Volume 18
Issue 4
Food Science and Technology
JOURNAL OF
POLISH
AGRICULTURAL
UNIVERSITIES
Available Online: http://www.ejpau.media.pl/volume18/issue4/art-09.html
QUALITY CHANGES OF SARDINE FILLETS MARINATED WITH VINEGAR, GRAPEFRUIT AND POMEGRANATE MARINADES
Meltem Serdaroğlu1, Pelin Barıs2, Müge Urgu1, Eisa Doostifard1, Gulen Yıldız-Turp1
1 Ege University, Engineering Faculty, Food Engineering Department, Izmir, Turkey
2 Izmir Institute of Technology, Engineering Faculty, Food Engineering Department, Izmir Turkey
Sardine (sardina pilchardus) fillets were marinated
by using three different marinade solutions prepared with vinegar (VM), grapefruit
juice (GM) and pomegranate juice concentrate (PM). All marinade formulations
contained 4% salt and 0.1% black pepper. Samples were stored at 4ºC for
28 days. Proximate composition, pH, acidity, salt content, moisture content,
penetrometer value, peroxide value and TBA value of marinated samples were evaluated
during storage of 28th days. Sardines marinated with grapefruit juice had the
highest pH value at each evaluation period. On day 28 the highest acid value
(0.94%) was obtained in VM samples and the lowest acid value (0.62%) was obtained
in GM samples. No significant differences in salt content were found between
marinade treatments at each evaluation period except day 28. At each evaluation
period GM samples had higher (softer in texture) and PM samples had lower penetrometer
values (harder in texture). PM samples had the lowest peroxide and TBA value
at each evaluation period. It’s concluded that pomegranate sauce could
be used as a functional marinade solution in sardine marination.
Key words: marination, sardine, grapefruit, pomegranate, vinegar.
INTRODUCTION
Sardine (Sardina pilchardus) is one of the important species in Turkey and the total catch is 30,091 tons/year. Most of the yield comes from the Aegean Sea (14,107 tons/year) [4]. It is generally consumed in fresh, salted or canned. One possible alternative method for sardine processing is marination, which preserves fish through the simultaneous action of salt and organic acids and it involves increasing the ionic strength and decreasing the pH [15]. During the marination process salt and acids diffuse into the fish muscle, denaturate the protein and lowering the pH value and activating the lysosomal cathepsins to yield the typical flavour. Marinating is also used to tenderize or to change textural and structural properties of raw material [17].
Marination process is usually completed within 1 to 2 weeks at 4ºC. Marinated fish can be used for human consumption after being packed in glass or plastic containers with the addition of a final marinade solution containing sugar and spices [29].
Another key step in marinades production includes the packaging of semi-marinades with cover brine. The semi-marinades applied in this production step are still maturing in the cover brine and their properties are changing in time [56]. Marinate quality depends on several parameters including, among others, freshness and maturity of fish, its fat content and composition, fishing season and area, hygiene of processing plant, marinating method and composition of marinating solution [61].
Sardine is very suitable for marination process because of it’s high fat content [28]. Marinades are semi-preserves; acid and salt are added to the fish to retard the action of bacteria and enzymes, resulting in a product with a characteristic flavour and having a limited shelf-life of 1–6 months in chilled storage [30, 40]. Previous published work focused on using acetic acid in marinade solutions [19, 29, 44, 45, 50, 55], however only a limited number of work carries on using low pH fruit juices in marinade formulations. It is reported that pomegranate sauce [20] and olive oil-pomegranate sauce [60] produced desirable flavour and showed antioxidant activity in anchovy marinades. Kilinc and Çakli [29] investigated the chemical and textural changes in sardine marinated in tomato sauce and lemon juice. Serdaroglu et al. [53] concluded that grapefruit juice marinade can be used in marinade solution for turkey meat.
Grapefruit is cultivated in the west and south coast of Turkey principally to obtain the juice. In recent years, the grapefruit (Citrus paradise) has received much attention because of its nutritional and antioxidant properties, besides ascorbic acid, it also contains abundant flavonoids, which are reported to be the important part of active ingredients [36].
