Histamine Formation and Bacterial Spoilage of Albacore Harvested off the U.S. Northwest Coast

Iced and previously frozen albacore were monitored for histamine formation and bacterial growth during storage at 0–37°C. The optimum temperature for histamine formation in albacore tuna (Thunnus alalunga) was 25°C, and whole fish were more susceptible to histamine formation than dressed fish at that temperature. Storage at 25°C resulted in the highest histamine level, 60.4 mg/100g in whole fish stored for 7 days. When albacore were frozen prior to storage, reduced amount of histamine was found at 7.14 mg/100 g after 7 day storage at 25°C, only after decomposition became obvious. No histamine was found in any of the albacore samples stored in ice for 18 days.     

Occurrence of Histamine-Forming Bacteria in Albacore and Histamine Accumulation in Muscle at Ambient Temperature

Distribution of histamine‐producing bacteria in fresh albacore and their proliferation in muscle during storage at 25 °C were monitored. Histamine formers constituted a minor portion of the bacterial flora in albacore. Only weak histamine formers were detected in the gill and skin of fresh fish after enrichment. Histamine formers were isolated from the muscles when APC reached >10⁷ CFU/g during storage. Hafnia alvei was most prevalent in both fresh and temperature‐abused fish. The most prolific histamine former, Morganella morganii, was rarely isolated even from spoiled muscles. The prevalence of weak histamine formers resulted in low levels of histamine accumulation in muscle, 67.1 mg/100 g, for 6 d of storage.     

Control of Histamine‐Producing Bacteria and Histamine Formation in Fish Muscle by Trisodium Phosphate

Scombrotoxin fish poisoning remains the primary cause of seafood poisoning outbreaks despite preventive guidelines. The purpose of this study was to investigate the use of pH for the control of growth and histamine formation by histamine‐producing bacteria in fish muscle. We examined pH effects on growth and histamine formation in tuna fish infusion broth and in inoculated tuna and mahi‐mahi fish muscle. Histamine production was significantly less for all bacterial strains at pH 8.5 compared to pH 5.5 in tuna fish infusion broth with no significant difference in growth. Elevated pH due to phosphate treatment of fish muscle tissues significantly reduced histamine formation with no effect on the growth of histamine‐producing bacteria. This study revealed that phosphate treatment of mahi‐mahi and tuna fish muscle resulted in significantly lower histamine production over 4 d of storage at 10 °C. Phosphate treatment of fish muscle may serve as a secondary barrier in addition to FDA recommended time and temperature controls for reducing public health concerns of scombrotoxin fish poisoning.     

Growth and histamine production by Morganella morganii under various temperature conditions

The generation times (G) for Morganella morganii were determined using absorbance measurements (at 0–10°C) or conductance measurements (at 15–25°C). Growth was rapid at 15–25°C (G = 2.6 at 15°C and G = 1.08 h at 25°C) but at the lower temperatures growth was greatly reduced. Growth and histamine production by M. morganii in histidine-containing broth (HDB) and in mackerel (packed in air-permeable plastic bags) was studied. It was found that large amounts of histamine are formed at low temperatures (0–5°C), where no growth takes place, following storage at higher temperatures (10–25°C). Measurements of conductance can be used to separate between samples with no or only insignificant content of histamine (< 50 ppm) which had detection times (DT) above 10 h and those with elevated content of histamine (> 50 ppm) which had shorter DT.     

Bacterial Growth and Histamine Production on Vacuum Packaged Tuna

Vacuum and nonvacuum packaged samples of tuna or tuna spiked with Klebsiella oxytoca T₂, Morganella morganii JM or Hafnia alvei T₈ were stored at 2°C and 10°C and examined for bacterial growth and histamine production on day 3, 6, 10 and 15. Unlike those stored at 2°C, tuna samples stored at 100°C showed significant bacterial growth over time and had high levels of histamine (>200 mg/100g tuna on day 15). Vacuum packaging did not show any beneficial effect in controlling bacterial growth and histamine production on tuna samples at these two temperatures. Low temperature storage was more effective than vacuum packaging in controlling histamine production by the bacteria tested.     

