take (36, 33), (30,
31), (23, 60), (22, 30) and (21, 30) days to be lost completely. Results also indicated that refrigeration slowed down or
conferred some stability on the vitamin C content except in the orange juice. The percentage losses of vitamin C in the analytes
were found to be: water melon (71.00), pawpaw (60.00), pineapple (58.00), mango (52.00) and orange (35.00) respectively.
The respective models could be used to simulate the concentration of vitamin C at any particular time (days). This would save
time and cost of experimentation and would therefore give an estimate of the concentration of the vitamin present in such fruits
when refrigerated or stored in the open air given the post-harvest number of days.
Keywords:
Modeling, Vitamin C, Iodometric Titration and Quadratic
1. Introduction
Vitamin C also known as ascorbic acid is a water soluble
anti-oxidant that plays a vital role in protecting the body from
infections and diseases. It is not synthesized by the human
body and therefore must be acquired from dietary sources
primarily from fruits and vegetables [1]. The vitamin is easily
absorbed in the body, but cannot be stored and must be
consumed on daily basis for optimum health, particularly in
guiding against diseases like scurvy (disease of the gums,
bones and blood vessels), acts as an antioxidant, a nutrient
that chemically binds and neutralizes the tissue-damaging
effects of substances in the environment known as free
radicals. Vitamin C is therefore vital for the growth and
maintenance of healthy bones, teeth, gums, ligaments and
blood vessels. It also plays a role in the formation of collagen,
the body’s major building protein, a central component of all
body organs and plays vital roles in reducing the risk of
chronic diseases like cardiovascular diseases and cancer [2].
215 Timothy Marhiere Akpomie et al.: Modeling the Rate of Vitamin C Loss in Five
Different Fruits During Storage
Vitamin C increases the rate of absorption of iron, calcium
and folic acid and hence reduces allergic reactions, boosts the
immune system, stimulates the formation of bile in the gall
bladder and facilitates the excretion of various steroids [3].
Many vitamins are lost in fruits and vegetables during
handling, processing and storage. The retaining ability of
vitamins under chemical, physical and/or thermal stress is
called stability [4]. In the United States for instance, fruits
and vegetables grown in the North, may spend up to 5 days
in transit following harvest before arriving distribution center.
Transportation time for fruits and vegetables grown in the
Southern hemisphere for winter and spring consumption
ranges from as little as few days if transported by air freight
to several weeks if sent by refrigerated ship. At the retail
store, fruits and vegetables may further spend 1–3 days on
display prior to being purchased by the consumer, who may
store them for probably up to 7 or more days prior to
consumption. This means that fresh fruits and vegetables
may not be consumed for a significant length of time
following harvest, during which time nutrient degradation
may occur [5].
Most fruits and vegetables are composed of 70–90% water
and once separated from their source of nutrients (tree, plant,
or vine); they undergo higher rates of respiration which can
lead to moisture loss, quality and nutrient degradation as well
as potential microbial spoilage. Changes in the nutrient
composition of fruits and vegetables from harvest to
consumption depend to a certain degree on the particular
nutrient, the commodity and the post-harvest handling,
storage and home cooking conditions. Initial nutrient content
is affected by the particular cultivar (e.g. red delicious and
fuji apples), soil type, production system (conventional,
organic etc.) and weather conditions (temperature, humidity,
daylight hours etc.) during growth [6]. Fruits and vegetables
are generally harvested by hand, with the of roots and tubers,
while many commodities meant for exception processing are
mechanically harvested. Mechanical harvesting generally
causes more stress to the plant tissue and may result in more
damage than hand harvesting where nutrient retention is
optimized [5].
