Article Type : Research Article
Authors : Mohhdaly AA, Mahmoud AA, Selim K and Ali Shimaa M
Keywords : Sardina pilchardus; Salting; Quality characteristics; TBARS; TVB-N; Microbiological analysis; Ripening
In recent years,
sardines (Sardina pilchardus) are pelagic ?shes of notable gastronomic and
economic importance around the world, and their consumption is very large.
Therefore, the effect of different salting methods on physicochemical
properties, quality characteristics and microbiological analysis of sardine
during ripening at ambient storage conditions for 90 days were investigated.
The proximate chemical composition of fresh sardine was: 69.46 ± 0.77%
moisture, 18.41 ± 0.12% crude protein, 10.77 ± 0.33% crude fat, 1.28 ± 0.21%
ash, 0.08% carbohydrate on ww. It was found that the protein, ash, and salt
contents of the salted sardine samples increased, while the contents of
moisture, and pH decreased during ripening at storage period. Lipids content
did not show a typical trend of changes within salting duration at ambient
temperature. TBARS and TVB-N values of sardine were found to be 0.17 ± 0.48 mg
MA/kg and 27.52 mg/100g at the beginning, 4.74 ± 0.9 and 5.28 ± 0.135 mg
malonaldehyde/kg, 83.16 and 85.68 mg/100g at the end of the ripening period for
scientific and commercial samples, respectively. The microbiological quality
parameters analyzed in this study indicates that the sardine samples were of
high quality and safe for utilization either as fresh sardine or for salting
processing and use. Generally, characterization of salted sardines in terms of
their safety and chemical composition will greatly help in designing the
optimum conditions in developing the method of salting process, leading to
higher consumer acceptability of the salted sardines. In conclusion, the
present data suggest the superiority of scientific salting method over
commercial salting method applied.
Fish is one of the most important sources for the
provision of animal protein and has been widely accepted as a good source of
protein for the maintenance of healthy human's body [1]. In addition, it
provides several other essential nutrients such as vitamins A and B
particularly in liver, K and E vitamins, and it is a good source of some
minerals like phosphorus, iron, zinc, iodine and calcium [2]. In general, the
proximate composition of fresh fish is given as 66–81% water, 16–21% protein,
0.2–15% fat, 1.2–1.5% ash and 0–0.5% carbohydrate. The global contribution of
fish and fish products as sources of protein is high, ranging from 10 % to 15%
of the human food across the world [3]. Small pelagic fishes such as sardine
(Sardina pilchardus), anchovy, herring, mackerel and sardinella (Sadinella
aurita) have a strong worldwide economic, livelihood, nutrition and ecological
importance, as (i) they represent about 25% of the global landings of capture
fisheries and (ii) they function a key role in maintaining environmental
processes in marine systems, occupying a fundamental intermediate trophic level
in pelagic ecosystems [5-6]. The nutritional assessment of small pelagic fishes
and more specifically sardines exhibited their richness in essential fatty and
amino acids, minerals, vitamins and are characterized by their high
digestibility. Sardines are an excellent source of polyunsaturated fatty acids
such as docosahexaenoic acid (C22:6n-3, DHA), docosapentaenoic (C22:5n-3, DPA)
and eicosapentaenoic acid (C20:5n-3, EPA), which have various health enhancing
properties [7,8]. Regular consumption of sardines allows the prevention of
considerable many diseases such as diabetes, cardiovascular and cancer
inflammatory diseases [9]. Thus, sardines consumption for human being is
advisable due to its high nutritional quality given by the appropriate balance
of amino acids and healthy unsaturated fatty acids [10,11]. The annual average
price registered for sardines ranged between 1.02 and 1.58 Euros per kilogram.