Pomegranate (Punica granatum L.) is one of the important fruits grown in Turkey, the edible part of the fruit contains considerable amount of acids, sugars, vitamins, polysaccharides, polyphenols and minerals [2, 39, 63]. Pomegranate juice presents high anti-oxidative properties due to its polyphenols, tannins and anthocyanins [49]. The pomegranate juice concentrate is commonly used for salads and many dishes in Turkey [39]. Phenolic compounds of plant origin have attracted considerable attention due to their beneficial functional and nutritional effects including antioxidant and antimicrobial activity [8]. Although some organic acids are used in fish marinades, there are limited studies about the effects of fruit juices that have antioxidant properties in sardine marination. The present work was therefore aimed to evaluate some quality changes of sardine fillets marinated in vinegar, grapefruit juice and pomegranate juice marinades during storage.
MATERIAL AND METHODS
Raw material
The samples of sardine (Sardina
pilchardus)
each approximately in weight 60–80 g and 14–16 cm in length were
obtained from a local fish market in Izmir in February (Aegean Region of
Turkey). Fish were iced and transported to the laboratory and fillets were removed
on the same day. The commercial pomegranate juice concentrate (Tunca Gıda,
Mersin, Turkey), white grape vinegar (Fersan, İzmir, Turkey) and grapefruits
were purchased from a local market.
Marination process
All the fillets
were immersed into a solution consisting of 20 g/l NaCl to carry out the pre-salting
process. The ratio of fish to solution was 1:1 (w:v). Pre-salting was performed
at 20ºC for one
hour. Then fillets were removed from the solution and washed under the tap water
to remove the excess salt. Three different marinade solutions were used for marinating
process. Vinegar marinade (VM) was prepared from white grape vinegar and distilled
water at a ratio of 1:2 (pH 4.82, acid value 0.70%). Grapefruit marinade (GM)
was prepared from freshly squeezed and filtered grapefruit juice (pH 5.03, acid
value 0.79%). Pomegranate marinade (PM) was prepared using pomegranate juice
concentrate and distilled water (pH 4.78, acid value 0.73%). The selected ratio
of pomegranate juice concentrate to water was 2:1. The brix of pomegranate juice
concentrate which was measured with a digital refractometer (A. Krüss, DR201-95,
Germany) was 70.9 and final brix of pomegranate sauce was 47.1. NaCl (4%) and
black pepper (0.1%) were added to all marinade solutions.
Fish fillets were randomly submitted to the three different marinade formulations, the fish marinade ratio was 1.5:1 (w:v), glass jars with tap were used for marination process. All samples were stored at 4ºC for 28 days and analyzed to determine the quality changes weekly. Six jars of each marinade formulation were used at each sampling period. Marinades from each jar were randomly taken drained and homogenized using a kitchen blender. All assays were conducted on duplicate samples of the homogenates. Proximate composition, pH, acidity, salt content, moisture content, penetrometer value, peroxide value and TBA value of marinated samples were evaluated on 7th, 14th, 21th and 28th days of storage.
Determination of total phenolics
Total phenolic
compounds in brines before marinating were determined by the method of Negi et
al. [41]. Samples (0.2 ml) were mixed with 1.0 ml of 10-fold diluted Folin–Ciocalteu reagent
(Merck, Darmstadt, Germany) and 0.8 ml of 7.5 g/100 g sodium carbonate (Merck,
Darmstadt, Germany) solution. After standing for 30 min at room temperature,
the absorbance was measured at 765 nm using UV–visible spectrophotometer.
The results were expressed as milligram gallic acid equivalents (GAEs) per 100
g of matter.
Antioxidant activity
The antioxidant activity of samples was measured
by using a 2,2-diphenyl-1-picrylhydrazyl (DPPH) method reported by Singh
et al. [54] . A volume of 10 μl of diluted sample in methanol solution
was added to 1 ml of DPPH solution and diluted to 25 ml with methanol. The solution
was shaken vigorously with vortex and incubated at room temperature for 20 min.
The decrease in absorbance at 517 nm was determined at the end of incubation
period with a spectrophotometer. The control was prepared as above without any
extract and methanol was used as blank. Radical scavenging activity was expressed
as the inhibition percentage [%].
Proximate composition.
Moisture content was measured by using
the oven-drying procedure according to the AOAC [5]. Fat content was determined
by the chloroform- methanol extraction according to Flynn and Bramblett [14].
