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Journal ArticleDOI

Effect of Prolonged Storage in Ice on Nutrient Composition and Sensory Quality of Whole Fresh Pond Raised Tilapia Fish ( Oreochromis shiranus )

26 Jul 2016-American Journal of Food and Nutrition (Science and Education Publishing)-Vol. 4, Iss: 5, pp 127-130
TL;DR: It is demonstrated that fleshly harvested Oreochromis shiranus from ponds stored in ice can remain acceptable for purchasers for up to 15 days, an advantage especially to rural small scale fish farmers who can hardly afford to preserve their fresh fish in refrigerators but may locally access ice.
Abstract: A study was conducted to determine the effect of prolonged storage in ice of fresh pond raised Tilapia fish (Oreochromis shiranus) on its nutrient composition and quality. Live fish were collected from Bunda College Fish Farm ponds and stored in clean block ice. Sensory, proximate and pH analyses were conducted at a three day interval to determine changes in nutrient composition and quality of the fish while kept in ice. Crude protein and crude fat decreased significantly (P<0.05) while ash increased significantly (P<0.05) with storage time in ice. pH increased with storage time in ice (R2=0.815). Fish remained in acceptable freshness condition up to day 15 while highest sensory demerit score was recorded on the 18th day suggesting complete rejection. Sensory demerit scores of the fish increased with storage time in ice (R2=0.886) indicative of a decline in acceptability with storage time in ice by the sensory panel. This study demonstrated that fleshly harvested Oreochromis shiranus from ponds stored in ice can remain acceptable for purchasers for up to 15 days. This is an advantage especially to rural small scale fish farmers who can hardly afford to preserve their fresh fish in refrigerators but may locally access ice. However, there is need for future research to assess the microbiological load to ascertain safety of the product beyond 15 days storage period.