Optimum Postmortem Chilled Storage Temperature for Summer and Winter Acclimated, Rested, Chinook Salmon (Oncorhynchus tshawytscha) White Muscle

Chemical anaesthesia (AQUI‐S^TM) was used to harvest 2 groups of tank‐reared chinook salmon (Oncorhynchus tshawytscha), naturally acclimated to summer (18.8 °C) and winter (10.7 and 12.4 °C) temperatures, in a “rested”state. Carcasses were stored in 35% seawater at temperatures between approximately 2 and 19 °C to investigate the effects of acclimation and storage temperature on the postmortem metabolic rate of rested epaxial white muscle tissue. Muscle pH, [lactate], and adenosine triphosphate/inosine monophosphate measurements made 20 h postharvest indicated that winter acclimated fish were 2.2 times more sensitive to temperature than summer fish. A 3^rd group of winter acclimated fish, stored between –1.2 and 6 °C, indicated that significant cold injury only occurred on freezing.     

Histamine production by Enterobacter aerogenes in sailfish and milkfish at various storage temperatures

Enterobacter aerogenes was studied for its growth and ability to promote the formation of total volatile base nitrogen (TVBN) and histamine in sailfish (Istiophorus platypterus) and milkfish (Chanos chanos) stored at various temperatures from -20 to 37 degrees C. The optimal temperature for bacterial growth in both fish species was 25 degrees C, whereas the optimal temperature for histamine formation was 37 degrees C. The two fish species inoculated with E. aerogenes, when not properly stored at low temperatures such as 15 degrees C for 36 h, formed histamine at above the U.S. Food and Drug Administration hazardous guideline level of 50 mg/100 g. Milkfish was a better substrate than sailfish for histamine formation by bacterial histidine decarboxylation at elevated temperatures (> 15 degrees C). Although higher contents of TVBN were detected in the spiked sailfish than milkfish during the same storage time at temperatures above 15 degrees C, the use of the 30-mg/100 g level of TVBN as a determination index for fish quality and decomposition was not a good criterion for assessing potential histamine hazard for both fish species. Bacterial growth was controlled by cold storage of the fish at 4 degrees C or below, but histamine formation was stopped only by frozen storage. Once the frozen fish samples were thawed and stored at 25 degrees C, histamine started to accumulate rapidly and reached levels greater than the hazardous action level in 36 h.     

Chemical Changes and Visual Appearance of Albacore Tuna as Related to Frozen Storage

Fresh albacore tuna (Thunnus alalunga) were frozen and stored at –18°C and –25°C for 1 yr. Chemical and visual analyses were carried out at 1, 3, 6, 9 and 12 mo storage. Storage time correlated (P<0.05) with the low loss of moisture at –18°C, slight reduction of TVBN at –25°C and low increases of DMA, TMA, and TBARS at both temperatures. TMAO concentration (p=0.07), drip loss on cooking (p=0.52), peroxide value (p=0.059), FFA concentration (p=0.33) and pH (p=0.20)did not change significantly with period of storage but ?25°C resulted in a lower production of DMA and FFA than ?18°C. Results from chemical analyses correlated well with basic visual appearance.     

Formation of 4‐hydroxynonenal (4‐HNE) in frozen mackerel (Scomber scombrus) in the presence and absence of green tea

BACKGROUND: Aldehydes are secondary lipid oxidation products formed during processing and storage of food. 4‐Hydroxynonenal (4‐HNE) is a major toxic lipid peroxidation product which has been extensively investigated in the clinical field but less so in food products. The aim of the present study was to investigate the formation of aldehydes in stored frozen fish (Atlantic mackerel, Scomber scombrus) with and without antioxidant (green tea). RESULTS: The presence of 4‐HNE in frozen fish was detected for the first time. 4‐HNE was extracted from frozen fish and identified using high‐performance liquid chromatography and liquid chromatography/mass spectrometry. The amount of 4‐HNE increased throughout storage for 26 weeks at ? 10 °C in the absence of antioxidant. A significant decrease was observed in fish samples stored at ?10 °C with green tea. Minimal amounts of 4‐HNE were formed in fish stored at ?80 °C. A similar increase in 4‐HNE was found for methyl linoleate and extracted fish oil exposed to UV irradiation. CONCLUSION: The toxic aldehyde 4‐HNE can be formed in badly stored frozen mackerel and is an indicator of reduced texture quality and nutritional value of fish. Addition of instant whole green tea as an antioxidant can provide a cheap and effective way of enhancing safety, especially in developing countries. Copyright © 2008 Society of Chemical Industry     

Effects of Frozen Storage on Survival of Staphylococcus aureus and Enterotoxin Production in Precooked Tuna Meat

