Decomposition of trimethylamine oxide during iced storage of blue whiting (Micromesistius poutassou)

Products of the decomposition of trimethylamine N-oxide (TMAO) during iced storage of blue whiting were monitored over 15?days. Increasing amounts of trimethylamine (TMA) and dimethylamine (DMA) were found in the white muscle with increasing storage time. The production of TMA was interpreted as a consequence of bacterial growth, while DMA production was due to enzymatic activity of trimethylamine N-oxide demethylase (TMAOase). TMAOase activity was monitored with time in different organs. The highest activities always corresponded to kidney and spleen. Also, TMAOase was found to remain active during the 15 days of iced storage. A relationship was found between TMAOase in kidney and DMA concentrations in white muscle.     

Decomposition of trimethylamine oxide during iced storage of blue whiting (Micromesistius poutassou)

 Products of the decomposition of trimethylamine N-oxide (TMAO) during iced storage of blue whiting were monitored over 15 days. Increasing amounts of trimethylamine (TMA) and dimethylamine (DMA) were found in the white muscle with increasing storage time. The production of TMA was interpreted as a consequence of bacterial growth, while DMA production was due to enzymatic activity of trimethylamine N-oxide demethylase (TMAOase). TMAOase activity was monitored with time in different organs. The highest activities always corresponded to kidney and spleen. Also, TMAOase was found to remain active during the 15 days of iced storage. A relationship was found between TMAOase in kidney and DMA concentrations in white muscle.     

Partial purification and biochemical characterization of TMAOase from kidney of European hake (<Emphasis Type="Italic">Merluccius merluccius</Emphasis>)

The trimethylamine N-oxide aldolase (TMAOase) activity from kidney of European hake (Merluccius merluccius) was characterized by using chromatographic and electrophoretic techniques. Soluble TMAOase was obtained using a differential centrifugation protocol with CHAPS and NaCl buffer. Two TMAOase fractions were isolated by ion exchange chromatography using a FPLC system. For this purpose the weak anion exchanger ANX Sepharose 4 Fast Flow (high sub), suited for high molecular mass proteins, was employed. After anion exchange chromatography, fractions were separated by native electrophoresis. One of the fractions eluted at 0.45 M sodium chloride concentration, and had a charge/mass ratio in electrophoresis similar to bovine serum albumin, with a molecular weight of approximately 100 kDa. The second fraction eluted at 0.7 M sodium chloride concentration, and presented a very low electrophoretic mobility due to either a low charge/mass ratio or due to the presence of protein aggregates of different sizes of between 440 and 2,000 kDa. Proteins present in both TMAOase fractions showed acid isoelectric points of between 4.55 and 5.85.     

Relevance of trimethylamine oxide demethylase activity and haemoglobin content to formaldehyde production and texture deterioration in frozen stored minced fish muscle

Minces were prepared from white muscle or fillets of gadoid and non-gadoid fish species. After the addition of blood, kidney or formaldehyde the minces were stored frozen for 6 months at ?8 and ?30°C. Blood and kidney of the gadoid species contained trimethylamine oxide demethylase (TMAOase), whereas in the tissues of the other species no activity of this enzyme could be detected. The formation of dimethylamine (and formaldehyde) was correlated with the TMAOase activity of the added tissues. The concentration of haemoglobin in the minces had no influence on the dimethylamine and formaldehyde production during frozen storage. The formaldehyde production was accompanied by an increase in the firmness of the texture as measured by mechanical and sensory tests.     

不同贮藏温度下阿根廷鱿鱼内源性甲醛及相关物质的变化规律

探究不同贮藏温度下阿根廷鱿鱼内源性甲醛及相关物质的变化规律,研究了4 ℃、0 ℃、-20 ℃贮藏条件下鱿鱼体内甲醛(FA)、二甲胺(DMA)、三甲胺(TMA)、氧化三甲胺(TMAO)、氧化三甲胺脱甲基酶活性(TMAOase)、肌原纤维蛋白溶解度、菌落总数的变化。结果表明,随着贮藏时间的延长,鱿鱼体内FA、DMA、TMA和菌落总数呈现上升趋势;TMAO和蛋白溶解度呈现下降趋势;在4 ℃和0 ℃下TMAOase活性呈先上升后平缓的趋势,-20 ℃下TMAOase活性呈先上升后略微降低的趋势;各温度下的甲醛含量和氧化三甲胺脱甲基酶(TMAOase)酶活之间具有显著相关性(r4 ℃=0.791,r0 ℃=0.863,r-20℃=0.825)。本研究为不同贮藏条件下甲醛的控制提供了理论基础。     

