CHANGES IN PHYSICOCHEMICAL PROPERTIES AND SHELF LIFE ...

Journal of Food Processing and Preservation ISSN 1745-4549

CHANGES IN PHYSICOCHEMICAL PROPERTIES AND SHELF LIFE ABILITY OF KUTUM (RUTILUS FRISII KUTUM) SLICES DURING PACKAGING AND STORAGE IN ICE jfpp_760

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YASAMAN ETEMADIAN and BAHAREH SHABANPOUR

Faculty of Fisheries Science, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran

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Corresponding author. TEL: +98-171-2245965; FAX: +98-171-22425886; EMAIL: [email protected] Accepted for Publication April 15, 2012 doi:10.1111/j.1745-4549.2012.00760.x

ABSTRACT Under normal refrigerated storage conditions, the shelf life of fish products is limited by enzymatic and microbiological spoilage, so in this study applied methods like vacuum packaging with a cryoprotectant agent. Results of fresh Rutilus frisii kutum slices packed in vacuum with a cryoprotectant agent (sodium tripolyphosphate) and under ice storage conditions showed higher water holding capacity and a reduction of sulfhydryl groups’ oxidation. Thiobarbituric acid, total volatile base-nitrogen contents and psychrophilic bacterial count in samples treated with sodium tripolyphosphate and under ice storage conditions decreased during ice storage (P < 0.05). The pattern of gel electrophoresis did not show considerable difference between all treatments with increase in storage time. In total, the final results based on sensory evaluation and bacteria counts concluded that the shelf life of fresh kutum slices packed using vacuum packaging and sodium tripolyphosphate was longer than the shelf life of fresh kutum slices packed using only with a cryoprotectant agent.

PRACTICAL APPLICATIONS We test changes in the level of information about phosphate effects with vacuum pack. Use of polyphosphates with vacuum packaging can cause more quality in foods. Polyphosphate treatment with vacuum packaging will increase water holding capacity. Polyphosphates are legally additives that use for improve eating quality of foods.

INTRODUCTION Fish and other marine species give rise to products of great economic importance in many countries (Aubourg and Ugliano 2002). During processing and storage, fish quality may decline in result of several factors. One of the most important of them is the oxidation of highly unsaturated lipids (Ackman 1989), which is directly related to the production of off-flavors and odors. (Hsieh and Kinsella 1989). Inorganic polyphosphates are generally recognized as safe food additives and are widely used in the meat and dairy industry to enhance major functional properties (Akhtar et al. 2008). Also, the use of vacuum packaging and other methods to extend the shelf life of a large number of food products has been of great interest to many scientists during

the last year. However, the shelf life extension of fish products has remained problematic, owing to the high perishable nature of these products. Because of this, some researchers have tried to use vacuum packaging and other preservation methods to extend the shelf life of the packed fish. Shakila et al. (2005) studied the shelf life of seer fish chunks under vacuum packaging, Ozogul et al. (2004) evaluated the shelf life extension of sardines (Sardina pilchardus) under modified atmosphere packaging conditions, Manju et al. (2007) studies effects of sodium acetate dip treatment and vacuum packaging on shelf life of pearlspot (Etroplus suratensis) during chill storage and Alvarez et al. (1996) evaluated the shelf life extension of hake slices treated with sodium tripolyphosphate under modified atmosphere packaging conditions. In this article, the overall

Journal of Food Processing and Preservation •• (2012) ••–•• © 2012 Wiley Periodicals, Inc.

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CHANGES IN SOME PHYSICOCHEMICAL PROPERTIES

Y. ETEMADIAN and B. SHABANPOUR

objectives in treating fresh kutum slices with a common cryoprotectant, sodium tripolyphosphate before packaging them in a vacuum packs was first to increase the water holding capacity (WHC) and reduce the exudate production (exudates causes commercial problems when marketing the product) and secondly to study shelf life extension by using both vacuum packaging and sodium tripolyphosphate.

