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This article was downloaded by: [North Dakota State University]On: 17 October 2014, At: 18:59Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,UK
Journal of Aquatic FoodProduct TechnologyPublication details, including instructions forauthors and subscription information:http://www.tandfonline.com/loi/wafp20
Effect of Oxygen Absorberon the Shelf Life of GiltheadSeabream (Sparus aurata)Amparo Gonçalves MSc a , Rogério Mendes PhD a &Maria Leonor Nunes PhD aa Instituto Nacional de Investigação Agrária e dasPescas-INIAP/IPIMAR , Av. de Brasília, 1449-006,Lisboa, PortugalPublished online: 11 Oct 2008.
To cite this article: Amparo Gonçalves MSc , Rogério Mendes PhD & Maria LeonorNunes PhD (2004) Effect of Oxygen Absorber on the Shelf Life of Gilthead Seabream(Sparus aurata), Journal of Aquatic Food Product Technology, 13:3, 49-59, DOI:10.1300/J030v13n03_05
To link to this article: http://dx.doi.org/10.1300/J030v13n03_05
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Effect of Oxygen Absorber on the Shelf Lifeof Gilthead Seabream (Sparus aurata)
Amparo GonçalvesRogério Mendes
Maria Leonor Nunes
ABSTRACT. The effectiveness of oxygen absorber on the shelf life ofscaled and gutted seabream packed in air during 10 days chilled storage(~5°C) was studied. The quality changes were evaluated by sensory, mi-crobial and chemical methods. Absorbers reduced oxygen concentrationby 54% within the first two days and levels attained 0.1% after 6 days ofstorage. Significant differences in K values were not observed betweenpacked batches with and without O2 absorber. Positive effects of O2 ab-sorber on the reduction of lipid oxidation and sensory attributes, mainly onthe appearance, were observed. [Article copies available for a fee from TheHaworth Document Delivery Service: 1-800-HAWORTH. E-mail address:<[email protected]> Website: <http://www.HaworthPress.com> 2004 by The Haworth Press, Inc. All rights reserved.]
KEYWORDS. Active packaging, oxygen absorber, gilthead seabream,shelf life
Please note that this electronic prepublication galley may contain typographical errors and may be missingartwork, such as charts, photographs, etc. Pagination in this version will differ from the published version.
Amparo Gonçalves, MSc, Rogério Mendes, PhD, and Maria Leonor Nunes, PhD, areaffiliated with Instituto Nacional de Investigação Agrária e das Pescas–INIAP/IPIMAR,Av. de Brasília, 1449-006, Lisboa, Portugal.
Address correspondence to: Amparo Gonçalves, MSc, Instituto Nacional deInvestigação Agrária e das Pescas–INIAP/IPIMAR, Av. de Brasília, 1449-006, Lisboa,Portugal (E-mail: [email protected]).
The authors wish to thank TIMAR (Portugal) for the kindly supply of giltheadseabream, to Dr. Horácio Cruz and Dra. Teresa Batista for their support and to Dra.Almudena Huidobro (CSIC, Madrid) for the participation in the setting up of this work.
This work was financially supported by EU-QCA III-MARE/FEDER: Project“Quality and Innovation of Fishery Products.”
Journal of Aquatic Food Product Technology, Vol. 13(3) 2004http://www.haworthpress.com/web/JAFPT
2004 by The Haworth Press, Inc. All rights reserved.Digital Object Identifier: 10.1300/J030v13n03_05 49
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INTRODUCTION
Consumer demand for fresh fish is increasing the importance of giltheadseabream (Sparus aurata) as one of the main fish species farmed in the Mediter-ranean countries. In Portugal the production of this species has grown in recentyears and is mostly marketed iced and ungutted. The seasonal growth in the sum-mer period generates an abundant supply of fresh seabream that has to be com-mercialized in a short time. Demand for fresh convenient products that offerhealthy, tasty and fast meal solutions stresses the need for new ways of marketinggilthead seabream. A good alternative could be a product in a convenient pack-age, scaled and gutted, ready to cook. Active packaging has emerged as a newtechnological development in the field of food packaging and is used wheneverthe package requires a function other than providing an inert barrier to externalconditions. In this packaging, a wide range of techniques is used in order to extendshelf life and improve safety during the distribution chain (Alvarez, 2000). Theseinclude the incorporation of antimicrobial agents and regulators of atmospherecomposition inside the packages, as moisture absorbers, carbon dioxide (CO2)emitters and oxygen (O2) absorbers.