Vitamin C occurs naturally in many fruits and vegetables,
particularly in mango, pineapple, orange, water melon,
tomato, citrus fruit, cantaloupe, broccoli, spinach, green
pepper, cabbage, pineapple, melons and potatoes. The
vitamin is easily destroyed by cooking or canning and on
exposure to air and light. A healthy diet generally contains
sufficient quantities of ascorbic acid, but the body requires
more of the vitamins after serious injury, major surgery,
burns and when exposed to extreme temperature. Those that
are at risk of deficiency are smokers, women taking
contraceptives containing the female sex hormone estrogens
and people who live in cities with high concentrations of
carbon (II) oxide from traffic. Conflicting evidence shows
that taking large doses of ascorbic acid will either prevent the
common cold or reduce the severity of its symptoms [6].
Figure 1. Some Assorted Fruit Samples.
It is a common practice for fruit sellers and consumers to
store fruits for a long period of time or even sell them under
the sun without prior knowledge of the nutritional deterioration
or reduction in the vitamin C content due to the changing
moisture content, temperature and pH. This research work is
aimed at developing a model to determine the rate of vitamin
C loss during storage in five different fruits.
2. Materials and Methods
In the preparation of all the solutions, chemicals used were
of analytical grade and distilled water was also used. All the
glass and plastic wares used were thoroughly washed with
detergent solution and repeatedly rinsed with water prior to
use.
2.1. Sampling of Fruit Samples
Five different ripe and fresh samples of fruit namely:
Mangifera indica (mango), Ananas comosus (pineapple), Citrus
sinesis (orange), Citrllus lanatus (water melon) and Asimina
triloba, (pawpaw) were respectively purchased from different
farms at Mararaba Akunza, Agyaragun-Tofa and Asakio all in
Lafia Local Government Area, Nasarawa State, Nigeria.
2.2. Treatment of Samples
Samples were thoroughly washed with water to remove
dust and unwanted particles. 100.00 g of each fruit sample
was cut into small pieces and grinded in a blender using
50.00 cm
3
of water. The mixture was quantitatively
transferred into a 100 cm
3
volumetric flask and water was
added to capacity [7]. The mixture was then filtered using
Whatman Filter Paper Number 1. The resulting analytes were
separately kept in screw-capped polyethylene bottles and
labeled appropriately for further analysis.
2.3. Analytical Procedure
2.3.1. Determination of Vitamin C
Aliquot portion (25.00 cm
3
) of the sample solution
prepared in section 2.2 was pipetted into a 250 cm
3
conical
flask, 150.00 cm
3
of water was added. 5.00 cm
3
of 0.60
mol/dm
3
of potassium iodide solution was also added to the
same conical flask. 5.00 cm
3
and 1.00 cm
3
of 1.00 mol/dm
3
of hydrochloric acid and starch indicator solution were
respectively added. The solution was then titrated with 0.02
mol/dm
3
potassium iodate solution until the end point was
Mathematical Modelling and Applications 2020; 5(4): 214-220 216
reached which was the appearance of a permanent trace of
dark blue-black color. Each sample was determined in
triplicates [7]. The same procedure was used for all the
analytes investigated for each of the 1
st
, 4
th
, 8
th
, 12
th
, and 15
th
day of storage.
2.3.2. Determination of pH
The pH of fruit samples investigated was determined using
a pH meter Model HI 2214/ORP. The instrument was
calibrated using pH 4.1, 7.1 and 10.1 buffers respectively to
check the linearity. 20.00cm
3
of each freshly prepared fruit
juice was placed in a glass beaker and the glass electrode was
dipped and agitated with a magnetic stirrer for 1 min until
reading was stable before being read. Between readings, the
electrode was rinsed with distilled water to ensure that no
cross-contamination occurred. The pH of each fruit sample
was measured in triplicates. [8, 9].
2.3.3. Modeling Procedure
The computer statistical software (Minitab 18) was used to
automatically generate suitable models for the rate of vitamin
C degradation in all the fruit samples. This was achieved by
using the experimental data obtained for each respective fruit.
The vitamin C content was used as the response or dependent
variable, while the pH and number of days of storage were
used as the independent variables respectively. The statistical
validity and strengths of the obtained models (regression
equations) were provided alongside the figures using the
statistical software.
