The impact of applying natural clinoptil

International Journal of Food Science and Technology 2012, 47, 1977–1985 Original article The impact of applying natural clinoptilolite (zeolite) on the chemical, sensory and microbiological changes of vacuum packed sardine fillets Esmeray Kuley,* Fatih Ozogul, Mustafa Durmus, Saadet Gokdogan, Cigdem Kacar, Yesim Ozogul & Yilmaz Ucar Department of Seafood Processing Technology, Faculty of Fisheries, Cukurova University, 01330 Adana, Turkey (Received November 2011; Accepted in revised form 12 March 2012) Summary Different doses (1% and 5%) of natural zeolite were applied to determine quality changes in vacuum packaged sardine fillets during 19 days at ± °C Zeolite had an effect to improve sensory quality of sardine especially for removing off-odour The acceptable shelf life of vacuum packaged sardine was days for control and 12 days for groups treated with 1% and 5% zeolite The zeolite application resulted in significant reduction in total volatile basic nitrogen values, except for group treated with 5% zeolite at 15 days Although the effect of zeolite depended on dose and specific storage days, application of zeolite had no effect on free fatty acid analysis The use of zeolite significantly reduced ammonia and biogenic amine accumulation, especially for histamine and tyramine The result of the study showed that the efficacy of zeolite as natural antimicrobials was high and lower dose of zeolite has to be applied to get maximum preservation effect Keywords Ammonia, antimicrobials, clinoptilolite, histamine, sardine, zeolite Introduction The growth of microorganisms makes food organoleptically unacceptable for consumption because of changes in colour, odour and texture (Oăzogul et al., 2004) Onefourth of the world’s food supply (Huis in’t Veld, 1996) and 30% of landed fish (Amos, 2007) are lost through microbial activity alone (Ghaly et al., 2010) The shelf life of fish is limited in the presence of normal air by the chemical effects of atmospheric oxygen and the growth of aerobic spoilage microorganisms (Oăzogul et al., 2004) Sardine is an important species in Turkey Sardine lipids have important nutritional characteristics because of their high level of x3 fatty acids (Bandarra et al., 1997) The highly unsaturated fatty acids are easily susceptible to oxidation that results in a rancid smell and taste as well as alterations in texture, colour and nutritional value during storage (Olafsdottir et al., 1997) The rate and extent of oxidative deterioration depend on factors such as the storage period and temperature, saturation degree of fatty acids, presence of antioxidants or prooxidants and availability of oxygen (Gogus & Kolsarici, 1992) *Correspondent: E-mail: eboga@cu.edu.tr Natural products in the global food industry are considered as healthy as there is increasing resistance at regulatory and consumer levels against chemical food preservatives (Agatemor, 2009) In recent times, great attention has been given to natural zeolites Clinoptilolite is a member of the naturally occurring zeolite family of minerals and is formed by the devitrification of volcanic ash in lakes and marine waters millions of years ago They are characterised by the ability to lose and gain water reversibly and to exchange constituent cations without major changes of structure (Mumpton & Fishman, 1977) Natural zeolites are the main absorptive, low-cost material used in agriculture and industry (Sakadevan & Bavor, 1998) There is a favourable situation for potential applications of zeolite in industrial and agricultural wastewater purification, aquaculture, animal feeding, agriculture and horticulture (Colella, 1996; Pavelic & Hadzija, 2003) Zeolite shows remarkable