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American Journal of Food and Nutrition, 2016, Vol. 4, No. 5, 127-130
Available online at http://pubs.sciepub.com/ajfn/4/5/2
©Science and Education Publishing
DOI:10.12691/ajfn-4-5-2
Effect of Prolonged Storage in Ice on Nutrient
Composition and Sensory Quality of Whole Fresh Pond
Raised Tilapia Fish (Oreochromis shiranus)
Chisomo Goliat
1
, Fanuel Kapute
2,*
, Joshua Valeta
1
1
Department of Aquaculture & Fisheries Science, Lilongwe University of Agriculture & Natural Resources, Lilongwe, Malawi
2
Department of Fisheries Science, Mzuzu University, Mzuzu, Malawi
*Corresponding author: fkapute@email.com
Abstract A study was conducted to determine the effect of prolonged storage in ice of fresh pond raised Tilapia
fish (Oreochromis shiranus) on its nutrient composition and quality. Live fish were collected from Bunda College
Fish Farm ponds and stored in clean block ice. Sensory, proximate and pH analyses were conducted at a three day
interval to determine changes in nutrient composition and quality of the fish while kept in ice. Crude protein and
crude fat decreased significantly (P<0.05) while ash increased significantly (P<0.05) with storage time in ice. pH
increased with storage time in ice (R
2
=0.815). Fish remained in acceptable freshness condition up to day 15 while
highest sensory demerit score was recorded on the 18
th
day suggesting complete rejection. Sensory demerit scores of
the fish increased with storage time in ice (R
2
=0.886) indicative of a decline in acceptability with storage time in ice
by the sensory panel. This study demonstrated that fleshly harvested Oreochromis shiranus from ponds stored in ice
can remain acceptable for purchasers for up to 15 days. This is an advantage especially to rural small scale fish
farmers who can hardly afford to preserve their fresh fish in refrigerators but may locally access ice. However, there
is need for future research to assess the microbiological load to ascertain safety of the product beyond 15 days
storage period.
Keywords: nutrient composition, quality, ice storage, Oreochromis shiranus
Cite This Article: Chisomo Goliat, Fanuel Kapute, and Joshua Valeta, Effect of Prolonged Storage in Ice on
Nutrient Composition and Sensory Quality of Whole Fresh Pond Raised Tilapia Fish (Oreochromis shiranus).”
American Journal of Food and Nutrition, vol. 4, no. 5 (2016): 127-130. doi: 10.12691/ajfn-4-5-2.
1. Introduction
The species of fish that were used in this study is
Oreochromis shiranus - a tilapiine endemic to Lake
Malawi and the Upper Shire River in Malawi. It is the
commonly cultured fish in ponds by small scale farmers in
all parts of the country due to its ease of breeding and
tolerance to harsh conditions. Due to poor fish holding
facilities in markets that result into spoilage of fresh fish,
most farmers in Malawi are exploring the idea of
preserving fish in ice because it is locally available. An
earlier study on Lake Malawi tilapia revealed that fresh
fish can remain in acceptable condition while kept in ice
for no less than two weeks [1]. This notion stems from the
background that temperature plays a key role in fresh fish
spoilage which directly causes changes in the nutritional
composition of fish [2]. In the high ambient temperatures
of the tropics, fresh fish will spoil within 12 hours [3]. It is
widely reported that chilling or icing of fish immediately
after catch reduces its spoilage [4,5]. On the other hand,
physical properties of fresh fish such as firmness and
appearance of the skin are greatly influenced by storage
time due to cellular flaking of autolytic and microbial
changes [6,7]. The most obvious change in fresh fish flesh
after capture is rigor mortis due to loss of the elastic
texture of the muscle as a result of a series of complicated
chemical changes in the muscle of a fish culminating into
spoilage [4]. Fish undergoing spoilage has one or more of
the following signs: slime formation; discolouration;
changes in texture; off-odours; off-flavours and gas
production [8,9].
Since spoilage causes changes in the freshness and
nutritional composition of fresh fish, it is necessary to
assess the extent of the changes with respect to time so
that consumers have maximum nutritional benefits from
fish. This is also important for fish processors to avoid
processing fish which has compromised nutritional and
fresh quality.
The objective of the study was to assess the effect of
prolonged storage in ice on nutrient composition and
sensory quality of whole fresh pond raised Tilapia fish
(Oreochromis shiranus).
2. Materials and Methods
2.1. Fish Sample Collection
Live fish samples, with an average weight of 100g were
collected from Bunda College Fish Farm (Malawi), stored