Crude protein, using the Kjeldahl method by multiplying 6.25 (nitrogen-to-protein
conversion factor) was determined [3]. Ash content was measured according to
the AOAC [5] procedure.
pH
The pH value was recorded using a pH meter (HANNA precision model
pH meter, Sigma, St. Louis, MO), with the glass electrode applied directly to
the homogenate according to the method of Lima Dos Santos et al. [35]. Samples
were prepared by blending 10 g of the homogenate with 100 ml distilled water
at room temperature by using an Ultra-Turrax (IKA T 25 Basic, Staufen, Germany).
Acid value
Acid value was determined as anhydrous acetic acid according
to the method given by Karl [27]. The method was based on titration using 0.1
N sodium hydroxide and phenolphthalein as an indicator.
Salt content
NaCl content of samples was determined according to the
method given by Ludorf and Meyer [38]. The method was based on titration using
0.1 N silver nitrate and potassium
chromate (%5, w/v) as an indicator.
Texture evaluation
Sur penetrometer (Sommer Runge-Model KG PNR-6,
Berlin, Germany) equipped with a total 100 g load was used to evaluate hardness
of the samples. Depth puncture was determined to 1/10 mm in triplicate for each
sample. A lower depth of penetration indicates a harder texture.
Lipid oxidation parameters
Thiobarbutiric acid values
were determined according to Tarladgis et al. [58] and the results were expressed as mg
malonaldehyde equivalents/kg of sample. Peroxide value was assessed by the AOAC
[5] method.
Statistical analyses
Six jars of each marinade formulation
were used at each sampling period. Each analysis was performed in duplicate.
The data was analysed by two-way analysis of variance (ANOVA) using the SPSS
software [57]. Significance of differences was defined as P < 0.05.
RESULTS AND DISCUSSION
Total phenolic compounds and antioxidant activity of marinade
solutions
Total
phenolic concentration of vinegar, grapefruit juice, and pomegranate juice concentrate
were found as 35.0, 61.8, 150 mg GEA/100 g, respectively. Gokoglu et al. [20] reported
56 mg GAE /100 g and Topuz et al. [60] reported 132.75 mg GAE/100 g total
phenolic content in pomegranate juice concentrate. Content of soluble polyphenols
in pomegranate juice varies within the limits of 0.2–1.0%, depending on
variety and include mainly tannins, ellagic tannins, anthocyanins, catechins,
gallic and ellagic acids [16].
Antioxidant activities of vinegar, grapefruit and pomegranate concentrates were found as 16.47, 41.25, and 98% respectively. As a result, pomegranate juice concentrate has the highest antioxidant activity among the samples. Tezcan et al. [59] determined the antioxidant activity of seven commercial pomegranate juices from Turkey, all marks contain 100% pomegranate juices as 10.37–67.46%.
Acid value and salt content
Increment in acid value
is a protective factor and becomes important in the brine and salt combination
which has a conserving effect and this in turn plays an important role in a decrease
in pH and inhibition of microorganisms. Changes in acid values [%] of marinated
sardine fillets are seen in Figure 1.
![]() |
Fig. 1. Changes of acidity values
of sardine fillets marinated in (VM) vinegar, (GM) grapefruit and (PM) pomegranate
brine |
On the first day of marination acid values of fillets marinated with VM, GM and PM treatments were found to be 0.80, 0.46, and 0.49% respectively, GM and PM samples had similar acid values. There was a significant increase (P < 0.05) in acid values of GM and PM treatments on day 7. Similar results were reported in other investigations showing increasing acetic acid concentration of fish fillets during marination [32]. Acid values of PM samples decreased after 14 days of storage and reached to 0.62%. On day 28, the highest acid value (0.94%) was obtained in VM samples and the lowest acid value (0.62%) was obtained in GM samples. These values are in parallel with the results of other researchers, Cosansu et al. [11] reported acid value for marinated anchovy as 0.45% and Celik [9] for marinated clams as 0.68%.