3. Results and Discussion
3.1. Results
The variations of vitamin C contents (mg/100 cm
3
) of all
the fruit samples investigated under different days and pH at
29±1and 4°C are depicted in Tables 1 to 5. The developed
model of estimated days for obtaining 0.00 mg/100 cm
3
of
vitamin C in various fruits at 29 and 4°C are presented in
Table 6 as well as in Figures 2 to 13. Figure 14 shows the
number of days (time) for complete loss of vitamin C at 29
and 4°C in fruit samples, whilst Figure 15 shows the
percentage stability of vitamin C in fruit samples investigated.
Tables 1 to 5 indicated that in all the analytes (fruits), there
is an inverse relationship between time (days) and pH values
as well as between time (days) and the concentration of
vitamin C. This shows that both pH and vitamin C levels
continuously decrease with time.
Table 1. Variation of Vitamin C Content (mg/100 cm
3
) of Orange Fruit.
Time
(Days)
At 29±1°C At 4°C
pH [Vitamin C] pH [Vitamin C]
1 3.6±0.05 15.45±1.04 3.6±0.05 15.45±1.04
4 3.5±0.16 13.85±0.66 3.5±0.22 14.25±2.21
8 3.1±0.09 12.95±0.76 3.3±0.28 13.45±0.25
12 2.7±0.08 11.95±1.22 2.9±0.11 12.95±0.06
15 2.5±0.04 10.05±0.54 2.7±0.93 10.75±2.14
Values are mean±standard deviation (n=3).
Table 2. Variation of Vitamin C Content (mg/100 cm
3
) of Mango Fruit.
Time
(Days)
At 29±1°C At 4°C
pH [Vitamin C] pH [Vitamin C]
1 5.8±0.14 7.82±1.76 5.8±0.14 7.82±1.76
4 5.4±0.31 6.32±1.32 5.6±0.28 7.12±0.84
8 5.2±0.41 5.32±0.86 5.4±0.06 6.12±1. 05
12 5.0±0.27 4.77±0.43 5.2±0.06 5.17±1.30
15 4.9±0.50 3.75±0.56 5.1±0.12 4.35±0.88
Values are mean±standard deviation (n=3)
Table 3. Variation of Vitamin C Content (mg/100 cm
3
) of Water Melon Fruit.
Time
(Days)
At 29±1°C At 4°C
pH [Vitamin C]
pH [Vitamin C]
1 4.5±0.60 6.05±0.94 4.5±0.60 6.05±0.94
4 4.3±0.06 3.75±0.96 4.4±0.82 5.25±1.27
8 4.1±0.29 3.05±1.05 4.3±0.80 5.15±1.05
12 3.9±0.91 2.65±0.91 4.1±0.73 4.74±0.37
15 3.8±0.78 2.55±0.90 3.9±0.49 3.72±0.71
Values are mean±standard deviation (n=3).
Table 4. Variation of Vitamin C Content (mg/100 cm
3
) of Pawpaw Fruit.
Time
(Days)
At 29±1°C At 4°C
pH [Vitamin C]
pH [Vitamin C]
1 5.4±0.16 5.48±0.94 5.4±0.16 5.48±0.94
4 5.0±0.31 3.36±0.91 5.2±0.70 4.05±0.64
8 4.7±0.37 2.65±0.61 4.9±0.04 3.65±0.25
12 4.4±0.08 2.10±0.30 4.6±0.04 3.40±0.03
15 4.1±0.11 1.60±0.51 4.2±0.08 1.60±0.21
Values are mean±standard deviation (n=3).
Table 5. Variation of Vitamin C Content (mg/100 cm
3
) of Pineapple Fruit.
Time
(Days)
At 29±1°C At 4°C
pH [Vitamin C] pH [Vitamin C]
1 5.6±0.05 8.35±1.09 5.6±0.05 8.35±1.09
4 5.2±0.32 7.55±1.43 5.3±0.06 7.95±0.77
8 4.9±0.09 5.90±0.76 5.1±0.10 6.30±0.55
12 4.7±0.07 5.35±0.74 4.9±0.05 5.05±0.29
15 4.2±0.14 3.35±0.77 4.5±0.13 4.35±1.03
Values are mean±standard deviation (n=3).
