Application of antimicrobial ice for extending shelf life of fish

In this study, we investigated whether wild-thyme (Thymus serpyllum) hydrosol had a preserving effect against spoilage of freshwater fish. Sensorial characteristics, chemical freshness indicator contents, and microbial counts (total aerobes, psychrotrophics, Enterobacteriaceae, fecal coliform bacteria, Aeromonas spp., and Pseudomonas spp.) of whole ungutted and gutted Transcaucasian barb (Capoeta capoeta capoeta Guldenstaedt, 1772) stored on ice produced from wild-thyme hydrosol and tap water at 4 degrees C for 20 days were compared. The results did not reveal any significant (P > 0.05) differences in the microbial counts, sensorial characteristics, pH, and total volatile basic nitrogen values between gutted and ungutted groups. Sensory evaluation and microbiological and chemical analyses indicated that the storage of the fish on ice produced from wild-thyme hydrosol had a significant increase in shelf life by at least 15 to 20 days.     

Quality assessment of whole and gutted sardines (Sardina pilchardus) stored in ice

The quality and shelf life of whole ungutted and gutted sardines ( Sardina pilchardus ) stored in ice were studied. The changes in the fish were investigated by sensory assessments, chemical analyses and microbiological analyses. The sensory scores of uneviscerated and gutted sardines stored in ice at +4 °C were 7 days. The chemical indicators of spoilage, total volatile basic nitrogen and trimethylamine values of gutted sardine increased very slowly, whereas for whole ungutted samples higher values were obtained reaching a final value of 15.03–29.23 mg per 100 g and 2.36–4.16 mg per 100 g, respectively (day 9). Peroxide and thiobarbituric acid values remained lower for whole ungutted sardine samples until day 9 of storage, whereas for gutted fish were higher. The level of histamine exceeded the legal limit in whole ungutted sardine after 7 days of storage in ice, during which sardines were rejected by the sensory panel. Mesophilic aerobic bacteria count, H₂S-producing bacteria, sulphide reducing anaerobe Clostridias, Enterobacteriaceae count of whole ungutted sardine samples are higher than gutted sardine samples during the storage. Psychrotrophic bacteria counts of the two groups were not different. The limits of microbiological data were not exceeded throughout the storage in both the groups' samples.     

Gutted and Un-Gutted Sea Bass (Dicentrarchus Labrax) Stored in Ice: Influence on Fish Quality and Shelf-Life

The sensory characteristics, chemical freshness indicator contents, and microbial counts (total aerobe, psychrotrophic bacteria, H₂S-producing bacteria, and Pseudomonas spp.) of whole un-gutted and gutted sea bass stored in ice were compared. Results of this study indicated that the acceptability quality of whole and gutted sea bass as determined by sensorial data is 11 days, respectively. No significant differences (p > 0.05) were found in the level of sensory score between whole and gutted sea bass samples. Total volatile basic nitrogen (TVB-N) values showed no significant increase for whole and gutted sea bass during storage. Trimethylamin (TMA-N) values of whole and gutted sea bass increased very slowly, reaching final values of 3.94 and, 3.38 mg/100g, respectively (day 13). Development of initial decomposition (after 7 days) occurred when bacterial counts were > 4 log CFU/g. Microbial counts showed a significant increase for whole and gutted sea bass during storage. Significant differences (p < 0.05) were found in the microbial counts between whole and gutted sea bass samples. This difference, may be attributed either to gutting procedures, which most probably were the cause of cross-contamination of fish or to the significantly higher fish flesh surface area exposed to environmental microbial contamination in the case of gutted fish.     