Fish quality is spontaneous in nature and is very complicated concept, which
includes physiochemical, microbiological, nutritional and biochemical
attributes. The freshness of fish degrades after death due to the changes in
lipid and protein fractions, the formation of biogenic amines and the
microbiological spoilage. This results in the deterioration of nutritional
value and sensory quality of fish and therefore led to a very short of shelf
life and hence needs at-most attention to maintain the quality of fish for longer
duration [12]. Preservation of fish considers greater importance to prevent the
loss of this nutritionally rich natural resource. Drying, salting and canning
are the most common methods used for preserving fish and seafood products
primarily small pelagic from spoilage and decay [13]. Of the various
preservation techniques, food salting process represents an effective obstacle
to the microbial growth in fishery products, especially in anchovies and
sardines. However, when salt fails to penetrate fish tissues and remove water
(water available for the encouragement of microbial growth which causes the
spoilage) potential pathogenic and spoilage microorganisms can easily grow.
Concentration of salt from 6 to 10% in the tissues will prevent the activity of
most spoilage bacteria. Salting is performed either by brine, dry, or injection
salting or a combination of these methods. Dry salting has been the most widely
used methods by the industry. It is the traditional salt-curing method used
during processing of salted fish in many countries. The salting method leads to
obtain a tender fishery product particularly pleasant aroma and taste, due to
the diffusion of salt into fish tissues and subsequently to the enzymatic
reactions that decompose proteins and fats during marinating [14]. In Egypt,
sardines fish consumption is very large and generally consumed as fresh or
salted and also used as fish meal. Furthermore, the implementation of
innovative technique for the preservation of sardines might represents an important
economic way for several manufacturing companies located around the world.
Therefore, the main objective of the present research was to characterize the
chemical composition of fresh sardine (Sardina
pilchardus) obtained from Fayoum governorate, Egypt and to evaluate the
effect of different salting methods on physicochemical properties (proximate
composition, lipid oxidation indices, pH, and salt content), quality
characteristics and microbiological analysis of sardine during ripening at
ambient storage conditions for 90 days.
About
15 kg of fresh sardine fish (S.
pilchardus) were purchased from
local fish market (Fayoum governorate). After that, they were transferred to
the laboratory of food science and technology department, faculty of
agriculture, Fayoum University in polyethylene bags with crushed ice at within
1 hour. Up on arrival to the laboratory, the sardine was quickly washed with
tap water. The average length and weight of fish sardine samples were 22 cm and
88 g, respectively.
Raw
sardine fish was divided into two equal batches: (a) Traditional batch: whole
fish samples were washed with tap water, left on ambient temperature (22 ± 2)
for 24 hours before salting technique. (b) Scientific batch: Fish samples were
washed carefully by tap water and salted directly. Sardine fish batches
(traditional and scientific) were salted by commercial salt at 20 % salt
concentration (w\w). Each batch was dry salted as follows: Different layers of
fish with salt were well mixed as well as abdomen cavity and gills of fish were
filled with salt and finally packed in polyethylene bags. In addition, the
bottom and surface layers of salt were added. The polyethylene bags were put into
plastic containers and tightly closed. All containers were covered by black
polyethylene bags and stored at room temperature (22 ± 2ºC) for 90 days.
Preparation of samples
for analysis
Raw sardine fish
and salted samples picked in salt were picked up from the container, and the
salt above the fish surface was completely removed. Then fresh and salted
samples.
Moisture,
crude protein, fat, ash and salt contents were determined according to method
described by [15].
5
g of raw and salted sardine fish samples were homogenized with 50 ml of
distilled water and filtered using filter paper. The pH value of filtrate was
measured using digital pH meter according to the method of [16].
TBA
was determined calorimetrically in minced fish flesh samples as described by
[18]. Ten grams of minced fish flesh
were macerated with 50 ml of distilled water for 2 min, washed into a
distillation flask with 47.5 ml distilled water, and 2.5 ml of hydrochloric
acid (4 N) were added. A volume of 50 ml distillate was collected, and from
which 5 ml were pipette into glass coppered tube and mixed with 5 ml of TBA
reagent. The mixture was heated in boiling water bath for 35 min. after cooling;
the optical density was measured against the blank at 538 nm. The method based
on the spectrometric quotation of the pink complex formed
after reaction of one molecule
of malonaldhyde (MDA) with two molecules of TBA. The TBA value was
expressed as mg malonaldehyde per kg sample.
