EFFECT OF SLAUGHTER METHOD ON DEGRADATION OF INTRAMUSCULAR TYPE V COLLAGEN DURING SHORT-TERM CHILLED STORAGE OF CHUB MACKEREL SCOMBER JAPONICUS

The present paper demonstrates that a nonstntggling slaughter method can delay degradation of type V collagen in meat of chub mackerel Scomber japonicus and softening of the meat during postharvest chilled storage. The fish were slaughtered by piercing a knife into nape (nonstruggling method) or by leaving on ground (struggling method) and then stored in an ice box. Sensory study revealed that the postharvest softening of the meat was moderated at 4 and 8 h by the non‐struggling slaughter method in comparison with the struggling method. On the basis of the specific solubilization of type V collagen and reduced tyrosine content in it, a cleavage of the nonhelical regions (telopeptides) of the type V collagen occurred during the chilled storage in the fish slaughtered by the struggling method. The degradation of type V collagen was also slower in the meat of the fish slaughtered by the nonstruggling method, which can be directly linked to the moderation of the postharvest softening.     

Effect of brine freezing on the rancidity development during the frozen storage of small pelagic fish species

Brine freezing was applied to two small pelagic underutilised fish species (mackerel, Scomber scombrus; horse mackerel Trachurus trachurus). Rancidity development was studied during their frozen (–18 °C) storage up to 9 months, and quality change results were compared to common freezing conditions (control treatment). Fish samples treated under brine freezing conditions showed a higher lipid oxidation development (peroxide value and thiobarbituric acid index) and worse marks on some sensory attributes (general aspect, odour and colour) than control fish. However, samples treated under brine freezing conditions provided a lower lipid hydrolysis development (free fatty acid formation) and better scores for consistency. Comparison between both fish species led to a higher secondary lipid oxidation formation (thiobarbituric acid index) for mackerel, while horse mackerel showed to be more prone to interaction compound formation (fluorescence detection); however, both fish species showed the same shelf-life times (3 and 5 months for brine and control freezing conditions, respectively). As a result of the brine freezing conditions, an increase in NaCl content in white muscle of both species was observed. According to the results obtained in the present work, the brine freezing treatment is not recommended for these two small pelagic fish species.     

Biochemical Characterization of Collagen in Myocommata and Endomysium Fractions of Carp and Spotted Mackerel Muscle

Myocommata and endomysium fractions were prepared from the different parts of body muscle of carp and spotted mackerel. Both type I and V collagens were detected in the myocommata and endomysium fractions of both fish. The relative concentration of type V collagen to type I collagen was higher in the endomysium fraction than in the myocommata fraction. Both type I and V collagens were less soluble in the endomysium fraction than in the myocommata fraction. These results indicated that the biochemical property of the collagen in the pericellular connective tissue was different from that of the collagen in the interstitial connective tissue of fish.     

Relationship between total mercury concentration and fish size in two pelagic fish species: implications for consumer health

Total mercury concentrations were determined in different size classes of two pelagic fish species of great commercial importance, horse mackerel (Trachurus trachurus) and Mediterranean horse mackerel (Trachurus mediterraneus), to evaluate the relationship between total mercury concentration and fish size and to determine whether any differences might affect the quantitative assessment of mercury exposure for consumers. Mercury concentrations in horse mackerel and in Mediterranean horse mackerel were between 0.16 and 2.41 microg g(-1) of weight wet (mean, 0.68 microg g(-1)) and between 0.09 and 1.62 microg g(-1) (mean, 0.51 microg g(-1)), respectively. The regression curves revealed a significant relationship between mercury concentration and fish size (length and weight) for both species. Concentrations exceeding the proposed limit for human consumption were observed in 33.3% of the samples of both species and were associated with larger specimens. The consumption of the larger specimens could lead to an increase in mercury exposure for consumers. Estimated weekly intakes, calculated on the basis of concentrations relative to each size class, revealed a high exposure associated with the consumption of fish larger than 30 cm (horse mackerel, 11.63 to 20.16 microg/kg of body weight; Mediterranean horse mackerel, 5.86 to 13.55 microg/kg of body weight). An understanding of the factors leading to an increase in mercury exposure can help consumers make informed decisions about eating fish.     