Effect of gutting on microbiological,chemical, and sensory properties of aquacultured sea bass (Dicentrarchus labrax) stored in ice

The effect of gutting on microbiological, chemical, and sensory properties of aqua-cultured sea bass (Dicentrarchus labrax) stored in ice was studied. Pseudomonads and H₂S-producing bacteria (including Shewanella putrefaciens) were the dominant bacteria at the end of the 16-day storage period in ice for both whole ungutted and gutted sea bass. Brochothrix thermosphacta and Enterobacteriaceae were also found in the spoilage microflora of ungutted and gutted sea bass but their counts were always less than those of Pseudomonads and H₂S-producing bacteria. Bacterial counts of whole ungutted sea bass were always higher than those obtained for gutted sea bass samples. Mesophilic counts for gutted and ungutted fish exceeded 7 log cfu g⁻¹ after 9 and 15 days of ice storage, respectively. Of the chemical indicators of spoilage, TMA values of ungutted sea bass increased very slowly whereas for gutted samples higher values were obtained reaching a final value of 0.73 and 4.39 mg N 100 g⁻¹, respectively (day 16). TVB-N values showed no significant increase for whole ungutted sea bass during storage reaching a value of 27.7 mg N 100 g⁻¹ (day 16) whereas for gutted fish 36.9 mg N 100 g⁻¹ was recorded. TBA values remained low for ungutted sea bass samples until day 16 of storage, whereas for gutted fish were variable. Of the chemical indices used, none proved useful means of monitoring early ungutted and gutted sea bass freshness in ice. Sensory assessment using the EC freshness scale gave a grade E for up to 5 days for the ungutted sea bass, a grade A for a further 2 days and a grade B for an additional 4 days, after which sea bass was graded as C (unfit). Gutted sea bass was given a grade E for up to 3 days, a grade A for the 4–7th days, and a grade B for the 8–10th days of storage, whereas on day 11 it was graded as unfit. Acceptability scores for odor, taste and texture of cooked ungutted and gutted sea bass decreased with time of storage. Results of this study indicate that the shelf-life of whole ungutted and gutted sea bass stored in ice as determined by the overall acceptability sensory scores and microbiological data is 13 and 8 days, respectively.     

Effects of gutting and ungutting on microbiological, chemical, and sensory properties of aquacultured sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) stored in ice

The effect of gutting and ungutting on microbiological, chemical, and sensory properties of aqua-cultured sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) stored in ice were studied. The total viable mesophilic and psychrophilic bacterial counts increased throughout the storage period of gutted and ungutted sea bream and sea bass. The mesophilic counts reached 8.19 log cfu/g for ungutted sea bream and 7.93 log cfu/g for ungutted sea bass after 14 days of storage. The mesophilic counts reached 8.89 log cfu/g for gutted sea bream and 8.16 log cfu/g for gutted sea bass after 14 days of storage. On day 14 of storage the psychrophilic counts of ungutted sea bream and sea bass were 8.24 log cfu/g and 8.03 log cfu/g, respectively, and for gutted sea bream and sea bass were 8.93 and 8.22, respectively. At the end of the storage period of 14 days, TVB-N, TBA, and TMA-N values of ungutted sea bass were determined as 50.13 +/- 0.25 mg/100 g, 2.66 +/- 0.06 mg malonaldehit/kg, 9.86 +/- 0.01 mg/100 g respectively. TVB-N, TBA, and TMA-N values of ungutted sea bream reached 55.90 +/- 0.36 mg/100g, 2.51 +/- 0.21 mg malonaldehit/kg, 9.79 +/- 0.01 mg/100 g on day 14 respectively. And also at the end of the storage period of 14 days, TVB-N, TBA, and TMA-N values of gutted sea bass were determined as 48.00 +/- 0.26 mg/100 g, 2.48 +/- 0.03 mg malonaldehit/kg, 8.71 +/- 0.06 mg/100 g respectively. TVB-N, TBA, and TMA-N values of gutted sea bream reached 49.66 +/- 0.77 mg/100g, 2.64 +/- 0.07 mg malonaldehit/kg, 8.97 +/- 0.01 mg/100 g on day 14 respectively. The result of this study indicates that the shelf-life of whole ungutted sea bass and sea bream stored in ice as determined by the overal acceptibility sensory scores, chemical quality, and microbiological results show us that the fish were spoilt on day 14. Each chemical, sensory, and microbiological result for sea bream showed us that there was a correlation and similarity and on day 14 it was spoilt.     

Quality changes in frozen whole and gutted anchovies during storage at −18°C

Fresh samples of whole and gutted anchovies were blast frozen at −35°C and stored at −18°C. The quality of the samples was examined as organoleptic, microbiological and chemical changes during the storage period. Gutting had no significant effect on the quality of the final product. Sensory quality was good for up to 90 days of storage. No increase in microbial activity was detected, but some oxidative and hydrolytic deterioration of fats were observed. The final product was still edible after 180 days.     

