冻结速率和冻藏温度对鲢肉蛋白质冷冻变性的影响

研究了冻结和冻藏温度对鲢肉肌原纤维Ca-ATPase活性和盐溶性蛋白溶解度的影响并作了冷冻切片观察，结果发现，冻结速率对具有一定细胞形态的鲢肌蛋白质的冷冻变性有一定的影响，对无完整细胞形态的碎鱼肉和鱼糜基本无影响，而冻藏温度对鱼肌、碎鱼肉和鱼糜蛋白质冷冻变性都有显著的影响，即温度越低，变性越小，而抗冻剂可有效防止蛋白质的冷冻变性，尤其是使鱼糜肌原纤维蛋白质的稳定性大大提高。     

Cryoprotective effects of shrimp head protein hydrolysate on gel forming ability and protein denaturation of lizardfish surimi during frozen storage

ABSTRACT:   The effects of shrimp head protein hydrolysate (SHPH) from three species of shrimp (northern pink shrimp [ Pandalus eous ], endeavour shrimp [ Metapenaeus endeavouri ], black tiger shrimp [ Penaeus monodon ]) on gel forming ability and protein denaturation of lizardfish surimi during frozen storage at −25°C were evaluated. The quality of lizardfish surimi with 5% (dried matter) of any of the three SHPH or sodium glutamate (Na-Glu) was examined in terms of gel strength, whiteness, Ca-ATPase activity and the amount of unfrozen water, comparing with those of surimi without additive as the control. The residual Ca-ATPase activity and gel strength of surimi with SHPH were higher than those of the control throughout 180 days of frozen storage, regardless of shrimp species. The highest effect was found in surimi with Na-Glu. The gel strength and Ca-ATPase activity found a high positive correlation. The addition of SHPH to surimi also increased the amount of unfrozen water by approximately 1.29–1.36 fold higher than the control, however kamaboko gels of the control was significantly whiter. From these results, freeze-induced denaturation of lizardfish muscle protein could be lessened by the addition of SHPH, resulting in a high gel strength and Ca-ATPase activity.     

Preparation of Water-Soluble Chitosan and its Suppressive Effect on the Denaturation of Scallop Adductor Muscle Myofibrillar Protein During Frozen Storage

ABSTRACT

In the present study, investigated were the preparation of water-soluble chitosan (WSC) by hydrolysis of original chitosan with commercial α-amylase and the suppressive effect of WSC on denaturation of bay scallop adductor muscle myofibrillar protein (Mf) during frozen storage at ?18°C for 12 months. The WSC (2.5- to 10-g dry weight) was added to 100 g of the Mf, and the changes in the Ca-ATPase activity, solubility, and sulfhydryl content were examined during frozen storage. The addition of WSC significantly reduced the denaturation of the Mf Ca-ATPase. Moreover, a significant increase in Mf solubility and sulfhydryl content was observed in the WSC-treated bay scallop adductor muscles compared with the control (p < 0.05) during frozen storage at ?18°C.     

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.     

红藻糖苷的提取及其对草鱼鱼糜抗冻性能的影响

为探讨红藻糖苷的醇提工艺以及红藻糖苷对冷冻草鱼鱼糜蛋白变性作用的影响,首先采用响应面分析法对乙醇浓度、提取温度、时间和液料比4个因素进行优化,随后以冷冻鱼糜的盐溶性蛋白含量、巯基含量及肌原纤维蛋白Ca~(2+)-ATP酶活性等参数为指标,探测冷冻草鱼鱼糜在冷藏过程中添加红藻糖苷对蛋白质变性作用的影响。结果显示,红藻糖苷的最佳醇提条件为乙醇72.3%、提取温度60°C、时间4 h、液料比14∶1(m L/g),在此条件下的提取率为3.46%;抗冻性能结果显示,随红藻糖苷浓度升高,抗冻效果增强;以10%红藻糖苷处理冷冻鱼糜4周后,盐溶性蛋白含量和巯基含量分别比空白组高30.62%、32.80%,肌原纤维蛋白的Ca2+-ATP酶活性的下降率比空白组低37.51%,解冻失水率的增长率比空白组低133.07%。研究表明,红藻糖苷能有效延缓草鱼鱼糜肌原纤维蛋白的冷冻变性。     