selectivity for removing ammonia from water and is already in use in the food industry (Cowan et al., 2003) All natural zeolite is sold as a food supplement Zeolite is an important mineral group for human health as they have a positive effect on detoxification of the body, removal of pollutants and capture of free radicals, increasing the stability of the immune system, controlling mineral metabolism, increasing doi:10.1111/j.1365-2621.2012.03060.x Ó 2012 The Authors International Journal of Food Science and Technology Ó 2012 Institute of Food Science and Technology 1977 1978 The effect of zeolite in sardine fillets E Kuley et al mental and physical performance, inhibition of the aging process and stress reducing effect (Hecht, 2010) Synthetic silver zeolite has been directly incorporated into food contact packaging film because of their role in allowing slow release of antimicrobial silver ions into the surface of food products (Brennan & Day, 2006) Zeolite containing copper ions exhibit good antibacterial activity for both gram-negative and gram-positive bacteria, and the effect developed in a short period of time (Cowan et al., 2003) There is limited study with regard to sensory, chemical and microbiological effect of natural zeolite in fish fillets Therefore, the aim of the study was to investigate antimicrobial and antioxidant effect of natural zeolite on vacuum packaged sardine during refrigerated storage Materials and methods Sample preparation assessment before the experiment Triplicate samples were taken at regular intervals for sensory analysis The panel members were asked to state whether the fish were acceptable or not for the determination of shelf life of sardine Sensory evaluation for cooked fish fillets was carried out according to the method of Paulus et al (1979) Fish fillets were cooked in a microwave for (300 w) and then served to the panellists to assess Panellists scored for colour, odour, flavour, general acceptability and texture, using a nine-point hedonic scale (1, dislike extremely to 9, like extremely) Analytical methods The total volatile basic nitrogen (TVB-N) content was determined according to the method of Antonocopoulus (1973) and expressed as mg TVB-N per 100 g muscle The value of thiobarbituric acid reactive substances (TBARs) was analysed according to method of Tarladgis et al (1960) for sardine fillets to evaluate the oxidation changes during storage, and the results are expressed as TBARs value, miligrammes of malondialdehyde per kg of fish flesh Free fatty acid analysis (FFA), expressed as % of oleic acid, was carried out by AOCS method (1994) Peroxide value (PV), expressed in milliequivalents of peroxide oxygen per kilogramme of fat, was analysed according to AOCS method (1994) Biogenic amine (BA) analysis was done using the method of Oăzogul et al (2002) Sardine (Sardinella aurita) was caught by gill net in Mersin Bay, Turkey The average weight and length of fish were 20.03 ± 2.88 g and 13.40 ± 0.81 cm, respectively They were stored in boxes with ice when fish were on board after catching and delivered to the laboratory The fish were immediately filleted The fish fillets were divided into three groups Two groups were immersed in a L of distilled sterile water containing 10 g (1% zeolite group) or 50 g zeolite (5% zeolite group) for The control (C group) was not treated with zeolite and was only immersed in distilled sterile water The control and the treated groups were packaged in pouches of polyamide film (Polinas, Manisa, Turkey) using a vacuum packaging (VP) machine (Reepack RV50; Seriate (BG), Via dell Artigianato, Italy) The thickness of the film was 90 lm and water and oxygen permeability were 8.5 g m)2 24 h and 160 cm3 m)2 24 h respectively