Physicochemical properties and gel-forming ability of surimi from three species of mackerel caught in Southern Thailand

Physicochemical and gelation properties of surimi prepared from three species of mackerel were investigated. The highest whiteness with the lowest redness index corresponding to the lowest myoglobin content especially its oxidised form, metmyoglobin, was found in short-bodied mackerel (Rastrelliger brachysoma) surimi (p < 0.05). Frigate mackerel (Auxis thazard) surimi contained the highest lipid content (p < 0.05). The pH of all surimi was in the range of 6.58–6.80. The highest sulfhydryl group and Ca²⁺-ATPase activity was found in natural actomyosin extracted from short-bodied mackerel surimi (p < 0.05). The highest TCA-soluble peptide content was found in frigate mackerel surimi gels (p < 0.05). Kamaboko gel of short-bodied mackerel surimi exhibited the highest breaking force with the lowest expressible drip (p < 0.05). Heating regime had no effect on deformability of gels from Indian mackerel (Rastrelliger kanagurta) and short-bodied mackerel but not for frigate mackerel. The highest metmyoglobin content with the lowest whiteness was found in frigate mackerel surimi gel (p < 0.05). Therefore, short-bodied mackerel was the best suited for the production of surimi with superior functional attributes including whiteness and gel-forming ability.     

Characteristics and gel properties of muscles from sardine (Sardinella gibbosa) and mackerel (Rastrelliger kanagurta) caught in Thailand

Dark and ordinary muscle from sardine (Sardinella gibbosa) and mackerel (Rastrelliger kanagurta) were characterized. Lipid and myoglobin contents were higher in dark muscle than in ordinary muscle of both species, and higher contents of both constituents were found in sardine muscle than mackerel muscle. The extractable myoglobin contents in sardine dark and ordinary muscle were 14.27 and 2.18 mg/g, while mackerel dark and ordinary muscle contained 4.88 and 1.37 mg myoglobin/g sample, respectively. Alkali-soluble protein and stroma contents were greater in dark muscle than ordinary muscle. Mackerel muscle comprised a higher content of non-protein nitrogenous compounds than sardine muscle. The effect of washing conditions on the myoglobin extractability was investigated. A large amount of myoglobin was removed in the first washing cycle and only a small amount was removed in the second washing cycle. The highest removal of myoglobin from sardine (32.10–46.55%) and from mackerel muscle (103.20–313.66%) was achieved when the mince was washed with 0.2% NaCl and 0.5% NaCl, respectively. Washing media showed the marked effect on the color, expressible drip and textural properties of sardine and mackerel mince gels. The breaking force of directly heated and kamaboko gels from both sardine and mackerel mince washed with NaCl solution was higher than that of unwashed mince and water washed mince. However, no difference in deformation was observed. Washing also resulted in increased whiteness and lowered expressible moisture. In general, sardine surimi showed the superior gel-forming ability and whiteness to mackerel surimi.     

Effect of reducing agents on physicochemical properties and gel-forming ability of surimi produced from frozen fish

Effects of different reducing agents (cysteine, ascorbic acid and sodium bisulfite) at various levels on physicochemical properties of protein, transglutaminase activity and gel properties of surimi produced from frozen croaker, lizardfish, threadfin bream and bigeye snapper were studied. Addition of cysteine resulted in the highest increase in the breaking force and the deformation of surimi gels, compared with other reducing agents. The optimum levels of cysteine were 0.05, 0.1, 0.05 and 0.1% (w/w) for surimi from frozen croaker, lizardfish, threadfin bream and bigeye snapper, respectively. Surimi from frozen croaker with cysteine added showed a similar breaking force and deformation to that produced from fresh fish. With addition of cysteine, an increase in sulfhydryl content with a concomitant decrease in disulfide bond content was generally observed. Ca²⁺ ATPase activity also increased, indicating the renaturation of the myosin molecule. T_max of peak 1 (myosin peak) of all surimi sols in the presence of cysteine was shifted to higher temperature. The increased transglutaminase activity was observed with addition of cysteine. Therefore, reducing agents, especially cysteine, recovered the denatured muscle proteins and activated the transglutaminase in the muscle, leading to the increased gel-forming ability of surimi produced from frozen fish.     