Effects of different cooling techniques on bacterial succession and other spoilage indicators during storage of whole, gutted haddock (Melanogrammus aeglefinus)

Effective cooling of newly caught fish is of great importance to inhibit bacterial growth and therefore increase quality, safety and shelf life of the product. In this study, two commercial cooling media (liquid ice A and B) were tested and their performance was compared to conventional plate ice during chilled 8-day storage of whole, gutted haddock. Temperature was monitored, and deteriorative changes were followed by conventional microbiological counts [(total viable psychrotrophic; specific spoilage organisms and physicochemical methods (pH, TVB-N, TMA, salt content)]. A cultivation-independent method (16S rRNA clone analysis) was used to study the effect of cooling treatments on the bacterial community of haddock initially and at the end of storage. The results show that the bacterial growth behaviour observed for differently cooled fish was not supported by their temperature profiles. Growth of the SSOs, Photobacterium phosphoreum and H₂S-producing bacteria was delayed at early storage, independently of the cooling methods. With further storage, little or no count differences were seen among traditionally iced fish and those cooled in liquid ice with a top ice layer. At the end of storage, significant (p < 0.05) increase in P. phosphoreum and H₂S-producing bacteria counts of skin and flesh sampled from liquid ice with no top ice layer was observed along with higher salt, TVB-N and TMA flesh content. Cultivation-independent analysis confirmed the dominance of P. phosphoreum in fish stored in liquid ice B with no top layer (up to 76% dominance) and liquid ice A with top layer (44% dominance). Psychrobacter and Flavobacterium dominated the microbiota of fish stored in conventional plate ice and liquid ice B with ice top layer. The study shows that the use of liquid ice prepared from brine provides faster initial cooling of whole fish but may create unfavourable conditions under extended storage where the active spoiler P. phosphoreum becomes dominant. Plate ice may therefore be an optimal medium for extended fish storage.     

Combination of bulk storage in controlled and modified atmospheres with modified atmosphere packaging system for chilled whole gutted hake

Whole gutted hake placed in boxes of ice were kept in modified and controlled atmospheres for 12 days with the gas mixture 60%CO₂/15%O₂/25%N₂ (v/v/v) at 2 ± 1 °C. Each lot of hake was then subdivided into two other lots and these were packed on trays, some of them in air and some in the same mixture of gases. The trays were kept at 2 °C until spoilage. The shelf‐life of the hake stored in these conditions was assessed by physical (pH), chemical (TVBN (total volatile basic nitrogen) and TMA‐N (trimethylamine nitrogen)) and sensory (inspection and taste panel) analyses. The results of these analyses indicated that the control lot (stored in air throughout) was rejected before the lots kept in adjusted atmospheres. However, the taste panel accepted all the lots, including the control lot, after 24 days of storage. The sample which was kept at 2 °C in a controlled atmosphere for 12 days and then packed in a modified atmosphere of the same gas mixture did not exceed pH 7 after 31 days of storage, nor the limits of TVBN and TMA‐N of 40 and 12 mg per 100 g respectively. As regards oxidative rancidity, TBA (2‐thiobarbituric acid) levels were very low under all storage conditions and did not exceed 2.5 mg malonaldehyde per 100 g muscle. According to the results of this study, bulk storage of whole gutted hake in boxes in ice under a controlled atmosphere could be combined with later packaging in a modified atmosphere on trays stored at 2 °C to extend the shelf‐life of the hake. © 2001 Society of Chemical Industry     

Changes in physico-chemical properties and gel-forming ability of lizardfish (Saurida tumbil) during post-mortem storage in ice

Changes in physico-chemical properties and gel-forming ability of lizardfish muscle (Saurida tumbil), stored in ice, were investigated up to 15 days. Heading and eviscerating, prior to iced storage, retarded myosin heavy chain degradation and formaldehyde formation. Additionally, denaturation of myosin and troponin was slightly impeded as monitored by the lower decrease in Ca²⁺-ATPase and lower increase in Mg²⁺–EGTA-ATPase, respectively. Gel-forming ability of surimi, prepared under different setting and/or heating conditions, decreased as storage time increased (P<0.05). However, superior breaking force and deformation of surimi gel, from headed/eviscerated fish, to that from whole fish was observed throughout the storage. Whiteness of surimi gel from headed/eviscerated fish was much higher than that from whole fish, especially when the storage time increased. Therefore, storage time and pretreatment were found to be crucial factors, determining the changes in physico-chemical properties and gel-forming ability of lizardfish during iced storage.     