Table 6. Developed Models used to Estimate 0.00 mg/100 cm
3
of Vitamin C in Analyzed Fruit Samples.
Fruits Model At 29±1°C Model At 4°C Days
Orange Vit. C=15.48 – 0.2814 t - 0.0042 t
2
Vit. C=15.34 – 0.135 t – 0.0099
2
36 & 33 days
Mango Vit. C=8.113- 0.3962 t + 0.0077
2
Vit. C=8.050 – 0.229 t – 0.0011
2
30 & 31
Water Melon Vit. C=5.793 – 0.573 t + 0.0203
2
Vit. C=5.338 – 0.175 t + 0.003
2
23 & 60
Pawpaw Vit. C=8.534 – 0.227 t - 0.0069 t
2
Vit. C=8.804 –0.291 t – 0.0009
2
22 & 28
Pineapple Vit. C=6.459 – 0.673 t + 0.0282
2
Vit. C=5.937 – 0.069
– 0.0044
2
21 & 30
217 Timothy Marhiere Akpomie et al.: Modeling the Rate of Vitamin C Loss in Five
Different Fruits During Storage
Figure 2. Linear Model of Orange at 29±1°C.
Figure 3. Quadratic Model of Orange at 29±1°C.
Figure 4. Cubic Model of Orange at 29±1°C.
Figure 5. Quadratic Model of Orange at 4°C.
Figure 6. Quadratic Model of Mango Fruit at 29±1°C.
Figure 7. Quadratic Model of Mango Fruit at 4°C.
Figure 8. Quadratic Model of Water Melon at 29±1°C.
Figure 9. Quadratic Model of Water Melon Fruit at 4°C.
1614121086420
16
15
14
13
12
11
10
S 0.5 14 8 5 7
R-S q 96 .8 %
R-S q(a dj ) 93 .5 %
Ti me (D ays )
Vit. C (mg/100 ml)
Vi t. C (m g/ 100m l) = 15.4 8 - 0.2 814 t - 0.0 04 24 t^ 2
1614121086420
16
15
14
13
12
11
10
S 0 .0 15 2 5 38
R-S q 100.0 %
R-S q (ad j ) 100 .0%
Ti me (D ays )
Vit. C (mg/100ml )
Vi t. C (m g/ 100m l) = 16.3 1 - 0 .96 01 t + 0.10 36 t^ 2 - 0 .00 449 1 t^ 3
1614121086420
16
15
14
13
12
11
S 0 .6 29 7 3 8
R-S q 9 3 .5 %
R-S q(a d j) 8 6 .9%
T ime (D ays )
Vi t. C (m g/10 0m l)
Vi t. C (m g/ 10 0m l) = 15 .34 - 0.13 51 t - 0.0 09 88 t^ 2
1614121086420
8
7
6
5
4
S 0 .2 78 12 8
R-S q 9 8 .4 %
R-S q (ad j ) 9 6 .9 %
Ti me (D ays )
Vit. C (mg/100ml )
Vi t. C = 8.113 - 0.3 962 t + 0 .00 76 99 t^ 2
1614121086420
8
7
6
5
4
S 0.0 2 9 3 6 76
R-S q 100 .0 %
R-S q( ad j) 100 .0 %
T ime (D ays )
Vit . C (m g/100ml )
Vi t. C = 8.0 49 - 0.2 29 4 t - 0.0 0109 1 t^ 2
1614121086420
6
5
4
3
2
S 0.4 4 122 7
R-S q 9 5 .8%
R-S q (ad j ) 91.5 %
T ime (D ays )
Vit . C (mg /10 0ml)
Vi t. C = 5.7 93 - 0.5 73 2 T im e+ 0.0 20 34 Tim e^ 2
Mathematical Modelling and Applications 2020; 5(4): 214-220 218
Figure 10. Quadratic Model of Pawpaw at 29±1°C.