The preservative effect of salt has been recognized as being due to a decrease in water activity, less availability to microbial attack and enhancement of functional properties, leading to an increase of the shelf life time [6, 64]. After pre-salting process for one hour the salt content of fillets was 7.94%. As soon as the marinating bath comes into contact with the fish, a diffusion of marinate solutions take place into the tissue of the sardine fillets until a concentration equilibrium is reached. Salt and acid concentrations and the brine to fish ratio determine the rate of absorption and contents of salt and acid in the tissue [48].When fish is immersed into a concentrated salt solution it could be considered that the high osmotic pressure will be responsible for the movement of the solute into the fish muscle. This process will continue, until a kind of barrier is formed in the surface layer of the muscle tissue. Changes in percent salt content of marinated sardines are seen in Figure 2.
![]() |
Fig. 2. Changes of salt content of
sardine fillets marinated in (VM) vinegar, (GM) grapefruit and (PM) pomegranate
brine |
Salt content of marinated sardines were recorded as 4.78, 4.24 and 4.15% in VM, GM, and PM treatments respectively on the first day of marination. Salt content of fish flesh increased (P < 0.05) during the storage period and reached to 6.66, 7.44, and 7.07% in VM, GM, and PM treatments at day 28 respectively. No significant differences in salt content were found between marinade treatments at each evaluation period except day 28, on that day sardines marinated in vinegar marinade had lower salt content than other treatment groups (P < 0.05).
The rate of salt penetration into the fish muscle depends upon many factors. The salting method is the most important and then temperature during salting, purity of the salt and the characteristics of the fish used [65]. Brine concentration exerted a great influence on salt penetration into the muscle [46]. At higher acid and salt concentrations the moisture uptake after marination was higher. The more moisture means the meat absorbed more acid during marination [1].
Proximate composition and pH of sardine fillets
The initial proximate
composition of the sardine fillets for moisture, fat, protein and ash was 70.8,
9.7, 17.3 and 1.4% respectively. Those values were generally in line with the
results reported by Gokoglu et al [18], Kilinc [28] and Serdaroglu and Felekoglu
[48]. The pH value is a fundamental datum to be monitored during the salting
or marination process, because it gives a reasonably good indication of the final
meat quality [36].
The pH changes of marinated samples are seen in Figure 3. pH value in raw sardine flesh was 6.3. Post mortem pH can vary from 5.4–7.2 depending on fish species [24]. The pH value in sardine recorded as 6.3 by Gokoğlu et al. [19] and 6.25 by Kilinc et al. [33]. After 24 hours of marination process pH values of samples decreased and were found as 4.82, 5.03 and 5.06 in VM, GM and PM samples respectively. Diffusion of acids of vinegar, grapefruit and pomegranate marinades into fish muscle caused this initial decrease in pH. Sardines marinated with grapefruit juice had the highest pH at each evaluation period. pH values of all samples did not change markedly until 28 days of marination (P > 0.05). At the end of the storage period pH values were recorded as 4.65, 5.12 and 4.77 for VM, GM, and PM samples respectively. Investigations have confirmed that the pH value of marinades depends on the rate of marinade diffusion to tissue [48], on changes in tissue structure after freezing-thawing (fiber shrinkage and bigger extracellular space), as well as on the enzymatic and microbiological activity during freezing, storage, and thawing of fish [55]. Szymczak et al. [56] demonstrated the poor correlation between acidity and pH so it was, probably, affected by acid binding with protein and by buffering properties of protein hydrolysis products.
![]() |
Fig. 3. Changes of pH values of
sardine fillets marinated in (VM) vinegar, (GM) grapefruit and (PM) pomegranate
brine |
Similarly other researchers reported insignificant changes in pH levels of marinated fish during storage. Poligne and Collignan [45] determined that the pH levels of anchovies pickled with acetic acid increased from 3.90 to 4.21 after 20 days of storage and then remained constant until the end of the storage. Gokoglu et al. [19] stated that pH levels of sardine marinated with 2 and 4% acetic acid and stored for 150 days at 4ºC were recorded as 4.5 and 4.1 respectively. Kilinc and Cakli [31] reported that pH levels of pasteurized and non-pasteurized sardine marinades in tomato sauce increased from 3.84 to 4.09 and 4.19 respectively at the end of the storage period.