Effect of oxidised tannic acid on the gel properties of mackerel (Rastrelliger kanagurta) mince and surimi prepared by different washing processes

Effect of oxidised tannic acid (OTA) at different levels (0, 0.25, 0.50 and 0.75% of protein content) on the gel properties of mackerel (Rastrelliger kanagurta) mince and surimi prepared by different washing processes was investigated. Breaking force and deformation of gels varied with washing processes and concentrations of OTA. The gel of alkaline-saline washing process surimi (ASWPS) added with 0.25% OTA had the increases in breaking force and deformation by 166.2 and 45.9%, respectively, compared with that of conventional washing process surimi (CWPS) without OTA addition. Those increases were associated with the lowered expressible moisture content. Electrophoretic studies revealed that the greater polymerisation was found in ASWPS added with 0.25% OTA. Slight retention of myosin heavy chain (MHC) with lowered trichloroacetic acid (TCA) soluble peptide contents was observed in ASWPS gel added with 0.25% OTA, suggesting the decreased degradation induced by indigenous proteases. The microstructure of ASWPS gels became more ordered, compact and denser with the addition of 0.25% OTA. The use of OTA in conjunction with alkaline-saline washing process could improve the properties of gel from mackerel surimi without adverse effect on sensory properties.     

Effects of washing with oxidising agents on the gel-forming ability and physicochemical properties of surimi produced from bigeye snapper (Priacanthus tayenus)

The effects of washing with hydrogen peroxide (H₂O₂) and sodium hypochlorite (NaOCl) solutions on the gel-forming ability and physicochemical properties of surimi produced from bigeye snapper (Priacanthus tayenus), stored in ice for up to 14 days, were investigated. Generally, pH and the trichloroacetic acid (TCA)-soluble peptide content of washed mince varied, depending on the type of oxidizing agent and storage time of the fish. With increasing time of storage, the pHs of water- and H₂O₂-washed mince were lower than that of NaOCl-washed mince (P < 0.05). However, no differences in the TCA-soluble peptide contents of the resulting mince washed with any media were observed (P > 0.05). Washing with 20 ppm NaOCl resulted in the highest increase in both the breaking force and the deformation of mince from fish stored in ice for all the times studied (P < 0.05). Natural actomyosin (NAM) extracted from NaOCl-washed mince had higher surface hydrophobicity and disulfide bond (SS) content than that of water-washed mince (P < 0.05). With no effect on Ca²⁺-, Mg²⁺-, or Mg²⁺–Ca²⁺-ATPase activities, NaOCl washing resulted in an increase in Mg²⁺–EGTA-ATPase activity of NAM (P < 0.05). The results suggested that washing mince with the appropriate type and concentration of oxidizing agent can improve the gelling ability of surimi, particularly from low quality fish.     

Physicochemical characteristics,protein hydrolysis,and textual properties of surimi during fermentation with Actinomucor elegans

Solid-fermentation is a promising way of producing novel surimi-based food. In the present study, changes in physicochemical characteristics, protein hydrolysis, and textual properties of surimi during the fermentation, including pehtze preparation, salting, and ripening stages, were studied. The protease produced by Actinomucor elegans led to continuous hydrolysis of surimi protein, reflected from the high value of protease activity which reached 69.34 U/g after pehtze preparation stage, the decrease of protein bands intensity in sodium dodecyl sulfate polyacrylamide gel electrophoresis image especially for bands of 200, 43, and 36 KDa, and the increasing contents of free amino acids and trichloroacetic acid-soluble nitrogen. Hardness, springiness, and cohesiveness of the surimi all decreased during pehtze preparation stage, increased after salting, and decreased again after ripening, while adhesiveness kept increasing until the ripening stage started. Scanning electron microscopy images showed a dense and soft microstructure of surimi after ripening. The final surimi product showed high overall acceptability and no Enterobacteriaceae was detected.     

Lipase activity in different tissues of four species of fish: rohu (Labeo rohita Hamilton), oil sardine (Sardinella longiceps Linnaeus), mullet (Liza subviridis Valenciennes) and Indian mackerel (Rastrelliger kanagurta Cuvier)

Lipase activity in stomach and pyloric caeca, liver, intestine and red muscle of rohu (Labeo rohita Hamilton), oil sardine (Sardinella longiceps Linnaeus), mullet (Liza subviridis Valenciennes) and Indian mackerel (Rastrelliger kanagurta Cuvier) was studied. Distinct differences in lipolytic activity in different tissues of these fish were observed. Rohu showed the highest activity in all tissues in comparison with the other three species of fish. Among the three size groups of mullet, medium‐sized mullet showed higher activity than the other two groups in all tissues except intestine. Rohu hepatopancreatic lipase exhibited more hydrolytic activity on fish oil than rohu intestinal lipase. Copyright © 2003 Society of Chemical Industry     

