Effect of Microbial Transglutaminase,Dietary Fiber,and Low-Salt Levels Upon Heat-Induced Meagre (Argyrosomus regius) Gels

The effects of microbial transglutaminase (MTGase; 5 g/kg, w/w) and dietary fiber (40 g pea fiber/kg product and 20 g carrageenan + 20 g konjac flour/kg product) on heat-induced meagre (Argyrosomus regius) gels with 25 and 10 g salt/kg, w/w were analyzed.

MTGase addition increased the magnitude of texture variables. Inner pea fiber had an increasing effect on gel texture. The combination of carrageenan and konjac hardened meagre gels (from 22.2 ± 1.4 to 47.3 ± 4.5 N) and enhanced water-holding capacity. Salt reduction with MTGase ensured a gelling quality similar to that of gels from Alaska pollock surimi.     

Gel Properties of Surimi from Silver Carp (Hypophthalmichthys molitrix): Effects of Whey Protein Concentrate,CaCl2, and Setting Condition

The effects of setting time, whey protein concentrate (WPC), and calcium chloride (CaCl₂) on textural properties of silver carp surimi were investigated. Response surface methodology was used to evaluate and compare the effects of setting time (30–90 min), WPC (1–9% of protein ratio), and CaCl₂ (1–59 mmol/kg) on the gel strength. Models for breaking force, breaking distance, and gel strength of surimi gel were established. The maximum gel strength was achieved at the setting time of 60 min, WPC and CaCl₂ at 5% protein ratio, and 15–18 mmol/kg. CaCl₂ was the most significant factor affecting the gel strength.     

Algal biomass accrual in relation to nutrient availability and limitation along a longitudinal gradient of a karst riverine system

Textural property of surimi products is a prime factor in determining the acceptability of consumer as well as market value. Gelatin is one of the most popular biopolymers widely used in food industry as gelling agent with the unique textural properties. Therefore, the addition of gelatin along with the use of protein cross-linkers could be a means to modify the texture of surimi gel, which can fit the demand of consumers. Surimi from the threadfin bream (Nemipterus bleekeri) was added with bovine gelatin (BG) and bovine/fish gelatin mix (BFGM; 1:1, 2:1, 1:2, 4:1, and 1:4) at 10% protein substitution in combination with and without microbial transglutaminase (MTGase) at 1.2 units/g surimi. Textural properties, whiteness, expressible moisture content, protein pattern, and microstructure and sensory properties of gels were determined. When MTGase at 1.2 units/g surimi was incorporated, the increases in breaking force and deformation were noticeable in both surimi gels, with and without 10% BG added ( p < 0.05). On the other hand, surimi gels added with BFGM at all bovine/fish gelatin ratios had the higher breaking force and deformation, compared with that added with BG, when MTGase was incorporated. Addition of BG or BFGM lowered the expressible moisture content and whiteness of surimi gel ( p < 0.05). Based on SDS-PAGE, band intensity of myosin heavy chain and actin of surimi gel decreased when surimi gel was added with all gelatins, regardless of MTGase addition. The microstructure study revealed that surimi gel network became finer and denser with the addition of MTGase (1.2 units/g surimi), but the coarser and irregular structure was obtained when gelatin was incorporated. Gelatin, especially bovine/fish gelatin mix, at an appropriate level could be used as the protein additive in surumi gel in conjunction with MTGase in order to improve the textural and nutritive properties of the products.     

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.     

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.     

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.     

Using Antioxidants for Extending the Shelf Life of Frozen Nile Karmout (Claries lazera) Fish Mince

Abstract

Nile karmout (Claries lazera)fish mince was treated with 0.5% sodium tripolyphosphate (STPP), 0.5% ascorbic acid, 0.5% citric acid, and 0.1% Na EDTA, then stored at -18°C for 6 months. Yield, proximate composition, thiobarbitunc acid value (TBA), free fatty acid (FFA), salt soluble protein (SSP), non-protein nitrogen (NPN), water holding capacity (WHC), and cooking loss were determined at 0, 2, 4, and 6 months of storage. The yield of skinned fillet from whole fish was 47.0%. Moisture, protein, fat and ash offish mince were 72.9%, 17.6%, 8.5% and 1.0%, respectively. TBA values and FFA levels indicated that ascorbic acid and Na₂EDTA were the most effective antioxidants. Samples treated with STPP had the highest salt soluble protein. STPP was effective in maintaining the WHC of treated sample. Samples treated with citric acid had the highest cooking loss. Results of the study suggested that karmout is an excellent source for producing fish mince for further processing. Samples treated with antioxidants retarded the rancidity during frozen storage.     