New extraction method suitable for immunoblotting analysis of fish allergens

Immunoblotting is a simple method to analyze allergens in biological samples. In previous immunoblotting studies on fish allergens, however, collagen, an important allergen next to parvalbumin (major fish allergen), has not been detected in fish muscle extracts probably due to its unique chemical properties. This study was aimed to develop an extraction method suitable for immunoblotting analysis of fish allergens including collagen as well as parvalbumin. When various extracts from the Japanese eel white muscle were analyzed by SDS–PAGE, heating of the muscle homogenate at 80 °C for 20 min was found to be the most effective method to extract collagen as well as parvalbumin. The same extraction method was also effective for the other five species of fish analyzed (rainbow trout, Japanese horse mackerel, crimson sea bream, Pacific mackerel, and Japanese flounder). Furthermore, parvalbumin and/or collagen were successfully identified as allergens in the six species of fish by immunoblotting using the heated extracts prepared by the method described above. It can be concluded that the extraction method (heating of the muscle homogenate at 80 °C for 20 min) developed in this study is useful not only for analyzing fish allergens by immunoblotting but also for preparing antigens for diagnosis of fish allergy by RAST (radioallergosorbent test).     

Glutathione Peroxidase Activity During Storage of Fish Muscle

Activity of fish muscle glutathione peroxidase, which presumably protects muscle from oxidative deterioration during storage and processing, was found in both Japanese jack mackerel and skipjack tuna. Activity of the peroxidase and level of reduced glutathione (enzyme substrate) decreased during 5 days storage at 4°C. Lipid hydroperoxides were substantially formed in the fish muscles during the storage.     

New processing technology of small pelagic fish protein

Abstract

Small pelagic fishes, such as sardine and mackerel, generally rich in lipid, have a large amount of superficial dark muscle. The proportion of dark to ordinary muscle is 20–30%. Since the dark muscle is red‐colored due to high myoglobin content and different in protein properties from the ordinary muscle, there have been many difficulties in the efficient utilization of small pelagic fish proteins as food resources.

Effective processing of frozen surimi from small pelagic fishes is as follows: 1) washing of meat with NaHCO₃ solution to remove fat, 2) mechanical removal of dark muscle to make use of only ordinary muscle. However, it is impossible to make surimi from small pelagic fishes that are not fresh, even if the effective processing technique is applied. Frozen minced fish block can be made from sardine and mackerel meats to employ the washing technique and mixing of suitable additives. Recently, fish protein concentrate (Marinbeef) from small pelagic fishes has been developed. It can be rehydrated easily and cooked to acceptable foods. In the processing of Marinbeef, a wider margin of freshness of material fish can be allowed.     

Effect of bleeding treatment and perfusion of yellowtail on lipid oxidation in post-mortem muscle

The present study investigated the effects of bleeding treatment and perfusion of antioxidant compounds on lipid oxidation in ordinary and dark muscles of yellowtail in the early stage of ice storage. The lipid hydroperoxide contents of dark muscles obtained from yellowtails with and without bleeding treatment were higher and increased more rapidly than those of ordinary muscles. There were no significant differences in the rates of change of the lipid hydroperoxide content (up to 48 h), fatty acid composition and metmyoglobin formation between dark muscles with and without bleeding treatment. Physiological saline containing ascorbic acid or 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox^®) was perfused into live yellowtail or added to minced dark muscle. Trolox^® significantly (P < 0.01) delayed the accumulation of lipid hydroperoxide in dark muscle compared to ascorbic acid in perfusion experiment. These results indicate that simply removing a portion of the blood from live yellowtail by bleeding is not sufficient to prevent lipid oxidation in the early stage of ice storage. Contrary to this, addition of antioxidants into fish flesh is effective to delay lipid oxidation in post-mortem muscle.     

Change of volatile compounds in fresh fish meat during ice storage

Abstract: The change of volatile compounds in fresh fish meat during 3‐ to 4‐d ice storage was investigated for several fishes using an electronic nose system and a gas chromatography‐mass spectrometer (GC/MS) with headspace solid‐phase micro‐extraction (SPME). Principal component analyses for samples using the electronic nose system revealed that the increase of some volatile compounds during storage was rapid in sardine (Sardinops melanostictus), jack mackerel (Trachurus japonicus), and chub mackerel (Scomber japonicus); moderate in yellowtail (Seriola quinqueradiata), skipjack (Katsuwonus pelamis), and young oriental bluefin tuna (Thunnus thynnus). In contrast to these fishes, the change was little in “white meat” fishes such as red seabream (Chrysophrys major), Japanese seabass (Lateolabrax japonicus), flatfish (Paralichthys olivaceus), puffer (Lagocephalus wheeleri), and bartail flathead (Platycephalus indicus). SPME‐GC/MS analysis showed that some aldehydes and alcohols such as 1‐heptanol, (E)‐2‐octenal, (E)‐2‐hexenal, 1‐pentanol, (E,E)‐2,4‐heptadienal,2,4‐hexadienal, 1‐hexanol, 4‐heptenal, and so forth increased rapidly in jack mackerel and chub mackerel, slowly in skipjack, and a little in red seabream and puffer during the storage. The increase of these compounds was considered to have an effect on the change of electronic nose response. Hexanal was a dominant compound increased from the beginning of the storage in jack mackerel. The increase of volatile compounds was little in red seabream and puffer. The increase of these aldehydes and alcohols was thought to be an appropriate marker for monitoring the freshness of “fresh” fish except for white meat fish. Practical Application: The results of this study are ready to apply for preventing fishy off‐flavor of fisheries products. Lipid oxidative derivatives other than trimethylamine contributed to fresh fish flavor; therefore, to prevent lipid oxidation seemed important.     