Gel properties,physicochemical properties,and sensory attributes of white leg shrimp (Litopenaeus vannamei) surimi gel treated with sodium chloride (NaCl) substitutes

This study investigated the effects of different NaCl substitutes on the gel properties, physicochemical properties, and sensory attributes of shrimp surimi gel to produce high-quality reduced-salt shrimp surimi gel. The results showed that CaCl₂, calcium ascorbate (Vc-Ca), and L-arginine (L-Arg) could significantly improve the gel strength and texture of shrimp surimi gel compared to NaCl. The addition of CaCl₂, Vc-Ca, and L-Arg significantly increased the number of disulphide bonds and the content of β-sheet structures compared to NaCl. The electrophoretic analysis revealed that CaCl₂, Vc-Ca, and L-Arg had protective effects on the myosin heavy chain during thermal gelation. Additionally, CaCl₂ and L-Arg promoted the cross-linking of myofibrillar proteins to form the denser and less porous microstructures, and thus improved the gel properties of shrimp surimi gel. In general, the introduction of L-Arg as a substitute for NaCl acquired the best gel properties and sensory attributes of shrimp surimi gels, followed by CaCl₂ and Vc-Ca.     

Effects of konjac glucomannan on physicochemical properties of myofibrillar protein and surimi gels from grass carp (Ctenopharyngodon idella)

The cryoprotective effect of konjac glucomannan (KGM) on myofibrillar protein from grass carp (Ctenopharyngodon idella) during frozen storage at −18 °C and the influence of five levels of KGM (0%, 0.5%, 1%, 1.5%, and 2%) on texture properties, water-holding capacity, and whiteness of grass carp surimi gels were investigated. KGM as a novel cryoprotectant could significantly mitigate the decrease in salt extractable protein (SEP), Ca²⁺-ATPase activity, and total sulphydryl and active sulphydryl contents of myofibrillar protein during frozen storage. KGM at the level of 1% showed the same good cryoprotective effect as a conventional cryoprotectant (10% sucrose–sorbitol, 1:1, w/w). As the levels of KGM increased, breaking force and deformation of grass carp surimi gels increased significantly. Water-holding properties of the surimi gels are improved with the increasing addition of KGM, but the whiteness decreased and the colour became darker. The optimum addition level of KGM was suggested to be 1%.     

Gel properties of surimi from silver carp (Hypophthalmichthys molitrix) as affected by heat treatment and soy protein isolate

The effects of setting conditions and soy protein isolate (SPI) on textural properties of surimi produced from silver carp were investigated. Effects of setting temperature, setting time and protein concentration on the gel strength were evaluated and compared utilizing response surface methodology. Models for breaking force and breaking distance of silver carp surimi were established. The total protein content was 13.4% in all experimental samples. Setting temperature and protein concentration were the major factors affecting the gel strength. In the range of the additive SPI protein (10–40%), breaking force and distance of silver carp surimi gels decreased when the protein ratio of SPI was increased in the total protein at 30 and 40 °C for 60 min setting and heating at 85 °C for 30 min, but the breaking force obtained for 90% surimi protein plus 10% SPI protein was higher than surimi alone at 50 °C for 60 min incubation and heating at 85 °C for 30 min.     

Physicochemical and functional properties of a protein isolate produced from safflower (Carthamus tinctorius L.) meal by ultrafiltration

BACKGROUND: The protein isolate obtained from safflower meal by aqueous extraction and ultrafiltration was evaluated for its physicochemical and functional properties. RESULTS: Protein, ash and moisture contents of the safflower protein isolate were 901, 51 and 45 g kg^?1 respectively. Its water and oil absorption capacities were 2.22 mL H₂O g^?1 protein and 2.77 mL oil g^?1 protein respectively. Least gelation concentration was 20 g kg^?1 at pH 2, 6, 8 and 10 but 100 g kg^?1 at pH 4. Emulsifying properties were also affected by the pH: emulsifying activity and emulsion stability at pH 6 were 82.5 and 100% respectively. The highest foaming capacity (126%) occurred at pH 2; however, it increased by 104% with the addition of 0.25 g glucose g^?1 protein to the foam system. CONCLUSION: In the light of its functional properties found in this study, safflower protein isolate produced by ultrafiltration is recommended for use as an ingredient in food products such as salad dressing, meat products, mayonnaise, cakes, ice cream and desserts. Copyright © 2010 Society of Chemical Industry     