鲟鱼鱼糜漂洗工艺优化及其对品质的影响

本研究以鲟鱼(Acipenser sinensis)肉为原料,通过正交实验对鲟鱼鱼糜的漂洗工艺进行了优化,对鱼糜漂洗前后的蛋白质含量及其组成、水分分布、凝胶性能等进行了研究。结果显示,鲟鱼鱼糜的最佳漂洗工艺为：水漂洗1次,盐水漂洗1次,盐的质量分数为0.25%,漂洗时间为1 min。鲟鱼鱼糜经漂洗后,其盐溶性蛋白比例显著升高(P<0.01);鱼糜中的水分受到的束缚力增加,自由度减小,形成了更为致密的凝胶网状结构;破断力、凹陷距离、凝胶强度、持水力、白度等表征凝胶性能和鱼糜品质的指标明显提升。研究表明,采用恰当的漂洗工艺可显著提高鲟鱼鱼糜的品质。     

Effects of Olive Leaf Powder on Mechanical Properties of Heat-Induced Surimi Gel

The effects of addition of olive leaf powder (OLP) to surimi on the mechanical properties of surimi gel were investigated. The OLP contained a high polyphenol content of 7% (w/w). The breaking stress and breaking strain of surimi gel increased with increasing OLP concentration. The addition of 0.3% OLP increased the breaking stress of surimi gel by 80% and the breaking strain by 38%. The addition of 2.0% OLP resulted in a 100% increase in the breaking strain. The OLP gels had finer and denser protein networks than the control gel, probably due to integration of additional crosslinks into the protein networks via polyphenols or their derivatives. Although the addition of OLP had a detrimental effect on whiteness of surimi gel, OLP is still a useful functional ingredient for improving mechanical properties of surimi gel products in which the color is not an important quality.     

Effect of β-Glucan Stabilized Virgin Coconut Oil Nanoemulsion on Properties of Croaker Surimi Gel

Effects of virgin coconut oil (VCO) nanoemulsion stabilized by β-glucan and β-glucan solution at final β-glucan levels of 5–20% (based on solid weight of surimi) on croaker surimi gel were comparatively studied. Increases in breaking force, deformation, and fracture constant were found in surimi gel containing VCO nanoemulsion stabilized by 5% β-glucan, whereas a decrease in all properties was observed as the level of β-glucan in nanoemulsion increased. The addition of β-glucan solutions led to continuous decrease in breaking force, deformation, and fracture constant, compared to the control. Addition of both β-glucan stabilized nanoemulsion and β-glucan solutions resulted in decrease in viscoelastic moduli. Power law model represented viscoelastic behavior of all the gels. Expressible moisture content decreased, while whiteness increased with the addition of β-glucan-stabilized nanoemulsion, compared with gel containing VCO. However, both expressible moisture content and whiteness increased with the addition of β-glucan solutions, at all levels used. Addition of β-glucan-stabilized nanoemulsion resulted in finer gels compared to the control gel added with only VCO. Generally, overall likeness score increased for gel containing VCO nanoemulsion stabilized by 5% β-glucan. The surimi gel containing both medium chain fatty acids and β-glucan, functional ingredients, could be developed as a new product.     