This study investigated the survival of Staphylococcus aureus in precooked tuna meat for producing canned products during frozen storage (?20 ± 2 °C) as well as its growth and enterotoxin production at 35 to 37 °C after the storage. Samples (50 ± 5 g) of precooked albacore (loin, chunk, and flake) and skipjack (chunk and flake) tuna were inoculated with 5 enterotoxin‐producing strains of S. aureus at a level of approximately 3.5 log CFU/g and individually packed in a vacuum bag after 3 h incubation at 35 to 37 °C. Vacuum‐packed samples were stored in a freezer (?20 ± 2 °C) for 4 wk. The frozen samples were then thawed in 37 °C circulating water for 2 h and incubated at 35 to 37 °C for 22 h. Populations of S. aureus in all precooked tuna samples decreased slightly (<0.7 log CFU/g) after 4 wk of storage at ?20 ± 2 °C, but increased rapidly once the samples were thawed and held at 35 to 37 °C. Total S. aureus counts in albacore and skipjack samples increased by greater than 3 log CFU/g after 6 and 8 h of exposure to 35 to 37 °C, respectively. All samples became spoiled after 10 h of exposure to 35 to 37 °C, while no enterotoxin was detected in any samples. However, enterotoxins were detected in albacore loin and other samples after 12 and 24 h of incubation at 35 to 37 °C, respectively. Frozen precooked tuna meat should be used for producing canned tuna within 6 to 8 h of thawing to avoid product spoilage and potential enterotoxin production by S. aureus in contaminated precooked tuna meat.     

Effect of lipid oxidation and frozen storage on muscle proteins of Atlantic mackerel (Scomber scombrus)

The effect of storage on the lipids and proteins in Atlantic mackerel stored for up to 24 months at ?20 and ?30 °C was studied. Traditional methods including the peroxide value, thiobarbituric acid‐reactive substances (TBARS) and a reverse phase HPLC method were used to determine the primary and secondary lipid oxidation products. All tests showed an increase in lipid oxidation products with storage time and at a higher storage temperature of ?20 °C compared with samples stored at ?30 °C. Antioxidants had a significant effect (P < 0.01) on the inhibition of lipid oxidation, as shown by the reduction in peroxide value and hydroxides, and malondialdehyde formation. Similarly, deterioration of protein structure and functionality in mackerel stored for 3, 6, 12 and 24 months was greater at ?20 than ?30 °C. ATPase activity in the myosin extract of Atlantic mackerel showed a significant decrease (P < 0.01) with progressive frozen storage. Protein solubility in high salt concentration (0.6 M NaCl) decreased (P < 0.01) during storage at both ?20 and ?30 °C but was greater at ?20 °C. Interestingly, antioxidants BHT, vitamin C and vitamin E protected the proteins against complete loss of ATPase activity and protein solubility to a significant level (P < 0.01) for up to 1 year at ?20 °C compared with samples stored without antioxidants. This study confirms the deleterious effect of lipid oxidation products on protein structure and function in frozen fatty fish. © 2002 Society of Chemical Industry     

Bacterial Histamine Production as a Function of Temperature and Time of Incubation

Optimal temperature, lower temperature limit, extent, and rate of histamine production in a tuna fish infusion broth (TFIB) varied for the strains of Proteus morganii, Klebsiella pneumoniae, Hafnia alvei, Citrobacter freundii, and Escherichia coli studied. P. morganii and K. pneumoniae produced large quantities of histamine in a relatively short incubation period (<24 hr) at 15°C, 30°C, and 37°C; production was fastest at 37°C. H. alvei, C. freundii, and E. coli produced toxicologically significant levels of histamine (>2500 nmoles/ml) only at 30°C and 37°C on prolonged incubation (≥48 hr). At 72 hr of incubation, optimal temperature for histamine production was 37°C for E. coli and C freundii; 30°C for P. morganii strain 110SC2, K. pneumoniae, and H. alvei; and 15°C for P. morganii strain JM. The lower temperature limits for production of toxicologically significant levels of histamine in TFIB were 7°C for K. pneumoniae; 15°C for both P. morganii strains; and 30°C for H. alvei, C. freundii, and E. coli.     