MATERIALS AND METHODS Chemicals Sodium tripolyphosphate (STPP), ethylendiaminetetraacetic acid (EDTA), 5-5′-dithiobis(2-nitrobenzoic acid), urea, tris–hydrochloride buffer (Tris–HCl), sodium dodecyl sulfate (SDS), sodium chloride, magnesium oxide, potassium chloride, 2-thiobarbituric acid, sulphuric acid, boric acid, methyl red, bromocresol green, hydrochloric acid, sodium hydroxide, methanol, b-mercaptoethanol were purchased from Sigma Chemical Co. (St. Louis, MO, USA), and all chemicals for electrophoresis were obtained from Bio-Rad (Richmond, CA, USA).

Fish Preparation Kutum (Rutilus frisii kutum) with an average weight of 800 g were caught with beach seine in the Caspian Sea, Miankaleh, Iran, in February 2010. Fish were placed in crushed ice with a fish/ice ratio of 1:3 (w/w) and transported to the fish processing laboratory of Gorgan University of Agricultural Sciences and Natural Resources within 2–3 h after catch. They were then washed with tap water, were scaled, filleted and cut into slices with a thickness of 1 cm and about 500 g weight of different fish fillets, for example, three number of 170 g slices of three fish that their selection was quite random.

muscle (2 g) was homogenized thoroughly with 10 mL of distilled water, and the homogenate was subjected to pH determination according to the method of Masniyom et al. (2005).

Determination of Thiobarbituric Acid (TBA) TBA was determined according to the method proposed by Tarladgis et al. (1960) and Kilinc et al. (2007). Ten grams of meat was homogenized for 2 min with 97.5 mL distilled water and 2.5 mL 4 N HCl solution, and three drops of antifoam and some boiling stones were added. The blend was distilled until a 50 mL solution was obtained. Five milliliters of the distilled and 5 mL of the TBA reagent (0.02 M of the of 2-thiobarbituric acid in 90% acetic acid) were blended and heated in a boiling water bath for 35 min. After cooling under running tap water for 10 min, the absorbance was measured at 538 nm against a blank. Blank contains 5 mL of the distilled water and 5 mL of the TBA reagent.

Determination of Total Volatile Base-Nitrogen (TVB-N) TVB-N in muscle was determined according to the method proposed by Parvaneh (2007). Ten grams of meat was homogenized with 2 g MgO and 300 mL distilled, and seven drops of anti-foam and some boiling stones were added. The blend was heated for 45 min until the volume of boric acid solution reach to 150 mL. Boric acid containing methyl red reagent (0.016 g methyl red and 0.083 g bromocresol green in 100 section of ethanol), which initially due to its acidic characteristics was red, but gradually alkalic and became to the green color in the end of experiment by distillation system. Finally, the solution obtained from the accumulation of distillation gases by 0.1N sulfuric acid to reach the onion skin color was titer.

Phosphate Pretreatments of Kutum Slices

Preparation of Actomysion

STPP was dissolved in distilled water to obtain a final concentration of 2 g/100 mL. Kutum slices were soaked in five volumes of the solution (4C) for 10 min and drained for 10 min at 4C. Control samples were soaked in the distilled water and drained under the same condition. After draining, the slices weighing approximately 500 g were packed in a usual zip bag and vacuum packs. All samples kept in cold room at 4C and in ice vicinity and stored for 18 days prior to analyses.

Actomyosin was prepared according to the method of Benjakul et al. (1997). Fish muscle (4 g) was homogenized in 40 mL chilled (4C) 0.6 M KCl, pH 7.0 for 4 min using a Polytron (Brinkmann Instruments, Westbury, NY, USA). The beaker containing the sample was placed in ice, and each 20 s of blending was followed by a 20-s rest interval to avoid overheating during extraction. The extract was centrifuged at 5,000 ¥ g for 30 min at 0C. Three volumes of chilled deionized water were added to precipitate actomyosin. Actomyosin was collected by centrifuging at 5,000 ¥ g for 20 min at 0C, and the pellet was dissolved by stirring for 30 min at 0C in an equal volume of chilled 1.2 M KCl, pH 7.0. Undissolved material was removed from the preparation by centrifugation at 5,000 ¥ g for 20 min at 0C.