乳酸菌半连续发酵虾头虾壳过程中甲醛的生成规律研究

本文以嗜酸乳杆菌半连续发酵虾头、虾壳回收蛋白质和甲壳素。对半连续发酵过程中氧化三甲胺酶(TMAOase)酶活、甲醛含量以及pH值的变化进行监测,初步探索了发酵过程中甲醛的生成规律。研究结果表明,在发酵过程中,当发酵液pH值为4.5-5.0时,TMAOase活性最高,半连续发酵五个批次的甲醛含量的变化趋势与TMAOase活性变化相一致,说明TMAOase活性是造成甲醛含量增高的重要原因,其中发酵至第五批时甲醛含量最高达30.79 mg/kg。     

Effect of some additives on the inhibition of lizardfish trimethylamine-N-oxide demethylase and frozen storage stability of minced flesh

Effects of some additives on the inhibition of trimethylamine‐N‐oxide demethylase (TMAOase) from lizardfish (Saurida tumbil) muscle were investigated. Sodium citrate and pyrophosphate could inhibit TMAOase activity in a concentration‐dependent manner, most likely because of their chelating property. Sodium alginate was the hydrocolloid possessing the inhibitory activity towards TMAOase (P < 0.05). During the storage of lizardfish mince at ?20 °C for 24 weeks, the addition of 0.5% sodium alginate and 0.3% pyrophosphate in combination with 4% sucrose and 4% sorbitol as the cryoprotectants resulted in the retarded increase in TMAOase activities with the coincidental lowered formation of dimethylamine and formaldehyde (FA), compared with the control (without additives) (P < 0.05). The loss in solubility of muscle proteins was also impeded with the addition of those compounds, suggesting their role in the inhibition of TMAOase as well as the retardation of protein denaturation induced by FA.     

Influence of Gonadal Stage of Hake (Merluccius Hubbsi Marini) on Biochemical Properties of Myofibrils Stored at 2 to 4 °C

ABSTRACT: The influence of the gonadal stage of hake on the biochemical properties of myofibrils stored at 2 to 4 °C was studied. At 0 time and during storage, both Mg²⁺-Ca²⁺-ATPase activity and Ca²⁺ sensitivity of myofibrils from post-spawned hake were significantly higher (p < 0.01) than those of pre-spawned fish. The profiles of SDS-PAGE gels of unstored and stored myofibrils from pre-spawned hake showed a partially denatured myosin heavy chain. The actin-myosin ratio in myofibrils from pre-spawned hake was significantly lower (p < 0.01) than the ratio in post-spawned hake. Irrespective of the gonadal condition of fish, no changes in the myosin-actin ratio of stored myofibrils were observed.     

Effect of trimethylamine-<Emphasis Type="Italic">N</Emphasis>-oxide demethylase from lizardfish kidney on biochemical changes of haddock natural actomyosin stored at 4 and −10 °C

The addition of partially purified trimethylamine-N-oxide demethylase (TMAOase) from lizardfish kidney to haddock natural actomyosin (NAM) in the presence of cofactors (FeCl₂, ascorbate, and cysteine) accelerated formaldehyde (FA) formation throughout the storage either at 4 or −10 °C (p < 0.05). ¹H NMR spectroscopic study revealed that the formation of dimethylamine was enhanced with a concomitant decrease in trimethylamine oxide (TMAO) content when TMAOase was added, particularly at higher concentration. The loss of protein solubility increased as the result of FA formation, which was associated with the increased denaturation/aggregation of proteins. Lipid oxidation determined as hexanal content occurred during extended storage at different degrees. Generally, simulated systems without TMAOase and TMAO contained the highest hexanal content. Differential scanning calorimetry of NAM after storage at 4 and −10 °C for 15 days and for 8 weeks, respectively, showed the lower T _m and enthalpy of endothermic peaks corresponding to myosin and actin, suggesting the conformational changes induced by FA formed. Therefore, TMAOase exhibited the detrimental impact on haddock NAM, mainly caused by FA formation.     