10
gm. of fish sample were aseptically weight and homogenized with 90 ml of
sterile saline water for 1 min from each treatment. The homogenized samples
were serially diluted using 9 ml sterile saline for bacteriological analysis.
Total viable count (TVC), yeasts and molds count were examined during ripening
periods. Total viable count was determined by using nutrient agar medium [19]. Yeasts and molds count were enumerated
on malt agar as mentioned by [20].
The
statistical analysis of the results obtained was carried out according to SPSS
version 16 software program 2007.
Over
the last decades Arabian countries have witnessed a rapid growth and
development in different industrial and economic sectors, with increase in
population Chemical and biochemical procedures for the evaluation of food
quality are more credible and accurate, since they eliminate personal opinions
on the product quality. Moreover, the knowledge of proximate analysis of
seafood is fundamentally important for the application of different processing
techniques and for storage stability. The proximate composition of raw sardine
fish obtained from local market, Fayoum governorate, Egypt conducted at day 0
is shown in (Table 1).
Table
1: Proximate
composition biochemical characteristics (pH, TVB-N and TBARS) and salt content
of fresh sardine samples.
|
Quality attributes |
Sardine (Sardina
pilchardus) |
|
Moisture
% |
69.46 ±
0.77 |
|
Ash % |
1.28 ±
0.21 |
|
Crude fat % |
10.77 ±
0.33 |
|
Crude protein % |
18.41 ±
0.12 |
|
Carbohydrate** % |
0.08 |
|
Salt content % |
1.08 ±
0.58 |
|
pH value |
5.75 |
|
TBA(mg MA\ kg ) |
0.17 ±
0.48 |
|
TVB-N (mg\100 g) |
27.52 |
The
results indicated that the proximate chemical composition of raw sardine fish
used in the experiments on wet weight basis was: 69.46 ± 0.77% moisture, 18.41
± 0.12% crude protein, 10.77 ± 0.33% crude fat, 1.28 ± 0.21% ash, 0.08%
carbohydrate. These results are comparable to previous findings for similar
sardine pelagic fish samples that protein being the main constituents, followed
by lipids, ash and carbohydrate content is low, around 0.5 % reported that the
chemical composition of raw sardine was 69.20% moisture, 24.1% protein, 3.6%
fat and 2.22% ash, while found the proximate composition of sardine (Sardinella Brasiliensis) was 70.41%, 22.73%, 2.75% , 4.41, 1.08 and
0.08% moisture , protein , fat , ash , NaCl and carbohydrate contents,
respectively. Another author reported that proximate chemical composition of
sardine (Sardina pilchardus) was
66.0%; 13.5%; 16.0 and 2.7% for moisture; lipid; protein; and ash, respectively
[20-21]. Data are mean ± SD of three replicates; TVB-N is the total volatile
base nitrogen; TBARS is the thiobarbituric acid reactive substances value.
Based on wet weight % by difference reported that the proximate chemical
composition of sardine varies greatly from one species to another and from one
individual to another depending on nutrition, habitat, age, size of fish,
gender, and months of capture, as well as variations in environmental season
conditions. Also suggested that harvesting season and species specific physiological
characteristics due to physiological reasons and changes in environmental
conditions, such as spawning, migration, and starvation or well-feeding, can
bring variability in the proximate composition of small- sized ?sh species. Of
notes, the total fat content of sardine (10.77 %) was higher than those
reported by who found that the small pelagic fish include sardine had a crude
fat content between 3.26% and 3.85%. Besides the species, Fish lipid content
variation depends on the season, geographic regions, type of production,
typical maturity, and nutrition as well as whether the species is being
cultured or living in the wild [22-24]. According to the classification of fish
by whereby fish can be classified as lean fish (< 2% fat); low fat (2–4% fat);
medium fat (4–8% fat); and high fat (> 8% fat), the fresh sardine in our
study can be classi?ed as high-fat ?sh. These findings were supported by
previous reports of, who reported
that the flesh of fast-moving, migratory species (such as tuna, mackerel,
herring, anchovy, and sardine) contains more dark muscle tissue and more fat.
