Effect of trehalose on the gel-forming ability,state of water and myofibril denaturation of horse mackerel <Emphasis Type="Italic">Trachurus japonicus</Emphasis> surimi during frozen storage

The cryoprotective effects of trehalose on fish myofibrillar protein were compared with those of sucrose, glucose and sorbitol. The frozen surimi with trehalose exhibited significantly higher Ca²⁺-ATPase activity through-out the storage periods, resulting in higher gel-forming ability than that of without trehalose. The amount of unfrozen water was significantly increased in the surimi upon addition of trehalose at any concentrations tested. The findings suggest that trehalose constructed bound water molecules in protein structure, consequently suppressed freeze-induced denaturation of protein and maintained gel-forming ability. An addition of 5.0% to 7.5% concentration of trehalose showed threshold behavior to increase the amount of unfrozen water and to prevent freeze-induced denaturation of protein. The effects of trehalose were almost similar to those of other sugars.     

Physicochemical and Gel Properties of Myofibrillar Protein from Sin Croaker (Johnius dussumieri) Fish During Ice Storage

The physicochemical and gel properties of myofibrillar protein (MFP) from sin croaker fish were studied during ice storage for 18 days. Significant changes in the trends of solubility, Ca²⁺ ATPase enzyme activity, surface hydrophobicity, and water holding capacity of extracted MFP were observed by the 6th day of storage. The Ca²⁺ ATPase enzyme activity reduced significantly (p < 0.05) by the 6th day of storage. However, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) did not show a remarkable change in the concentration of myosin heavy chain. Surface hydrophobicity increased almost four times from its original value of 18.98 µg; whereas, water holding capacity showed a fluctuating trend during storage. The emulsion capacity of the MFP was in the range of 0.89- to 1.92-mL oil/mg protein during storage. The gel strength value (313.45 g.cm) of heat-induced gel prepared from fresh minced meat decreased significantly (p < 0.05) by the 6th day of ice storage. Texture profile analysis revealed that changes in hardness and gumminess were concurrent to steeply reducing breaking force up to the 6th day. The histological observation showed gradually increasing gaps between muscle fibers. The histological observations and physicochemical quality indicated that the sin croaker fish can be used for producing good quality surimi when stored for up to 6 days in ice.     

关于鱼糜在冷藏过程中蛋白质变性的研究——冷藏过程中Ca++-ATPase活性变化的探讨

本文就草鱼鱼糜在冷藏过程中肌原纤维蛋白Ca^ -ATPase活性的变化及几种因素对其活性的影响作了初步探讨。并与VBN值的变化作了比较。冷藏过程中，鱼糜的肌原纤维蛋白Ca^ -ATPase活性变化明显，而VBN值变化不大，因此可用肌原纤维蛋白Ca^ -ATPase活性的大小来鉴别冷藏前期鱼糜蛋白质的变性程度。几种因素对蛋白质变性具有不同程度的影响。对于已腐败的鱼糜，不宜用鱼糜肌原纤维蛋白Ca^ -ATPase活性来鉴定其品质的优劣。     

Effects of Bicarbonate,Xanthan Gum,and Preparation Methods on Biochemical,Physicochemical, and Gel Properties of Nile Tilapia (Oreochomis niloticus Linn) Mince

This study was aimed to determine the effects of phosphate compound substitutions (sodium bicarbonate and xanthan gum) and preparation methods—headed, gutted whole fish, and mince; fresh and after frozen storage (?20°C for 3 months)—on Nile tilapia mince qualities. Results showed that bicarbonate (0.3% with 8% sucrose/sorbitol) is an efficient phosphate compound replacement as evidenced by the comparative values of salt extractable protein, Ca²⁺-ATPase activity, total sulfhydryl content, and textural properties to those of the phosphate-added—0.3% sodium tripolyphosphate (STPP) with 8% sucrose-sorbitol—sample after 3-month frozen storage (p > 0.05). Both cryoprotected samples containing STPP or bicarbonate exhibited higher denaturation temperatures of myosin than others. Xanthan gum (0.5%) could neither stabilize the biochemical and physicochemical properties of mince during 3-month frozen storage nor improve textural properties of gel from frozen whole fish.     