Effects of Whitening Agents and Frozen Storage on the Quality of Sardine (Sardina pilchardus) Surimi: Physicochemical and Mechanical Properties

This work is focused on the effect of using whitening agents (WA) during a process followed by frozen storage (4 months at ?18°C) on the whiteness, quality parameters, and mechanical properties of sardine surimi. The whiteness of surimi exhibited a significant improvement when whitening agents (calcium carbonate and peroxide hydrogen) were used (48.75 to 60.24). Dynamic rheological measurement showed that storage moduli, G′, was considerably higher than loss moduli, G″, for both surimi with WA and control; however, the highest viscoelastic moduli were found in the treated surimi. In addition, the microstructure of surimi with WA showed more compact matrix and higher water holding capacity. On the other hand, most tested indexes showed quality losses throughout the frozen storage in both samples. Proteins underwent denaturation as indicated by the reduction in band intensities, especially myosin heavy chain (MHC) bands. Peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) measurements showed that lipid oxidation took place during storage; however, the degree of lipid oxidation was not relevant. Therefore, it was proved that the addition of whitening agents had a marked effect on the production of surimi with better functional attributes including whiteness, water holding capacity, and mechanical properties.     

Effect of Squid Melanin-Free Ink and Pre-Emulsification on Properties and Stability of Surimi Gel Fortified with Seabass Oil during Refrigerated Storage

ABSTRACT

The effects of melanin-free ink (MFI) and pre-emulsification on gel properties and stability of bigeye snapper surimi gel fortified with seabass oil during refrigerated storage of 10 days were studied. Lipid oxidation as determined by peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) of surimi gel increased as the level of seabass oil increased (P < 0.05). When MFI was incorporated into surimi gel, lower PV was obtained throughout the storage (P < 0.05). Addition of seabass oil pre-emulsified with soy protein isolate (SPI) in the presence of MFI yielded surimi gel with the highest breaking force and could improve oxidative stability during refrigerated storage (P < 0.05). Slight decrease in whiteness was found in surimi gel added with MFI, while those added with MFI along with pre-emulsified seabass oil showed increased whiteness (P < 0.05). Addition of MFI did not affect total viable count and psychrophilic bacterial count in surimi gels. Thus, the incorporation of pre-emulsified seabass oil prepared using SPI in conjunction with MFI could improve quality and oxidative stability of gel from bigeye snapper surimi.     

Quality Characteristics of Tilapia Surimi: Effect of Single Washing Cycle and Different Washing Media

Surimi was prepared by washing with single washing cycle with cold water (T-1), alkaline saline (0.2% NaHCO₃ and 0.15% NaCl; T-2) solution, and with calcium chloride and salt (0.2% CaCl₂ and 0.1% NaCl; T-3), respectively, and compared with conventional washed (CW) surimi. T-2 exhibited significantly (p ≤ 0.05) increased moisture content, which correlated with increased yield, pH and also significantly decreased lipid and ash content. A significant (p ≤ 0.05) decrease in expressible moisture content was also observed in T-2, which suggested higher water holding capacity compared to other treatments. Heat-induced surimi gels exhibited highest L* (p ≤ 0.05), followed by surimi in all the treatments. In the case of L*, T-1 showed highest lightness, followed by T-2, which was comparable to CW. The lowest myoglobin content was exhibited by CW surimi (p ≤ 0.05), which is due to repeated washings. T-2 gel showed higher elasticity, texture, and overall acceptability than others (p ≤ 0.05), except for the whiteness. In all the aspects, T-2 was comparable with CW. Washing with one cycle of T-2 solution can not only improve the quality of surimi but can reduce the wastage of water that is released into the environment without further treatment.     