In contrast reported that sardine species and Indian mackerel are low and
medium-fat fish. The results showed also that the sardine small pelagic fish
possessed considerably higher protein content (18.41%) and therefore can be
considered as a good source of protein [25-28].
Moisture content: Shows
the moisture content of sardine samples salted by scientific and commercial
methods and stored for 90 days at ambient temperature [29]. Salting process
reduces the moisture content in foods, due to osmotic dehydration, whereby in
our research salting led to a reduction of up to 10% in moisture content of the
fresh sardine (Table 2). Moisture content of raw sardine samples was 69.46%,
this values decreased to 48.04 and 49.44% after 15 days of salting by
scientific and commercial methods, respectively. There was a further decrease
in the moisture content after 30 days of ripening, while after 45 days the
moisture content was increased in both scientific and commercial samples. After
60 days moisture content was decreased again to 45.68 and 49.38% for scientific
and commercial samples, respectively. While after 90 days moisture content was
increased to 50.57 and 51.03% for scientific and commercial treatments,
respectively. Same trend found by who found that after salting process of
anchovy, the moisture content decreased from 75.5% in fresh fish to 54.16% in
salted fish and the loss in moisture content was accompanied by increase in the
salt and ash contents. Also, reported that moisture content of fresh sardine
fillets (Sardina aurita) (73.62%) decreased continuously from the surface to the
bottom of the fillets. However, found no significant change in moisture content
values for salted-pressed spotted sardine samples stored under ambient
conditions during the ripening period of 6 weeks. Another study by who reported that moisture and lipid contents
in raw European eels varied during ripening and storage The lower
moisture content of the food helps prolong its shelf-life, quality and prevents
propagation of pathogenic and spoilage microorganisms, due to a decrease in
water activity. From the it could be concluded that the decreasing in moisture
content of salted sardine was slightly higher in scientific treatment samples
than commercial salting samples.
Protein content: Data
presented in showed the protein content of scientific and commercial salted
sardine samples during ripening at ambient storage (22 ± 2ºC) for 90 days.
Protein content of sardine samples increased during the ripening period whereby
the protein content of scientific and commercially salted sardine samples were
found to be 24.34 ± 1.15 and 20.60 ± 0.325 %after 90 days, respectively [30].
This increase in protein content may due to the reduction in moisture contents
during storage of salted sardine samples. These data are not in accordance with
that obtained by Michael who found that the crude protein did not significantly
change throughout the six weeks of salting. Also, reported that during the
salting method, the changes in protein structure like protein denaturation of
cod occurred when brine concentration raised from 20 to 25% due to the protein
salting-out and the amount got lower than that obtained when using 20% brine.
Therefore, the present data suggest the superiority of scientific salted
sardine in protein content during ripening over commercial salted sardine.
Table
2: Effect
of salting methods on proximate chemical composition of salted sardine during
ripening at ambient temperature.
|
Ripening period in (day/ambient) |
Moisture content % (ww) |
Protein content % (ww) |
Lipid content % (ww) |
Ash content % (ww) |
||||
|
Scientific |
Commercial |
Scientific |
Commercial |
Scientific |
Commercial |
Scientific |
Commercial |
|
|
0 |
69.46 ±
0.77 |
69.46 ±
0.94 |
18.41
± 0.12 |
18.41
± 0.12 |
10.77 ± 0.33 |
10.77 ± 0.33 |
1.28 ± 0.21 |
1.28
± 0.21 |
|
15 |
48.04 ±
0.62 |
49.44 ±
0.25 |
23.69 ± 2.66 |
21.38
± 2.33 |
13.61 ± 0.29 |
15.29 ± 0.59 |
14.04 ± 0.63 |
13.37 ± 0.03 |
|
30 |
46.83 ±
0.64 |
48.48 ± 0.24 |
25.07 ± 8.48 |
24.52
± 2.01 |
13.90 ± 0.42 |
13.77 ± 0.03 |
13.75 ± 0.72 |
13.33 ± 0.93 |
|
45 |
48.11 ± 0.21 |
50.39 ± 0.74 |
22.93 ± 1.15 |
21.73
± 0.90 |
12.33 ± 1.28 |
11.69 ± 0.34 |
16.07 ± 1.45 |
15.40 ± 0.33 |
|
60 |
45.68 ± 0.13 |
49.38 ± 0.89 |
26.33 ± 1.13 |
21.15 ± 0.78 |
11.28 ± 0.41 |
12.76 ± 0.29 |
16.11 ± 0.41 |
15.79 ± 0.25 |
|
75 |
46.64 ± 0.21 |
50.26 ± 0.26 |
25.06 ± 1.76 |
21.95
± 2.04 |
13.68 ± 0.45 |
13.13 ± 0.92 |
15.72 ± 0.08 |
15.25 ± 0.98 |
|
90 |
50.57 ± 0.32 |
51.03 ± 0.39 |
24.34 ± 1.15 |
20.60 ± 0.33 |
7.04 ± 0.48 |
11.63 ± 0.6 |
17.05 ± 1.04 |
16.57 ± 0.96 |
Table
3: Hanges
in salt content, pH values, total volatile base nitrogen (TVB-N), and
thiobarbiuturic acid (TBARS) values of salted sardine during ripening at
ambient temperature.