蛇鲻冰藏和冻藏过程中鲜度指标的变化以及高压处理对其凝胶形成能的影响

研究了蛇鲻(Saurida wanieso)冰藏和冻藏过程中K值、挥发性盐基氮(TVBN)、Mf Ca^2 -ATPase全活性等鲜度指标的变化,并研究了高压加工法制备对蛇鲻鱼糕凝胶形成能的影响。结果表明：冰藏过程中鲻鱼的鲜度急剧降低,其货架期仅为10d左右,冻藏过程中蛇鲻保藏90d,鲜度缓慢降低。随着K值和TVBN的增加,鲻鱼的凝胶形成能降低,Mf Ca^2 -ATPase全活性与凝胶形成能关系不明确。通过加热处理,冰藏和冻藏的蛇鲻能保持正常凝胶形成能的时间分别为6d和60d,而高压处理蛇鲻能保持正常凝胶形成能的时间分别为至少14d和90d,高压处理能够显著提高蛇鲻的凝胶形成能从而延长其可利用期限。     

Preliminary Characterization of European Sardine Transglutaminase

Abstract

The significant role of transglutaminase (TGase) in the setting of surimi led us to perform its preliminary characterization in sardine muscle. The time course of the reaction and the effect of enzyme level were studied. The temperature optimum was around 35°C and the thermal stability was studied in the 15-55°C range. Higher TGase activity was measured in sardine dark muscle than in the white muscle. A slow decrease of TGase activity during ice storage of sardine was recorded, but after eight days in ice it was about 50% of its initial activity. Cold storage of sardine for a short period did not affect TGase activity.     

Effect of Cryoprotectants on Suppression of Protein Structure Deterioration Induced by Freeze-thaw Cycle in Pacific White Shrimp

This study aimed to elucidate the changes in Pacific white shrimp (Litopenaeus vannamei) myofibrillar protein as influenced by multiple freeze-thaw cycles as well as the stabilization effects of sucrose and trisodium citrate on shrimp myofibrils. Shrimp myofibrils in 0.1 M NaCl, 20 mM Tris-HCl (pH 7.5) were mixed individually with sucrose and citrate at concentrations of 0.05 M and were evaluated for Ca²⁺-ATPase activity, salt solubility, total and reactive sulfhydryl, and surface hydrophobicity during three freeze-thaw cycles. Sucrose and citrate had strong cryoprotective effects against freeze denaturation by retaining higher Ca²⁺-ATPase activity and salt-soluble myosin and actin, by slowing the reduction of reactive sulfhydryl (SH) and by exposing less hydrophobic groups at the surface of the protein compared with the no-additive sample. Results indicated that both cryoprotectants had suppressive effect against protein denaturation and helped stabilize white shrimp myofibrillar protein during the freeze-thaw process. This study suggests that sucrose and citrate stabilized the protein structure by retarding the unfolding of protein; thus, the native protein could be protected during frozen storage.     

Effects of Chilled Storage,Freezing Rates,and Frozen Storage Temperature on Lipid Oxidation in Meat Blocks from Cultured Bluefin Tuna Thunnus thynnus

ABSTRACT

The effects of a short chilled storage period before freezing, frozen storage temperature, and freezing rate on lipid oxidation of bluefin tuna (Thunnus thynnus) meat during frozen storage were investigated. After 12-months storage, all samples had increased in peroxide value though they were less at the lower temperatures (?45 and ?60°C). Peroxide values in all samples stored at ?20°C increased after 3 months storage, particularly those processed and stored 51 h after harvest. The lowest increase in peroxide value occurred in the samples frozen rapidly 3 h after harvest. Vitamin E levels decreased faster during frozen storage at ?20°C. There were no apparent differences in levels of triacylglycerides nor in n-3 fatty acid levels between treatments, storage periods, and storage temperatures. After 12-months storage, headspace oxidative volatiles were highest in samples stored at ?20°C and lowest in those stored at ?60°C. Lipid oxidation in tuna meat stored at ?45°C is similar to that at ?60°C, and rapid freezing rather than slow freezing should be used.     