128 American Journal of Food and Nutrition
in a cooler box and preserved in block ice. Initially, three
fish samples were taken for proximate composition,
sensory analysis and pH before storing them in ice and
later at intervals of three days. The melted ice water in the
cooler box was decanted periodically and fresh clean ice
was added throughout the experimental period.
2.2. Fish Sample Analysis
2.2.1. Sensory Analysis
Sensory analysis was carried out by a pre-trained
sensory evaluation panel consisting of 6 members. A
developed quality index scheme (QIM) [7] was used to
assess the quality changes of the fresh fish at a 3 day
interval involving the following parameters: skin
appearance, slime, fresh firmness, odour, colour of the
eyes and colour of the gills. The sensory demerit scores
ranged from 0 to 3 where 0 and 3 represented very fresh
and spoiled fish, respectively (Table 1).
Table 1. Quality Index Method (QIM) Scheme developed for the
assessment of whole fresh pond raised Oreochromis shiranus stored
in ice
Quality parameter
Description
Scores
Appearance
Skin
Shiny grey
0
Grey, not shiny
1
Scale
Firm
0
Loose
1
Eyes Cornea
Very clear (glass-like)
0
Cloudy 1
Milky
2
Opaque pupil
3
Gills
Colour
Bright red
0
Pale red
1
Dull red
2
Brown 3
Smell
Fresh, cut grass, aquatic weed 0
Neutral
1
Musty
2
Mucus
Clear
0
Cloudy
1
Milky
2
Brown-reddish
3
Texture
Backside
Firm & elastic (in-rigor)
0
Soft
1
Very soft/ depression when pressed
2
Belly
Firm
0
Soft
1
Quality Index
(QI)
0-16
2.2.2. pH Determination
Ten grams of fish muscle (flesh) was removed, crushed
in a mortar and weighed. Fifty (50) millilitres of distilled
water was added to the paste and mixed for 5 minutes. pH
values were checked and recorded for each set of fish
samples using a pH meter (Model No. WTW-8120, West
Germany) by inserting the electrode into the mixture of
fish muscle and distilled water as earlier followed by
Kapute et al. [1,10].
2.2.3. Proximate Analysis
Proximate composition was done using analytical
standard methods developed by AOAC [11]. Three fish
samples were collected for analysis at a three day interval.
Crude protein, crude fat, moisture and ash were analysed.
2.3. Data Analysis
Data was analyzed using a statistical package SPSS
version 16.0. Changes in mean proximate composition,
pH and sensory scores were compared using one way
analysis of variance (ANOVA). Means and standard errors
(±SE) were reported at 5% level of significance. Duncan’s
Multiple Range Test (DMRT) was used to separate
significantly different means. A linear regression was
plotted on sensory quality data to show the relationship
between fish spoilage and ice storage time.
3. Results
3.1. Sensory Analysis
The sensory scores increased with storage time with a
strong correlation (R
2=
0.890) indicating the increased
rejection of the fish by the panellists with time (Figure 1).
Figure 1. Sensory Quality Index scores of fresh Oreochromis shiranus
stored in ice for 18 days
The highest total demerit score of 15.9 was observed on
the 18
th
day and the results implied that Oreochromis
shiranus should be kept for no more than 15 days (Figure 1).
3.2. pH
The initial pH was 5.59 rising sharply from day 0 to day
15. pH on day 15 was 7.02 then dropped to 6.92 on the
18
th
day (Figure 2).
Figure 2. Changes in pH of Oreochromis shiranus stored in ice for 18
days