The pH Measurement The pH measurement was carried out using a Metrohm model 713 pH meters (Metrohm, Herisau Switzerland). Fish 2



Determination of Total Sulfhydryl Content One milliliter of actomyosin (0.4 g/100 mL) solution was added to 9 mL of Tris–HCl buffer (0.2 mol/L), pH 6.8, containing urea (8 mol/L), SDS (2 g/100 mL) and EDTA (10 mmol/L). To 4 mL-aliquot of the mixture, 0.4 mL of DTNB (0.1 g/100 mL) solution was added. The mixture was incubated at 40C for 25 min, and the absorbance was measured at 412 nm with a spectrophotometer ( Biochrom Ltd., Cambridge). A blank was prepared by replacing the sample with KCl (0.6 mol/L); pH 7.0. SH content was calculated from the absorbance using the molar extinction coefficient of 13,600/M/cm and was expressed as mol/105 g protein (Benjakul et al. 1997; Masniyom et al. 2005).

A = εcd where A = Absorbance, e = extinction coefficient, c = concentration, d = cell length (1 cm).

Determination of WHC Each minced meat sample (10 g) and 15 mL of 0.6 M NaCl solution were added into a 50 mL centrifuge tube and mixed with a vortex mixer for 1 min. The tube was then refrigerated at 4C for 15 min before being centrifuged at 4C at 3,000 g for 15 min according to the method of Zhuang et al. (2008).

100 × (Wpellet − Wraw ) Wraw where Wraw = Initial weight, Wpellet = Sample weight after centrifuging.

Microbiological Analyses Samples of 10 g of fish fillets were taken and mixed with 90 mL of 0.1% peptone water and homogenized in a M400 stomacher for 1 min. In all cases, serial dilutions from the microbial extracts were prepared in 0.1% peptone water. Psychotrophic bacteria total counts (PTC) were determined by the pour plate method, using Plate Count Agar as the medium. Plates were incubated at 10C for 7 days (Arashisar et al. 2004; Kilinc et al. 2007). Microbial counts were expressed as log cfu/g.

Sensory Evaluation The assessment was conducted for the odor of raw muscle samples using multiple sample difference tests as described by Beirao (1979). For cooked samples, fish slices were placed in the tray with aluminum foil, cooked in steaming pot until the core temperature of each sample reached 80C. Stick water was drained and allowed to cool to room temperature


(25–28C). For doing this test, initially we selected about 20 panelists and trained whole of them about sensory examination for this work, then among them, seven people selected that had similar ideas together; this selection was done with very high accuracy. Scores was on a structured 5-point descriptive table (Kilinc et al. 2009). The odor of raw muscle at the moment of opening the pack was based on the following criteria (0, off-odors; 1, strongly fishy; 2, fishy; 3, neutral; 4, sea-fish), and the flavor acceptability of cooked samples was based on the following criteria (0, dislike; 1, dislike very much; 2, dislike slightly; 3, like moderately; 4, like extremely).

SDS-Polyacrylamide Gel Electrophoresis (SDS-PAGE) SDS-PAGE was carried out according to the method of Laemmli (1970) using 5% stacking gel and 15% separating gel. Proteins (10 mg) were loaded on to each well. Mobility of the protein bands were calibrated with standards of molecular weight markers. After staining and distaining, the gel was scanned using a gel documentation system (Bio-Rad).

Statistical Analysis For data analysis used of quite random pattern in Factorial Spillet Plot model. Analysis of variance was performed, and mean comparisons were obtained by Duncan’s multiple range test at P < 0.05. Statistical analysis was performed using the Statistical Package for Social Sciences (SAS 9.1 for windows; SAS Institute Inc., Cary NC).

