Modelling quality changes in Songpu mirror carp (Cyprinus carpio) fillets stored at chilled temperatures: comparison between Arrhenius model and log‐logistic model

To understand the quality changes in Songpu mirror carp (Cyprinus carpio) fillets during chilled storage, sensory score, total aerobic counts (TAC), total volatile basic nitrogen (TVB‐N) and electrical conductivity (EC) of the fillets stored at 270, 273, 276, 282 and 288 K were investigated. Furthermore, both Arrhenius model and log‐logistic model were established to predict the quality changes. The high regression coefficients (R² > 0.90) represented the acceptability of both Arrhenius model and log‐logistic model. Relative errors between predicted values and observed values were all within ±5% for models based on EC, within ± 25% for models based on TAC and TVB‐N (except the TVB‐N value on 9th and 15th day). The relative errors of sensory score were all within ±35% in the first 9 days. It is concluded that both Arrhenius model and log‐logistic model based on EC, TAC or TVB‐N can be applied in modelling quality changes in Songpu mirror carp fillets during storage within 270–288 K.     

Effect of O2 scavenger on the shelf‐life of catfish (Pangasius sutchi) steaks during chilled storage

BACKGROUND: Active packaging for preserving meat products, including seafoods, has been gaining importance in recent times. The present study was undertaken to assess the effectiveness of O₂ scavenger, the most widely used active packaging technology, on the shelf‐life of catfish steaks in chilled storage conditions. RESULTS: O₂ scavenger was effective in reducing the oxygen concentration inside the packaging to as low as 0.42% within 24 h. This reduction in oxygen in O₂ scavenger packages showed positive effects on quality parameters compared to control air packs. Total volatile base nitrogen (TVB‐N), thiobarbituric acid value and peroxide value of catfish steaks packed in O₂ scavenger was significantly different (P < 0.05) compared to air‐packed samples. Based on the sensory, microbiological and TVB‐N values, the control samples were acceptable only up to 10 days, compared to 20 days in O₂ scavenger‐packed samples, extending the shelf‐life by 10 days. CONCLUSION: O₂ scavenger reduced the oxygen concentration inside the package significantly within 24 h compared to control air packs. By using this technique, the use of a vacuum packing machine can be avoided. Further, O₂ scavenger extended the product's shelf‐life up to 20 days, compared to 10 days in control packs. Copyright © 2007 Society of Chemical Industry     

Establishment of quality predictive models for bighead carp (Aristichthys nobilis) fillets during storage at different temperatures

Quality predictive models were developed to predict the freshness of bighead carp (Aristichthys nobilis) fillets during storage at different temperatures. Quality indices [sensory score, total volatile base nitrogen (TVB‐N), total aerobic counts (TAC) and K value] at ?3, 0, 3, 9 and 15 °C were estimated and kinetically modelled by the Arrhenius equation. The activation energy (E_A) of sensory score, TVB‐N, TAC and K value was 78.17, 75.93, 106.53 and 76.21 kJ mol^?1, and the corresponding rate constants (k₀) were 1.16 × 10¹⁵, 2.60 × 10¹⁴, 4.05 × 10¹⁹ and 1.36 × 10¹⁵. The high regression coefficients (R² > 0.87) indicated the acceptability of the zero‐order reaction for sensory score, TVB‐N, TAC and K value. Relative errors between predicted and observed freshness indicators values of sensory score, TVB‐N, TAC and K value were all below 10% except the values at 6th day of K value, 3rd day and 9th day of TVB‐N. These results indicated that the models based on sensory score, TVB‐N, TAC and K value could effectively predict the freshness indicators of bighead carp fillets at the range of ?3 to 15 °C.     

Survival of probiotic bifidobacteria in buffalo curd and their effect on sensory properties

The feasibility of incorporating Bifidobacterium longum NCTC11818 in buffalo curd to produce a probiotic product was investigated. Fermentation at tropical ambient temperature (29 ± 2 °C), two storage temperatures (29 ± 2 °C and 4 ± 2 °C), and in three packaging materials (clay pots, plastic cups, and glass bottles) was investigated. Bifidobacteria survived for 3 days above the required population level of 10⁶ CFU g^?1 in buffalo curd packed in clay pots at 29 ± 2 °C. They did not persist at acceptable levels over the 4‐day shelf life because of the combined effects of temperature, acidity, and redox potential. Chill storage slows post‐fermentation acidification and prolongs bifidobacterial viability while packaging materials, which present a greater barrier to oxygen, had a similar effect. The results indicated that bifidobacteria could be successfully incorporated into buffalo curd to give a product which has improved acceptability. Probiotic buffalo curd, when compared to uninoculated curd, had significantly higher (P < 0.05) sensory scores for properties such as taste and mouth‐feel resulting in a significantly higher (P < 0.001) overall acceptability.     