Physicochemical,micro-structural,and textural properties of different parts from farmed common carp (Cyprinus carpio)

The fish body of cultured common carp (Cyprinus carpio) was divided into six sections, including the upper back, lower back, jaw, chest, belly, and tail. Differences in the physicochemical, micro-structural, and textural properties of different muscle tissues were investigated. The upper and lower back, with high content of protein, low content of fat, high water-holding capacity, and desirable textural properties, was proven to be the most valuable part of common carp from both a nutritional point-of-view and an organoleptic perspective. This could provide a theoretic basis for the comprehensive utilization of freshwater fish.     

Physicochemical,thermal, rheological,and morphological properties of flour from different guar seed (Cyamopsis tetragonoloba) cultivars

In the present study, physicochemical, thermal, rheological, and morphological properties of flours from guar seed cultivars (G80, Ageta 112, and HG365) were assessed. Ageta 112 flours showed the highest protein content (26.78%) and varied significantly from G80 and HG365. The fiber, ash, and carbohydrate displayed significant differences in all three guar cultivars. Maximum gum content was extracted from G80 (41.19%), followed by HG365 and Ageta 112. Assessment of thermal properties revealed G80 flours with highest onset, peak, and endset temperature. Flours from cultivar Ageta 112 were recorded with highest paste temperature and peak viscosity and G80 flours showed lowest setback viscosities. Scanning electron microscopy was used to observe the morphological structure of different guar seed flour. Scanning electron micrographs presented the internal structure containing the galactomannans. Several significant correlations between physicochemical, gum yield, and thermal properties were revealed by Pearson correlation.     

Rheological and functional properties of gelatin from the skin of Bigeye snapper (Priacanthus hamrur) fish: Influence of gelatin on the gel-forming ability of fish mince

The rheological and functional properties of gelatin from the skin of bigeye snapper (Priacanthus hamrur) fish were assessed. The protein content of dried gelatin was 94.6% and moisture content was 4.2%. The amino acid profile of gelatin revealed high proportion of glycine and imino acids. The bloom strength of solidified gelatin was 108 g. The average molecular weight of fish skin gelatin was 282 kDa as determined by gel filtration technique. The emulsion capacity (EC) of gelatin at a concentration of 0.05% (w/v) was 1.91 ml oil/mg protein and with increase in concentration, the EC values decreased. The gelling and melting temperatures of gelatin were 10 and 16.8 °C, respectively as obtained by small deformation measurements. The flow behavior of gelatin solution as a function of concentration and temperature revealed non-Newtonian behavior with pseudoplastic phenomenon. The Casson and Herschel–Bulkley models were suitable to study the flow behavior. The yield stress was maximum at 10 °C with the concentration of 30 mg/ml. Thermal gelation behavior of threadfin bream (Nemipterus japonicus) mince in presence of different concentration of gelatin was assessed. Gelatin at a concentration of 0.5% yielded higher storage modulus (G′) value than control. Frequency sweep of heat set gel with gelatin revealed strong network formation.     

Extraction and functional properties of gelatin from the skin of cuttlefish (Sepia officinalis) using smooth hound crude acid protease-aided process

The characteristics and functional properties of gelatin from skin cuttlefish (Sepia officinalis) were investigated and compared to those of halal bovine gelatin (HBG). The gelatin extraction efficiency was improved by an acid-swelling process in the presence of smooth hound crude acid protease extract (SHCAP). The yields of gelatins from cuttlefish skin after 48 h with acid and with crude acid protease (15 units/g alkaline-treated skin) were 2.21% and 7.84%, respectively. The gelatin from skin cuttlefish had high protein (91.35%) but low fat (0.28%) contents. Compared to HBG, the cuttlefish-skin gelatin (CSG) has different amino acids composition than halal bovine gelatin. CSG contained slightly low hydroxyproline and proline (180‰) than HBG (219‰), whereas the content of serine was higher (49‰ versus 29‰). The gel strength of the gelatin gel from CSG (181 g) was lower than that of HBG (259 g) (p < 0.05) possibly due to lower hydroxyproline content. Cuttlefish-skin gelatin exhibited a similar emulsifying activity but greater emulsifying and foam stability than the halal bovine gelatin (p < 0.05). Foam formation ability, foam stability and water-holding capacity of CSG were slightly lower than those of the HBG, but fat-binding capacity was higher in the cuttlefish gelatin.     