Comparison of Conventional Washing Processing and pH Shift Processing on Gelation Characteristics of Bighead Carp (Aristichthys nobilis) Muscle Proteins

In this study, gelation characteristics of bighead carp (Aristichthys nobilis) protein isolates prepared by pH shift processing were investigated as compared with those of surimi prepared by conventional wash processing. Results showed that the gel from alkali-aided protein isolate exhibited a higher breaking force than that from conventional washed surimi (p < 0.05). However, the gel from conventional washed surimi had higher whiteness (p < 0.05) and lower expressible moisture (p < 0.05). The rheological study showed that protein isolates exhibited different storage modulus and loss tangent patterns from conventional washed surimi during heating. Acid-aided processing could lead to higher denaturation and dissociation for fish muscle myosin and a coarser gel network from the sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) pattern and the scanning electron microscopy (SEM). Overall, there is a potential to apply pH shift processing, especially alkali-aided processing, to extract more proteins from bighead carp muscle for the production of surimi-based food.     

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.     

Effect of Dimethyl sulfoxide (DMSO) and egg yolk on sperm motility,fertility and hatching rates of depik Rasbora tawarensis (Pisces: Cyprinidae) eggs after short‐term cryopreservation

Cryoprotectant is the crucial factor in the cryopreservation process. In general, there are two types of cryoprotectant, permeating and non‐permeating cryoprotectants. Dimethyl sulfoxide (DMSO) and egg yolk are common permeating and non‐permeating cryoprotectants respectively. Hence, the objective of the present study was to determine the best proportion of DMSO and egg yolk for the cryopreservation of Rasbora tawarensis sperm. A completely randomized experimental design was used in this study which involves two types of cryoprotectant and their combination at different concentrations, namely 5% DMSO, 5% egg yolk, 5% DMSO + 5% egg yolk and 2.5% DMSO + 2.5% egg yolk. Every treatment was conducted in three replicates. Combination of 5% DMSO + 5% egg yolk gave the best results cryoprotectant treatment had significant effects on sperm motility, fertilization and hatching rate of the R. tawarensis eggs (p < .05). It is concluded that the best proportion of cryoprotectants for sperm cryopreservation in this species is 5% DMSO + 5% egg yolk.     

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.     

Effects of Varying Sucrose Concentrations in Pacific Whiting (Merluccius productus) Stabilized Mince Used for Surimi Production

Stabilized mince (SM) was made from fresh Pacific whiting mixed with varying levels of sucrose (6 to 12% w/w) including 0.2% w/w polyphosphates. SM samples were maintained in frozen storage and used at different time intervals for surimi production. Comparisons with control surimi made from fresh mince showed that acceptable surimi can be produced from SM stored at -20°C with cryoprotectant levels at 6% w/w sucrose and 0.2% w/w polyphosphates. There was a slight decrease in whiteness in surimi made from the SM samples when compared to the control. Surimi yields from SM were comparable to yields of surimi made from fresh mince.     

Effect of different permeable and non-permeable cryoprotectants on the hatching rate of rainbow trout (<Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>) embryos

The purpose of the present study was to investigate the toxicity of cryoprotectants on the hatching rate of rainbow trout (Oncorhynchus mykiss) embryos. Epiboly and first eye pigmentation stage embryos were immersed in six permeable cryoprotectants, dimethyl sulfoxide (DMSO), glycerol (Gly), methanol (MeOH), propylene glycol (PG), ethylene glycol (EG), and acetamide (Ac), in concentrations of 1–5 M for 5 or 10 min and two non-permeable cryoprotectants, sucrose (Suc) (10%, 15%, 20%) and polyvinyl pyrrolidone (PVP) (5%, 10%, 15%) for 5 min. The embryos were then washed and incubated until hatching occurred. The toxicity of the cryoprotectant was assessed by the hatching rate. The results illustrated that permeable cryoprotectant toxicity for rainbow trout embryos increased in the order of PG < DMSO < MeOH < Gly < EG < Ac. The hatching rate of the embryos treated with permeable cryoprotectants decreased (P < 0.05) with increased concentration and duration of exposure. There were no significant decreases in hatching rate of embryos treated with sucrose and PVP with the increase of concentration; sucrose had higher hatching rates than PVP. Rainbow trout embryos at first eye pigmentation stage exhibited greater tolerance to cryoprotectants than embryos at epiboly stage.     