Effect of nano‐TiO2‐LDPE packaging on microbiological and physicochemical quality of Pacific white shrimp during chilled storage

Nano‐TiO₂‐modified low‐density polyethylene (NTLDPE) packaging was prepared by blending LDPE with nano‐TiO₂. The effects of NTLDPE packaging on quality of Pacific white shrimp during storage at 4 °C were investigated. Results showed that NTLDPE lowered the K value by 28.50%, while increased sensory score by 30.77% in comparison with the control. NTLDPE packaging retarded the decrease of whiteness and water holding capacity and the increase of melanosis score based on the signs of freshness and deterioration of shrimp. Furthermore, NTLDPE packaging reduced total viable counts (TVC) by 6.42% and total volatile basic nitrogen (TVB‐N) contents were 14.82% lower than that of control. TVB‐N content and TBARS value, as well as polyphenol oxidase activity and TVC, were maintained and shrimp remained a commercial acceptability for 8 days. The overall results indicated that NTLDPE packaging could preserve the quality and extend the shelf‐life of Pacific white shrimp.     

The effects of rosemary extract combination with vacuum packing on the quality changes of Atlantic mackerel fish burgers

The effects of the use of antioxidant technology on the quality of mackerel burgers stored at 4 °C were investigated in terms of sensory, biochemical [thiobarbituric acid (TBA), total volatile basic nitrogen (TVB‐N), peroxide value (PV) and free fatty acids (FFA)] and microbiological analyses [total viable count (TVC)]. Fish meat was divided into three groups; the control (C) without rosemary extract, the second group with 0.4% rosemary extracts (Group A) and the third with 0.8% rosemary extracts (Group B). Results showed that the TVB‐N level did not exceed acceptability limit (30–35 mg 100 g^?1) for all groups. TBA value for the control significantly increased from 1.47 to 4.80 MA kg^?1 whereas it slightly increased in treatment groups as the storage time increased. Significantly higher PV and FFA (P < 0.05) were obtained from the control group. Rosemary extract, in combination with vacuum pack was effective in controlling the growth of bacteria and biochemical indices.     

DETERMINATION OF THE QUALITY AND SHELF LIFE OF SOUS VIDE PACKAGED BONITO (SARDA SARDA,BLOCH, 1793) STORED AT 4 AND 12C

ABSTRACT

The aim of this study was to determine the quality and shelf life of sous vide bonito stored at 4 and 12C. The total volatile basic nitrogen (TVB‐N) values of cold stored samples exceeded the recommended limit on 35th day of storage, while they were unacceptable according to sensory scores. The TVB‐N and trimethylamine‐N values of sous vide samples stored at 12C exceeded the limits at the 18th day, while sensory scores were very close to the acceptability limit. For all samples, mesophilic and psychrophilic bacterial counts exceeded the limits after they were regarded as spoiled. Therefore, the shelf life of the sous vide bonito, cooked at 70C for 10 min, was 28 days at 4C while 15 days at 12C. It was seen that sous vide packaging provided a long shelf life for bonito.

PRACTICAL APPLICATIONS

Sous vide is a long established but relatively little known cooking process. The data regarding the effect of storage temperature on shelf life and quality of sous vide fish are very limited. Therefore, this study aimed to determine the sensory, microbiological and chemical quality of sous vides packaged bonito during refrigerated storage (4 ± 1C) and abuse temperature conditions (12 ± 1C). The results of this study can be utilized by researchers in future studies as well as by manufacturers to determine the processing and storage conditions of sous vide fish.     