Effect of blood deposition phenomenon on flesh quality of yellowtail (Seriola quinqueradiata) during storage

We examined the influence of blood deposition on flesh quality of ordinary muscle in yellowtail. This study compared the flesh quality changes in upper and under‐sides of yellowtails killed by two different methods: spinal‐cord destruction (SCD) with blood removal and suffocation in air without blood removal (SA). The under‐sides of the SA group showed the highest values for a*, cathepsin B and B + L activities, the lowest value in breaking strength and the greatest degradation of myosin heavy chain (MHC) among the four groups. However, the values of the SCD‐upper group indicated the best flesh quality. In addition, the white blood cells presented the highest cathepsin B and B + L activities among the blood components. These results indicate that blood has the tendency to deposit downward in accordance with the direction of placement. This phenomenon influences the distribution of white blood cells which contain enzymes that accelerate the deterioration of flesh quality. The texture of fish muscle is an important part of the flesh quality. In captured fishery (purse‐seine fishery and dragnet fishery), it is impossible to immediately and completely remove blood. Therefore, suffocation in air is the common method after the fish is caught. The commercial value of fish is decreased and the price varies greatly when these fish enter market circulation. In our study, we examined the influence of blood deposition on the flesh quality of yellowtail during storage. The degradation of structural proteins accelerated in the deposited blood which contain proteases. The movement and deposition of blood caused the difference of quality on both sides, which seriously affected the quality of fish during preservation. Our study has some theoretical guidance for muscle softening and give a better understanding of the adverse effect of blood during preservation.     

鲈鱼在4℃冷藏过程中的肌肉品质变化

目的：探究4℃冷藏过程中鲈鱼肌肉品质的变化。方法：测定4℃冷藏过程中鲈鱼肌肉pH值、菌落总数、总挥发性盐基氮（total volatile base nitrogen,TVB-N）含量、K值和质构等指标,综合评价鲈鱼生理生化品质的变化,采用Masson染色和免疫组化分析评价组织形态学变化,利用酶解荧光肽底物测定特异性酶解胶原蛋白的基质金属蛋白酶（matrix metalloproteinases,MMPs）活力变化。结果：鲈鱼在贮藏期间pH值呈先下降后升高趋势,菌落总数、TVB-N含量和K值随贮藏时间的延长而增加,并在第8天超过临界值。十二烷基硫酸钠-聚丙烯酰胺凝胶电泳分析结果显示,贮藏至6 d鲈鱼肌肉蛋白组成没有明显变化,而在第8天肌球蛋白重链降解明显。Masson染色和I型胶原免疫组化分析结果显示,随贮藏时间的延长,肌内膜逐渐被降解,至第12天,肌膜I型胶原蛋白和肌纤维之间出现明显间隙。MMPs活力随贮藏时间的延长而明显增加,而鱼肉硬度不断下降。结论：鱼类冷藏期间肌肉的软化与胶原蛋白分解密切相关,而MMPs对I型胶原蛋白的降解可能是鱼死后肌肉软化的主要原因。     

Essential elements and contaminants in tissues of commercial pelagic fish from the Eastern Mediterranean Sea

BACKGROUND: It is important to determine the concentrations of essential and non‐essential metals in fish for human health. The essential elements and contaminants (Pb and Cd) were determined seasonally in the muscle and liver of some pelagic fish species round herring (Etrumeus teres), chub mackerel (Scomber japonicus), golden grey mullet (Liza aurata) and Mediterranean horse mackerel (Trachurus mediterraneus) from the Iskenderun Bay, Eastern Mediterranean Sea. RESULTS: The Na, K, Ca and Mg were the most abundant elements in muscle and liver tissues. The Na, K, Ca and Mg concentrations in fish tissues were between 51.7 and 3426 mg kg^?1. Muscle accumulated the lowest levels of elements. Trace element and contaminant levels in muscle were highest in spring and summer. The Cu, Zn and Cr concentrations were highest in summer. The Ni, Mn and Fe concentrations were highest in spring. The maximum Pb concentrations in the muscle and liver of fish species was 0.39 and 0.80 mg kg^?1 in autumn. The maximum Cd concentration in the muscle of fish was 0.27 mg kg^?1 in spring and the maximum Cd concentration in the liver was 0.78 mg kg^?1 in summer. CONCLUSION: The Cr, Pb, Cd, Cu and Zn levels in muscle were found to be lower than permissible limits reported by various authorities. Estimated weekly and daily intake for Pb and Cd by consumption of fish muscle were far below the PTWI and PTDI values established by FAO/WHO. Copyright © 2009 Society of Chemical Industry     