RESULT AND DISCUSSION Changes in pH Most fishes contain small amounts of carbohydrate (less than 0.5%) in their muscle tissue, so that after the death of fish, the amount of produced lactic acid by the reaction of glycolysis is low and pH of fish meat will be higher than six after rigor mortis. This feature is especially important related to fish meat. Decomposition of nitrogenous compounds during storage of fish lead to increased pH of fish, that part of this increase may be related to the production of alkaline compounds. Such an increase in pH of fish could indicate bacterial growth, the reduction of quality and ultimately spoilage of fish (Gram and Huss 1996; Chomnawang et al. 2007). In this experiment, results showed that pH of all samples increased with increasing storage time in ice (P < 0.05) (Table 1). There was no significant difference between control groups and samples treated with sodium tripolyphosphate except on 15 day. However, there was a


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TABLE 1. CHANGES IN pH AND TBA CONTENTS OF KUTUM SLICES TREATED WITH POLYPHOSPHATES STORED IN ZIP BAG AND VACUUM PACKS DURING ICE STORAGE Days of storage in ice Factor pH

TBA

0 y

STPP +VP STPP Control STPP+VP STPP Control

z

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6.34 ⫾ 0.006 6.34 ⫾ 0.006a 6.34 ⫾ 0.006a 0.56 ⫾ 0.032q 0.56 ⫾ 0.032q 0.56 ⫾ 0.032q a

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6.43 ⫾ 0.031 6.4 ⫾ 0.012ab 6.42 ⫾ 0.108b 0.97 ⫾ 0.015p 0.99 ⫾ 0.025p 1.15 ⫾ 0.061pon b

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6.45 ⫾ 0.049 6.46 ⫾ 0.05bcd 6.47 ⫾ 0.047bcd 1.2 ⫾ 0.015pon 1.13 ⫾ 0.070pon 1.23 ⫾ 0.056pon cb

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6.42 ⫾ 0.012 6.46 ⫾ 0.05bcd 6.52 ⫾ 0.023d 1.27 ⫾ 0.010ponm 1.57 ⫾ 0.035kl 2.12 ⫾ 0.047higf cb

15

6.44 ⫾ 0.026 6.5 ⫾ 0.032de 6.54 ⫾ 0.042de 1.88 ⫾ 0.206ij 1.87 ⫾ 0.183ij 2.69 ⫾ 0.035abc cb

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6.43 ⫾ 0.026 6.52 ⫾ 0.075de 6.59 ⫾ 0.01f 1.91 ⫾ 0.121hij 2.67 ⫾ 0.122abc 2.92 ⫾ 0.116a cb

6.43 ⫾ 0.031cb ... ... 2.31 ⫾ 0.165def ... ...

The different letters in table indicate the significant differences (P < 0.05). y STPP, sodium tripolyphosphate; z VP, vacuum packaging.

statistically significant difference between them and samples treated and stored in vacuum packaging. The samples treated and stored in vacuum packaging had the lowest and best pH. These results were consistent with studies of Masniyom et al. (2005) on sea bass (Lates calcalifer) slices pretreated with polyphosphate kept under modified atmosphere packaging and Manju et al. (2007) on pearspot (Etroplus suratensis) fillets pretreated with sodium acetate stored in vacuum packaging. Further increase of pH in the control groups and treated samples without vacuum can be because of higher production of volatile compounds such as ammonia by bacteria.

compared with control samples during ice storage. Thepnuan et al. (2008) also observed lower TBA values in samples treated with sodium tripolyphosphate stored under modified atmosphere packaging during storage at 4C. A TBA value in the range 1–2 mg malonaldehyde/kg of muscle is usually taken at the limit of acceptability (Shakila et al. 2005). In this study, TBA value was higher than 2 mg malonaldehyde/kg of muscle in control groups, samples treated with sodium tripolyphosphate and samples treated and stored in vacuum packaging on the 9th, 15th and 18th days of storage, respectively.