|
Ripening period
in (day/ambient)b |
Salt content % (ww) |
pH values |
TVB-N values (mg/100gm) |
TBARS values (mg/kg) |
||||
|
Scientific |
Commercial |
Scientific |
Commercial |
Scientific |
Commercial |
Scientific |
Commercial |
|
|
0 |
1.08 |
1.08 |
5.75 |
5.75 |
27.52 |
27.52 |
0.17
± 0.48 |
0.17 ± 0.48 |
|
15 |
18.91 |
22.68 |
5.48
± 0.005 |
5.54 ± 0.005 |
39.56 |
42.58 |
6.06
± 0.09 |
5.17 ± 0.03 |
|
30 |
16.45 |
26.32 |
5.57
± 0.005 |
5.60 ± 0.005 |
103.32 |
57.96 |
5.07
± 0.06 |
4.95 ± 0.92 |
|
45 |
20.01 |
30.45 |
5.60
± 0.005 |
5.43 ± 0.005 |
60.48 |
40.44 |
4.21
± 0.74 |
5.86 ± 0.12 |
|
60 |
23.55 |
18.42 |
5.54
± 0.095 |
5.61 ± 0.005 |
52.92 |
80.64 |
4.02
± 0.1 |
4.96 ± 0.78 |
|
75 |
20.41 |
15.843 |
5.35
± 0.005 |
5.24 ± 0.005 |
83.16 |
85.68 |
4.42
± 0.39 |
5.58 ± 0.25 |
|
90 |
29.54 |
24.00 |
5.34
± 0.005 |
5.32 ± 0.005 |
66.15 |
95.50 |
4.74
± 0.9 |
5.28 ± 0.14 |
and
exhibited no significant differences relative to the fresh raw sample.
Ash content: Ash
content is a good index of the mineral content in fish product. The given data
in show the contents of ash in scientific and commercial salting treatments of
sardine samples during ripening at ambient storage (22 ± 2°C) for 90 days.
There was a general increase in ash content during ripening at ambient
conditions. At the end of storage the ash content of scientific and commercial
salted sardine samples were found to be 17.05 ± 1.04 and 16.57 ± 0.96%,
respectively [35-37]. The increasing in ash content during salting process
duration probably due to the effect of extracted lipid which helps to make a crusted
surface on every dried fish and the effect of crashed scales and bones in dried
fish and meat. Moreover, the presence of remains of salt during preparation of
samples for determination and this consequently causes an increase in the ash
content. The obtained results agreed with who found that the ash content of
salted sardine ranged between 15.15-17.04 %. Another study by Michael who
observed that the ash content of salted-pressed sardine throughout the six
weeks of storage ranged from 11.8 to 13.0%. Variations in chemical composition
are not unusual as who observed variations in chemical composition of salted
fish, mainly in protein and moisture during salting process.
Salt content: It is important to
determine the salt content of fresh seafood so as to establish a baseline for
future preservation procedures include salting. NaCl is added to foods for its
effects on functional, preservation and sensory characteristics (Table 3).