Biochemical,Physical, Chemical,and Microbiological Assessment of Blue Shrimp (Litopenaeus stylirostris) Stored in Ice

Postmortem changes in blue shrimp (Litopenaeus stylirostris) muscle were studied on the basis of biochemical, chemical, physical, and microbiological changes during an 18 day storage period at 0°C. Adenosine 5′-triphosphate (ATP) content, breakdown products, K-value, pH, trimethylamine nitrogen (TMA-N), total volatile basic nitrogen (TVB-N), water holding capacity (WHC), color, and texture (shear force) changes were examined. Also, total mesophilic and psychrophilic bacterial counts were measured. K-value increased linearly (r² = 0.98) from an initial value of 1.37 ± 0.59 to 59.42 ± 6.05% at Day 18. Spoilage indicators TVB-N and TMA-N increased from 29.56 ± 1.33 and 0.69 ± 0.25 to 39.04 and 2.04 ± 0.59 mg of N/100 g at Day 18, respectively; meanwhile, the total viable counts of mesophilic and psychrophilic bacteria increased from 3.48 ± 0.44 and 2.61 ± 0.29 log CFU/g to 6.27 ± 0.21 and 7.14 ± 0.39 log CFU/g, respectively, which indicated spoilage at the end of the storage period. The pH, texture, WHC, and color were affected (p < 0.05) during the storage period. Overall, results indicate that blue shrimp muscle quality was maintained for 12 days of storage in ice.     

Effects of Injection of Protein Solutions Prepared from Fish By-products on Yield and Chemical Properties of Chilled and Frozen Saithe (Pollachius virens) Fillets

Fish gelatine and protein solutions prepared from saithe by-products were injected into saithe fillets. Effects on weight changes, water holding capacity, and chemical composition of the fillets were investigated after chilled (2, 5, and 7 days) and frozen (14 and 49 days) storage. The results showed that higher weight yields were obtained by adding proteins and salt to the fillets in comparison with only salt, especially in chilled fillets. The drawback of the injection was that higher drip losses were found during storage and thawing than for untreated fillets. Effects of injection on water content were only significant after 2 days of chilled storage, but differences leveled out after longer storage time and with freezing and thawing of the fillets. The procedure applied in this study seems to be promising for utilization of by-products such as trimmings as an ingredient in higher value products like fillets, in comparison to mince products.     

Chilled Storage of Pangasianodon hypophthalmus Fillets Coated with Plant Oil Incorporated Alginate Gels: Effect of Clove Leaf,Clove Bud,Rosemary and Thyme Oils

Essential oil incorporated alginate coating provides a novel way to improve the safety and shelf life of pangasius (Pangasianodon hypophthalmus) fillet. Oils from the leaves and buds of clove, flowering tops of rosemary, and dried seeds of thyme were incorporated separately in alginate coating. All the plant oils showed antibacterial activity, but the zone of inhibition was relatively larger for thyme oil. Alginate coating was performed using sodium alginate (1.5%), glycerol (10%), and calcium chloride (2%) and plant oil at 1% (v/v). The coated fillets were stored under chilled conditions and samples were analyzed for bacteriological, chemical, sensory, color, and texture parameters. Psychrotrophic counts crossed 7 log cfu/g by the 13^th day and 15^th day of chilled storage in control and plant oil treated fillets, respectively. The peroxide value of treated fillets was relatively low. Texture profile analysis indicated that plant oil incorporated alginate coating reduced the rate of loss of texture (softening) during chilled storage. Plant essential oil incorporated alginate gels were relatively better compared to control fillets in preserving pangasius fillet quality during chilled storage, and incorporation of thyme oil was relatively better compared to clove leaf oil, clove bud oil, and rosemary oils.     

Preliminary results on quality and quality changes in reared meagre (Argyrosomus regius): body and fillet traits and freshness changes in refrigerated commercial-size fish