Changes in TVB-N Changes in TBA Lipid oxidation in fishes after death because of high levels of unsaturated fatty acid is very important and as the main factors of unpleasant taste in them is considered (Guillén and Ruiz 2004). In order to assess the degree of fat oxidation in fish, many of the indicators used are TBA, (Cakli et al. 2006; Erkan et al. 2006; Mendes and Goncalvez 2008) that this index the amount of secondary oxidation products especially malonaldehyde shows (Erkan et al. 2006). Changes in TBA value are presented in Table 1. The TBA values increased from an initial 0.56 mg malonaldehyde/kg of muscle to 2.92, 2.67 and 2.31 mg malonaldehyde/kg of muscle in control groups, samples treated with sodium tripolyphosphate and samples treated and stored in vacuum packaging on the 15th, 15th and 18th days of storage, respectively. Results indicated an increasing trend in all the samples during storage (P < 0.05). Similar observations were made by several authors (Arashisar et al. 2004; Masniyom et al. 2005; Manju et al. 2007). Between treatments, there was a significant different especially of ninth days (P < 0.05). Samples treated and stored in vacuum packaging exhibited lower TBA value than the control and other samples. This is in agreement with Weilmeier and Regenstein (2004) observed a reduction in TBA values of sodium tripolyphosphate and tetra sodium pyrophosphate-treated lake trout and mackerel fishes 4

TVB-N in fish is mainly composed of ammonia and primary, secondary and tertiary amines (Beatty 1938). A level of 30–35 mg TVB-N/100 g of fish muscle is usually regarded as spoiled (Shakila et al. 2005; Mendes and Goncalvez 2008). Changes in TVB-N values are shown in Fig. 1. Values were found to increase in all samples during ice storage. TVB-N contents increased from an initial value

FIG. 1. CHANGES IN TVB-N OF KUTUM SLICES STORED UNDER DIFFERENT CONDITIONS IN ICE: CONTROL (䉬); SAMPLES TREATED WITH SODIUM TRIPOLYPHOSPHATE (䉱); SAMPLES TREATED WITH SODIUM TRIPOLYPHOSPHATE STORED IN VACUUM PACKAGING (䊏) Bars represent the standard deviation from triplicate determinations.



of 3.91–37.37 mg TVB-N/100 g of fish muscle in control groups, 31.93 mg TVB-N/100 g of fish muscle in samples treated with sodium tripolyphosphate and 19 mg TVB-N/ 100 g of fish muscle in samples treated and stored in vacuum packaging on the day of rejection. Values were found to be lower in the case of treated samples and stored in vacuum packs than other samples. Low levels of TVB-N in treated samples in vacuum packs were due to either a reduced bacterial population or decreased capacity of bacteria for oxidative deamination of nonprotein nitrogen compounds or both (Banks et al. 1980; Mendes and Goncalvez 2008). These results are consistent with studies of Masniyom et al. (2005), Kilinc et al. (2007) and Thepnuan et al. (2008). In all samples, the TVB-N values were found to be higher than the limit, except in samples treated and stored in vacuum packaging in the end of storage time in ice. Increase in TVB-N values was related to increasing in pH and psychrophilic bacterial contamination, especially in control groups.

Changes in Total Sulfhydryl Content Total sulfhydryl content of actomyosin in samples treated and stored in vacuum packaging increased slightly after 6 days storage followed by a continued decrease up to 15 days (Fig. 2). This confirmed results of Sompongse et al. (1996) and Benjakul et al. (1997) that the total sulfhydryl group content of carp and pacific whiting actomyosin, decreased constantly, especially after 2 and 3 days storage in ice, respectively. In this experiment, there was no significant difference between control groups and samples treated with sodium tripolyphosphate, but there was a significant difference between them and samples treated and stored

FIG. 2. CHANGES IN TOTAL SULFHYDRYL CONTENT (SH) OF KUTUM SLICES STORED UNDER DIFFERENT CONDITIONS IN ICE: CONTROL (䉬); SAMPLES TREATED WITH SODIUM TRIPOLYPHOSPHATE (䉱); SAMPLES TREATED WITH SODIUM TRIPOLYPHOSPHATE STORED IN VACUUM PACKAGING (䊏) Bars represent the standard deviation from triplicate determinations.