High-Resolution NMR and Magnetic Resonance Imaging (MRI) Studies on Fresh and Frozen Cod ( Gadus morhua) and Haddock (Melanogrammus aeglefinus)

Changes in the fish muscle from cod ( Gadus morhua ) and haddock ( Melanogrammus aeglefinus ) were investigated by high-resolution NMR and magnetic resonance imaging (MRI). Water- and salt-soluble extracts from fish stored at −20°C and −30°C were analysed by high-resolution proton NMR and enabled the identification of metabolites including trimethylamine oxide, trimethylamine (TMA) and dimethylamine. It was not possible to detect formaldehyde by NMR either in the stored fish samples or in spiked water or salt extracts even at high levels of formaldehyde addition, probably due to polymerisation. Systematic and controlled storage trials indicated the presence of dimethylamine at around 9 months for samples stored at −20°C, whereas no changes were detected at the control storage temperature of −30°C. A comparison of cod and haddock fillets stored for 1 year at −20 and −30°C confirmed the production of dimethylamine only in cod stored at −20°C. It was interesting to note that ‘fresh’ cod and haddock samples purchased from a local supermarket showed high levels of TMA indicating a breakdown of trimethylamine oxide to TMA by bacteria. TMA was not detected in the fish fillets especially obtained for the storage trials. MRI of fresh cod and fish stored at −8 and −30°C indicated that the fish half stored at −8°C exhibited dense lines or arches which are indicative of gaps in the tissue due to possible breakdown of the connective tissue. The images of fish stored at −30°C did not indicate any differences compared with the fresh fish. MRI also showed the presence of frozen and unfrozen areas in the fish non-destructively.     

Growth or Survival of Listeria monocytogenes in Ready-to-Eat Meat Products and Combination Deli Salads During Refrigerated Storage

Growth or survival of Listeria monocytogenes in cold‐smoked salmon; sliced, cooked ham; sliced, roasted turkey; shrimp salad; and coleslaw obtained at retail supermarkets stored at 5 °C, 7 °C, or 10 °C (41 °F, 45 °F, or 50 °F, respectively) for up to 14 d was evaluated. Cold‐smoked salmon, ham, and turkey were obtained in case‐ready, vacuum packages. All food products were stored aerobically to reflect additional handling within the retail supermarket. Cold‐smoked salmon, ham, and turkey supported the growth of L. monocytogenes at all 3 storage temperatures. Fitted growth curves of initial populations (about 3 log₁₀ colony‐forming units [CFU]/g) in cold‐smoked salmon, ham, and turkey stored at 5 °C achieved maximal growth rates of 0.29, 0.45, and 0.42 log₁₀ CFU/g growth per day, respectively. Storage at 10 °C increased the estimated maximal growth rate of the pathogen by 0.56 to 1.08 log₁₀ CFU/ g growth per day compared with storage at 5 °C. A decline in populations of L. monocytogenes was observed in shrimp salad and coleslaw, and the rate of decline was influenced by storage temperature. Retention of viability was higher in shrimp salad than in coleslaw, where populations fell 1.2, 1.8, and 2.5 log₁₀ CFU/g at 5 °C, 7 °C, and 10 °C, respectively, after 14 d of storage. Inability of shrimp salad and coleslaw to support the growth of L. monocytogenes may be attributed to the acidic pH (4.8 and 4.5, respectively) of the formulations used in this study. Results show that the behavior of L. monocytogenes in potentially hazardous ready‐to‐eat foods is dependent upon the composition of individual food products as well as storage temperature.     

Biogenic amine production by<Emphasis Type="Italic"> Morganella morganii</Emphasis> and<Emphasis Type="Italic"> Klebsiella oxytoca</Emphasis> in tuna

Biogenic amine formation in tuna inoculated with two micro-organisms reported as powerful in vitro histamine producers, Morganella morganii and Klebsiella oxytoca, was investigated. Inoculated and non-inoculated tuna samples were stored in ice, under refrigeration at 8–10 °C and at 20±1 °C. Ten biogenic amines were studied and changes were found only in cadaverine and histamine in inoculated samples. Therefore, the in vitro ability of K. oxytoca to form cadaverine and that of both microorganisms to form histamine was confirmed in inoculated samples. Storage temperature had a crucial effect on the amount and intensity of amine production. On the other hand, the potential ability of M. morganii to form putrescine was not shown in the inoculated samples, regardless of the storage temperature.     