Effect of pH and prefreezing treatment on the texture of yellowtail rockfish (Sebastes flavidus) as measured by the Ottawa Texture Measuring System

Texture is very important to the organoleptic quality of fish products. Poor frozen storage conditions or improper prefreezing treatment can result in unacceptably tough fillets. With some species, undesirable soft, mushy texture develops during chill storage.
This study is concerned with the influence of treatment prior to freezing (samples were frozen pre-rigor, in-rigor, post-rigor and after 6 days' chill storage in ice or refrigerated sea water) on the texture of yellowtail rockfish stored frozen as whole gutted fish or as fillets. The effect of pH was also studied. Texture was measured objectively using the Ottawa Texture Measuring System on samples stored for 6 months at −28°C.
A very good negative correlation was found between pH level and toughness as measured using a Kramer shear-compression cell in the Ottawa Texture Measuring System. Fish stored in refrigerated sea water prior to freezing were appreciably more tender. There was no statistical difference in texture (shear press force) values between samples stored as whole fish versus samples stored as fillets.     

Biochemical changes in freshwater rainbow trout (Oncorhynchus mykiss) during chilled storage†

The sensory characteristics and biochemical freshness-indicator contents of rainbow trout (Oncorhynchus mykiss) stored for up to 12 days (a) in ice without previous gutting (group A), (b) in ice after gutting (group B) and (c) under refrigeration (4–5 °C) after gutting and vacuum-packing (group C) were compared. Acceptable freshness was maintained for five days in groups A and C, and for six days in group B. The results indicate that the hypoxanthine ratio ie hypoxanthine content: (inosine monophosphate + inosine + hypoxanthine content) and K₁ ie (inosine + hypoxanthine content): (inosine monophosphate + inosine + hypoxanthine content) are both useful indicators of the freshness of trout stored in ice, regardless of whether or not they have been gutted beforehand. © 1999 Society of Chemical Industry     

On-board quality preservation of megrim (Lepidorhombus whiffiagonis) by a novel ozonised-slurry ice system

The use of a combined ozonised-slurry ice system was investigated as a new refrigeration system for the on-board storage of megrim (Lepidorhombus whiffiagonis), a fish species that is usually stored aboard fishing vessels for 1 to 2 weeks. The time elapsed between the catch and unloading at the harbour affects its quality and commercial value directly. Microbiological, chemical and sensory analyses were carried out in megrim after 2 weeks of on-board storage in ozonised slurry ice, slurry ice or flake ice, and for an additional period of 6 days. Sensory analyses revealed that megrim specimens stored in ozonised slurry ice (oSI₆₀₀ batch) maintained A quality even after 20 days of storage, while counterpart batches stored in flake ice showed B quality at unloading, after 14 days of on-board storage. Storage in ozonised slurry ice (oSI₆₀₀ batch) also led to significantly (p<0.05) lower counts of aerobic mesophiles, psychrotrophic bacteria, Enterobacteriaceae and proteolytic microorganisms in megrim muscle as compared with flake ice. Biochemical analyses revealed that the use of ozonised-slurry ice or slurry ice alone slowed down the formation of total volatile base-nitrogen (TVB-N) and trimethylamine-nitrogen (TMA-N) in comparison with storage in flake ice, also allowing a better control of pH. Lipid hydrolysis and oxidation events also occurred at a lower rate in the ozonised-slurry ice and slurry ice batches than in the flake ice batch. The present study demonstrates that the combination of slurry ice and ozone for the on-board storage of megrim is advisable, thus improving the quality and extending the shelf life of this fish species.     