Prevention of thaw-rigor during frozen storage of bigeye tuna Thunnus obesus and meat quality evaluation

Thaw-rigor is often found in frozen meat of bigeye tuna Thunnus obesus. Excessive amounts of drip loss and stiffness greatly lower the commercial value of tuna meat. In order to prevent thaw-rigor in meat stored at −60°C post-capture, we adapted a temperature shift technique that stores the meat at −7°C for 1 day or −10°C for 7 days before thawing. Biochemical changes in muscle of bigeye tuna before and after the temperature shift to −7 or −10°C were characterized. Contents of ATP, NAD⁺, glycogen, and creatine phosphate decreased after the temperature shift. NAD⁺ levels decreased faster than ATP levels and were highly correlated with the rigor index. Thaw-rigor occurred in muscle containing NAD⁺ at 1 μmol/g and ATP at 7 μmol/g. On the other hand, the meat color of tuna during frozen storage changed to brown depending on the storage temperature and reflected the rate of metmyoglobin (met-Mb) formation. Met-Mb formation increase was dependent on the decrease in NADH levels during the frozen storage. A temperature shift technique with storage at −7°C for 1 day or −10°C for 7 days before thawing prevented thaw-rigor and met-Mb formation.     

Response of ATPases in the osmoregulatory tissues of freshwater fish Oreochromis niloticus exposed to copper in increased salinity

An increase in salinity of freshwater can affect the physiology and metal uptake in fish. In the present study, Nile tilapia Oreochromis niloticus were exposed to copper (1.0 mg/l) in increased salinities (2, 4, and 8 ppt) for 0, 1, 3, 7, and 14 days. Following the exposures, the activities of Na⁺/K⁺-ATPase, Mg²⁺-ATPase, and Ca²⁺-ATPase were measured in the gill, kidney, and intestine to evaluate the changes in osmoregulation of fish. Results showed that increases in salinity and Cu exposure of fish significantly altered the ATPase activities depending on the tissue type, salinity increase, and exposure durations. Salinity-alone exposures increased Na⁺/K⁺-ATPase activity and decreased Ca²⁺-ATPase activity. Na⁺/K⁺-ATPase activity decreased following Cu exposure in 2 and 4 ppt salinities, though the activity increased in 8 ppt salinity. Ca²⁺-ATPase activity decreased in the gill and intestine in all salinities, while the activity mostly increased in the kidney. However, there were great variations in Mg²⁺-ATPase activity following exposure to salinity alone and salinity+Cu combination. Cu accumulated in the gill and intestine following 14 days exposure and accumulation was negatively correlated with salinity increase. Data indicated that ATPases were highly sensitive to increases in salinity and Cu and might be a useful biomarker in ecotoxicological studies. However, data from salinity increased freshwaters should carefully be handled to see a clear picture on the effects of metals, as salinity affects both metal speciation and fish osmoregulation.     