All samples were stored at ± °C Sensory, chemical and microbiological analyses were performed on days 0, 4, 8, 12, 15, and 19 Data were obtained from three fish fillets from each of three bags for each treatment Fish muscle (5 g) was taken from the dorsal part of the fish fillet without skin and transferred to a 50 mL centrifuge tube The sample was then homogenised using the Ultra-Turax with 20 mL 6% trichloroacetic acid (TCA) for min, centrifuged using a Hettich 32R centrifuge (Tuttlingen, Germany) at 11180 g for 10 at °C and filtered through Whatman No filter paper (Maidenstone, UK) The aliquot was brought to 50 mL with distilled water and was stored in a freezer ()18 °C) until derivitisation Sensory analysis Derivatisation procedure For sensory analysis, the Quality Index Method scheme developed by Bonilla et al (2007) for fresh cod (Gadus morhua) fillets with minor modification was used The scheme is consisted of eight quality parameters (e.g skin brightness, skin mucus, flesh texture, flesh-blood, -odour, -colour, -bright and – gaping) The scheme had four simple descriptors, scoring demerit points from to a maximum of 3, where represented best quality and higher score indicated poorer quality The total sum of demerit points was 18 The panel consisted of seven regular assessors who were trained in fish quality Derivatisation procedure of amine was made according to Oăzogul et al (2002) A stock solution was prepared by dissolving 2% benzoyl chloride in acetonitrile to enhance the reaction with amines For derivatisation of standard amine, 50 lL was taken (2 mL for extracted fish samples) from each free base standard solution (10 mg mL)1) One millilitre of m sodium hydroxide was added, followed by lL benzoyl chloride (2%) and mixed on a vortex mixer for The reaction mixture was left at room temperature (24 °C) for 20 The benzoylation was stopped by adding mL of saturated International Journal of Food Science and Technology 2012 Sample preparation for Biogenic Amine analysis Ó 2012 The Authors International Journal of Food Science and Technology Ó 2012 Institute of Food Science and Technology The effect of zeolite in sardine fillets E Kuley et al sodium chloride solution and the solution was extracted two times with mL of diethyl ether The upper organic layer was transferred into a clean tube after mixing and evaporated to dryness in a stream of nitrogen The residue was dissolved in 500 lL of acetonitrile and lL aliquots were injected into the HPLC Apparatus and columns A Shimadzu Prominence HPLC apparatus (Shimadzu, Kyoto, Japan) equipped with a SPD-M20A diode array detector, two binary gradient pumps (Shimadzu LC-10AT), auto sampler (SIL 20AC), column oven (CTO-20AC) and valve unit FCV-11AL with a communication bus module (CBM-20A) was used The column was a reverse-phase, ODS Hypersil, l, 250 · 4.6 mm (Phenomenex, Macclesfield, Cheshire, UK) Oven temperature was 30 °C and mobile phase was acetonitrile and HPLC grade water Table Total volatile basic nitrogen changes in vacuum packaged sardine fillets during refrigerated storage Storage days Control 12 15 19 16.70*† 21.31 24.92 39.96 41.83 49.39 Chromatographic separation was carried out using continuous gradient elution with acetonitrile (eluant A) and HPLC grade water (eluant B) The gradient was started at %40 acetonitrile and was then increased to 70% in 15 The total separation was 20 and gradient was run for 20 to ensure full separation The injection volume was 10 lL (Oăzogul et al., 2002) Microbiological analysis Triplicate samples were taken to estimate total viable counts (TVC) from each of three different groups Fish muscle (10 g) was mixed with 90 mL of sterile Ringer solution (1 ⁄ strength) and then stomached for Further