Quality changes of farmed cobia steaks held in cold stores (−18 °C)

Cobia (Rachycentron canadum) steaks held in cold store (?18 °C) were analysed aseptically in triplicates for the sensory, total aerobic bacterial count, proximate composition, pH, thiobarbituric acid‐reactive substance (TBA‐RS), formaldehyde, total volatile base nitrogen (TVB‐N), trimethyl amine‐nitrogen (TMA‐N), salt soluble nitrogen (SSN), nonprotein nitrogen (NPN), sodium dodecyl sulphate‐poly acrylamide gel electrophoresis (SDS‐PAGE) pattern. Steaks were sensorially acceptable up to 5 months of storage and the total bacterial counts did not exceed 6 log CFU counts. There were no significant changes in the pH values. TBA‐RS values increased significantly (P < 0.05) and reached 7.34 mg of malonaldehyde kg^?1 fat at the end. Formaldehyde content remained constant upto 4th month and later increased to 2.06 μg g^?1 (P < 0.05). TVB‐N and TMA‐N values did not exceed the acceptable limits. NPN contents showed no change, while SSN contents increased to 1.24% after 5 months. SDS‐PAGE pattern indicated no protein denaturation in the fish tissue. Results indicated that TBA‐RS value can only be considered as the valuable indicator in determining the quality of fish steaks held in cold stores.     

Shelf‐life extension of refrigerated seabass slices under modified atmosphere packaging

The effect of CO₂‐enriched atmosphere in combination with either oxygen or nitrogen on the keeping quality of seabass slices stored at 4 °C was investigated. The inhibitory effect on bacterial growth increased proportionally to the CO₂ concentration in the packaging, maximum inhibition being achieved with 100% CO₂ (P < 0.05). Seabass slices stored in CO₂‐enriched atmosphere had lower total volatile base, trimethylamine, ammonia and formaldehyde contents than those stored in air (P < 0.05). However, increases in lightness and exudate loss were observed for samples packaged in high‐CO₂ atmosphere, suggesting the denaturation of both muscle and pigment proteins by carbonic acid formed. Thiobarbituric acid‐reactive substances (TBARS) increased as the CO₂ concentration increased (P < 0.05). However, odour, flavour and overall acceptability of CO₂‐enriched packaged samples, particularly with 80 and 100% CO₂, were acceptable throughout storage for 21 days. Chemical and microbial changes in all samples were generally in agreement with sensory panel evaluations. The shelf‐life of seabass slices packaged in 80–100% CO₂ atmosphere could be extended to more than 20 days at 4 °C, compared with 9 days for those packaged in air. © 2002 Society of Chemical Industry     

Quality Assessment of Commercially Processed Carbon Monoxide‐Treated Tilapia Fillets

Carbon monoxide (CO) has been used to stabilize the color of fish muscle during frozen storage and distribution. This study compared changes in the quality profiles of CO‐treated and untreated (UT) tilapia fillets stored at 21 to 22 °C (room temperature), 4 to 5 °C (refrigerated), and 0 °C (iced). Samples (n = 3) were analyzed at different time intervals for chemical, lipid oxidation, microbiological, color, and expert sensory profiles. CO samples contained greater (P < 0.05) apparent ammonia and total volatile base nitrogen (TVB‐N) at day 0, with greater (P < 0.05) TVB‐N throughout refrigerated and iced storage. At time 0, peroxide values (POV) and thiobarbituric‐acid‐reactive substances were lower (P < 0.05) for CO samples and continued to have lower trends throughout all storage temperatures. Microbiological analysis at time 0 did not show any differences between UT and CO samples. Redness (a*) color values were greater (P < 0.05) in CO tilapia at time 0; however, treated product showed a more rapid decline in a* throughout all storage temperatures. While expert sensory evaluation showed no statistical differences between UT and CO tilapia at time 0, CO product failed sensory assessment sooner than UT product when stored refrigerated and in ice.     

Alginate–calcium coating incorporating nisin and EDTA maintains the quality of fresh northern snakehead (Channa argus) fillets stored at 4 °C

BACKGROUND: Antimicrobial packaging is a novel food packaging technology for controlling the growth of food‐borne pathogens or spoilage bacteria in ready‐to‐eat food products. Fresh fish are highly perishable foodstuffs and are extremely susceptible to microbial activities. An alginate–calcium coating incorporating nisin and ethylenediaminetetraacetic acid (EDTA) was used as an antimicrobial packaging to maintain the quality of northern snakehead (Channa argus) at refrigeration temperature (4 ± 1 °C). Northern snakehead fillets were left untreated (CK), or were treated with 1000 IU mL^?1 nisin and 150 µg mL^?1 EDTA (T1), alginate–calcium coating (T2), or alginate–calcium coating incorporating 1000 IU mL^?1 nisin and 150 µg mL^?1 EDTA (T3). RESULTS: All treatments retarded the decay of the fish fillets. T1 more efficiently inhibited the growth of total viable mesophilic bacteria (P < 0.05) and total psychrophilic bacteria (P > 0.05) than did T2 or T3. Coating treatments predominantly reduced chemical spoilage, reflected in total volatile base nitrogen (P > 0.05), trimethylamine (P > 0.05), pH (P < 0.05), and thiobarbituric acid (P < 0.05), retarded water loss (P < 0.05), and increased the overall sensory scores of fish fillets (P < 0.05) compared with those of T1. There was no significant difference between the coating treatments T2 and T3 (P > 0.05). CONCLUSION: Alginate–calcium coating treatments efficiently enhanced the quality of northern snakehead fillets during storage. Copyright © 2009 Society of Chemical Industry     

