Helena M. Moreno

Improvement of Cold and Thermally Induced Gelation of Giant Squid (Dosidicus gigas) Surimi

Depending on the season of capture, giant squid (Dosidicus gigas) surimi processed by isoelectric precipitation presents low gel strength. Addition of microbial transglutaminase (MTGase) and application of high isostatic pressure (300 MPa) to improve physicochemical properties were assayed for purposes of making “suwari” gels and heated gels for use in restructured products which have a raw or cooked appearance. The physicochemical properties of both pressurized and unpressurized gels induced by application of 30°C/1 h improved when MTGase was added. In contrast, addition of MTGase was less effective in gels subsequently heated at 90°C/30 min after 30°C/1 h. High pressure treatment for 30 min at 300 MPa and 15°C helped to produce gels with better mechanical and water binding properties, whether treated for 30°C/1 h only or for 30°C/1 h plus 30-min heat treatment at 90°C. High pressure treatment also reduced lightness.

Collagen characteristics of farmed Atlantic salmon with firm and soft fillet texture

The possible role of collagen in texture variations among Atlantic salmon (Salmo salar L.) grown under commercial conditions at a Norwegian farm was studied. The texture was determined instrumentally as the breaking strength, and collagen and its salt (SSC), acid (ASC), pepsin (PSC) and insoluble (IF) fractions were analysed in order to determine the collagen aggregation degree. The collagen solubility and its overall amino acid (AA) composition showed no correlation to the breaking strength, but a positive correlation was observed between the breaking strength and glycine (r=0.74) and alanine (r=0.87) contents of the PSC fraction. Salmon with high breaking strength had higher T(peak) (temperature of transition) and ΔH (enthalpy of transition), and the collagen seemed to have triple helix structures mainly stabilized by covalent associations as compared to salmon with low breaking strength. The glycosylation degree was also positively correlated to the breaking strength (r=0.88, p ≤ 0.05). It is concluded that firmness of salmon muscle was not related to the total amount of collagen in the muscle, but rather higher collagen stability.

Different additives to enhance the gelation of surimi gel with reduced sodium content.

This study tested the effect of adding tetra-sodium pyrophosphate, cystine and lysine as surimi gelation enhancers (Alaska Pollock) in order to reduce the sodium content of gels up to 0.3%. These gels were compared with others that contained 3% NaCl content (the amount typically used for surimi processing). To induce protein gelation, gels were first heated and then set at 5 °C/24 h. Once the physicochemical and rheological properties of the gels were determined, cystine and lysine were found to be the most effective additives improving the characteristics of low NaCl surimi gels. The action of these additives is mainly based on the induction of myofibrillar protein unfolding thus facilitating the formation of the types of bonds needed to establish an appropriate network. It was found that a setting period was needed for gel processing to maximize the effect of the additives.

New Alternatives in Seafood Restructured Products.

A general overview, focusing on new trends in the different techniques used in restructured seafood product processing has been described in this work. Heat-induced gelation has been more widely studied in scientific literature than cold gelation technology. This latter technology includes the use of hydrocolloids (alginates and glucomannan) or enzymes (microbial transglutaminase) for making both raw and cooked restructured products. In restructuration processes, fortification processing with some functional ingredients is studied, giving as a result extra value to the products as well as increasing the variety of new seafood products. The process of alleviating heavy metals and organic pollutants from the raw material used has also been reviewed in the present paper.

Raw-appearing Restructured fish models made with Sodium alginate or Microbial transglutaminase and effect of chilled storage

A reestruturacao pela adicao de Alginato de sodio ou Transglutaminase microbiana (MTGase) utilizando a tecnologia de gelificacao pelo frio torna possivel a obtencao de diversos produtos crus, a partir de musculo de peixe picado, que sao apropriados para serem usados como base de novos produtos reestruturados com diferentes propriedades fisico-quimicas e ate com composicoes diferentes. Consideracao especial deve ser dada ao prazo de validade e as mudancas que podem ocorrer durante a refrigeracao, tanto no aspecto visual como nas propriedades fisico-quimicas. Apos o armazenamento refrigerado de modelos reestruturados feitos com diferentes tamanhos de particulas musculares e composicoes a baixas temperaturas (5 °C), foi observado um crescimento microbiano que limita o prazo de validade para 7 a 14 dias. As propriedades mecânicas aumentaram (p < 0,05) durante o tempo, e os valores mais altos foram mais observados nas amostras elaboradas unindo particulas de musculo de tamanho pequeno do que nas elaboradas por homogeneizacao. O rendimento apos cozimento e a perda de purga nao apresentaram uma evolucao clara nem foi detectada qualquer mudanca significativa na cor.