Shows the NaCl contents of salted sardine fish during ripening at ambient
storage (22 ± 2ºC) for 90 days. There was a variation of salt content during
salting process period, and this may be due to changes in the muscle structure
of the fish, which has an effect on water-holding capacity and concomitant salt
retention ability of fish [38-40]. For commercial and scientific treatment
samples, NaCl contents markedly increased from an initial value of 1.08% to
24.00 and 29.54% at the end of ripening at ambient storage, respectively. The
obtained data are agreed with who found that the salt content of salted mullet
at 20% salt was 18.88% after 15 days and 29.3% after 90 days of ripening at
ambient storage. Also found that the weight gain of salted products depends not
only on the brine concentration, but also on the brining temperature and time.
However, other findings indicated lower salt content (5.14–6.12%) throughout
salting for Eritrean sardines. The salt content of the fresh sardine fish
samples were comparable to the findings of Negasi. pH values: pH is the most
critical factor affecting microbial growth, quality and spoilage of foods. pH is widely used to measure fish deterioration; it has been common
to measure the pH of the muscle tissue. Mean pH values of the salted sardine
samples in our study was acidic (5.75), which is in agreement with who found
the pH of fish ranged from 5.7 to 6.6. These results also agreed with who found
that pH values ranged between 5.47 and 6.31 in traditional salted mullet fish
samples obtained from some Egyptian markets. Found that pH value of salted
sardine and salted mackerel ranged from 4.89- 5.60 and 4.68-5.32, respectively
[41-43]. The pH of newly killed fish is neutral, but after death there is a
speedy fall as glycogen breaks down and consequently the formation of lactic
acid. On contrast found that the mean pH values of salted small pelagic fish
ranged from 7.08–7.30 involve spotted sardine 7.08 ± 0.01. A post-mortem pH of
7 or above is a guide of starvation with depleted carbohydrate stores. The
difference can be due to life history before and after harvest, the species
chemical composition, fishing ground, and the pH of the aquatic environment.
The change in pH of fish could owe to stress during harvesting leading to
gathering of lactic acid and/or production of volatile bases by the autolytic
action on protein and other compounds. As shown in pH values decreased during
ripening at ambient storage in both treatments samples. Same trend found by
Hernandez-herrero who found that pH of anchovy muscle appreciably decreased
from 6.13-5.72 during the first week of ripening. But in a study by Ana who
observed a slight pH increment for sardine samples during the period of
ripening. The decrease in pH value from 5.75 to 5.34 and 5.32 of 7.1% and 7.5%
of scientific and commercial salted sardine fish, respectively may be due to
the ionic strength of the solution inside of the cells. Indeed, salting methods
can have an effect on the dissociation of amino acids and small peptides
leading to a decrease in pH.
The highly
unsaturated fatty acids of ?sh are easily susceptible to oxidation, resulting
in alterations in colour, texture and nutritional value as well as a rancid
smell and taste. TBARS is a good indicator of the quality of the ?sh and is
commonly used to measure the secondary oxidative products produced by lipid
hydroperoxides decomposition. Shows the effects of the two different salting
methods and the ripening period on the formation of thiobarbituric acid
reactive substances in sardine [44-45]. The initial value of TBARS (0.17±0.48
mg malonaldehyde /kg) was in agreement with those mentioned by some authors for
the same species indicating that the sardine sample in the present study has a
good quality. Results showed that the TBARS levels in both salting methods
increased sharply to 6.06 and 5.17 mg malonaldehyde /kg after 15 days in
scientific and commercial samples, respectively. This is may be due to higher
release of free iron and other prooxidants from the muscle and home proteins
might undergo degradation, thus lipid oxidation become more pronounced.
Consequently the produced secondary oxidation compounds should arise especially
from peroxides breakdown. Additionally, the marked increase in TBARS of sardine
may be related with the laboratorial analysis conditions, which promoted some
lipid oxidation. In agreement with
the current results, an increased formation of secondary oxidation products was
observed in canned sardine (Sardina pilchardus) during storage [46]. Reported a
marked increase in protein hydrolysis in lizardfish during extended storage.