Microbiological,physical and chemical characteristics of freshwater prawns (Macrobrachium rosenbergii) in modified‐atmosphere packaging

This study evaluated the influence of packaging atmosphere (air versus 50% N₂/50% CO₂) on microbiological (mesophiles, psychrotrophs), physical (gas measurement) and chemical (pH, total volatile basic nitrogen [TVB‐N], NH₃, H₂S and biogenic amines) parameters in freshwater prawns during storage at 0 ± 1 °C for 240 h. To select the most appropriate packaging, 21 batches of each treatment were analysed. Both the packaging permeability and the combination of gases affected the shelf life, but the modified‐atmosphere packaging (MAP) was more efficient than air packaging, increasing the shelf life by 40 h. The parameters of pH and TVB‐N showed no statistical difference between the two atmosphere conditions all along the storage period. The biogenic amine agmatine showed potential for use as a quality indicator due to the increased concentration during storage. In further studies, this amine can be applied as an indicator for public health issue.     

Application of Electronic Nose for Measuring Total Volatile Basic Nitrogen and Total Viable Counts in Packaged Pork During Refrigerated Storage

The objective of this study was to predict the total viable counts (TVC) and total volatile basic nitrogen (TVB‐N) in pork using an electronic nose (E‐nose), and to assess the freshness of chilled pork during storage using different packaging methods, including pallet packaging (PP), vacuum packaging (VP), and modified atmosphere packaging (MAP, 40% O₂/40% CO₂/20% N₂). Principal component analysis (PCA) was used to analyze the E‐nose signals, and the results showed that the relationships between the freshness of chilled pork and E‐nose signals could be distinguished in the loadings plots, and the freshness of chilled pork could be distributed along 2 first principal components. Multiple linear regression (MLR) was used to correlate TVC and TVB‐N to E‐nose signals. High F and R² values were obtained in the MLR output of TVB‐N (F = 32.1, 21.6, and 24.2 for PP [R² = 0.93], VP [R² = 0.94], and MAP [R² = 0.95], respectively) and TVC (F = 34.2, 46.4, and 7.8 for PP [R² = 0.98], VP [R² = 0.89], and MAP [R² = 0.85], respectively). The results of this study suggest that it is possible to use the E‐nose technology to predict TVB‐N and TVC for assessing the freshness of chilled pork during storage.     

Effect of modified atmosphere packaging and vacuum packaging on the shelf-life of refrigerated chub mackerel (<Emphasis Type="Italic">Scomber japonicus</Emphasis>): biochemical and sensory attributes

The effect of modified atmosphere packaging (MAP 1: 70% CO₂/30% N₂ and MAP 2: 50% CO₂/30% N₂/20% O₂) and vacuum packaging (VP), on the shelf-life of chub mackerel (Scomber japonicus) fillets stored under refrigeration was studied. Quality assessment was based on sensory analysis and biochemical indices determination. Increase in total volatile basic nitrogen (TVBN) and trimethylamine nitrogen (TMAN) followed the order: MAP 1 < MAP 2 < VP < air (control samples). The presence of oxygen into the fish package (air or MAP) resulted in an increase in the 2-thiobarbituric acid (TBA) values in comparison with samples packaged in the absence of oxygen. The most effective MAP used was MAP 1 which contributed to a considerably slower rate of fish spoilage. Based primarily on odour scores it was observed that raw chub mackerel fillets stored in the presence of air remained acceptable up to ca. 11 days, VP and MAP 2 samples up to ca. 15–16 days, while MAP 1 samples up to ca. 20–21 days of storage. On the other hand, flesh texture and flesh colour of all packaged samples received scores above or equal than the acceptability limit up to ca. 13–14 days of storage.     