FIG. 3. CHANGES IN WATER HOLDING CAPACITY (WHC) OF KUTUM SLICES STORED UNDER DIFFERENT CONDITIONS IN ICE: CONTROL (䉬); SAMPLES TREATED WITH SODIUM TRIPOLYPHOSPHATE (䉱); SAMPLES TREATED WITH SODIUM TRIPOLYPHOSPHATE STORED IN VACUUM PACKAGING (䊏) Bars represent the standard deviation from triplicate determinations.

in vacuum packs. A decrease in total sulfhydryl group was reported to be due to formation of disulfide bonds through oxidation of total sulfhydryl groups or disulfide interchanges (Hayakawa and Nakai 1985). Increase in total sulfhydryl group may be due to open structure of protein (Li-chen et al. 1985). Increase in total sulfhydryl groups was related to increasing in TVB-N values. It should be mentioned that this experiment was done every 6 days during storage.

Changes in WHC WHC is one of the most important quality parameters that affects directly on the product, efficiency and quality of products such as juiciness (Olsson et al. 2003; Zhuang et al. 2008). The decrease of WHC in muscle of fish after death is often described as the effect of structure changes in muscle and such changes can cause network contraction of myofibril, myosin protein deformation and increase extracellular space (Olsson et al. 2003). WHC of kutum slices are shown in Fig. 3. In this study, the initial WHC of samples were 77.73%. There was a significant difference between samples treated and stored in vacuum packaging with control groups and samples treated with sodium tripolyphosphate from 6 and 9 days to end of storage period in ice, respectively (P < 0.05). WHC of all samples decreased as the storage times increased (P < 0.05). So time was significant. In this experiment, WHC of fish muscle from 77.73% in the first of period reached to 61.16%, 57.29% and 43.95%, respectively, in the samples treated and stored in vacuum packaging, samples treated with sodium tripolyphosphate and control groups in the end of exam period that this


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problem was probably due to the greater denaturation of proteins with increasing storage time. Polyphosphates might show the synergistic effect with vacuum conditions and interact with positive charges of the protein molecule to increase the net negative charge, resulting in the increased WHC (Matsumoto 1992; Thorarinsdottir et al. 2001). As a result, the repulsive forces between protein molecules may increase, leading to the increase in water retention.

Changes in PTC Psychrophilic bacteria counts of all samples increased with increasing time of storage in ice (P < 0.05) (Table 2). Psychrophilic bacteria counts of control groups increased rapidly from an initial value of 103 to 108 cfu/g sample in the end of storage period and was generally higher than other treatments (P < 0.05). Among all treatments, samples treated and stored in vacuum packaging had the lowest psychrophilic bacteria counts, especially when kept for a longer time (P < 0.05). This result was different with Masniyom et al. (2005) studies that reported samples of sea bass slices treated with pyrophosphate and kept under modified atmosphere packaging had the lowest psychrophilic bacteria counts. Psychrophilic bacteria counts of all samples treated with sodium tripolyphosphate and stored in vacuum packaging were below 106 cfu/g sample to 9 days, but with extending time, their counts reached 107 cfu/g samples in 18 days. Lower psychrophilic bacteria counts of samples treated with phosphate and stored in vacuum packs in compared with samples stored in usual zip bags, indicated that O2 absence and the production of CO2 of fish meat could inhibited the growth of aerobic bacteria and indicated that phosphates might show the synergistic effect on the retardation of bacterial growth in this type of packs. Therefore, it suggested that vacuum packaging with soaking in phosphate might prevent the growth of bacteria, leading to the

safety of products. Changes in psychrophilic bacteria counts of kutum slices had proximate relation with sensory quality of fillets in both of type of packs. Scullen and Zaika (1994) reported that growth inhibition of Listeria monocytogenes by sodium polyphosphate increased with decreasing temperature, decreasing pH and increasing NaCl concentration. Growth inhibition induced by sodium polyphosphate was accompanied by changes in cellular morphology (Zaika et al. 1991). The results indicated that pretreatment by soaking the kutum slices in phosphate solution prior to storage in vacuum packs was more effective in reducing microbial numbers on the kutum slices, compared with the use of other treatments. Polyphosphates may suppress the growth of bacteria by complexing metal ion essential for cell division (Davidson and Juneja 1990) in vacuum condition.