Meagre (Argyrosomus regius) intensively reared in tank by a Tuscany farm and fed commercial diets, were examined to study a) marketable and flesh nutritional traits in commercial-size fish and b) loss of freshness under refrigerated storage condition. Eighty fish, sampled in May, July and November (at 24, 26, 30 months of age) were submitted to linear measurements and weight of the most important body components. Whole fillets were analysed for moisture, lipid and fatty acid composition. Data were analysed by ANOVA (sampling date). A sub sample of fifty-four meagre (902–1840 g b.w.) was stored at 1 °C with ice cover and evaluated every 24 h after death until spoilage for the EU freshness classes, dielectric properties, rigor index, muscular and eye liquor pH, K₁% freshness index. Data were analysed by regression on time after death. A small sample of meagre (n = 6) and sea bass (Dicentrarchus labrax) (n = 6), reared in analogous rearing condition in the same farm were compared by ANCOVA on body weight (average b.w. 668 g). Meagre were characterised by 1.04 condition factor, 44% fillets, 6% viscera, negligible mesenteric fat (1%) and 94.5% dressing yield. The head incidence increased (P < 0.01) with b.w. increase. Moisture increased while lipid decreased (P < 0.01) in fillet from July to November (74.47 vs 75.96%; 2.93 vs 2.06%). An index of thrombogenicity calculated from the quantitative fatty acid composition was very low (0.10). In comparison with sea bass of the same body weight, meagre had greater length (41.2 vs 37.6 cm), head incidence (29.9 vs 20.7%) and dressing (94.8 vs 89.2%) and lower viscera (5.2 vs 10.9%), mesenteric fat (0.9 vs 7.9%) and intramuscular fat (2.24 vs 12.78%) incidences. Meagre had a 9-day shelf-life (E class from 1^st to 3^rdd and A class from 4^th to 7^thd). Rigor index and impedance remained higher than 90% and 66, respectively until the 3^rdd after death. The quality traits found for this species indicated meagre as a promising candidate for Mediterranean aquaculture.     

Processing Method Effect on Texture,Color, and Microbial Load of Channel Catfish Fillets

Abstract

Catfish shelf life depends largely on post-harvest handling and storage conditions. Three methods of processing catfish fillets were studied to evaluate quality and shelf life. In one method catfish were hand-dressed, chilled in water at 0°C, and hand-filleted (HC). In the other methods, catfish were mechanically filleted and chilled immediately (MC) or held unchilled for one hour at 18°C prior to chilling (MU). All fillets were stored in HDPE bags at 2°C for analyses at 0, 3, 6, and 9 d. Shear force for MC and MU fillets decreased (P ≤ 0.05) to the same levels as HC fillets after 3 d storage. HC fillets had higher (P ≤ 0.05) ‘L’ and ‘b’ and lower ‘a’ values than MU or MC fillets throughout storage. Initial psychrotrophic counts (PPC) were lower (P ≤ 0.05) for MC (3.9 log CFU/g) and MU (4.1 log CFU/g) than for HC fillets (5.2 log CFU/g). The PPC increased (P ≤ 0.05) after 3 and 6 d in HC and MU fillets, respectively. Coliform growth showed similar patterns as PPC. Spoilage levels indicated a doubling in shelf life of machine-cut fillets (～8 d) as compared to hand-cut fillets (～4 d).     

The Influence of Cooking Parameters and Chilled Storage Time on Quality of Sous-Vide Atlantic Mackerel (Scomber scombrus)

The aim of the present study was to evaluate the effects of various sous-vide time–temperature regimes and their interactions on quality parameters of Atlantic mackerel (Scomber scombrus) during chilled storage. The mackerel ?llets were exposed to sous-vide treatment at 60, 75, and 90°C for 10, 15, and 20 min and further stored for 1, 3, and 7 days at 4 ± 1°C before analysis. Changes in pH, water content and cook loss, amount of water- and salt-soluble proteins, texture, and color parameters, as well as accumulation of lipid oxidation products in sous-vide-cooked mackerel were assessed. Sous-vide cooking time and temperature had the lowest contribution to the formation of primary and secondary products of lipid oxidation, as well as increase in yellowness of the fish flesh due to their accumulation; whereas duration of chilled storage led to a significant increase in oxidation and yellowness (p < 0.05). Duration of chilled storage also affected structural and textural properties of the fish muscle, leading to a decreased cook loss. At the same time, sous-vide cooking decreased the firmness of the fish muscle. Duration of chilled storage was found to have the highest significant effect (p < 0.001) on all physicochemical characteristics of sous-vide-cooked mackerel.     