Changes in moisture content
Table 1 shows the
changes in moisture content of marinated sardine fillets. All treatments showed
significant (P < 0.05)
decrease in moisture content between the 1st and 2nd evaluation period. During
the marination process salt initially dissolves in the surface of fish, after
maintain the brine at saturation point as salt penetrates the fish and water
comes out. Marination treatment had significantly affected the moisture content
of sardine fillets. At each evaluation period PM samples had lowest moisture
content (P < 0.05).
In a study, it was determined that pomegranate juice includes glucose and fructose and glucose contents changes between 3.98 and 6.91 g/100 ml and fructose between 4.55 and 9.36 g/100 ml [59]. High moisture content decrement in PM samples could be related to the effects of sugar with salt on the water activity of samples. According to Kolakowski and Bednarczyk [34], the acetic acid in the marinating solution caused the decrease in the water content of fillet. Moisture content of VM samples decreased from 80.60 to 71.44%, GM samples decreased from 79.74 to 74.13%, and PM samples decreased from 63.65 to 54.92% at the end of the storage period.
Penetrometer values
Texture is a very important quality
parameter to take into account when preparing a food product from fish flesh.
This is especially true for determining the quality of fish during the storage [32].
One of the aims of the marination process tenderizing the raw material [12].
Marinade treatment significantly (P < 0.05) affected the penetrometer values of fish fillets. Table 1 shows the changes in penetrometer values of marinated fillets in different marinade solutions. Usage grapefruit solution as a marinade resulted softer texture of sardine fillets according to the other samples (P < 0.05). There is a high relationship between pH and moisture diffusivity and textural properties in meat. Low pH could induced protein denaturation and harder texture in sardine samples.
Tab. 1. Changes in penetrometer values and moisture content of sardine fillets in VM, GM, and PM during storage |
|
||||||
(1/10 mm) |
||||||
a–c Different superscripts in the same row indicate significant
differences (p<0.05) x–y Different superscripts in the same column indicate significant differences GM: Grapefruit juice marinade, VM: Vinegar marinade, PM: pomegrenade juice marinade |
At each evaluation period PM samples had lower (harder texture) penetrometer values. This result is in accordance with the moisture content of PM samples that have the lowest moisture content during storage. Storage period significantly affected the penetrometer values of fillets marinated in vinegar solution that increased from 13.05 to 15.55 (1/10 mm). However penetrometer values of GM and PM samples did not significantly change during the storage (P>0.05). Texture parameters are changed by enzymatic and chemical reactions that lead to softening, changes in elasticity or development of toughness under certain conditions [32].
The marinating temperature, fish species, thickness of fish flesh, fish: solution ratio and concentrations of acid and sodium chloride are the important factors which affect the texture of marinated fish. For the samples salted in the solution of sodium chloride and marinated with PM, a decrease in flesh succulence was also observed; it was defined as dry or slightly fibrous.
Peroxide and TBA Values
Lipid oxidation is a major
quality problem since it leads to the development of off-odors and off-flavors,
called oxidative rancidity, in edible oils and fat containing foods. The highly
unsaturated lipids in fat-rich fish are easily susceptible to oxidation that
results in a rancid flavour and taste as well as alterations in texture, colour
and nutritional value [43]. Peroxide value and thiobarbituric acid reactive substances
showed primary and secondary oxidation, respectively [37]. Figure 4 shows the
changes in the peroxide values of marinated samples. On the first day of marination
process there were no significant (P >0.05) differences in peroxide values
of samples. Peroxide values of VM, GM, and PM treatments were 3.61, 4.67, and 4.10
meq PO/kg, respectively.
![]() |
Fig. 4. Changes of peroxide values (PV) of sardine fillets marinated in (VM) vinegar, (GM) grapefruit and (PM) pomegranate brine |
The peroxide values of all marination treatments increased significantly (P<0.05) during the storage, at day 14, peroxide values for VM, GM, and PM treatments were recorded as 87.13, 94.61, and 51.87 meq PO/kg, respectively. Marination treatment significantly affected (P<0.05) the peroxide values of sardine fillets. Slightly oxidized fat and oil having peroxide values at levels of only 100 meq PO/kg are reported to be neurotoxic [23]. While GM and VM samples showed the same effect on peroxide value, PM samples had the lowest peroxide value at each evaluation period. This is related to pomegranate juice has high antioxidative capacity seemingly the result of the remarkably high content and unique composition of soluble phenolic compounds [22]. At day 21 peroxide values of all marination treatments decreased due to the decomposition to secondary products such as aldehydes, ketones, alcohols, hydrocarbons and polymers. Serdaroglu and Felekoglu [52] reported that PV of sardine mince ranged from 20 to 30 meq PO/kg after 5 months of storage at -20ºC. Similar results were reported by Oduor-Odote and Obiero [42].