Importance of salt and temperature in myosin polymerization during surimi gelation

To address the effect of absence of NaCl on myosin heavy chain polymerization during two-step surimi gelation (different setting temperatures/times -5°C/24h and 30°C/30min-followed by heating at 90°C/30min) were considered. In gel samples made without salt (Lot A), no myosin heavy chain (MHC) polymerization was observed, only aggregation, as indicated by the electrophoresis in polyacrylamide/agarose gel profile. Moreover, these gels were characterized by weakly stabilized protein networks as denoted by the dynamic oscillatory measurement and FTIR analysis, resulting in poor quality gels. On the other hand, in gels made with added salt, MHC polymerization occurred, as evidenced by the electrophoresis, and the gelation resulted in a well-stabilized protein network with good physicochemical properties.

Effect of selective breeding on collagen properties of Atlantic salmon (Salmo salar L.)

Collagen content and properties of skeletal muscle were studied among selected (FP) and unselected (WP) Atlantic salmon lines that were reared together to avoid any environmental effects. The FP group had significantly higher body weight at harvesting, softer texture and lower connective tissue yield compared with the WP group. The relative collagen fractions (acid, pepsin, insoluble) were similar, but the FP group had a greater abundance of amino acids involved in collagen triple helix conformation and stabilisation (Gly, Pro, Hyp and Hyl), whilst the Lys content was greater for the WP group, indicating a more aggregated collagen. The connective tissue denaturation temperature was lower for the FP group, coinciding with a lower degree of collagen self-assembly and intermolecular-crosslinks. It is concluded that selective breeding has resulted in lower connective tissue stability of Atlantic salmon fillets.

Raw-appearing Restructured fish models made with Sodium alginate or Microbial transglutaminase and effect of chilled storage Reestrutura do modelo peixe feito com transglutaminase alginato de sódio e microbiana e o efeito do armazenamento refrigerado

A reestruturacao pela adicao de Alginato de sodio ou Transglutaminase microbiana (MTGase) utilizando a tecnologia de gelificacao pelo frio torna possivel a obtencao de diversos produtos crus, a partir de musculo de peixe picado, que sao apropriados para serem usados como base de novos produtos reestruturados com diferentes propriedades fisico-quimicas e ate com composicoes diferentes. Consideracao especial deve ser dada ao prazo de validade e as mudancas que podem ocorrer durante a refrigeracao, tanto no aspecto visual como nas propriedades fisico-quimicas. Apos o armazenamento refrigerado de modelos reestruturados feitos com diferentes tamanhos de particulas musculares e composicoes a baixas temperaturas (5 °C), foi observado um crescimento microbiano que limita o prazo de validade para 7 a 14 dias. As propriedades mecânicas aumentaram (p < 0,05) durante o tempo, e os valores mais altos foram mais observados nas amostras elaboradas unindo particulas de musculo de tamanho pequeno do que nas elaboradas por homogeneizacao. O rendimento apos cozimento e a perda de purga nao apresentaram uma evolucao clara nem foi detectada qualquer mudanca significativa na cor.

Structural and rheological properties of weakly deacetylated glucomannan gels after high-pressure treatment

ABSTRACT Native glucomannan (Lot A; pH = 5.3) and weakly deacetylated glucomannan (Lot L; pH = 9.1) gels were subjected to high hydrostatic pressure (HHP): 100, 200, 400, and 600 MPa and studied the influence of HHP on the structural and rheological properties of glucomannan gels. HHP improved the conformational stability, reticular deformability and the energy stability of hydrogen bonds in junction zones of the glucomannan matrix for lot A gels. For lot L gels, 600 MPa was needed to increase the energy content of physical bonds enhancing the solid-like character of the glucomannan matrix. Thermal profiles of pressurized lot A gels exhibited thermophobic behaviour and increased the gel-like character up to 90°C as compared with its unpressurized control. For Lot L gels, the rubber-like response was also shown at T > 70°C for the unpressurized sample, and was maintained at 100, 200, and 600 MPa.