Contrary, a marked decrease of the TBARS value has already been found for
canned fish. Thereafter, TBARS values were decreased after 30 days of ripening
to 5.07 and 4.95 mg malonaldehyde /kg, in both scientific and commercial
treatments samples, respectively. This is may be due to the autooxidation of
secondary oxidative products releasing aldehydes or carboxylic acids. TBARS are
reported to be interacted with nucleophilic compounds present in the muscle and
facilitate the fluorescent compounds formation. Moreover, TBARS probably lost
partly into the brine packaging medium and not be determined when analysing the
sardine. After the 45th day, for scientific method samples the TBARS values
were lower compared to commercial method samples and remained quite low
throughout the entire period of ripening. After this time, TBARS values did not
provide a general trend about the effect of the ripening period. At the end of
the ripening period, the samples reached the maximum values of 4.74 ± 0.9 and
5.28 ± 0.14 mg malonaldehyde /kg for scientific and commercial samples
respectively, which is below the reported critical values. In general, maximum
acceptable levels of TBARS in small pelagic ?sh are regarded to be consumed up
to 8 mg malonaldehyde /kg.
Total
volatile base nitrogen (TVB-N) is the most reliable measurement for evaluation
of freshness indices of seafood and indicates sign of spoilage and decay during
ripening and storage. Among the more general chemical parameters of fish
spoilage are total volatile bases, indicative of protein breakdown, and
trimethylamine (TMA) resulting from bacterial proteolysis [47-49]. High TVB-N
values is regarded as spoiled and unacceptable for consumption as
trimethylamineoxide (TMAO) is reduced to formaldehyde, dimethylamine and TMA by
spoilage bacteria or by the action of endogenous enzymes. Data presented in
show the effect of ripening periods at ambient storage condition (22 ± 2ºC) for
90 days and the method of salting on TVB-N content of salted sardine fish products.
At start, the initial TVB-N content of salted sardine was 27.52 mg/100g, which
increased with the ripening period up to 30 days to 103.32 and 57.96 mg/100gm
in scientific and commercial samples, respectively. Same trend found by Aimen
who found that the TVB-N content increased during the ripening and storage
time. They concluded that the enzymatic reaction and higher microbial counts,
particularly the growth of halophilic bacteria, which breakdown compounds like
amino acids, trimethylamine oxide (TMAO), peptides, etc., resulted in an
increase in the basic nitrogen fraction for sardine fish. Reported that the
initial TVB-N values for sardine and anchovy patties were 13.66 and 17.37
mg/100g, respectively and these values increased progressively throughout
salting. In another research, initial TVB-N levels of fishballs produced from
tench and pike perch were reported as 11.2 and 11.4 mg/100 g, respectively then these values
increased to 36.2 and 39.6 mg/100 g in 14 days
The TVB-N value in the salted sardine in this study was higher than reported by
Mohan for the sardine stored for 12 days. At 45 days TVB-N contents decreased
to 60.48 and 40.44 mg/100gm in scientific and commercial samples, respectively.
On other hand, after 60 days of ripening TVB-N contents increased until the end
of ripening of 90 days. These results agreed with who found that the amount of
TVB-N decreased in eviscerated and non- eviscerated Bori tissues during salting
which was due to leaching. Reported the decrease in anchovy TVB-N content may
be due to a part of TVB-N content diffused into the brine with other nitrogen
fractions. This fluctuation in TVB-N content in salted fish samples was
accordance relatively with that obtained by many authors such as [5. This wide range of TVB-N for the
finished product might be due to the effect of the different salting treatments
on the quality such products. The legal limits of acceptability set for this
index at 35 mg/100 g for TVB-N were exceeded throughout ambient storage period,
which indicates that the salted sardine samples is unacceptable, in contrast to
fresh sample. Generally, due to the
changes in climate conditions, season, processing, and industrial growth, there
could be wide differences in the biochemical constituents of the ?sh and fish
products.