The O2 absorber is one of the most widely used active packaging applications.It allows the reduction of oxygen concentration to values lower than 0.01%(Alvarez, 2000), and since it simplifies the process and reduces the costs of equip-ment, it could be advantageous, compared with modified atmosphere (MA) pack-aging (including vacuum packaging). O2 absorbers are composed of chemicalsubstances such as iron, ascorbic acid or enzymes (oxidoreductases), which areable to react with oxygen and present different absorption capacities, up to 2000cc of O2 from 10,000 cc of air (Church, 1994). The use of packaging films withlow O2 permeability is recommended in order to minimize the diffusion of O2 intothe package. The choice of absorber depends on the water activity of the product,expected shelf life and oxygen volume inside the package. For solid food prod-ucts, gas permeable sachets with iron power are mostly used (Alvarez, 2000). O2absorbers have been used in bakery products, like bread and cookies, pastry, curedor smoked meats, fish and cheese (Church, 1994). However, few studies regard-ing the use of O2 absorber in seafood products are published. Sivertsvik (1997)evaluated the effect of iron-based O2 absorber on different packed seafoods andconcluded that it can extend the shelf life of oxygen sensitive products. The aim ofthe present work was to study the effect of oxygen absorber on the shelf life ofscaled, gutted and packed farmed seabream during chilled storage.
50 JOURNAL OF AQUATIC FOOD PRODUCT TECHNOLOGY
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MATERIALS AND METHODS
Raw Materials and Experiments
Immature gilthead seabreams raised in salt ponds (Tavira, Portugal) werefasted for 48 h prior to slaughter by immersion in an ice:sea-water slurry (3:1).The fish were kept in ice and transported to laboratory within 24 h. Upon ar-rival they were scaled, gutted (including gills) and washed by hand. The aver-age weight was 222.6 ± 20.8 g. Two seabreams were placed in a polypropylenetrays (22 cm � 17 cm � 4.5 cm) together with one 300 cc iron-based O2 absorbersachet (Marathon, O-Buster, type FT-Oakland, USA) and packaged in a polyamide/polyethylene gas barrier bag (Vaessen-Schoemaker, Portugal) with transmissionrates of 25.0 for O2, 61.0 for CO2 and 8.8 for N2, cc/m2/24 h, at 75% RH and23°C–batch FTE. Batch CAE (control) was same as FTE except the absence of O2absorber. All packages (internal volume �2,635 cc) were sealed by a MultivacA 300/52 machine (Multivac Sepp Haggenmüller KG, Wolfertschwenden,Germany) and stored at 4.9 ± 0.3°C. Another batch, fish with crushed ice in poly-styrene boxes, was stored at 0.6 ± 1.1°C–batch CGE.