Setting Ability of Threadfin Bream (Nemipterus japonicus) Meat as Affected by Freezing and Frozen Storage with Special Reference to Transglutaminase Enzyme Activity and Rheological Properties

The effect of freezing and frozen storage of threadfin bream fish (Nemipterus japonicus) meat on the setting and gel-forming ability has been evaluated. The dynamic viscoelastic properties of fish meat during setting and thermal gelation process were evaluated using Controlled Stress Rheometer under oscillatory mode. A sharp decrease in setting ability was recorded immediately after freezing as revealed by storage modulus (G?) values. The transglutaminase (TGase) enzyme activity of fish meat decreased from the initial value of 81.09 to 51.46 U/g meat/min at the end of 200 days of frozen storage. A decrease in setting ability of fish meat beyond 160 days of frozen storage is probably related to lower TGase enzyme activity. The gel-forming ability was related to setting ability during the frozen storage period. Although the protein solubility showed a decreasing trend during 200 days of frozen storage, the decrease was not significant. The effect of freezing and frozen storage on calcium-activated adenosine triphosphatase (Ca²⁺-ATPase) enzyme activity of fish mince was significant (P < 0.05). A reduction in protein solubility and Ca²⁺-ATPase enzyme activity is an indication of aggregation/denaturation of myofibrillar proteins.     

Relationship between Lipid Oxidation,Protein Function Properties,and Freshness Changes of Salt-Treated Blunt-Snout Bream (Megalobrama amblycephala) Fillets Stored at 4°C

The aim of this study was to investigate the relationship between lipid oxidation, protein function properties, and freshness changes of blunt-snout bream (Megalobrama amblycephala) fillets treated with 2% and 4% salt during storage at 4°C. Salting with 2% and 4% salt could delay quality deterioration and protein denaturation, thus improving sensory attributes to some extent. But, 4% salt promoted lipid oxidation of blunt-snout bream fillets. There is a significant correlation (p < 0.05) between freshness indexes and lipid oxidation or protein function properties (total SH content, Ca²⁺-ATPase activity). Salting with 2% salt is an ideal treatment to control the quality of blunt-snout bream fillets stored at 4°C.     

Myosin and actin denaturation in frozen stored kuruma prawn Marsupenaeus japonicus myofibrils

Myosin and actin denaturation in kuruma prawn myofibrils stored frozen (0.1 M NaCl, pH 7.5) at ?20 °C was investigated. The inactivation profile of Ca²⁺-ATPase in the myofibrils was identical to that for myosin, indicating that myosin in myofibrils was not protected by actin. The presence of myosin detached from actin in the soluble fraction was proven by ammonium sulfate fractionation in the absence and presence of Mg-ATP. Actin denaturation in myofibrils was further confirmed by its increased susceptibility to chymotryptic degradation. In the frozen myofibrils, actin denatured more rapidly quicker than myosin: actin had completely denatured by storage day 1, followed by a gradual denaturation of myosin. Both myosin and actin in the frozen stored myofibrils retained their high salt-solubility, which decreased slowly during the frozen storage period. The presence of aggregated inactivated myosin in the salt-soluble fraction was proven by precipitation at 40 % saturation of ammonium sulfate in the presence of Mg-ATP, leaving active monomeric myosin in the soluble fraction. Almost no actin denaturation was observed with heated myofibrils.     