The microbiological safety of the fresh and salted sardines was ascertained through the assessment of microbiological parameters, including total viable count (TVC), yeasts and molds. Total viable count is an important criterion for quality evaluation of fish and fishery products. Since the International Commission Regulation 2073/2005 and subsequent modi?cations recommended the shelf-life threshold for fresh ?sh and their products at 107 cfu/g for total viable count, thus TVC was considered in this study to measure the microbiological quality of the considered samples. It could be recommended the standard levels of TVC of fish freshness are as following <104 cfu /g, 104 - 106 cfu /g and >106 cfu /g number of microbe colonies for fresh fish, sub fresh fish and deteriorated fish respectively [50-53]. The changes in total viable count (TVC) with the ripening duration for the scientific and commercial salted sardine samples are given in The initial total viable bacteria in the sardine samples at zero time was 4.5 ×103 cfu/g con?rming the data found by Mohan but was higher than the values reported by Stamatis and Arkoudelos for fresh sardines, which may be due to the handling in preparation, processing, distribution and storage of sardine. As evidenced by the (Table 4). The sardines used in this study were characterized by a good microbiological quality, as indicated by a low total viable count under the critical limits of microbe colonies for fresh fish. The limits of bacterial counts were 105 cfu/g in Egyptian standards specification (288, 2005).
Table
4: Changes
in microbiological characteristics of salted sardine (Sardina pilchardus)
during ripening.
|
Ripening period in (day/ ambient) |
TVC (×103cfu/g) |
Yeasts and molds (×102cfu/g ) |
||
|
Scientific |
Commercial |
Scientific |
Commercial |
|
|
0 |
4.5 |
4.5 |
1 |
1 |
|
5 |
1 |
4 |
1.5 |
2 |
|
0 |
3 |
10 |
3 |
3 |
At
the end of ripening period of 90 days, TVC reached 3 ×103 and 1 ×104
cfu/g for scientific and commercial samples, respectively. The increase of TVC
may be due to the multiplication of microbial counts that can able to growing
under commercial salting method conditions. The obtained results were lower
than found by Gennari who found the
aerobic bacterial count of fresh Mediterranean sardines (clupea pilchardus) was 3.5×104 cfu/g. Furthermore, found
that during 28 days of salting, TVC increased significantly and the sensory
analysis correlated well with microbiological analysis of fish. Yeasts and
molds are normally distributed in nature and generally contaminate fish during
processing, handling, storage and exposure to other unhygienic environmental
factors, and thus considered a causative agent for rapidly spoilage of such
foods. The yeasts and molds counts of the microbial investigated during the storage of salted sardines are reported
in Table 4. At a zero time yeasts and molds counts were 1×102cfu/g,
with the ripening period their counts showed an increasing trend in both
treatments. These results agreed with who found that the mean values of total
yeast count /g of vacuumed packed fesiekh and salted sardine fillet were 3.9×102
and 3×102, respectively. Also, Reported that the yeast and mold
counts of sardine were 20 cfu/g and 10 cfu/g, respectively. It could be
concluded that the commercial salted sardine contained more bacteria, yeasts
and molds than scientific one probably due to the type of method used.
Therefore, the present data suggest the superiority of scientific salting
method over commercial salting method during ambient storage [54-57]. In this study, the microbiological assessment
analyzed of sardines is indicative of superior sardine ?esh quality,
considering the proposed lower limits for TVC, yeast and mold.
Salting
is a simple, low-cost and appropriate technology for pretreatment of sardine, giving
a product with a good sensory properties, even at ambient conditions. The
present research provides valuable information on moisture, fat, protein, ash,
pH, and salt contents of fresh Egyptian sardine. Current study clearly shows
the effectiveness of salting methods on chemical, microbial, and quality
changes of sardine at ambient storage condition. Regarding the quality of the
sardine, TVN and TBARS analysis were ef?cient indicators for the extent of
oxidation during ripening. The extent of lipid oxidation were very low for
scientific method samples, indicating its effectiveness in restraining
secondary oxidation as well. Based on the oxidation and microbiological quality
indicators, the sardines from both salting treatments were below maximum allowable
levels and therefore, acceptable to the consumer. Thus, certain processes such
as salting could be used to obtain a product which maintains almost all its
nutritional characteristics with a longer shelf life.