decimal dilutions were made, and then 0.1 mL of each dilution was pipetted onto the surface of plate count agar (Fluka 70152; Steinheim, Switzerland) plates in triplicate Plates were then incubated for days at 37 °C (ICMSF, 1982) Statistical analysis The mean value and standard deviation were determined and presented in Tables to and Table S1 Data were subjected to analysis of variance and Duncan’s multiple range tests using the SPSS Version 18.0 statistical package (SPSS Inc., Chicago, IL, USA) Results and discussions Sensory changes Fig S1 and S2 show the total demerit points of raw and cooked sardine treated with zeolite stored in a refriger- ± ± ± ± ± ± 3.67àa 0.46a 0.40a 1.90a 1.08b 2.54a 16.70 19.53 20.72 27.11 27.95 38.38 ± ± ± ± ± ± 5% Zeolite 3.67a 1.34b 0.45b 0.98b 0.67c 1.05c 16.70 18.62 18.76 26.92 46.72 42.97 ± ± ± ± ± ± 3.67a 0.44b 1.38c 0.37b 2.52a 1.89b *Data are expressed as mean value of three samples † Mean value Standard deviation a–c Indicate significant differences (P < 0.05) between control and treated group in a column Table Free fatty acid analysis changes in vacuum packaged sardine fillets during refrigerated storage Storage days Chromatographic conditions 1% Zeolite 12 15 19 Control † 1.68* 2.11 3.36 3.35 5.05 7.03 ± ± ± ± ± ± 1% Zeolite àa 0.95 0.62a 0.76a 0.28b 0.36ab 0.69ab 1.68 1.93 2.39 6.12 5.78 5.45 ± ± ± ± ± ± 5% Zeolite a 0.95 0.49a 0.39ab 0.33a 0.37a 0.37b 1.68 1.50 1.24 3.36 4.66 6.47 ± ± ± ± ± ± 0.95a 0.08a 1.12b 0.52b 0.3b 0.21a *Data are expressed as mean value of three samples † Mean value Standard deviation a–c Indicate significant differences (P < 0.05) between control and treated group in a column ator Significant differences were observed among the control and treated groups (P < 0.05) Zeolite had an effect on sensory quality of fish fillets, especially for removing off-odour However, treated groups (especially 5% zeolite) had a perceivable zeolite odour at the beginning of the storage, but after days of storage periods, zeolite odour highly reduced The low dose of zeolite (1%) was more preferred than high concentration of zeolite (5%) by panellist, because of the appearance of zeolite and development of a dry or rough texture in fish treated with 5% zeolite High dose zeolite application changed the flesh colour to slightly white Demerit points of raw sardine increased with storage time Zeolite application provided a longer shelf life compared with the control The acceptable shelf life of vacuumpackaged sardine was found to be days for the control and 12 days for the treated groups (1% and 5% zeolite), corresponding with a demerit score of 7.4, and 8.25, respectively Similar results were found for vacuumpackaged sardine stored at C (Oăzogul et al., 2004), although Kenar et al (2010) and Ozogul et al (2010) reported longer shelf life (13 days) for vacuum-packaged sardine at ± °C Fresh fish products stored Ó 2012 The Authors International Journal of Food Science and Technology Ó 2012 Institute of Food Science and Technology International Journal of Food Science and Technology 2012 1979 1980 The effect of zeolite in sardine fillets E Kuley et al Table Peroxide value (PV) and TBA changes in vacuum packaged sardine fillets during refrigerated storage Storage days 12 15 19 PV 2.68*† ± 0.15à _ _ 4.25 ± 0.07a 3.37 ± 0.32ab 3.79 ± 0.50b 4.99 ± 0.82a 3.72 ± 0.85a 4.93 ± 0.86a 6.11 ± 0.99a 4.13 ± 0.44b 3.23 ± 0.69b 5.82 ± 1.59a 6.31 ± 0.51a 3.20 ± 0.17b 4.03 ± 0.40a 3.36 ± 0.11a 3.70 ± 0.22a TBA 0.56 _ _ 1.75 1.15 1.18 0.98 1.53 1.68 1.01 1.15 1.38 1.12 1.16 1.60 0.46 0.47 0.48 Groups ± 0.03 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 2.56a 0.04a 0.09a 0.04b 0.12a 0.09a 0.08c 0.09b 0.04a 0.05b 0.04b 0.05a 0.01a 0.02a 0.05a Control 1% zeolite 