Effects of laurel and myrtle extracts on the sensory,chemical and microbiological properties of vacuum‐packed and refrigerated European eel (Anguilla anguilla) fillets

The effects of extracted natural antioxidant (laurel and myrtle) on the sensory, chemical (TVB‐N, TBARS, PV, FFA and pH) and microbiological (total viable count, psychrotrophic bacteria and Enterbacteriaceae counts) properties of vacuum‐packaged European eel (Anguilla anguilla) stored at 4 ± 1 °C were investigated. The TBARS values of myrtle were significantly lower than that of other groups. The peroxide value was low for European eel treated with myrtle and laurel extract. The FFA‐free fatty acid concentration increased from 0.44 (% oleic acid) (2.03) in the eel during 24 days of storage. The values of pH showed statistically significant (P < 0.05) changes for all groups. The myrtle significantly reduced bacterial growth in fillets (P < 0.05). The microbiological limit of 7 log cfu per gram did not exceed in the treated groups. Data showed that the extracts of myrtle and laurel contain substances that inhibit oxidation of lipids and growth of bacteria in European eel, indicating the potential value of these extracts to extend the shelf life of fish.     

Quality changes and microbiological spoilage analysis of air‐packed and vacuum‐packed silver carp (Hypophthalmichthys molitrix) fillets during chilled storage

The effects of air‐packed (AP) and vacuum‐packed (VP) on quality and microbial characteristics of silver carp (Hypophthalmichthys molitrix) fillets during chilled storage (4 ± 1 °C) were investigated. The fillets were analyzed for sensory scores, total volatile basic nitrogen (TVB‐N), ATP‐related compounds (ATP, IMP, HxR, and Hx), K value, and biogenic amines (BAs). The results proved that VP inhibited the increase of microorganisms, TVB‐N, Hx, and putrescine in silver carp, and slowed the reduction in sensory score. Therefore, VP can be applied for preservation of the silver carp fillets to improve its quality. For identification, 16S rRNA genes of the isolated pure strains were sequenced and analyzed. On the initial day of storage, Chryseobacterium was the dominant bacterial genus. At the end of shelf life, Pseudomonas was the most common group in AP fillets and Aeromonas followed by Yersinia were found mainly in VP samples.

Practical applications

Silver carp (Hypophthalmichthys molitrix) are distributed widely in fresh water systems. The world aquaculture production of silver carp was 4,354,638 tons, and it ranked second highest among freshwater fish species in 2015, but they are perishable during storage because of microbial spoilage and biochemical reactions. Vacuum packaging (VP) has proved to be effective for extending the shelf‐life of aquatic products by excluding oxygen that prevents the growth of spoilage bacterial. However, little information is available on the microbial succession of VP silver carp. Therefore, this work was to determine the differences of microbiological succession on chilled silver carp fillets under air‐packed (AP) and VP conditions using a combination of culture‐based and 16S rRNA gene analysis methods. Furthermore, this study will give valuable information about development and spoilage of VP silver carp fillets.     

Evaluation of Shelf Life of Superchilled Cod (Gadus morhua) Fillets and the Influence of Temperature Fluctuations During Storage on Microbial and Chemical Quality Indicators

Quality changes of aerobically packed cod fillets stored under superchilling and abusive temperature conditions were characterized by the growth of specific spoilage organisms (SSO) and the production of microbial metabolites measured by an electronic nose along with traditional sensory and chemical analysis (total volatile basic nitrogen [TVB‐N], pH). A new process based on quick contact freezing and cold air blasting was used to achieve superchilling of fillets before chilled (0.5 °C) or superchilled (‐1.5 °C) storage. Photobacterium phosphoreum dominated under temperature abusive conditions coinciding with high levels of TVB‐N and increased electronic nose responses indicating increased levels of alcohols and aldehydes at sensory rejection. Dominating growth of Pseudomonas spp. in 1 batch was associated with the origin, the catching method, and the cooling conditions during processing. The superchilling process followed by superchilled storage (‐1.5 °C) extended the sensory shelf life of the fillets for at least 3 d compared with traditional process, resulting in a total shelf life of 15 d. High content of TVB‐N was observed in superchilled fillets at sensory rejection. P. phosphoreum counts were lower under superchilling conditions (6.0 to 6.8 log colony‐forming units [CFU]/g), compared with the traditionally processed chilled fillets (7.2 log CFU/g). However, H₂S‐producing bacteria appeared to grow steadily under superchilling conditions reaching counts as high as 7.6 log CFU/g at sensory rejection.     