Rancidity development in frozen pelagic fish: Influence of slurry ice as preliminary chilling treatment

The slurry ice technology has shown profitable advantages when employed instead of traditional flake ice for the manufacture of chilled aquatic species. The present work is aimed at evaluating the effect of slurry ice as a preliminary treatment prior to frozen storage. For it, specimens of a small pelagic fatty fish species (sardine; Sardina pilchardus) were stored in slurry ice for 2, 5 and 9 days, then subjected to freezing (-80 °C; 24 h) and finally kept frozen (−20 °C) during 1, 2 and 4 months. At such times, rancidity development in frozen sardine was measured by sensory (odour, skin, colour and flesh appearance) and biochemical (lipid hydrolysis and oxidation) analyses and compared to a control batch previously chilled in flake ice. Sensory analysis indicated an extended shelf-life time for frozen sardine that was preliminary stored under slurry ice for 2, 5 or 9 days, as compared to their counterparts subjected to flake icing. Sensory results were corroborated (P<0.05) by biochemical lipid oxidation indices (thiobarbituric acid reactive substances and the fluorescence formation). The present work opens the way to the use of slurry ice instead of flake ice as preliminary treatment of fish material prior to the frozen storage.     

Sensory and Chemical Evaluation of the Keeping Quality of the Brazilian Freshwater Fish Prochilodus scrofa in Ice Storage

The keeping quality of the freshwater fish Prochilodus scrofa in ice storage was investigated in two runs. Sensory evaluation of the raw fish reflected the progressive deterioration during storage. Sensory evaluation of the baked fish was less indicative of the state of freshness. None of the chemical analyses utilized (TVN, TBA, FFA, PV, qualitative tests) could be a reliable index of freshness. The keeping time was about 18 days in the first run and 12 days in the second run. Evisceration under commercial conditions did not extend the storage life.     

Quality assessment of gutted wild sea bass (Dicentrarchus Labrax) stored in ice, cling film and aluminium foil

The effects of aluminium foil and cling film on microbiological, chemical and sensory changes in wild sea bass (Dicentrarchus labrax) stored at chill temperature (4 °C) were studied. A quality assessment of wild sea bass stored in ice, in boxes without ice, wrapped in aluminium foil (WAF) and wrapped in cling film (WCF) at 4 °C was performed by monitoring sensory quality, nucleotide breakdown products, total volatile base nitrogen (TVB-N), and total viable counts (TVCs). The observed organoleptic shelf-life of sea bass was found to be 16 days in ice, 4 days in boxes without ice, 8 days in aluminium foil and 8 days in cling film. Demerit points did not differ significantly (P>0.05) between WCF fish and WAF fish. The nucleotide degradation pattern was found to be similar for all storage conditions except for inosine and hypoxanthine contents, which decreased after 12 days of storage for WAF and WCF. The content of TVB-N for all storage conditions showed similar tendencies until 12 days storage but reached the highest level (41.6 mg TVB-N 100 g^–1 flesh) for fish stored in WAF and WCF. No significant differences (P>0.05) were found in TVB-N concentrations within the treatments during the early stages of the storage period. Bacteria grew most quickly in the sea bass kept in boxes without ice, followed by those kept WAF, WCF and in ice. Significant differences (P<0.05) in TVC were observed amongst the treatments, especially between fish stored in boxes without ice and fish stored in ice     

Quality changes and storage life of common carp (Cyprinus carpio) at various storage temperatures

The shelf life and freshness changes in pond-grown common carp (Cyprinus carpio L) during storage at 0–2°C, 5–6°C and room temperature (26–29°C) were investigated by sensory, microbiological, physical and chemical analyses. The effect of gutting on the shelf life during storage at 0–2°C was examined. Iodine/starch and potassium sorbate were examined for their effects on shelf life of whole fish stored at 0–2°C and 5–6°C. Sensory results indicated that the whole fish had a maximum shelf life of 24 to 25 days at 0– 2°C. The life of the fish to the point beyond which it would be unsuitable for sale (commercial shelf life) was 17 days at 0–2°C. Storage at 5–6°C shortened shelf life 2- to 2.5-fold. At room temperature (26–29°C), spoilage was evident after 13 h. Gutting the carp shortened its storage potential at 0–2°C. Iodine treatment of this species stored at 0–2°C and at 5–6°C did not extend shelf life. The maximum shelf life of sorbate-treated fish at 0–2°C and 5–6°C was extended by 1–2 days, commercial shelf life by 3–4 days. Total volatile basic nitrogen, pH and penetrometer analyses were not reliable indicators of changes in freshness during shelf life. Thiobarbituric acid values were not useful as rancid odours or flavours were not detected during storage.     