5% zeolite Control 1% zeolite 5% zeolite Control 1% zeolite 5% zeolite Control 1% zeolite 5% zeolite Control 1% zeolite 5% zeolite Control 1% zeolite 5% zeolite *Data are expressed as mean value of three samples † Mean value Standard deviation a–c Indicate significant differences (P < 0.05) between control and treated group in a row under VP had an overall increase of shelf life of days over aerobically stored fish (Clingman & Hooper, 1986) A lower shelf life (3–7 days) was observed in aerobically stored sardine (Gokoglu et al., 2004; Erkan & Oăzden, 2008) compared with current study The sensory score of the cooked fillets decreased with storage time (Fig S2) There were significant differences (P < 0.05) among the groups Off-flavour and offodour of the control group, and and 5% the treated groups were detected on and 12 day of storage respectively As found for raw fish, zeolite application removed characterised fish odour Zeolite also resulted in softness in the fish texture and feeling of dryness in mouth Mostly preferred group by the panellists was the group treated with 1% zeolite Chemical changes Total Volatile Basic Nitrogen Table shows TVB-N changes in sardine fillets during chilled storage Initial TVB-N value was 16.70 mg 100 g)1, which is lower than results reported by Kenar et al (2010) for vacuum-packaged sardine held in cold temperature The TVB-N levels showed fluctuation at 19 days for group with 5% zeolite, whereas TVB-N content of control and the group with 1% zeolite increased with storage time Significant differences in TVB-N values were obtained between the control and the treated groups during periods International Journal of Food Science and Technology 2012 (P < 0.05) The zeolite application resulted in significant reduction on TVB-N values, except for the group with 5% zeolite at 15 days TVB-N values in fish are not always correlated well with microbiological results, as the total volatile bases detected in high level may be formed as result of endogenous enzymatic activity (Omar, 1998) Moreover, Huss (1995) reported that TVB-N values not reflect the mode of spoilage (bacterial or autolytic), and results depend to a great extent on the method of analysis (Huss, 1995) These could be reasons why a higher TVB-N value was observed for fish treated with 5% zeolite at 15 days when compared with the control group Erkan & Oăzden (2008) reported 22.03 and 12.87 mg 100 g)1 of TVB-N levels at the limit of acceptability of whole and gutted sardine Oăzogul et al., 2004 found that the release of total volatile bases increased up to 15 mg 100 g)1 for sardine stored in air, 19 mg 100 g)1 for sardine in VP and 17 mg 100 g)1 in modified atmosphere pack (MAP) at the last day of sensory acceptability for each storage condition However, in the present study, higher TVB-N values were observed for all groups When fish were unacceptable for panellist, TVB-N values were 24.92 mg 100 g)1 at day for the control group, 27.11 mg 100 g)1 for the group with 1% zeolite and 26.92 mg 100 g)1 at 12 days for the group with 5% zeolite Kenar et al (2010) found slightly higher TVB-N values for vacuum-packed sardine, when fish was unacceptable for panellist Lipid hydrolysis and oxidation Free fatty acid (FFA) changes in sardine fillets were given in Table FFA values ranged from 1.68 to 7.0 for the control, 6.12 for 1% zeolite and 6.47 (% of oleic acid) for 5% zeolite Slightly higher FFA value was found for vacuum-packed sardine (Ozogul et al., 2010) Initial FFA values of vacuum packaged sardine fillets were 2.72 and increased sharply after 13 days (Kenar et al., 2010) Although the effects of zeolite depended on dose used and specific storage days, application of zeolite had no effect on FFA values