Effects of ambient ion concentrations on gill ATPases in fresh water eel,Anguilla anguilla

Branchial activities of Na⁺,K⁺-ATPase (ouabain sensitive), Mg²⁺ ATPase (ouabain insensitive) and kinetic analysis of high and low affinity Ca²⁺ ATPase were measured inAnguilla anguilla that had been acclimated to demineralized water (DW, Ca < 10 M), freshwater (FW, Ca = 2 mM), and Low calcium freshwater (L-Ca, Ca = 0.9 mM). Na⁺,K⁺-ATPase activity decreased while ouabain insensitive activity increased when ambient Ca²⁺ decreased. Two kinetic forms of Ca²⁺ ATPase could be resolved in each environmental condition. The stimulation coefficients of both sites or enzymes were not affected by ambient Ca²⁺ concentrations. The maximal velocity of both the high and the low affinity Ca²⁺ ATPase was increased when external Ca²⁺ was decreased during acclimation. The low affinity Ca²⁺ ATPase and the Mg²⁺ stimulated enzyme could be a non specific enzyme accepting either Ca²⁺ or Mg²⁺. Results are compared with previous results in the literature and in relation to the branchial morphology and ionic exchanges in fish.     

Effects of Partial and Complete Replacement of Synthetic Cryoprotectant with Carrot (Daucus carota) Concentrated Protein on Stability of Frozen Surimi

ABSTRACT

The study aimed to evaluate the effects of carrot concentrated protein (CCP) as additive on the functional and textural properties of surimi from striped catfish (Pangasianodon hypophthalmus) during six months of frozen storage (?20°C). The CCP (82.22% crude protein) was used as an additive either a lone or with a synthetic cryoprotectant (sucrose-sorbitol-sodium tri-polyphosphate). Control was made with synthetic cryoprotectant only. Molecular weight of CCP was found to be 36 kDa. After six months, the results revealed that up to 50% of synthetic cryoprotectants could be replaced by CCP during frozen storage of surimi. Biochemical parameters such as protein solubility, Ca²⁺ATPase activity, and gel strength decreased significantly (p < .05) during storage. Treatment T-3 (CCP 0.5% + 50% of synthetic cryoprotectant) maintained quality of protein significantly superior (p < .05) in respect to denaturation and other functional and sensory attributes compared to all the treatments. The microstructure images of surimi confirmed that addition of CCP modified the ice crystal growth during frozen storage. This study suggests that CCP can be a potential additive to protect protein from denaturation along with partial replacement of chemical cryoprotectants.     

Effects of Conservation Method and Time on Fatty Acid Composition,Taste, and Microstructure of Southern King Crab (Lithodes santolla Molina, 1782) Meat

This study reports the changes in fatty acids, taste, and microstructure of cooked southern king crab meat (Lithodes santolla) during storage at 0°C for 10 days and at ?20°C for 90 days. At the end of both storage times, the iodine value decreased by 16.5%, while 83.5% of the initial fatty acid quality remained unchanged. The polyene ratio decreased by 32% at 0°C and 35.9% at ?20°C, whereas the atherogenic and thrombotic indices remained at values that do not represent any risk to human health. Free amino acids that contribute to taste (taste activity value, TAV > 1) were: glycine and alanine (sweetness), arginine (bittersweetness), and histidine (bitterness). The bittersweet taste imparted by arginine (initial TAV = 16.4) was prevalent even at the end of frozen storage (TAV = 7.9). The umami taste was elicited by disodium 5′-adenosine monophosphate (AMP) nucleotide. The equivalent umami concentration in g MSG/100 g meat changed from 0.031 to 0.045 in refrigerated samples and to 1.6 in frozen samples. A loss of the original fibrous structure of the meat was evidenced during both treatments. Refrigerated samples presented a disintegrated and homogeneous texture at 10 days, while freezing formed a spongy tissue at 90 days.     