Total mercury levels in commercial fish species from Italian fishery and aquaculture

ABSTRACT

Total mercury levels were measured in 42 commercial fish species caught off the Central Adriatic and Tyrrhenian coasts of Italy and in 6 aquaculture species. The study on wild fish covered species differing in living habitat and trophic level. The study on farmed fish covered marine and freshwater species from intensive and extensive aquaculture and their feed. Mercury levels were analysed by thermal decomposition–amalgamation–atomic absorption spectrophotometry. Total mercury concentrations in the muscle of wild fish showed a high variability among species (0.025–2.20 mg kg^?1 wet weight). The lowest levels were detected in low trophic-level demersal and pelagic–neritic fish and in young individuals of high trophic-level species. Levels exceeding the European Commission limits were found in large-size specimens of high trophic-level pelagic and demersal species. Fish from intensive farming showed low levels of total mercury (0.008–0.251 mg kg^?1). Fish from extensive rearing showed variable contamination levels, depending on the area of provenience. An estimation of the human intake of mercury associated to the consumption of the studied fish and its comparison with the tolerable weekly intake is provided.     

DEGRADATION OF PROTEOGLYCANS IN THE SKELETAL MUSCLE OF PACIFIC ROCKFISH (SEBASTES SP.) DURING ICE STORAGE

Soluble collagen, proteoglycans and two lysosomal enzymes known to degrade proteoglycans were studied during ice storage of skeletal muscle from Pacific rockfish. The solubility of muscle collagen progressively increased during storage in ice for 7 days. Proteoglycans isolated from prerigor muscle by extraction with guanidine HCl and density gradient ultracentrifugation contained only 43 μg hexuronic acid/100 g of wet tissue. The sulfated glycosaminoglycans portion of proteoglycans were isolated by trypsin digestion of an extract from muscle acetone powder and contained 58 μg hexuronic acid/20 g of acetone-dried muscle tissue. Sulfated glycosaminoglycans had several components which separated by sodium dodecylsulfate polyacrylamide gel electrophoresis. Electrophoresis of sulfated glycosaminoglycans from stored rockfish revealed disappearance/decrease of specific zones after 5 days at 0C. The degradation of proteoglycans occurs in postmortem fish muscle and this may contribute to the destabilization of the extracellular matrix and texture softening during postharvest storage of fish.     

Organochlorine pesticide residues in European sardine, horse mackerel and Atlantic mackerel from Portugal.

This paper reports the results for the surveillance of nine organochlorine pesticides (HCH isomers (alpha, beta, e, gamma), p,p'-DDD, p,p'-DDT, p,p'-DDE, p,p'-DDD, HCB and aldrin) in muscle of three fish species, European pilchard (Sardina pilchardus), Atlantic horse mackerel (Trachurus trachurus) and Atlantic mackerel (Scomber scombrus). Analytical methodology included n-hexane extraction, clean-up with 2% deactivated Florisil, and quantification with gas chromatography-electron capture detection (GC-ECD). The highest mean concentrations were found for p,p'-DDT in sardine and mackerel at levels of 30.1 and 109.9 microg kg(-1), respectively, and for p,p'-DDD in horse mackerel at 51.9 microg kg(-1). Three species had higher levels for S-DDT than S-HCH. The estimated daily intake of organochlorine pesticides in the three species showed that in sardine, the highest EDIs were found for aldrin, at 1.8 ng kg(-1) bw day(-1), which represents 1.8% of the acceptable daily intake (ADI), and for ss-HCH, at 4.0 ng kg(-1) bw day(-1), representing 0.4% of ADI. Lowest values were found for Atlantic mackerel. Statistical analysis to determine the differences in mean concentrations of pesticides between species, and any correlation between groups of residues related with each one of the species, was undertaken.     