during storage days, except for and 12 days At days of storage, the use of 5% zeolite resulted in lower FFA values in sardine fillets, whereas significant increases were observed for the group with 1% zeolite at 12 days At the acceptability limit of fish, FFA values were 3.36 for control, 6.12 for the group with 1% zeolite and 3.36 for the group with 5% zeolite Peroxide value (PV) and thiobarbituric acid reactive substances (TBARs) are the major chemical indices to measure the degree of oxidative rancidity Changes in PV and TBARs of control and treated groups during refrigerated storage were given in Table The initial PV of sardine fillets was found to be 2.68 meq kg)1 There were significant differences in PV between the control and treated groups (P < 0.05) at 4, 12 and Ó 2012 The Authors International Journal of Food Science and Technology Ó 2012 Institute of Food Science and Technology Ó 2012 The Authors International Journal of Food Science and Technology Ó 2012 Institute of Food Science and Technology 9.27 (0.10) 27.95a (0.87) 22.73b (1.41) 9.23c (0.28) 32.34a (1.33) 17.84b (0.01) 11.12c (1.22) 36.01a (1.90) 26.96b (0.53) 24.61b (0.18) 38.76a (1.25) 24.38b (1.89) 25.62b (1.73) 45.37a (3.49) 29.48b (2.58) 24.93b (1.22) † AMN* 6.06 (0.33) 13.58a (0.50) 6.79b (0.02) 5.62c (0.17) 15.23a (0.98) 8.61b (0.07) 6.75c (0.22) 17.22a (0.75) 13.49b (0.77) 11.53b (0.74) 30.03a (1.29) 18.43b (0.90) 17.66b (0.88) 44.11a (1.40) 21.46b (1.67) 20.83b (1.00) PUT 5.99 (0.07) 39.39a (1.64) 11.82b (1.12) 11.08b (0.56) 40.69a (2.84) 19.03b (1.12) 17.81b (1.30) 32.78a (2.18) 27.28ab (1.83) 24.49b (1.39) 30.13a (2.08) 28.70a (0.62) 27.35a (1.10) 59.85a (3.30) 38.72b (2.21) 41.15b (2.89) CAD 2.92 (0.17) 5.38a (0.08) 2.16b (0.11) 2.11b (0.17) 4.58a (0.24) 1.84b (0.06) 1.93b (0.03) 3.57a (0.30) 3.08ab (0.10) 2.43b (0.28) 3.82a (0.14) 3.32b (0.05) 3.28b (0.22) 4.18a (0.13) 3.29b (0.14) 3.25b (0.24) SPD 1.53 (0.06) 2.84a (0.04) 1.92b (0.18) 2.63a (0.02) 1.10b (0.01) 1.69a (0.11) 1.21b (0.03) 5.57a (0.40) 0.22c (0.02) 3.53b (0.31) 3.05b (0.02) 4.55a (0.23) 1.83c (0.07) 6.30a (0.59) 5.61a (0.37) 2.71b (0.09) TRPT 0.46 (0.01) 0.00c (0.00) 3.82a (0.20) 0.85b (0.08) 2.33a (0.07) 0.55b (0.02) 0.25c (0.00) 4.76a (0.25) 1.69b (0.11) 2.11b (0.12) 4.60a (0.05) 0.75b (0.01) 0.25c (0.00) 0.00c (0.00) 0.50b (0.01) 1.53a (0.03) PHEN 3.25 (0.05) 7.04b (0.35) 12.60a (0.40) 1.44c (0.05) 7.52a (0.03) 1.41c (0.01) 1.90b (0.13) 4.36a (0.18) 3.08c (0.11) 3.68b (0.20) 3.26a (0.24) 2.57b (0.03) 1.43c (0.06) 2.56a (0.30) 2.81a (0.08) 1.87b (0.05) SPM 0.73 (0.04) 8.39a (0.52) 2.64c (0.20) 4.84b (0.11) 14.73a (0.86) 6.46b (0.46) 2.36c (0.16) 26.77b (0.75) 22.99c (0.69) 32.13a (0.86) 14.31a (0.21) 9.77b (0.28) 15.55a (0.61) 27.18a (2.20) 23.23ab (2.18) 19.06b (0.93) HIS 11 75 (0.29) 3.17b (0.22) 3.96a (1.34) 3.93a (2.28) 6.99a (0.21) 1.49c (0.07) 4.32b (0.42) 3.94a (0.17) 1.80c (0.13) 2.70b (0.11) 1.70c (0.05) 2.32b (0.22) 3.58a (0.23) 2.33c (0.04) 2.58b (0.05) 4.37a (0.02) SER 3.07 (0.20) 21.79a (1.16) 11.75b (0.98) 2.80c (0.03) 30.52a (1.02) 7.21b (0.01) 6.64b (0.36) 33.11a (0.78) 22.72c (1.14) 27.43b (1.31) 21.41a (0.64) 15.89b (0.28) 13.71c (1.17) 30.50a (1.95) 22.31b (1.07) 11.21c (1.05) TYR 1.52 (0.03) 3.11a (0.09) 2.96a (0.28) 0.31b (0.03) 5.63a (0.07) 1.63b (0.05) 0.43c (0.01) 7.40a (0.12) 1.31b (0.09) 0.64c (0.00) 7.54a (0.45) 2.46b (0.22) 1.75b (0.17) 18.90a (1.16) 1.12b (0.13) 1.50b (0.50) TMA 6.27 (0.09) 54.27a (3.45) 6.18c (0.11) 17.98b (1.17) 90.67a (5.32) 27.59b (2.31) 15.01c (0.56) 66.23a (2.09) 33.62b (2.00) 31.97b (0.65) 92.84a (2.32) 18.79b (1.58) 11.42b (0.85) 71.75a (4.60) 23.56b (1.14) 13.23c (1.33) DOP 3.71 (0.27) 8.22a (0.09) 6.22b (0.22) 3.15c (0.08) 6.58a (0.22) 3.34b (0.00) 0.85c (0.07) 5.44a (0.38) 1.74b (0.14) 4.78a (0.29) 3.08a (0.00) 2.82b (0.25) 2.70c (0.18) 3.96a (0.37) 1.57c (0.08) 2.96b (0.11) AGM 5% zeolite 1% zeolite Control 5% zeolite 1% zeolite Control 5% zeolite 1% zeolite Control 5% zeolite 1% zeolite Control 5% zeolite 1% zeolite Control Control Groups *AMN, ammonia; PUT, putrescine; CAD, cadaverine; SPD, spermidine; TRP, tryptamine; PHEN, 2-phenylethyl amine; SPN, spermine; HIS, histamine, SER, serotonin; TYR, tyramine; TMA, trimethylamine; DOP, dopamine; AGM, agmatine † Mean Standard deviation (n = 3) a–c Indicate significant differences (P < 0.05) between control and treated group in a row 19 15 12 Storage days Table Changes of ammonia and biogenic amines in vacuum-packaged sardine during chilled-storage periods The effect of zeolite in sardine fillets E Kuley et al International Journal of Food Science and Technology 2012 1981 1982 The effect of zeolite in sardine fillets E Kuley et al 15 days Treated group with 1% zeolite had higher PV than the group with 5% zeolite at 15 days, although zeolite application generally resulted in lower PV The lowest PV was generally observed for 5% zeolite-treated group Gracey et al (1999) reported that PV below meq kg)1; the fat is considered fresh or the hydroperoxides have degraded into ketones, PV between and 10 meq kg)1commencing rancidity In the present study, PV in all groups remained below the 6.5 meq kg)1 However, Ozogul et al (2010) found considerable higher PV in vacuum-packaged sardine, with maximum value of 14 28 meq kg)1 at the end of the storage periods The concentration of TBARs in freshly caught fish is typically between and mg of malondialdehyde (MDA) equivalents per kilogram flesh, but levels of 5–8 mg of MDA equivalents per kilogram of flesh are generally regarded as the limit of acceptability for fish stored in ice (Schormuller, 1968; Beltran & Moral, 1990; Nunes et al., 1992; Oăzden & Gokoglu, 1997; Erkan & Oăzden, 2008) In the present study, low TBARs observed for all groups during the storage periods TBARs in sardine fillets ranged from 0.46 to 1.16 MA per kg for the treated group with 1% zeolite and from 0.48 to 1.68 MA per kg for the treated group with 5% zeolite Zeolite significantly increased TBARs content of sardine at and 15 days, whereas the use of zeolite had no effect on fish TBARs for other storage days When fish was unacceptable by panellist, TBARs for the control, treated groups with 1% and 5% zeolite were 0.98, 1.15 and 1.38 MA per kg respectively At the beginning of the storage periods, no significant differences in pH values were observed between groups (P > 0.05), whereas pH changes between the control and the treated group with 1% zeolite were significant at 8, 15 and 19 days (Table S1) pH value of the control group ranged from 6.61 to 6.83, whereas treated group with 1% zeolite had 6.49–6.71 pH values during storage periods The treated group with 5% zeolite had generally slightly higher pH values than the treated group with 1% zeolite Ammonia and biogenic amines Biogenic amine accumulation in foods requires the availability of precursors (i.e amino acids), the presence of microorganisms with amino acid decarboxylases, and favourable conditions for their growth and decarboxylating activity (Brink et al., 1990) BA and ammonia formation in sardine were given in Table There were significant differences in ammonia content among the control and treated groups (P < 0.05) Zeolite has capacity to adsorb mycotoxins and also excess moisture, ammonia and radionuclide (Djordjevic´ et al., 2003; Grubic et al., 2003; Koljajic´ et al., 2003) The use of zeolite resulted in significant reduction in ammonia accumulation in sardine muscle The zeolite International Journal of Food Science and Technology 2012 