Changes in TBA values of treatment groups are given in Figure 5. TBA value of sardine fillet before pre-salting was 0.67 mg MA/kg. On the first day of marination TBA values of VM, GM, and PM treatments were found to be 1.21, 0.72, and 0.90 mg MA/kg respectively. All samples showed an increment in TBA values with the storage period (P < 0.05). There was a sharp increment in TBA values of GM samples at day 7 and decrement after 14 days of storage. The decrement in TBA content after the peak point has been attributed to the interaction between malonaldehydes and decomposition products of protein to give tertiary degradation products [13, 47].
![]() |
Fig. 5. TBA values of sardine fillets marinated in (VM) vinegar, (GM) grapefruit and (PM) pomegranate brine |
The level of TBA and the pattern of its increase in marinated sardine in our study is similar to that reported for various fish species marinated in different marinade solutions, including sea bream [10], chub mackerel [21] and threadfin bream [25] in which the TBA value increased to the maximal level at a certain period during storage, and thereafter decreased gradually. On the other hand, fluctuations in the TBA levels during refrigerated storage of anchovies that were brined in different salt concentrations (14–26%) have been reported by Karaçam et al. [26], who also concluded that TBA may not be a reliable criterion for anchovies salted under the condition used.
TBA values of PM samples did not change after 7 days of marination and at the end of the storage the lowest TBA value was recorded as 2.67 mg ma/kg for the PM treatment. This result indicated that the use of pomegranate juice concentrate in marinade formulation is effective to reduce lipid oxidation. Antioxidative activity of pomegranate juice may be attributed to the high level of anthocyanin, ascorbic acid and phenolic acids. Gokoglu et al. [20] indicated that the use of pomegranate sauce in marinated anchovy is effective to reduce lipid oxidation. Similarly Topuz et al. [60] stated that 50% pomegranate juice containing sauce showed the highest antioxidant activity, according to 35 and 25% pomegranate juice containing sauces in anchovy marinading.
It was suggested that a maximum level of TBA value indicating the good quality of the fish frozen, chilled or stored with ice is 5 mg malonaldehyde/kg, while the fish may be consumed up to the level of 8 mg malonaldehyde/kg TBA value [51]. The present result indicated that oxidative rancidity in marinated samples remained relatively low throughout the entire period of storage in jars at 4°C and TBA values of samples were within the acceptable limits for fish consumption.
CONCLUSION
This study demonstrated that marination of sardine with different functional solutions offers a positive alternative to conventional marinade techniques. The present study revealed that marinated sardine fillets in pomegranate juice showed better oxidative stability. GM marinade was found as effective as VM marinade on oxidative changes of sardine samples. Considering consumer preferences for natural additives, grapefruit juice and pomegranate juice marinade can be used in marinade solutions however further research is necessary to improve marinade formulations and evaluate the shelf life of the products.
REFERENCES
Accepted for print: 18.11.2015
Meltem Serdaroğlu
Ege University, Engineering Faculty, Food Engineering Department, Izmir, Turkey
35100 Bornova, Izmir, Turkey
Phone: (+90 232) 3111314
Fax: (+90 232) 3427592
email: meltem.serdaroglu@ege.edu.tr
Pelin Barıs
Izmir Institute of Technology, Engineering Faculty, Food Engineering Department, Izmir Turkey
Müge Urgu
Ege University, Engineering Faculty, Food Engineering Department, Izmir, Turkey
35100 Bornova, Izmir, Turkey
Eisa Doostifard
Ege University, Engineering Faculty, Food Engineering Department, Izmir, Turkey
35100 Bornova, Izmir, Turkey
Gulen Yıldız-Turp
Ege University, Engineering Faculty, Food Engineering Department, Izmir, Turkey
35100 Bornova, Izmir, Turkey
Phone: (+90 232) 3882395
Fax: (+90 232) 3427592
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