冷藏温度对河豚鱼微生物及品质特性的影响

研究冷藏温度对河豚鱼微生物及品质特性的影响。将河豚鱼宰杀、清理、分块后,放置于(0±1)、(4±1)、(8±1)℃冰箱中冷藏。对鱼肉中几种优势菌种(肠杆菌、假单胞菌及乳酸菌),鱼肉质构、挥发性盐基氮、pH值、三甲胺、持水力等指标进行测定,评价河豚鱼冷藏过程中的品质变化。结果表明：(0±1)℃可贮藏6d左右,能够一定程度地抑制鱼肉中几种特定腐败菌的生长,减慢TVB-N值、pH值和TMA值的上升,延缓持水力的下降,并降低河豚鱼肉的硬度、弹性和回复性等质构特性的变化,有效延长河豚鱼的货架期,维持良好的鲜度。     

Freshness assessment of cultured sea bream (Sparus aurata) by chemical,physical and sensory methods

The quality changes of cultured sea bream (Sparus aurata) stored in ice for a period of up to 23 days were determined by K and related values, sensory assessment and texture by texturometer. Sensory schemes, based on the Tasmanian Food Research Unit (TFRU) scheme for raw fish and on the Torry scheme for cooked fish were modified to be appropriate for whole cultured sea bream, according to the trained panellists’ perceptions, during the storage period in ice. The TFRU sensory score of fish showed good agreement with K value and texture results throughout the storage period. The limit for acceptability of cultured sea bream stored in ice was about 17–18 days. Generally, K, K_i and G values had good correlation with the degree of freshness and can be used as freshness indicators.     

Freshness assessment of ray fish stored in ice by biochemical,chemical and physical methods

Ray fish were caught, filleted, and stored in ice. Fillets were analysed for 18 days to determine the chemical, biochemical and physical changes and their relation to the muscle eating quality. Trimethylamine (TMA-N), total volatile bases (TVB-N), ATP content and breakdown products, K value, pH, texture, water-holding capacity (WHC) and colour changes were monitored. At the beginning of the study, the ray fish muscle showed a low concentration of ATP and a high value of inosine 5′-monophosphate (IMP). Regarding to the signs of freshness and deterioration, K value presented an exponential increase (r2 = 0.95) with an initial value of 4.7% and a final value of 47.5%. Furthermore, the TBV-N and TMA-N significantly increased (P < 0.05) during the storage in ice. As for the physical analysis whereas the texture changed (P < 0.05); pH and the WHC were not affected (P < 0.05). The overall results of this study indicated that the edible quality of ray fish muscle was maintained during at least 15 days of ice storage.     

Quality of rainbow trout chilled-stored after post-catch holding

The shelf-life of headed and gutted rainbow trout (Salmo gairdneri) was evaluated over period of storage at 0°C. There were three groups of samples: (i) fish held at 10°C for 6h and iced, (ii) fish held at 20°C for 6h and iced and (iii) fish held at 30°C for 6h and iced. Quality was assessed over the period of iced storage by measurements of total volatile bases (TVB), hypoxanthine, thiobarbituric acid, pH, water holding capacity (WHC) and tissue compressibility (TC). The results indicated that holding at various time/temperature periods before icing influences quality over the period of iced storage. Deterioration in quality was most pronounced when the fish had been held at high ambient temperatures of 30°C. Hypoxanthine values appeared to give an accurate indication of quality of freshwater fish. There was a linear increase in hypoxanthine values over the period of iced storage for all samples. However, for trout held at 30°C for 6 h before icing the values appeared to be highest. The coefficients of linear regression for fish iced immediately on receipt were lowest per day. It is suggested that hypoxanthine values may be used as chemical indicators of quality of freshwater trout.