Changes in Protein Oxidation,Water-Holding Capacity,and Texture of Bighead Carp (Aristichthys Nobilis) Fillets Under Chilled and Partial Frozen Storage

This study aimed to evaluate the contribution of protein oxidation to the changes in the water-holding capacity (WHC) and texture of bighead carp (Aristichthys nobilis) fillets under chilled and partial frozen storage (4°C and ?3°C). The results indicated that less protein oxidation occurred to fillets at ?3°C than at 4°C, which was reflected by the higher value of salt-soluble protein contents (SSP), total sulfhydryl content (SH), Ca²⁺-ATPase activity, lower water-soluble protein contents (WSP), total disulfide content (SS), and surface hydrophobicity (So-ANS). However, the fillets had better WHC and texture at 4°C, as well as lower drip loss and higher centrifugal loss, hardness, and springiness. A significant linear relationship existed between protein oxidation parameters with WHC and texture characteristics for fillets under both types of storage, but the process of freezing and then thawing, instead of protein oxidation, was the main factor affecting the texture and WHC of fillets at ?3°C.     

Changes in Functional Properties of Protein in High Pressure-Treated Indian White Prawn (Fenneropenaeus indicus) during Chilled Storage

ABSTRACT

High pressure (HP) treatment of 250 MPa pressure, 6-min holding time, and 400 MPa/min ramp rate at 25°C was applied to headless Indian white prawn (Fenneropenaeus indicus) to investigate the significant modifications on the functional properties of protein during chilled storage. Muscle fibers were shrunk and extracellular space apparently reduced after HP treatment. Myofibrillar proteins denatured and sarcoplasmic proteins aggregated and were found to be stable in HP-treated sample during chilled storage. Water-holding capacity, solubility, viscosity, and Ca²⁺ ATPase activity of protein were diminished, whereas foam expansion, foam volume stability, and turbidity of proteins improved with HP treatment and storage period (p < .05). Turbidity of the protein was inversely proportional to viscosity, solubility, and Ca²⁺ ATPase activity in HP-treated samples.     

日本枪乌贼(Loligo japonica)不同温度冻藏过程中的品质变化

选取-20℃、-30℃和-50℃3个冻藏温度,以TVB-N值、肌原纤维蛋白含量、Ca2+-ATPase活性、巯基含量、TBARS值及肌肉组织微观结构为指标,结合感官评分,对比分析90 d内日本枪乌贼(Loligo japonica)的品质变化规律。结果显示,在不同冻藏温度下,随着时间的延长,Ca2+-ATPase活性和感官评分不断下降;肌原纤维蛋白和巯基含量,则先略微上升而后快速下降;TVB-N值和TBARS值呈不断上升的趋势,且温度越高上升速率越快;肌肉组织微观结构分析表明,枪乌贼肌纤维结构在冻藏过程中逐渐变得松散。相比-20℃,-30℃和-50℃冻藏温度条件下更能长久地保持枪乌贼品质,且品质无显著差异。综合分析认为,冻藏温度低于-30℃时,可较好地保持枪乌贼品质。     

Effects of Freezing and Frozen Storage on Protein Functionality and Texture of Some Cephalopod Muscles

The aim of this study was to investigate the effects of freezing and frozen storage on protein functionality and texture of squid (Loligo vulgaris), octopus (Octopus vulgaris), and cuttlefish (Sepia officinalis) muscles. Squid, octopus, and cuttlefish samples were cut into pieces of 4 × 4 cm. These pieces were packed in polyethylene bags. The bags were frozen in a blast freezer at ?45°C until the thermal center reached ?18°C. Frozen samples were stored in a deep freezer at ?18°C for 30 days. After freezing and during frozen storage, total soluble protein and water holding capacity decreased and total free amino acid and cooking loss increased in all cephalopod muscles. According to instrumental texture analysis results, freezing and frozen storage affected textural characteristics of squid and cuttlefish but not of octopus. Sensory hardness and chewiness values of all cephalopods increased after freezing, but elasticity values did not change. There were no significant differences between storage days in hardness values of squid and octopus. However, significant differences in hardness values of cuttlefish were observed between the 1st day of storage and the last day.     