Quality assessment of filtered smoked yellowfin tuna (Thunnus albacares) steaks

Abstract: Filtered smoke (FS) has been used to preserve taste, texture, and/or color in tuna and other fish species. This treatment is particularly important in color preservation during frozen storage. The objective of this study was to compare changes in the quality profiles of FS‐treated and untreated (UT) yellowfin tuna (Thunnus albacares) steaks stored in 3 ways: room temperature (21 to 22 °C), refrigerated (4 to 5 °C), and iced (0 °C). FS and UT steaks were processed from the same lot of fish and analyzed for chemical, microbiological, lipid oxidation, color, and sensory profiles. Similar trends were seen for microbial proliferation and accumulation of apparent ammonia and total volatile base nitrogen (TVB‐N) during the storage temperatures evaluated. Notable exception in quality profile was found in lipid oxidation which was, as expected, lower for treated samples at all storage temperatures for TBARS (P < 0.05) and lower or significantly (P < 0.05) lower for POV values. FS increased the initial redness value significantly (P < 0.05). Unlike UT product, there was no loss of color value concomitant with quality changes for FS‐treated tuna for all storage temperatures evaluated. Practical Application: The overall goal of this project was to evaluate filtered smoked tuna steaks as to the impact on the overall quality profile. As a color‐stabilizing technology, it could mask deteriorating quality.     

Shelf Life Determination of Sliced Portuguese Traditional Blood Sausage—Morcela de Arroz de Monchique through Microbiological Challenge and Consumer Test

Morcela de Arroz (MA) is a ready‐to‐eat blood and rice cooked sausage produced with pork, blood, rice, and seasonings, stuffed in natural casing and cooked above 90 °C/30 min. It is commercialized whole, not packed, with a restricted shelf life (1 wk/0 to 5 °C). The objective of this work was to establish sliced MA shelf life considering both the behavior of L. monocytogenes through a microbiological challenge test (MCT) and the consumer acceptability of MA stored: vacuum packed (VP), modified atmosphere packed (MAP: 80% CO₂/20% N₂), and aerobic packed (AP). The MCT was conducted inoculating ±3 log CFU/g of L. monocytogenes cell suspension on the MA slices. Packaged samples were stored at 3 ± 1 °C and 7 ± 1 °C until 20 d. At 3 ± 1 °C, L. monocytogenes behavior was not affected by packaging or storage time. At 7 ± 1 °C, the pathogen increased nearly 1 log CFU/g in the first 4 d. L. monocytogenes populations in AP were higher (P < 0.05) than in MAP. The pathogen may grow to hazardous levels in the 1st days if a temperature abuse occurs. Considering the acceptability by the consumers, the shelf life of MA stored at 3 ± 1 °C was 4.4 d for AP, 8.1 d for VP, and 10.4 d for MAP. The sensory shelf life established based on sensory spoilage is shorter than the shelf life to maintain the population of L. monocytogenes in safe levels.     

Determination of volatile compounds of precooked prawn (Penaeus vannamei) and cultured gilthead sea bream (Sparus aurata) stored in ice as possible spoilage markers using solid phase microextraction and gas chromatography/mass spectrometry

BACKGROUND: Solid phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS) have been reported as useful techniques for analysing volatile compounds to monitor fish freshness. In this study, SPME/GC/MS was applied to cultured gilthead sea bream and precooked prawn stored in ice for 6 days in order to find possible markers of spoilage. Total volatile basic nitrogen (TVB‐N) was also determined as a common index of spoilage. RESULTS: The TVB‐N value at the end of the storage period for cultured gilthead sea bream (302.40 ± 8.50 mg kg^?1) was within the range of acceptability for edible fish (300–400 mg kg^?1) but could be considered at the beginning of spoilage. For precooked prawn the TVB‐N value at day 6 (863.04 ± 7.84 mg kg^?1) was not acceptable for human consumption. SPME/GC/MS identified 30 compounds in cultured gilthead sea bream and 49 compounds in precooked prawn. In particular, 3‐methyl‐1‐butanol, 2‐methylbutanal, 3‐methylbutanal and 3‐hydroxy‐2‐butanone increased during refrigerated storage both in the two species investigated here and in other species reported elsewhere and could be considered as markers of spoilage. CONCLUSION: This study confirmed that SPME/GC/MS can be considered an efficient method suitable for analysing the volatile compounds of both raw fish and fishery products in order to monitor loss of freshness. Copyright © 2008 Society of Chemical Industry