氧化三甲胺酶研究进展

氧化三甲胺酶(trimethylamine-N-oxidedemethylase,TMAOase)是许多海洋鱼类体内存在的产生甲醛的重要的酶,与水产品甲醛的本底含量和鱼肉的腐败变质密切相关。本文对TMAOase的分布、活性测定、分离纯化以及酶学特性等方面研究进行了较为全面的综述。     

PHYSICOCHEMICAL AND BIOCHEMICAL CHANGES IN WHOLE LIZARDFISH (SAURIDA MICROPECTORALIS) MUSCLES AND FILLETS DURING FROZEN STORAGE

The physicochemical and biochemical changes in whole lizardfish (Saurida micropectoralis) muscles and its fillets kept in air and under vacuum during frozen storage at ?20C for 24 weeks were investigated. The formaldehyde (FA) and dimethylamine contents increased with a concomitant decrease in trimethylamine‐ N‐oxide (TMAO) content as the storage time increased (P < 0.05). The Ca²⁺–adenosine 5′‐triphosphatase activity continuously decreased with a coincidental decrease in salt‐soluble fraction. The disulfide bonds were increasingly formed throughout the storage (P < 0.05). The surface hydrophobicity increased and reached the maximum at week 12 with a subsequent decrease up to the end of storage. In general, the higher changes were observed in samples kept under vacuum than those kept in air. With the same atmosphere used, the whole fish showed slightly higher changes than the fillets. A marked increase in TMAO demethylase (TMAOase) activities was observed up to 12 weeks, followed by the continuous decrease up to 24 weeks of storage. The produced FA might play an important role in inducing protein denaturation and/or aggregation in lizardfish. The TMAOase activity as well as the FA formation could be reduced to some extent with the removal of internal organs and storage in the presence of oxygen. However, a detrimental effect of oxygen, especially on the promotion of lipid oxidation, would be an obstacle.     

Effects of previous frozen storage on chemical, microbiological and sensory changes during chilled storage of Mediterranean hake (Merluccius merluccius) after thawing

The present work aimed to investigate the influence of freezing (−20 °C for 6 months) on the susceptibility of hake to chemical, microbiological and sensory spoilage once thawed and stored in ice. Thus, volatile and biogenic amines, counts of psychrotrophic and mesophilic bacteria, enterobacteria, pseudomonads and Shewanella together with sensory evaluation (of raw and cooked samples) were monitored during 14 days of iced storage in both fresh and frozen-thawed hake (Merluccius merluccius). At the beginning of ice storage, freshness parameters were equivalent in both batches (fresh and frozen-thawed hake), but different behaviour was observed during the iced storage. Overall, levels of volatile and biogenic amines increased much later and then decreased to lower values in frozen-thawed hake in accordance with the delay of microbial development in comparison with fresh hake. On the contrary, sensory spoilage occurred earlier in frozen-thawed hake. Therefore, the usual accepted or regulated limits of acceptability of chemical and microbiological parameters would not be suitable for freshness assessment of frozen-thawed hake.     

Biochemical and Physicochemical Properties of Actomyosin from Pre- and Post-spawned Hake (Merluccius hubbsi) Stored on Ice

Biochemical and physicochemical properties of natural actomyosin (NAM) from pre- and post-spawned hake stored on ice were studied. At the beginning of storage both reduced viscosity and ATPases activities of NAM from post-spawned hake were about 3 times higher than those of the pre-spawned ones, except for the Mg²⁺-(Ca²⁺)-ATPase. Higher loss of functional components during pre-spawned hake NAM purification was found compared to NAM from post-spawned fish. Reduced viscosity and Mg²⁺-(EGTA)-ATPase activity of NAM from both pre- and post-spawned hake decreased following ice storage. SDS-PAGE patterns of NAM from pre-spawned hake showed an absence of the myosin heavy chain and the presence of a 160 kDa component at zero time of storage. No proteolysis occurred in ice-stored fish caught in both gonadal stages.     