Methods
At each sampling day the gas composition inside the packages was mea-sured with a gas analyzer ABISSPRINT (Abiss, Chatillon, France). Fourseabreams from each batch (two packages from each packed batch) weretaken: two for sensory evaluation and two for microbial and chemical analy-ses. Sensory evaluation of raw seabream was done by five panelists, accordingto a scale of 16 demerit points (d.p.) based on skin appearance (brightness/iri-descence), abdomen color, shape and color of eyes, and odor, adapted from afreshness scheme developed by Nunes and Pereira (2000) for whole giltheadseabream. For microbial counts, 10 g of fish muscle tissue was homogenized,diluted nine fold in tryptone salt solution (0.85%) and poured onto Plate CountAgar (Merck, Darmstadt, Germany). The plates were incubated at 30°C for 72h, under aerobic and anaerobic conditions. The pH was measured directly onfish mince, using a surface electrode. Total volatile bases nitrogen (TVB-N)was determined in extracts from 25 g of fish mince homogenized with 50 ml10% trichloracetic acid, by a microdiffusion method according to Cobb et al.(1973). Nucleotides and nucleotide catabolites were extracted from 5 g of fishmince homogenized with 25 ml 0.6 M perchloric acid (Mendes et al., 2001)and the separation was done by high performance liquid chromatography, asdescribed by Ryder (1985), on a reverse phase RP-18 10 µm, 200 mm � 4.6mm column. Phosphate buffer (0.1 M, pH = 6.95) composed the mobile phase;
Gonçalves, Mendes, and Nunes 51
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elution was isocratic and detection was done at 254 nm. K-value was calculatedaccording to Saito et al. (1959), using inosine monophosphate, inosine andhypoxanthine concentrations. Peroxide value (POV) was determined followingthe method of AOAC (1990), on fish oil extracted according to the method de-scribed by Bligh and Dyer (1959). Malonaldehyde (MDA) content was deter-mined on fish muscle according to Vyncke (1970). Statistical analysis (Two WayANOVA and Tukey Multicomparison Test) was conducted using softwareStatistica (vers. 5.0, StatSoft, Inc., Tulsa, OK, USA).
RESULTS AND DISCUSSION
The main changes in gas composition occurred in the batch containing O2absorber (FTE) within the first two days of storage; O2 decreased from 18.5 to aconcentration of 8.6% (Figure 1), corresponding to 54% reduction. At the 6th day,O2 levels attained 0.1% and remained constant until the end of storage. In the con-trol batch (CAE), O2 decreased slowly from 19.4 to 13.6% (30% reduction) overthe first 6 days. Such reduction was also observed by Sivertsvik (1997). The con-centration of CO2 in FTE remained below 2% throughout the storage period whilea steady increase from 0.6 to 12.7% at 10th day was observed in batch CAE. Thisincrease is mainly due to a higher microbial activity. In fact, after the 6th day aero-bic microbial counts were higher in CAE batch than in FTE, respectively 8 and 6log cfu/g, at day 10 (Figure 2). However, the anaerobic counts were not signifi-cantly different (P > 0.05) between CAE and FTE throughout the storage period,both reaching 5 log cfu/g at day 8. Iced batch (CGE) registered lower total viablecounts than the packed batches, which differ significantly (P < 0.05), probably asa result of the leaching effect of melting ice. It is usual to adopt the microbial crite-ria to define the shelf life of a product. The limit of 107 cfu/g of total bacteriacounts for raw fish products (ICMSF, 1986; IFST, 1999) was reached only inCAE batch, after 8 days of storage. Regarding the potential growth of anaerobicpathogen non-proteolytic Clostridium botulinum in FTE batch, Sivertsvik et al.(2002) pointed out a low risk when storage temperature and period of MA/vac-uum packed fish do not exceed 10°C and 10 days, respectively.
The changes in the pH of the flesh of the samples are shown in Figure 3. ThepH of very fresh gilthead seabream was initially 6.24 and then changed to6.52, 6.47 and 6.43, respectively, in batches FTE (8th day), CGE and CAE(10th day). At day 10, a decrease of pH value to 6.30 was observed in FTE.Taking into account the low levels of O2 in this batch early in the storage, thegrowth of facultative anaerobic lactic acid bacteria could explain that decrease.
TVB-N levels close to 19 mg N/100 g were found at the beginning ofchilled storage (Figure 4). Similar results have been found by other authors forthis species (Nunes and Pereira, 2000; Huidobro et al., 2001). During the first
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Gonçalves, Mendes, and Nunes 53
20
15
10
5
0
0 2 4 6 8 10
Storage days
% Gas composition
O -CAE2
O -FTE2
CO -CAE2
CO -FTE2
FIGURE 1. Changes in gas composition inside the packages, during the storageof packed, scaled and gutted gilthead seabream, at 4.9 ± 0.3°C. CAE–packed inair; FTE–packed in air + O2 absorber. Error bars are the standard deviation (n = 2).