Changes in Sensory Analysis Fresh kutum slices were generally considered to possess very high acceptability. All samples developed a fishy odor as the storage time increased (Table 2). For the control samples, the deterioration occurred after 3 days of storage as evidenced by strong fishy and putrid odor. Also, the deterioration in flavor occurred after 6 days during storage in ice. Samples treated and stored in vacuum packaging exhibited the higher score for odor and flavor, compared with the other samples. For such samples, extended shelf life of kutum slices was observed by maintaining the odor and flavor attributes. Our results indicated that soaking the kutum slices in sodium tripolyphosphate solution prior to vacuum packaging effectively extended the shelf life of kutum slices with high acceptability. Also, number of bacteria was less in these samples. Ozogul et al. (2004) reported the shelf life of Sardina pilchardus packaged in vacuum packaging and air were regularity, 9 and 3 days at 4C, and Pantazi et al. (2008) studies showed the shelf life of

TABLE 2. PSYCHROPHILIC BACTERIAL COUNTS AND SENSORY CHANGES OF KUTUM SLICES TREATED WITH POLYPHOSPHATES STORED IN ZIP BAG AND VACUUM PACKS DURING ICE STORAGE Days of storage in ice Factor PTC

Odor

Flavour

STPPy+VPz STPP Control STPP+VP STPP Control STPP+VP STPP Control

0

3

6

9

12

15

18

3.4 ⫾ 0.021x 3.4 ⫾ 0.021x 3.4 ⫾ 0.021x 4 ⫾ 0.00a 4 ⫾ 0.00a 4 ⫾ 0.00a 4 ⫾ 0.00a 4 ⫾ 0.00a 4 ⫾ 0.00a

3.06 ⫾ 0.085y 4.14 ⫾ 0.057u 4.99 ⫾ 0.014r 3 ⫾ 0.00b 2.57 ⫾ 0.54c 3 ⫾ 0.00b 3 ⫾ 0.00b 2.57 ⫾ 0.54cd 2.43 ⫾ 0.54cd

4.08 ⫾ 0.057vu 4.45 ⫾ 0.049s 6.81 ⫾ 0.028jk 3 ⫾ 0.00b 2.29 ⫾ 0.76dc 1.29 ⫾ 0.49hg 3 ⫾ 0.00b 2 ⫾ 0.00ef 2 ⫾ 0.00ef

5.23 ⫾ 0.049q 6.4 ⫾ 0.042m 7.1 ⫾ 0.007h 2.57 ⫾ 0.54c 1.57 ⫾ 0.54e 1 ⫾ 0.00h 2.71 ⫾ 0.49cb 1.71 ⫾ 0.49ghf 1 ⫾ 0.00i

6.21 ⫾ 0.007n 6.71 ⫾ 0.064k 7.81 ⫾ 0.071b 1.71 ⫾ 0.49ef 0.00 ⫾ 0.00i 0.00 ⫾ 0.00i 2.29 ⫾ 0.49ed 0.00 ⫾ 0.00j 0.00 ⫾ 0.00j

7.15 ⫾ 0.021gh 7.19 ⫾ 0.028gfh 8.67 ⫾ 0.007a 0.00 ⫾ 0.00i 0.00 ⫾ 0.00i 0.00 ⫾ 0.00i 0.00 ⫾ 0.00j 0.00 ⫾ 0.00j 0.00 ⫾ 0.00j

7.14 ⫾ 0.028gh ... ... 0.00 ⫾ 0.00i 0.00 ⫾ 0.00i 0.00 ⫾ 0.00i 0.00 ⫾ 0.00j 0.00 ⫾ 0.00j 0.00 ⫾ 0.00j

The different letters in table indicate the significant differences (P < 0.05). y STPP, sodium tripolyphosphate; z VP, vacuum packaging.