Storage life of chilled Patagonian hake (Merluccius hubbsi)

The storage life of iced Patagonian hake ( Merluccius hubbsi ) was studied. Seasonal changes were investigated by means of organoleptic assessments (raw and cooked), total volatile bases (TVB) and pH.
During summer-time (December to March) the keeping time, from the edibility point of view, for round hake in ice is not more than 9 to 10 days; in the remaining months the storage life under the same conditions is up to 14 to 15 days.
The difference could be due to the biological condition of hake during and after the spawning time (end of spring-beginning of summer), the shallow and temperate waters of the fishing grounds in summer, and the heavy feeding after spawning.
Comparison trials between gutted and ungutted hake in ice, and between ungutted hake in ice and in chilled sea water (CSW) were also performed.
The duration of rigor mortis of whole hake stored in ice, and the feasibility of quality assessment by an electronic device were also studied.     

Effect of high pressure processing on the quality of squid (Todarodes pacificus) during refrigerated storage

The influence of high pressure processing (HPP) on the inhibition of trimethylamine-N-oxide demethylase (TMAOase) activity and off-odour production in squid treated at 300 MPa for 20 min was investigated during 12 days of refrigerated storage. TMAOase activity of raw squid (21.5 nkat/g) was significantly decreased to approximately 5 nkat/g after 20 min of HPP. The production of dimethylamine (DMA) in HPP-treated squid for 20 min was significantly decreased to 0.31 μmol/g after 12 days of storage. The decrease in DMA was correlated with the decrease in TMAOase activity. At 300 MPa, the number of total aerobic bacteria in squid was reduced by 1.26 log units after 20 min of HPP. The HPP-treated samples effectively reduced the amount of trimethylamine (TMA). Therefore, the HPP could be used as a promising alternative technology to retard the quality deterioration of squid by inhibiting TMAOase activity and microbial growth.     

印度洋鸢乌贼氧化三甲胺脱甲基酶的分离纯化及生化特性的研究

对印度洋鸢乌贼肌肉中的氧化三甲胺脱甲基酶(TMAOase)进行了研究。将鸢乌贼肌肉用20 mmol/LTris-醋酸缓冲液萃取,经酸、热处理后通过DE52阴离子交换柱层析和Sephacryl S-300凝胶柱层析得到纯化300倍的TMAOase。纯化得到的TMAOase分子质量为18.2 ku,最适温度和pH分别为55℃和7.0;而且该酶在50℃和pH 7.0～9.0具有很好的稳定性。TMAOase的活性可被茶多酚、植酸和冰醋酸抑制。此外,TMAOase可以将TMAO等量转化成二甲胺(DMA)和甲醛(FA),Km为24.7 mmol/L。     

Glutathione peroxidase activity, and content of total and soluble selenium in five bovine and porcine organs used in meat production

Glutathione peroxidase (GSHPx) activity, and total and soluble selenium content were compared in five bovine and porcine organs. The highest GSHPx activity in porcine tissues was found in the liver (35.0 U/g), spleen (29.3 U/g) and kidney (27.3 U/g) with much lower values in the heart (1.8 U/g) and diaphragm (0.8 U/g). A different pattern with lower inter-organ variation in GSHPx activity was observed in cattle: kidney (8.5 U/g), spleen (8.0 U/g), heart (5.8 U/g), liver (4.0 U/g) and diaphragm (2.1 U/g). The total selenium content was similar in both species with the highest content in the kidney (1764 and 1665 ng/g; pig/bovine), followed by liver (533 and 307 ng/g), spleen (370 and 284 ng/g), heart (201 and 205 ng/g) and diaphragm (144 and 116 ng/g). The percentage of soluble selenium varied more among the pig organs (46–94%) than among bovine organs (61–75%). The results show a marked variation in the activity of the selenium-containing GSHPx among organs and species in spite of a similar rank order of selenium content in the two species. Since GSHPx has a role in food stability and the intake of selenium is marginal in many European countries, the results add to the background information concerning the use of selenium rich organs as human foods.     