Figure 11. Quadratic Model of Pawpaw at 4°C.
Figure 12. Quadratic Model of Pineapple at 29±1°C.
Figure 13. Quadratic Model of Pineapple at 4°C.
Figure 14. Number of Days (Time) for Complete Loss of Vitamin C in Fruit
Samples at 29 and 4 °C.
Figure 15. Percentage Stability of Vitamin C in Fruit Samples.
3.2. Discussion
Figures 2, 3 and 4 showed the linear, quadratic and cubic
models respectively developed from the observed mean
concentrations of vitamin C in the orange fruit samples
investigated at room temperatures of between 28 – 30°C. In
all the three models, the predictor was found to be the time
variable as it correlated highly (r
2
=0.954, 0.934 and 1
respectively) with the vitamin C content as given by the
Minitab statistical software. The pH showed little or no
correlation with the vitamin C content of the fruit, hence the
pH was said to be inestimable. The changes in pH may be as
a result of the biochemical reactions and microbial actions
that occurred during the storage period in the orange juice
and this may not necessarily be responsible for the
degradation or reduction in vitamin C level. By using any of
the models and given any number of days, the quantity of
vitamin C present in the fruit may be estimated at 95%
confidence level.
As regards the three models, the quadratic model was
found to be the most suitable. This is because the linear
model whose regression line assumed a perfect linear
relationship between the dependent and independent
variables (quantity of vitamin C and number of days or time)
and the cubic model whose regression line was the same as
the actual observations and that was why its coefficient of
correlation was observed to be 100%. This in reality, may not
be so. The quadratic model, not linear in nature and whose
line of best fit was not the same as the actual observations
was therefore more appropriate for estimating the quantity of
vitamin C in the orange sample.
Figure 5 shows the quadratic model for estimating the
1614121086420
9
8
7
6
5
4
3
S 0 .4 9 0 5 64
R-S q 9 6 .9 %
R-S q (ad j ) 93 .7 %
Ti me (D ays )
Vit. C (mg/100ml)
Vi t. C = 8.5 34 - 0.2 26 9 t - 0.0 06 88 t^ 2
1614121086420
9
8
7
6
5
4
S 0. 29 6 4 2 6
R-S q 9 8 .6 %
R-S q (ad j ) 97.1%
Ti me (D ays )
Vit. C (mg/100ml)
Vi t. C = 8.8 04 - 0.2 90 6 t - 0.0 00 87 9 t ^2
1614121086420
6
5
4
3
2
S 0.4 3 0 9 8 8
R-S q 9 5 .5 %
R-S q (ad j ) 9 1.1%
Ti me (D ays )
Vit. C (mg/100ml)
Vi t. C = 6.4 59 - 0.6 73 2 t + 0 .02 818 t^2
219 Timothy Marhiere Akpomie et al.: Modeling the Rate of Vitamin C Loss in Five
Different Fruits During Storage
quantity of vitamin C in the orange fruit at a refrigerated
temperature of 4°C. This model showed a similar trend with
that of orange at 29±1°C and its coefficient of correlation (r
2
)
was observed to be 86.9%.
Figures 6 and 7 are the derived models for the quantitative
estimation of vitamin C content of the mango fruits
investigated at the respective temperatures. Both models also
followed a similar trend with that of the orange sample. The
coefficients of correlation (r
2
=98.40 and 100.00%) for the
degradation of the mango fruit at the respective temperatures
was higher than those of orange. The model for the
degradation at 4°C in the mango fruit showed a 100.00%
inverse relationship between concentrations of vitamin C and
the number of days of storage.
A trend similar to orange and mango fruits is portrayed in
the models of water melon as illustrated in Figures 8 and 9, r
2
was 95.8 and 87.9% at 29 and 4°C in that order.
The models for Pawpaw are depicted in Figures 10 and 11
respectively at 29 and 4°C. The coefficients of correlation (r
2
)
in both models were observed to be 96.90 and 98.60%
respectively. It is evident that there is a high degree of
association between Vitamin C and time variables.