Ca2+- and Mg2+-Induced Conformational and Rheological Changes of Actomyosin Extracted from Fresh and Freeze-Thaw Tilapia

ABSTRACT

The conformational changes of natural actomyosins prepared from fresh and freeze-thaw tilapia (Oreochromis niloticus) in the presence of Ca²⁺ or Mg²⁺ were investigated. The Ca²⁺-activated adenosine triphosphatase (Ca²⁺-ATPase) activities of actomyosins extracted from fresh and freeze-thaw fish were comparable (p > 0.05). The denaturation temperatures (T_d) of actomyosins extracted from fresh fish were lower than those from freeze-thaw counterparts (p < 0.05). The addition of Ca²⁺ or Mg²⁺ reduced the T_d of actomyosins. Ca²⁺ and Mg²⁺ enhanced protein aggregation at ≥ 40°C (p < 0.05). Based on the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) pattern, the myosin heavy chain (MHC) and actin bands tended to form large aggregates to a greater extent in the presence of 100mM Ca²⁺ or Mg²⁺. Ca²⁺ and Mg²⁺enhanced disulfide linkages and hydrophobic interactions among actomyosin molecules. The onset temperature of elastic modulus (G′) of both actomyosins was shifted to lower temperature as 100mM of Ca²⁺ or Mg²⁺ was added. Mg²⁺ at 20mM increased the breaking force of washed tilapia mince at 40°C. Our results revealed that the intrinsic properties of actomyosins extracted from fresh and frozen fish were distinct, and divalent ions Ca²⁺ or Mg²⁺ affected their gelation differently.     

Effect of a Previous Washing Step with Tannic Acid on the Quality of Minced Horse Mackerel (Trachurus trachurus) During Frozen Storage

Fatty fish have been recognized as potential raw material for production of minced meat; however, they are prone to oxidation and further deterioration. In the present study, the effect of washing and antioxidant (tannic acid) treatment on the quality of minced meat of Trachurus trachurus (horse mackerel) during frozen storage was observed. Minced meat of Trachurus trachurus was divided into three lots (T0, T1, and T2). T1 was washed with cold water, T2 with cold water containing tannic acid (100 mg/kg), and T0 was not washed. All the lots were frozen at ?40°C and stored at ?20 ± 2°C for 125 days and were subjected to biochemical, microbiological, and sensory evaluation at regular intervals of 25 days. The antioxidant treatment with tannic acid at the dosage used was found effective in minimizing the rancidity problems of minced meat (T2), compared to T0 and T1. During the whole period of storage, samples from T2 showed good quality in terms of microbiological, biochemical, and sensory analysis compared to T1 and T0.     

Changes of activated factors and activation of calpain in tilapia muscle during storage

Calpain is known to be the most important endogenous protease responsible for degrading myofibril protein, thus affecting meat quality. This study aimed to investigate the activation of calpain and its potential influence in fish after slaughter. Calpain activity, expressions of the calpain inhibitor and activator (calpastatin and UK114, respectively), and effects of influencing factors on calpain activity and on the necessary Ca²⁺ activation concentration was investigated. Calpain activity increased significantly during the first 5 h of storage followed by rapid decline (P?<?0.05). Three calpastatin expression bands were detected, and the 120-kDa calpastatin was significantly down-regulated with storage time (P?<?0.05), whereas the level of UK114 in tilapia muscle was significantly up-regulated during postmortem storage (P?<?0.05). Calpastatin and UK114 showed opposite effects on calpain activity; a significant decrease and increase in calpain activity were observed when crude calpain was incubated with calpastatin and UK114, respectively (P?<?0.05). Furthermore, a significant increase was observed in calpain activity following co-treatment with calpastatin and UK114 (P?<?0.05), but lower than that of treatment with UK114. The calpain activity in the UK114-treated group was higher than that of the control and calpastatin with the same Ca²⁺ concentration. Calpastatin inhibited calpain activation, whereas UK114 promoted the activation of calpain by reducing the concentration of Ca²⁺ required. Therefore, we propose that UK114 may increase calpain activity by inhibiting that of calpastatin.