concentration was found to have a significant effect on the formation of ammonia Treated group with 5% zeolite was more effective to suppress ammonia formation than treated group with 1% zeolite at the beginning of storage Significant differences in BA formation were also found among the groups (P < 0.05) Zeolite generally reduced BA formation in sardine, although the effects of zeolite on BA varied depending on specific amine and storage time When fish was unacceptable by panellist, the main BA formed in fish fillets were dopamine, histamine, cadaverine, tyramine and putrescine Gokoglu et al (2004) found that putrescine was the main amine in sardine samples and reached a maximum level 30.34 mg 100 g)1 at °C, whereas cadaverine formation did not change significantly throughout the storage at °C In the present study, initial putrescine and cadaverine content of fish were 6.06 and 5.99 mg 100 g)1 and reached the maximum value of 44 11 and 59.85 mg 100 g)1 for the control at the end of the storage periods respectively Putrescine and cadaverine in sardine were reported to accumulate rapidly reaching levels of 30 and 105 mg 100 g)1 after 24 h storage at ambient temperature (Ababouch et al., 1991) The use of zeolite resulted in a lower putrescine and cadaverine accumulation (except for 15 days) in fish muscle during of storage periods The dose of zeolite used had no effect on cadaverine formation, whereas the use of 5% zeolite had higher impact on reduction of putrescine formation until days of storage When fish were unacceptable, putrescine and cadaverine were 15.23 and 40.69 mg 100 g)1 for the control, 13.49 and 27.28 mg 100 g)1 for the group with 1% zeolite, and 11.53 and 24.49 mg 100 g)1 for the group with 5% zeolite At the acceptability level of sardine, putrescine and cadaverine content were 48.74 and 102.64 mg 100 g)1 for vacuumpackaged sardine stored in a refrigerator (Oăzogul et al., 2011) Lower putrescine and cadaverine content were found for sardine held in vacuum-package conditions, with maximum 7.59 and 5.73 mg 100 g)1 of content of putrescine and cadaverine respectively (Oăzogul & Ozogul, 2006) Spermidine and spermine were naturally occurring BA in food and their formation is not related to bacterial spoilage (Veciana-Nogues et al., 1997) Initial spermidine and spermine values were 2.92 and 3.25 mg 100 g)1 and, remained below the 5.5 and 7.6 mg 100 g)1 during storage respectively Zeolite had generally significant effect on reducing initial spermidine and spermine accumulation in fish muscle, although application of zeolite at dose of 1% resulted in higher spermine accumulation in sardine muscle at days Triptamine accumulation in fish muscle was low (1.53 mg 100 g)1) and slightly increased the maximum levels of 6.30 mg 100 g)1 at 19 days for control The effectiveness of zeolite was dependent on the storage Ó 2012 The Authors International Journal of Food Science and Technology Ó 2012 Institute of Food Science and Technology The effect of zeolite in sardine fillets E Kuley et al days, whereas zeolite at dose of 1% increased triptamine formation at and 15 days 2-phenylethylamine was the lowest amine formed sardine muscle at days and absent in many days The use of 1% zeolite caused significant reduction on 2-phenylethylamine formation at 8, 12 and 15 days of storage, whereas significant increases in this amine were observed with 1% and 5% zeolite treatment at and 19 days respectively Initial histamine content of sardine muscle was below the mg 100 g)1 and increased gradually to a value of 27.18 mg 100 g)1 at the end of the storage period This finding is in agreement with the results of Oăzogul et al (2011) who found that histamine formation of vacuum-packaged sardine stored at ± °C was