American Journal of Food and Nutrition 129
A strong linear correlation (R
2
=0.815) was observed
suggesting an increase in pH with increase in ice storage
time.
3.3. Proximate Composition
There was a significant decrease in crude protein and
crude fat with increase in the number of days of storage in
ice (P<0.05). Initial moisture content increased from day 0
up to day 6 then decreased significantly up to day 18
(P<0.05). However, ash content increased significantly
with time. Highest ash content was recorded on day 18
(Table 2).
Table 2. Proximate composition of Oreochromis shiranus stored in
ice for 18 days
Days Moisture (%) Ash (%) Protein (%) Fat (%)
0 94.66±0.30
c
16.91±0.20
f
63.72±0.16
ab
16.80±0.04
a
3 96.77±0.14
b
16.6±1.15
g
63.69±0.06
ba
16.00±0.05
b
6 97.23±0.36
a
21.49±0.62
b
63.69±0.04
c
15.63±0.23
c
9 92.83±0.29
d
17.81±1.53
d
63.37±0.08
d
14.66±1.45
d
12 91.85±0.26
fe
21.11±1.29
c
62.07±0.03
e
10.56±0.08
e
15 91.02±0.33
g
17.64±5.12
e
61.76±0.10
f
10.43±0.05
f
18 91.88±0.49
ef
22.24±2.68
a
61.56±0.14
g
9.45±0.09
g
Means with same superscript in a column are not significantly different
(P>0.05).
4. Discussion
The accepted limit for acceptability of O. shiranus by
the sensory panellists was observed between 14 and 15
days while the highest total demerit score of 15.9 was
observed on day 18. This is close to the values reported by
Kapute et al. [1] where shelf life of Lake Malawi Tilapia
(Chambo - Oreochromis species) was estimated between
16 and 18 days with a highest demerit score observed on
the 16
th
day. Other workers [12], estimated shelf life for O.
mossambicus at 14 days. The longer shelf life of fresh fish
stored in ice could be attributed to the low temperature of
ice that hinders microbial growth [13].
The natural/normal fresh colour of the fish became
discoloured during storage. The pigments may have been
oxidized or affected by some other factors. It is known
that lipids convert to peroxides, aldehydes, ketones and
lower aliphatic acids when they are oxidized [14].
Although hydro-peroxides are tasteless, they can cause
brown and yellow discolouration of the fish tissue [15].
Some browning discoloration also occurs in fatty fishes
due to hydrolytic changes between fats and proteins [16].
These facts may therefore also explain the observed colour
changes of the fish gills in this study.
Texture became harder at the beginning due to
stiffening of the muscle during rigor mortis process. The
concave appearance of the eyes and scales becoming loose
could be as a result of prolonged storage in ice earlier
reported by Uchoi et al. [13].
Low initial pH during storage in ice may have
contributed to the longer shelf life because low pH is not
favourable for bacterial growth [5]. After death of the fish,
the glycogen present in the tissues gets oxidized to lactic
acid and the creatine phosphate in the muscle breaks down
releasing phosphoric acid [4]. A release of both lactic acid
and phosphoric acid triggers rapid change in pH of tissue
fluids [16] hence the rise in pH after day 0 approaching
the phosphoric acid range. The further increase in pH after
day 0 may reflect the production of alkaline bacterial
metabolites in spoiling fish [6]. Increase in pH is
accompanied by the completion of rigormortis ending up
in softening of the muscle [4]. The increase in pH after
day 12 correlated with rapid spoilage of the fish. Increased
pH values after sensory rejection have previously also
been reported by Liu et al. [17] implicating accumulation
of alkaline compounds as well as volatile bases produced
by autolytic activities and metabolism of spoilage bacteria.
Decomposition of fresh fish occurs as its constituent
compounds break down [18]. Hydrolysis of proteins,
nucleotides and sugar releases bases causing a drop in pH
[18] which could explain the fall in pH beyond day 15
from 7.02 to 6.92.
Reduction in the percentage of crude protein during the
period of ice storage could be due to gradual degradation
of the initial crude protein to more volatile products such
as Total Volatile Bases (TVB), Hydrogen sulphide and
ammonia [19]. Changes observed in protein and lipid
content during storage may have been due to leaching out
of some extractable soluble protein fraction and hydrolysis
of some of the lipid fractions [20]. The reduction in fat
content could also be due to oxidation and breakdown of
other fat components during storage [18]. The reduction in
protein and fat content agrees with Arannilewa et al. [21]
where the highest crude protein and fat content was
observed in fresh samples that were not subjected to
frozen storage while the least was observed in samples
that were subjected to frozen storage throughout the
period of the experiment.
Initial increase in moisture content of the fish with
increase in ice storage time could be due to the fact that
the fish absorbed moisture during the first days of storage.
The decrease in moisture after day 6 could be attributed to
the difference in the moisture of the fish relative to its
surrounding. This was also reported by Daramola et al.
[18] who also concluded that dehydration of the fish is an
important physical reaction caused by the evaporation of
ice due to differences in vapour pressure over the product
surface and the air of the store room. Loss of moisture by
evaporation of ice causes the fish surface to dry resulting
in dull appearance and even discoloration as observed by
Singh et al. [5] and earlier reported in this study.
Ash content is mainly determined by bone to flesh ratio
[18]. The increase in ash percentage during the experiment
might also be attributed to increase in the proportion of
bones as compared to the flesh since the flesh was being
degraded with increase in time of ice storage.
5. Conclusion
It can be concluded that sensory quality of fresh O.
shiranus declines with time when stored in ice and that
storage for not more than 15 days could maintain
acceptable quality. It can also be concluded that the
nutritional quality of O. shiranus deteriorates with time
when stored in ice. pH increases with time of storage in
ice until O. shiranus becomes of unacceptable quality. The
general conclusion is that like other tilapias, O. shiranus
has a relatively longer shelf life kept in ice.