TVC (aerobic conditions)log cfu/g10
8
6
4
2
0
0 2 4 6 8 10Storage days
CGE CAE FTE CGE CAE FTE
log cfu/g TVC (anaerobic conditions)10
8
6
4
2
0
0 2 4 6 8 10Storage days
FIGURE 2. Changes in total viable counts (TVC) during the storage of scaledand gutted gilthead seabream, in ice and packed in air. CGE–held in ice (0.6 ±1.1°C); CAE–packed in air (4.9 ± 0.3°C); FTE–packed in air + O2 absorber (4.9± 0.3°C). Error bars are the standard deviation (n = 2).
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54 JOURNAL OF AQUATIC FOOD PRODUCT TECHNOLOGY
pH value6.75
6.50
6.25
6.000 2 4 6 8 10
Storage days
CGE CAE FTE
FIGURE 3. Changes in pH values during the storage of scaled and guttedgilthead seabream, in ice and packed in air. CGE–held in ice (0.6 ± 1.1°C);CAE–packed in air (4.9 ± 0.3°C); FTE–packed in air + O2 absorber (4.9 ±0.3°C). Error bars are the standard deviation (n = 2).
TVB-N30
25
20
15
10
0 2 4 6 8 10Storage days
CGE CAE FTE
mg N/100 g
5
0
FIGURE 4. Changes in TVB-N contents during the storage of scaled and gut-ted gilthead seabream, in ice and packed in air. CGE–held in ice (0.6 ± 1.1°C);CAE–packed in air (4.9 ± 0.3°C); FTE–packed in air + O2 absorber (4.9 ±0.3°C). Error bars are the standard deviation (n = 2).
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8 days of storage, the volatile compounds content did not differ significantly(P > 0.05) and remained between 14-21 mg/100 g in all batches. After day 8than increase of TVB-N levels up to 25 mg/100 g was observed in the threebatches. Values around 20 mg/100 g and lower were reported for wholeseabream, during 18-20 days of iced storage (Nunes and Pereira, 2000;Huidrobo et al., 2001).
K value has been routinely used for many years to estimate freshness(Uchiyama et al., 1970; Ehira and Uchiyama, 1983). Figure 5 shows thechanges in K value during the chilled storage of scaled and gutted seabream.The K values increased from 12% to 45% and 50% for FTE and CAE, respec-tively, at the end of storage period. CGE, on the other hand, had significantly(P < 0.05) lower K value, probably as a result of the washing effect of meltingice and lower storage temperature on ATP degradation products. The slopewas higher in the batch without O2 absorber (K = 3.98t + 14.7, R2 = 0.9603,where K is K value and t time of chilled storage) than in that with absorber (K =3.34t + 16.9, R2 = 0.808). Differences observed between the packed batches werenot statistically significant (P > 0.05).
Regarding lipid oxidation, a regular increase both in POV (Figure 6) andMDA (Figure 7) contents took place during the storage period. After the 3rdday a significant (P < 0.05) increase of hydroperoxides was observed for all
Gonçalves, Mendes, and Nunes 55
K value60
50
40
30
20
0 2 4 6 8 10Storage days
CGE CAE FTE
%
10
0
FIGURE 5. Changes in K values during the storage of scaled and guttedgilthead seabream, in ice and packed in air. CGE–held in ice (0.6 ± 1.1°C);CAE–packed in air (4.9 ± 0.3°C); FTE–packed in air + O2 absorber (4.9 ±0.3°C). Error bars are the standard deviation (n = 2).