The developed model used in forecasting the concentration
of vitamin C in pineapple fruit based on the number of days
of storage and at 29 and 4°C are presented in Figures 12 and
13. The variables of the models were also noted to be highly
correlated (r
2
=95.50 and 90.90%).
Table 6 shows that the models follow the quadratic form,
= ± ±
, where y is the quantity of vitamin C in the
fruit, ‘a’ and ‘b’ are the coefficients of determination or slope
as evaluated by the statistical package while ‘c’ represents the
constant term or intercept respectively, and ‘t’ is the number
of days of observation or storage.
The models at 29 and 4°C of the fruit samples revealed
that it would take approximately 36 and 33 days respectively
for complete loss or reduction of vitamin C in orange, mango
at 29°C would require 30 days for complete reduction, while
at 4°C; the same fruit (mango) will take 31 days to reduce to
0.00 mg/100 cm
3
. Similarly, watermelon, pawpaw and
pineapple at 29 and 4°C would require 23 and 60, 22 and 28
as well as 21 and 30 days to be degraded completely. This is
illustrated in Figure 14.
The general trend as seen in Figure 14 showed clearly that
refrigeration of the various fruit samples conferred some
form of stability or preservation on the ascorbic acid content.
The vitamin C content took longer time (days) to be reduced
to 0.00 mg/100 cm
3
or lost completely at 4°C, but took a
shorter time for similar observations at 29°C. This is because
vitamin C, C
6
H
8
O
6
, is known to be very vulnerable towards
heat and the proximity of the highly electronegative oxygen
atoms on the hydroxyl (OH) groups makes the hydrogen
atoms to become easily detached from the structure. In the
presence of heat, this causes the hydroxyl bond to break and
the ascorbic acid is said to undergo “destruction” or oxidation
by losing hydrogen atoms, forming dehydroascorbic acid.
This implies that the rate of ascorbic acid destruction is
significantly greater at higher temperature hence the reduced
vitamin c content [10].
This trend was also observed and reported by [11-14] in
several other studies on ascorbic acid determination in fruits.
An exception to this trend was however noted in the orange
fruit juice, where it was observed that reduction of the
vitamin c content to 0.00mg/100cm
3
was faster at 4°C than at
29°C. This observation may not be out of place since [15]
had reported that the loss of vitamin C with time differs from
one fruit to the other under similar storage environments.
Additionally, a further study by [12] on the loss of vitamin c
in orange, lemon, lime, pineapple, paw-paw and carrot fruit
juices, found that only in orange was the organisms Bacillus
subtilis and Candida sp. was not isolated. The presence of
these species in the other fruit samples at room temperature
may be the catalyst for the instability of the vitamin at that
temperature and the converse for the orange fruit.
The loss of vitamin C observed in water melon, pawpaw,
pineapple, mango and orange were found to be 71.00, 60.00,
58.00, 52.00 and 35.00% respectively. The models of the
fruit samples could be used to simulate the concentration of
vitamin C at any particular time (days) by substituting the
number of days in the appropriate model and would therefore
save time and cost of experimentation.
4. Conclusion
Several models were developed for evaluating the rate of
loss of vitamin C in five different fruit samples. The developed
models were quadratic in nature and of the form, = ±
±
. The parameters of the model for all the fruit samples
at 29±1°C and 4±1°C were highly correlated (r
2
=86.90 –
100.00%) at 95% confidence level. Application of the
respective models for all fruit samples revealed that: orange
was simulated to take 36 and 33 days for its vitamin C content
to be completely lost at 29 and 4 (±1°C) respectively, mango
wound require 30 and 31 days, water melon would take 23 and
60 days, pawpaw would need 22 and 28 days and pineapple
would require 21 and 30 days. Loss of vitamin C was generally
observed to be slower at a refrigerated temperature of 4±1°C in
all the fruit samples except in orange which was more stable or
slower at 29±1°C. The order of stability of vitamin C in
decreasing magnitude for all the fruit samples was: water
melon > pawpaw > pineapple > mango > orange.
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