Storage of New Zealand Jack Mackerel (Trachurus novaezelandiae) In Ice: Chemical, Microbiological and Sensory Assessment

Physical, sensory, microbiological and chemical analyses were carried out on jack mackerel during 23 days of storage in ice. Sensory results indicate that jack mackerel used in this trial had a shelf-life of 7 days. Aerobic plate counts never exceeded 10⁶/g flesh during the first 11 days. The K value reached 20% after 7 days. Trimethylamine, total volatile base, pH and thiobarbituric acid analyses were not good indicators of changes in quality during the shelf-life. Proximate analyses were carried out on representative samples of the fish.     

Identification and Characterization of Molecular Species of Collagen in Fish Skin

ABSTRACT: Pepsin-solubilized collagen (PSC) prepared from the skin of 3 fish species—common horse mackerel, yellow sea bream, and tiger puffer—were separated into 2 fractions, major and minor, by ammonium sulfate precipitation. These collagen fractions were further purified by phosphocellulose column chromatography. From the results of SDS-PAGE, peptide mapping, and amino-acid analysis, the purified major and minor collagens were identified to be type I and V collagens, respectively. These results suggest that type V collagen might be widely present in fish skin as a minor collagen.     

Mercury content in Chilean fish and estimated intake levels.

The intake of fish products is a major public health concern due to possible methyl mercury exposure, which is especially toxic to the human nervous system. This pilot study (n = 46) was designed to determine mercury concentrations in fish products for national consumption (Chilean jack mackerel, hake, Chilean mussel, tuna) and for export (salmon, Patagonian toothfish, swordfish, southern hake), and to estimate the exposure of the general population. The fish products were collected from markets in Talcahuano, Puerto Montt and Santiago. Samples were analyzed at the National Environmental Center by cold vapor atomic absorption spectrophotometry. Mercury levels in swordfish and one canned tuna sample exceeded levels prescribed by national and international standards. The remaining two export products (Patagonian toothfish, also known as Chilean sea bass, and salmon) complied with international limits, which are more demanding than Chilean regulations. Theoretical estimates of mercury intake varied from 0.08 to 3.8 microg kg(-1) bw day(-1) for high fish consumers, exceeding the provisional tolerable intake for tuna, Chilean seabass, Chilean jack mackerel and swordfish. This group appears to be at the greatest risk from mercury contamination among the Chilean population.     

IDENTIFICATION OF TWO MATRIX METALLOPROTEINASES IN THE SKELETAL MUSCLE OF PACIFIC ROCKFISH (SEBASTES SP.)

Two heat-stable metalloproteinases with collagenase activity have been identified in the skeletal muscle of Pacific rockfish (Sebastes sp.) and partially characterized. The 47 kDa and 95 kDa enzymes appear to be similar to mammalian matrix metalloproteinases (MMPs), with respect to molecular weight, pH-activity profile, substrate specificity, dependence on calcium for activity, and inhibition-activation profiles. The fish metalloproteinases readily hydrolyzed collagen and gelatin, but not β- or K-casein, in SDS-PAGE substrate zymograms. They also hydrolyzed collagen and gelatin in solution, but showed very low activity in solubilizing native fibrillar collagen. They did not hydrolyze solutions of β- or K-casein, azocasein, hide powder azure or synthetic substrates for trypsin, chymotrypsin or collagenase. To our knowledge, this is the first report where fish muscle proteinases have been identified as possible members of the family of MMPs. The rockfish muscle MMPs appear to be different from other currently identified fish muscle proteinases in regard to molecular weight, substrate specificity and activation-inhibition profiles. These two enzymes could be partly responsible for the degradation of collagen and other extracellular matrix proteins in fish muscle and for the texture softening of seafood products.     

BACTERIAL FORMATION OF HISTAMINE IN JACK MACKEREL (TRACHURUS SYMMETRICUS)

Peak histamine concentrations of 0.023, 0.031 and 0.027 g histamine/100 g muscle and maximal bacteria concentrations of 1.75, 1.59 and 0.423 g dry cells/100 g muscle were observed in muscles of jack mackerel stored at 25, 15 and 5C, respectively. Incubated fish homogenates suggest rate and transport limitations in histamine formation in muscle. The Mulchandani model predicted bacterial growth in muscle. The Luedeking and Piret expression fitted histamine formation in muscle; α values were 3.0 × 10⁻³, 1.23 × 10⁻² and 4.17 × 10⁻² g histamine/g dry cells, while β-values were 4.5 × 104, 8.0 × 10⁻⁵ and 0 g histamine/g dry cells × h at 25, 15, and 5C, respectively. The model predicts that jack mackerel could be stored from 4.5 to 5.5 days in ice, from 1 to 2 days at 15C and from 17 h to 2 days at 25C before fishmeal quality might be affected.