Effect of extender composition and freezing rate on post-thaw motility and fertility of Arctic char, Salvelinus alpinus (L.), spermatozoa

The effects of extender composition and freezing rate on motility and fertility of frozen‐thawed Arctic char, Salvelinus alpinus, spermatozoa were investigated. Three freezing rates, two semen diluents and three cryoprotectants were tested. Semen frozen in 0.3 mol L^?1 glucose diluent with 10% methanol as a cryoprotectant or in a diluent described by Lahnsteiner with 10%N,N‐dimethylacetamide (DMA) resulted in the highest sperm motility. Fertility was the highest for semen frozen in a glucose–methanol extender but was not significantly different than that for semen frozen in Lahnsteiner's diluent with 10% DMA. Dimethyl sulphoxide (DMSO) at 10% was a relatively ineffective cryoprotectant with either semen diluent. Semen frozen at 6 cm above the surface of liquid nitrogen resulted in a higher post‐thaw sperm motility and fertility than semen frozen at 5 cm. The addition of 7% fresh egg yolk to glucose diluent containing methanol or DMSO did not improve the fertility of frozen‐thawed spermatozoa. However, the addition of 7% fresh egg yolk to glucose–DMA extender significantly improved the fertilization percentages of frozen‐thawed spermatozoa. In conclusion, dilution of semen 1:3 in 0.3 mol L^?1 glucose with 10% methanol and freezing 6 cm above the surface of liquid nitrogen (freezing rate of 40±8°C min^?1, mean±SD from ?5 to ?55°C) is a promising protocol for cryopreservation of Arctic char semen.     

Influence of Washing and Cold Storage on Lipid and Protein Oxidation in Catfish (Clarias lazera) Surimi

ABSTRACT

Lipid and protein oxidation in catfish (Clarias lazera) surimi during processing and storage were assessed. Catfish surimi were washed in deionized water: M0 (no washing step), M1 (one washing step), and M2 (two washing steps). Lipid, protein, water, and iron contents were determined. M0, M1, and M2 were stored for 0, 1, 4, 7, or 10 days at 4 ± 1°C; at each time point, samples were removed for analyses. Lipid oxidation was assessed by measuring malondialdehyde content. Protein oxidation was assessed by measuring protein solubility and protein sulfhydryl and carbonyl group contents. Based on the results, lipid content, L* and a* (color parameters), and fatty acid content in M1 and M2 were significantly reduced. Lipid oxidation development was faster in M1, and the ranking was as follows: M1 > M2 > M0, with M0 being significantly less oxidized than M1. Increasing the number of washes increased protein oxidation, and the ranking was follows: M2 > M1 > M0. Altogether, lipid and protein oxidation and physicochemical changes occurred simultaneously to different degrees in surimi during various processing and storage conditions.     

Improved Cryopreservation of Sperm of Paddlefish (Polyodon spathula)

Experiments were performed to improve protocols for sperm cryopreservation of paddlefish (Polyodon spathula), a species for which there has been limited study. The first experiment was conducted to investigate the effects of two extenders (modified Tsvetkova’s extender: mT and modified Hanks’ balanced salt solution: mHBSS) in combination with methanol (MeOH) and dimethyl sulfoxide in two concentrations (5 and 10%) on the postthaw motility and fertilization rates of cryopreserved sperm. The highest postthaw motility (85 ± 5%) was observed when sperm were frozen using mT extender with 10% MeOH as cryoprotectant. Extenders (P = 0.0018) and cryoprotectants (P = 0.0040) each had a significant effect on the postthaw motility of paddlefish sperm. The highest fertilization (80 ± 3%) was found when eggs were fertilized with sperm frozen with mT extender in combination with 10% MeOH. However, there was no significant difference among fertilization rates when MeOH was used as a cryoprotectant in either concentration or in combination with either mT or mHBSS extenders. In the second experiment, 4000 eggs were fertilized with the pooled contents of five straws of thawed sperm (total volume of 1.25 mL) using mT extender in combination with 5% MeOH, and hatch rates as high as 79 ± 5% were observed. A third experiment was also conducted to clarify the role of MeOH concentration; however, no significant difference was found among fertilization and hatch rates when either 5 or 10% MeOH was used as a cryoprotectant. These results suggest that MeOH is a safe and reliable cryoprotectant for freezing of paddlefish sperm and obtaining viable postthaw sperm for consistent fertilization and hatch rates. Further, this experimental protocol is relatively simple and applicable for commercial hatchery production of paddlefish.