130 American Journal of Food and Nutrition
6. Recommendations
The study recommends that Oreochromis shiranus fish
stored in ice should be kept for a limited number of days
of no more than 15 days. While these findings provide
preliminary knowledge regarding storage time of O.
shiranus in ice, the sensory data could be more
meaningful if validated with microbiological analyses.
Not all that is sensorily acceptable is safe to consume due
to pathogenic microbial loading.
While refrigeration is not available to most fish farmers
in rural areas of Malawi, the long shelf life of O. shiranus
in ice could be an advantage in preserving fresh pond
harvested fish while in markets to maintain quality.
Acknowledgement
We would like to thank the Department of Aquaculture
and Fisheries Science at Bunda College of Agriculture for
supporting this work technically and financially. Our
sincere gratitude also goes to Mr. E. Nyali and his staff in
the laboratory for assisting with analysis of the fish
samples.
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  • ...The further increase in pH after day 0 may reflect the production of alkaline bacterial metabolites in spoiling fish [6]....

    [...]

  • ...On the other hand, physical properties of fresh fish such as firmness and appearance of the skin are greatly influenced by storage time due to cellular flaking of autolytic and microbial changes [6,7]....

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Journal Article
TL;DR: An overview of lipids oxidation in foods, its main aspects and implications for the customer has been outlined in a concise form as discussed by the authors, where three different mechanisms of fatty acid oxidation yielding different products are described: autoxidation, photo-oxidation and lipooxygenase action.
Abstract: An overview of lipids oxidation in foods, its main aspects and implications for the customer has been outlined in a concise form. Three different mechanisms of fatty acid oxidation yielding different products are described: autoxidation, photo-oxidation and lipooxygenase action. Oxidation of sterols and fat-soluble vitamins (named A, D, E and K), all isoprenoic compounds, as a part of unsaponificable fraction of lipid are included to review. It is indicated that relatively little information exists on oxyphytosterols. The contents of these compounds in food products are presented. The crucial significance for the sensory aspect of food quality is ascribed to volatiles from lipid oxidation products. Some volatiles with low odour threshold are characterized. Nutritional problem of lipid oxidation products and products obtained by interactions with other food components is discussed. Use of antioxidants as important factors in reducing the risk of chronic diseases and its economical aspects is discussed. The need for search of natural antioxidant, commonly perceived as safe is stressed. Last part of review covers the methods for the assessment of lipid oxidation. Classic methods for the determination of lipid stability, for the measurement of lipid oxidation are described. Also chromatographic analyses of volatile compounds generated in the lipid oxidation process included static, dynamic head space and SPME are discussed. The novel approaches to the analysis of these volatiles such as chemometrical methods and electronic noses are also presented.

108 citations

Journal ArticleDOI
TL;DR: The quality deterioration of tray-packed tilapia fillets stored at 0°C were studied by integrated evaluations of sensory, microbiological, biochemical and physical analysis, to expound the mechanism of fish spoilage and develop the most reliable indicators for quality assessment.
Abstract: The quality deterioration of tray-packed tilapia (genetically improved farmed tilapia strain of Oreochromis niloticus) fillets stored at 0°C were studied by integrated evaluations of sensory, microbiological, biochemical and physical analysis, in order to expound the mechanism of fish spoilage and develop the most reliable indicators for quality assessment. The results showed that four quality index asPseudomonas counts, total volatile basic nitrogen (TVBN), cadaverine (CAD) and K value were highly correlated (r > 0.90) with storage time and sensory acceptability. Protein degradation was visible on SDS-PAGE when microbiological load exceeded 6 log cfu/g. Thiobarbituric acid reactive substances (TBARS) value remained at a very low level throughout the storage, suggesting low lipid oxidation in muscle. Hardness decrease tested by texture machine was consistent with texture softening of fillets in the sensory evaluation. Considering fish freshness and microbiological safety, the shelf life of tilapia fillets stored at 0°C was approximately 10 - 12 days. Key words: Tilapia fillet, chilled storage, quality, spoilage, shelf life.

103 citations


"Effect of Prolonged Storage in Ice ..." refers background in this paper

  • ...[17] implicating accumulation of alkaline compounds as well as volatile bases produced by autolytic activities and metabolism of spoilage bacteria....

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