Effect of laver powder on textual,rheological properties and water distribution of squid (Dosidicus gigas) surimi gel

In order to ameliorate the gel quality of Dosidicus gigas surimi, the effects of laver powder on gel properties, rheological properties, and water-holding capacity (WHC) were investigated. Results indicated that the addition of laver powder could significantly increase the hardness, chewiness, and breaking force of surimi gels. However, the texture indexes and gel strength began to decline when additional amount exceeded 0.6%. Rheological results demonstrated that the addition of laver powder increased the storage modulus (G′) and viscosity of surimi, prolonged protein denaturation temperature in surimi gels. Moreover, the WHC of surimi gel was improved with the increase of laver powder. Further analyses in low-field nuclear magnetic resonance revealed that laver powder could shorten the transverse relaxation time, enhanced the combination with water, and altered the distribution of different water categories. The proportion of bound water and immobilized water reached its maximum and minimum at 0.6% of laver powder, respectively. Correlation analyses showed that WHC of surimi gel was negatively correlated well with the proportion of loose-bound water, but positively correlated with the strong-bound water and free water. In conclusion, the results supported that 0.6% was the optimal additional amount of laver powder for the squid-based surimi production based on the current ingredients of surimi products.     

Physicochemical,thermal, and pasting properties of Chinese chestnut (Castanea mollissima Bl.) starches as affected by different drying methods

Starches from raw Chinese chestnut (Castanea mollissima Bl.) were isolated and dried by freeze drying and oven drying methods and the physicochemical, thermal, and the pasting properties were evaluated. Results showed that the two drying methods clearly affected the properties of the Chinese chestnut starches (CCS), both in composition, physicochemical, thermal, pasting properties, and functional characteristics. Freeze dried CCS presented the higher RS content, higher thermal properties, higher pasting values, higher solubility, lower syneresis to freezing, and thawing when compared with oven dried CCS. These properties of freeze dried CCS represented a unique starch for food ingredient usage of chestnut.     

Physicochemical,mineral and sensory properties of set‐type yoghurts produced by addition of grape,mulberry and carob molasses (Pekmez) at different ratios

This study investigated the effects of adding grape, mulberry and carob molasses (Pekmez) at 6%, 10% or 14% on titratable acidity, pH, viscosity, whey separation, water holding capacity (WHC), gel firmness, acetaldehyde, volatile fatty acids, colour values, mineral profile and sensory properties of set‐type yoghurts. Increasing concentration of the molasses decreased whiteness value, viscosity and WHC, but increased redness/greenness and yellowness/blueness values, whey separation and mineral contents of the samples significantly (P < 0.05). Nevertheless, the yoghurts produced by adding grape molasses had the highest points in the sensory evaluation, followed by mulberry and carob molasses.     

Physicochemical properties of gelatin gels from walleye pollock (Theragra chalcogramma) skin cross-linked by gallic acid and rutin

Gelatin gels were cross-linked by gallic acid and rutin. The gel strength, viscoelastic properties, thermal stability, swelling property, ultrastructure, X-ray diffraction patterns and FTIR spectra were determined to evaluate the physicochemical properties of the modified gels. The gel strength increased with increasing gallic acid concentration up to 20 mg/g dry gelatin, and then decreased at further elevated gallic acid concentration, while it continuously increased with increasing levels of rutin. Either cross-linking agent could enhance the elastic modulus (G′) and the viscous modulus (G″) of hydrogels, but the gelling and melting points didn’t show a notable improvement. Rutin boosted the thermal stability of xerogels, but decreased the equilibrium swelling ratio significantly, while as for gallic acid, there were no obvious effects on the thermal stability and equilibrium swelling ratio of xerogels. Scanning electron microscopy (SEM) was applied to observe the ultrastructure changes of the modified xerogels suggesting that gelatin xerogel at rutin concentration of 8 mg/g dry gelatin showed the highest cross-linking density. X-ray diffraction revealed that both gallic acid and rutin could enter the spacing of polypeptide chains of gelatin to reinforce the intermolecular interaction. And FTIR spectra verified that gallic acid and rutin molecules mainly interacted with skeletal C–N–C group and carboxyl group of gelatin molecules in the formation of gels. The results suggested that rutin was a better cross-linking agent for gelatin, and gels treated with rutin could be found with different physicochemical properties.