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FIG. 4. INCLUDES (FIGURE 4A, FIGURE 4B AND FIGURE 4C). ELECTROPHORESIS PATTERNS OF SODIUM DODECYL SULFATE-POLYACRYLAMIDE GEL ELECTROPHORESIS GELS OF ACTOMYOSIN FROM KUTUM SLICES STORED UNDER DIFFERENT CONDITIONS IN ICE MHC, myosin heavy chain; A, actin; TM, tropomyosin; MLCS, myosin light chains; MW, molecular weight markers. The 10 mg of protein (actomyosin) was loaded in each lane of the gel.




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swordfish (Xiphias gladius) fillets packaged in vacuum packaging and air were regularity, 9 and 7 days at 4C. Also Masniyom et al. (2005) reported the shelf life of sea bass slices packaged under modified atmosphere packaging with phosphate was 21 days. In this study, the shelf life of kutum slices was 9–12, 6 and 3 days in samples treated with phosphate and stored in vacuum packaging, samples treated with phosphate and without vacuum packaging and control groups, respectively.

Changes in SDS-Polyacrylamide Gel Electrophoresis The functional and textural characteristics of meat depend mainly on myofibrillar proteins (Thippeswamy et al. 2002; Paredi and Crupkin 2007). So such changes and the reduction of myofibrillar proteins during storage in ice show proteolytic activity in the muscle (Benjakul et al. 1997). Myosin and actin are the major proteins that contribute to most of the functional properties of myofibrillar proteins (Mohan et al. 2008). According to Fig. 4A–C, electrophoresis patterns of SDS-PAGE gels showed that gradually myosin heavy chain in the samples treated and packaged under vacuum and in usual zip bags that was about 200 KD, decreased during storage and at the full spoil time of slices in the samples treated and packaged under vacuum and in usual zip bags reached 190 KD after 12 days storage and 188 KD after 18 days storage, respectively. Also molecular weight of actin and tropomyosin proteins increased gradually in the both packs. Myosin light chain showed a constant trend in all periods. In total significant difference between treatments were not observed in band intensity of myosin, actin and tropomyosin proteins until the end of storage in ice, that this result compatible to Mathew and Shamasundar (2002) results on Scoliodon laticaudus meat stored in ice, Benjakul et al. (2003) on lizardfish (Sauruda tumbil) during storage in ice, Julavittayanukul et al. (2006) in the effect of use of phosphate compounds on gel-forming ability of surimi from bigeye snapper (Priacanthus tayenus), Paredi and Crupkin (2007) in study on actomyosin extracted of Paralichtys patagonicus stored in ice and Choi et al. (2008) in study on pacific whiting muscle. In this study, the comparison between treatments packaged under vacuum and usual zip bags showed that the bond intensity of myosin heavy chain in treatments packaged under vacuum was more than treatments packaged in usual zip bags, which can reason on microbial activity in treatments packaged in usual zip bags. It should be mentioned that the gels were prepared every 6 days during storage.

CONCLUSION In this experiment, results of chemical, microbial and sensory analysis were done in intervals of 0, 3, 6, 9, 12, 15 8

and 18 days of storage. Vacuum packaging with treatment of sodium tripolyphosphate in comparison with other treatments was better. The amount of total sulfhydryl groups oxidation, pH, TBA and TVB-N as the chemical indicators of fish quality in samples treated with sodium tripolyphosphate and stored in vacuum packaging was less than other treatments. Also, was retained higher percentage of WHC. Psychrophilic bacteria counts in samples treated and stored in vacuum packs were lower than other treatments during ice storage. So that control groups and treated samples in vacuum packs, after 9 and 15 days storage in ice, was reached to 107 log cfu/g, respectively. Determine the shelf life based on psychrophilic bacteria counts and sensory evaluation for treated kutum slices in vacuum packaging was to 15 and 12 days, respectively. Therefore, use of sodium tripolyphosphate in vacuum condition can be a way for better preservation of fish.

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