Comparison of gilthead sea bream (Sparus aurata) and hake (Merluccius merluccius) muscle proteins during iced and frozen storage

Gilthead sea bream (Sparus aurata) and hake (Merluccius merluccius) muscle behave differently during storage, whether in ice or deep frozen. Rapid changes have been observed in the texture of hake muscle during frozen storage, while gilthead sea bream has proved to be more stable. In order to ascertain the role of muscle proteins in the changes observed during storage, parameters related to protein functionality and the properties of extracted natural actomyosin (NAM) were studied initially and during storage in ice or at ?20 °C. Initially, the parameters related to functionality had higher values in hake muscle and extracted NAM than in gilthead sea bream. At the end of iced storage (22 days), less myosin heavy chain (MHC) and actin were extracted from hake, but there was practically no change in gilthead sea bream. This decrease was not accompanied by lower Ca²⁺‐ATPase activity. Freezing produced no drastic changes, with lower values for gilthead sea bream. However, this species was more stable after 1 year, except for the Ca²⁺‐ATPase activity of NAM. This suggests that the changes that hake proteins underwent during storage particularly affected properties related to aggregation, whereas in gilthead sea bream the changes hardly affected the formation of soluble or insoluble aggregates but did affect the active sites of myosin. © 2002 Society of Chemical Industry     

Influences of bioavailability, trophic position, and growth on methylmercury in hakes (Merluccius merluccius) from Northwestern Mediterranean and Northeastern Atlantic

Methylmercury (MeHg) determinations in hake, its food-chain, and the surrounding waters and sediments allowed us to show that the higher length or age normalized mercury concentrations of Northwestern Mediterranean (Gulf of Lions: GoL) muscle hakes compared to its Northeastern Atlantic (Bay of Biscay: BoB) counterpart are due to both biotic and abiotic differences between their ecosystems. Bioenergetic modeling reveals that the slower growth rate of Mediterranean hake favors the MeHg bioaccumulation in the fish muscle and explains most of the difference between GOL and BoB hake populations. In addition, the waters of the Mediterranean hake habitat favor a higher MeHg exposition, due to the upper position of the thermohalocline, where MeHg is formed. Furthermore, we show that, within the Mediterranean hake population, a major increase in the biomagnification power (the slope of the relationships between logMeHg and δ(15)N), from 0.36 up to 1.12, occurs when individuals enter adulthood, resulting from the combined effects of lowering growth rate and change in feeding habits. Finally, δ(15)N normalized Hg concentrations indicate that the highest Hg concentrations are for hake from the shelf edge and the lowest are for hake from the Rh?ne prodelta area, suggesting a lower Hg bioavailability in inshore environments, consistent with MeHg distributions in water, sediment, and preys.     

Cadmium, mercury, iron, copper, manganese and zinc in the liver and kidney of the Icelandic lamb

The purpose of this study was to evaluate the levels of cadmium, mercury, iron, copper, manganese and zinc in lamb liver and kidney from six areas in Iceland and to compare the results against aerial deposition data for the same elements obtained using moss as an indicator organism. The total number of samples was 96 for each organ. Cadmium was determined by graphite furnace atomic absorption spectrophotometry, mercury by coldvapour atomic absorption, and iron, copper, manganese and zinc by inductively coupled plasma atomic emission spectrophotometry. Analysis of variance determined significance differences among means for areas, and Pearson's correlation coefficients were calculated to study correlation among trace elements in liver and kidney. The mean fresh weight concentrations in lamb liver and kidney respectively were 0.045 and 0.058mg kg -1 for cadmium, 0.009 and 0.012mgkg -1 for mercury, 141 and 52.7mgkg -1 for iron, 28.1 and 2.89mgkg -1 for copper, 4.01 and 1.13mgkg -1 for manganese and 48.7 and 25.2mgkg -1 for zinc. Concentrations of cadmium, mercury and copper in the liver and kidney of the Icelandic lamb were low compared with data from other countries. Iron concentrations in the organs, however, were high. No sample exceeded 46% of the proposed maximum level for cadmium in organs for human consumption in the EC. Cadmium, mercury, iron and copper in the liver and kidney differed significantly between areas. Deposition of cadmium and copper in moss was not a useful indicator in the evaluation of the susceptibility of the Icelandic lamb to accumulation of cadmium and cop per. However, iron levels in Icelandic lamb liver showed the same pattern as results for iron from the moss study. The cadmium and mercury levels of organs from lambs grazing in the vicinity of Mount Hekla a few months after its eruption did not indicate a significant contamination from volcanic activity.