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batches, although FTE registered significantly (P < 0.05) lower values thanCAE and CGE, 38, 52 and 49 meq/kg, respectively, at day 8. Initial value ofMDA was 0.2 µmol/g of fat (fat content = 4.3%) and during the first 3 days ofstorage a significant (P < 0.05) increase was registered only for batch CAE. Atthe end of the storage, the lowest value (0.7 µmol/g) was observed in batch FTE,which differed significantly (P < 0.05) from the other two batches, 1.1 and 0.8µmol/g for CAE and CGE, respectively. Sivertsvik (1997) also recorded a reduc-tion of malonaldehyde formation on salmon fillets packed with O2 absorber com-pared with package only in air, respectively 0.3 and 0.6 mg/kg, after 14 days at4°C. Despite the high values of hydroperoxides, these compounds are odorless(Huss, 1995) and rancid odor became evident in fish when malonaldehyde wasabove 1-2 µmol/g of fat (Connell, 1975). This could explain the fact that sensorypanel did not notice rancid odor in any seabream batch.
Sensory evaluation (Figure 8) of the three batches was similar until the 3rdday. In the following days packed fish received better scores than ice storedfish (CGE), although statistical treatment did not evidence significant differ-ences (P > 0.05) between all batches. In general, seabream from all batchespresented only slightly bright/iridescent skin due to the elimination of scales.At the end of storage, FTE reached the lowest demerit points, mainly due to abetter appearance, in particular the color of abdomen. Nunes and Pereira
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Peroxide value60
50
40
30
20
0 2 4 6 8 10Storage days
CGE CAE FTE
meq/kg
10
0
FIGURE 6. Changes in peroxide value during the storage of scaled and guttedgilthead seabream, in ice and packed in air. CGE–held in ice (0.6 ± 1.1°C);CAE–packed in air (4.9 ± 0.3°C); FTE–packed in air + O2 absorber (4.9 ±0.3°C). Error bars are the standard deviation (n = 2).
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Gonçalves, Mendes, and Nunes 57
Malonaldehyde1.5
1.0
0.5
0 2 4 6 8 10Storage days
CGE CAE FTE
µmol/g
0.0
FIGURE 7. Changes in malonaldehyde content during the storage of scaledand gutted gilthead seabream, in ice and packed in air. CGE–held in ice (0.6 ±1.1°C); CAE–packed in air (4.9 ± 0.3°C); FTE–packed in air + O2 absorber (4.9± 0.3°C). Error bars are the standard deviation (n = 2).
Sensory evaluation16
12
8
0 2 4 6 8 10Storage days
CGE CAE FTE
DemeritPoints
4
0
FIGURE 8. Sensory changes (in raw) during the storage of scaled and guttedgilthead seabream, in ice and packed in air. CGE–held in ice (0.6 ± 1.1°C);CAE–packed in air (4.9 ± 0.3°C); FTE–packed in air + O2 absorber (4.9 ±0.3°C). Error bars are the standard deviation (n = 5).
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(2000) reported a maximum of 6 d.p. (in a total of 20) for top quality seabream,during 4-7 days of ice storage and 6-16 d.p. for acceptable quality until 10days. Huidobro et al. (2001) applied a similar freshness scheme and registered10 d.p. for seabream after 10 days of ice storage. In the present work, allbatches obtained 6 d.p. (in a total of 16) at the 3rd day. Between the 6 and 10thdays, 8-9 d.p were registered for seabream packed with O2 absorber, whereasbatches CAE and CGE were scored with 7-9 and 9-11 d.p., respectively. There-fore, acceptable sensory quality till 10 days was observed, no matter howseabream was stored, in ice or packed, with or without O2 absorber.
CONCLUSIONS
O2 absorber was very efficient in the reduction of oxygen concentration insidethe packages. However its effectiveness in extending the shelf life of scaled andgutted seabream was not clearly evidenced compared with ice storage. In bothcases, a shelf life of 10 days was registered while seabream packed without O2 ab-sorber had a shelf life of 8 days. Nevertheless, lipid oxidation was significantly re-duced in seabream packed with O2 absorber. Therefore, packaging containing O2absorber could prove advantageous for quality preservation when seabream hashigh fat content, as is usually the case of farmed seabream. This aspect assumesmajor importance in scaled and gutted seabream, which is particularly susceptibleto lipid oxidation due to higher exposure to the air than in the case of wholeseabream.
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