Gelation Characteristics of Surimi Gel from Silver Carp (Hypophthalmichthys molitrix) by Application of Acid-Alkali Processes

Textural characteristics of silver carp surimi gel prepared from acid- and alkali-produced protein isolates were investigated and compared to the surimi gels derived by conventional methods. The acid-aided method showed the most efficiency to recover proteins (86.2%) in comparison to the alkaline-aided (79.8%) and conventional (76.7%) methods. In the washing of fish mince, every step resulted in reduction of sarcoplasmic protein, and consequently the myofibrillar fraction became more concentrated, as shown by the protein patterns in wash water. Some myofibrillar proteins (mainly actin and myosin) were removed along with sarcoplasmic proteins during washing, reducing yield efficiency during the conventional method of making surimi. During the pH shifting process, myosin heavy chain (MHC) was degraded during low (2.5) pH solubilization, whereas there was only a minimal loss of MHC by either hydrolysis or proteolysis during alkaline solubilization. The breaking force and breaking distance of surimi gel prepared in the pH-shifting processes were significantly (p < 0.05) greater than those of surimi gel made by conventional methods, as were expressible moisture, cohesiveness, and springiness. In conclusion, the pH-shifting technique can be considered as an efficient alternative process in recovery of greater quantities of functional protein from silver carp fillet.     

Instrumental Textural Changes in Raw White Shrimp During Iced Storage

The general objective of this work was to evaluate the changes in the texture of raw white shrimp, stored whole in ice for up to 14 days, by instrumental texture analysis of the flesh after peeling off the carapace. Effect of test method (relaxation, compression, texture profile analysis, cutting, and penetration tests), test speed (0.1, 0.5, and 1.0 mm/s), and test position on sample (second, third, and fourth segments of abdominal musculature) were studied to measure the textural attributes of shrimp. Mechanical parameters (force at yield point, stiffness, toughness, and shear/penetration work) increased significantly during the 14 days of storage. Shrimp muscle maintained firm texture up to 4 days of storage after harvesting. At that time, the texture became soft, stiffness of the skin layer increased, and then pH values in the shrimp reached a value higher than 7 (alkaline). A linear model with a high coefficient of determination (R² > 0.75, for all parameters obtained from the penetration test with the spherical probe) described adequately the mechanical properties of iced shrimp during storage. Comparing several methods, the penetration test on the second flesh segment using a spherical probe at a speed of 0.1 mm/s and using penetration work as a parameter gave the best results to clearly indicate the changes in textural properties of iced shrimp with a high correlation coefficient during storage time (R² = 0.83), while other test methods failed to provide an indication of deterioration.     

Quality improvement by vacuum treatment of boiled skipjack loins for the production of dried skipjack

ABSTRACT: This study attempted to reduce the lipid and water contents in boiled skipjack loins by vacuum treatment and the quality of vacuumed boiled meat was then evaluated during the chilled and frozen storage. The boiled meats were vacuumed at a pressure of 400 Pa for 30 min using a vacuum freeze dryer as an experimental convenience in order to degrease, cool and dehydrate rapidly. The vacuumed boiled meats were stored at 0.0 ± 0.2°C for 10 days and at −20 ± 0.5°C for 90 days. The unvacuumed boiled meats were cooled by air-cooling and stored as the control. Lipid content on a wet basis (w.b.) was reduced as much as 0.5% in the ventral part and 0.4% in the dorsal part of the boiled meats after vacuum treatment. Water content (w.b.) was reduced as much as 2.5% in the ventral part and 3.0% in the dorsal part. The thiobarbituric acid and volatile basic nitrogen values in vacuumed boiled meats were significantly lower ( P < 0.05) than that in unvacuumed boiled meats during storage. Inosine monophosphate (IMP) was only detected as a major nucleotide (about 70%) in boiled meats, and the decomposition of IMP in vacuumed boiled meats was smaller than that in unvacuumed boiled meats during storage. It was concluded that the quality of boiled skipjack loins could be improved by vacuum treatment as a preprocessing procedure in the production of dried skipjack such as katsuobushi .     

Preliminary observations of chilled and deep-frozen storage of grouper (Epinephelus tauvina) sperm

Trials of chilled (5–10° C) and cryogenic storage of grouper sperm revealed that sperm suspended in two different solutions containing 10% dimethyl sulfoxide (DMSO) were active after 2 days of chilled and deep-frozen storage, whereas those suspended in the same solutions containing 10% glycerol were not. Sperm suspended in the 10% DMSO sulutions were more active after chilled storage than were those in undiluted milt under the same conditions.