Rheological and differential scanning calorimetry studies on structural and textural changes in frozen Atlantic mackerel (Scomber scombrus)

The viscoelastic behaviour and thermal stability of Atlantic mackerel fillets stored at ?20 and ?30 °C for up to 2 years were investigated. An increase in elastic (G′) and viscous (G″) modulus values, reflecting protein aggregation, was observed in samples stored at ?20 °C compared with those stored at ?30 °C, as well as with storage time. The results indicate that toughening on frozen storage is not just limited to lean gadoid fish but also occurs in fatty fish, leading to texture deterioration. Differential scanning calorimetry of fillets stored at ?20 °C showed a shift to a lower transition temperature (T_m) and a decrease in enthalpy (ΔH) compared with control fillets stored at ?30 °C; this change was enhanced when fillets were stored for a longer period of time, confirming protein denaturation and the formation of aggregates reported previously by the authors (J Sci Food Agric 82: 579–586 (2002)). The contribution of lipid oxidation to protein aggregation was shown by storing minced mackerel with or without the antioxidant vitamin E at ?10 °C. The G′ and G″ values were higher in samples stored without vitamin E than in samples stored with vitamin E; thus antioxidants may be used to minimise protein aggregation in fatty fish. The role of lipid oxidation in promoting protein aggregation and deterioration in the texture of fatty fish has not been reported hitherto. Antioxidants such as vitamin E may be used not only to prevent lipid oxidation but also to minimise protein damage in order to prolong the shelf‐life of fatty fish. Copyright © 2004 Society of Chemical Industry     

Temperature conditions for the frozen storage of representative marine products in Japan

Abstract

Four representative seafoods in Japan were examined for quality changes during frozen storage up to 1 year, and reasonable temperature conditions for their frozen storage were determined.

Tuna meat was stored at ‐20 ～ ‐80°C for 1 year and its quality changes were followed by using parameters such as the metmyoglobin to total myoglobin ratio, water‐holding capacity, and pH. Ikura, a salted product of salmon eggs, was stored frozen. Quality changes were followed by using the following parameters: toughness of the egg membrane, carotenoid content, and TBA value. Surimi, meat paste from Alaska pollack, was kept frozen, and the quality changes were followed by analyzing protein composition, SDS‐gel electrophoretic and ultracentrifugal patterns, and the gel strength of kamaboko processed therefrom. Finally, prawn was stored frozen. At selected time intervals, the meat was analyzed for changes in water‐holding capacity, pH, tyrosine content, protein composition, and SDS‐gel electrophoretic pattern.

From the present experiments, it was concluded that ‐20°C is low enough for frozen storage to keep the quality unchanged for 2–3 months, irrespective of the types of seafood tested. In frozen storage for 1 year, however, lower temperatures are needed to maintain the quality. Temperatures between ‐30 and ‐40°C seemed to be more reasonable from the viewpoint of energy saving.     

Gilthead seabream (Sparus aurata): suitability for freezing and commercial alternatives

The quality of portion‐size farmed gilthead seabream (Sparus aurata) during frozen storage and the influence of post‐mortem treatments were studied in order to find new ways of marketing this species. Portion‐sized gilthead seabream, fasted for 48 h prior to slaughter, were frozen and stored at ?20 °C for up to one year. Whole fish were frozen immediately after rigor mortis; gutted fish were frozen immediately after rigor and after 5 days of storage in ice. All lots were stored at ?20 °C for up to one year. The myofibrillar protein of this species was very stable and a slight decrease of solubility in salt solutions was found only after one year of frozen storage. A slight decrease in water‐holding capacity and a slight increase in shear strength were observed, but these were lower than in other species. These changes were reflected as increased toughness and reduced juiciness in sensory analysis of the cooked fillets after one year. The main changes in the cooked fillets were observed in odour and flavour. No significant detrimental effect due to the guts was detected during frozen storage. Storage in ice prior to freezing was reflected in sensory assessment of the raw fish, mainly in terms of initial higher demerit points for fishy odour, gills and eyes; however, no effect was observed in the cooked fillets. Copyright © 2004 Society of Chemical Industry     

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.     

Deterioration of European hake (Merluccius merluccius) during frozen storage

European hake (Merluccius merluccius (L)) was frozen as whole fish and as fillets and stored at ?18°C, ?24°C and ?30°C for up to 39 weeks. Sensory properties, peroxide value and thiobarbituric acid value, lipid fatty acid composition, adenosine nucleotide degradation products, dimethylamine and formaldehyde were measured at intervals during storage. Changes at ?30°C were negligible, otherwise fillets deteriorated faster than whole fish. Hedonic rating gave a storage life of around 9 months for whole fish stored at ?18°C.