Carmen Gómez-Guillén

Effect of heating temperature and sodium chloride concentration on ultrastructure and texture of gels made from giant squid (Dosidicus gigas) with addition of starch,l-carrageenan and egg white

This paper seeks to compare the ultrastructure of gels made from frozen muscle of giant squid (Dosidicus gigas) at various temperatures with a number of different rheological parameters, with reference to a variety of added ingredients (non-muscle proteins and hydrocolloids) and to NaCl concentration. Interesting data on gel rheological properties were found where formulae containedl-carrageenan, starch and egg white, with a low salt concentration (1.5%). This seems to be because carrageenan forms an independent network which supports the principal structure formed by the fish protein; starch is incorporated into the network and retains water; and egg white forms a supplementary network which helps to improve rheological properties.

Thermal gelation properties of two different composition sardine (Sardina pilchardus) muscles with addition of non-muscle proteins and hydrocolloids

Abstract A Thermal Scanning Rigidity Monitor was used to study heat gelation in two sardine minces (S1 and S2) differing in compositional properties (fat content (S1 = 4.3%, S2 = 9.6%) and water content (S1 = 76.5%, S2 = 72.0%)), protein functionality (soluble protein (S1 = 62.6%, S2 = 49.8%) and viscosity (S1 = 3140 cP, S2 = 2323 cP)), as well as the contribution to gelation of a number of non-muscle proteins (egg white, soy protein, sodium caseinate, wheat gluten) and hydrocolloids (iota-carrageenan and starch). The batter of the mince, characterised by higher protein solubility and viscosity and lower fat content (S1), exhibited greater structural stability at temperatures above 50 °C. The addition of gelling ingredients always produced an increase in maximum rigidity values, except in the case of sodium caseinate or starch-containing batters of mince with low protein solubility and viscosity (S2), where the rigidity is considerably inferior throughout the experimental temperature range. Of the non-muscle proteins assayed, batters contanining egg white presented the highest rigidity at maximum gelation peak, mainly in the low quality mince (S2). Iota-carrageenan also increased rigidity considerably with respect to the controls. Addition of starch gave less rigidity than iota-carrageenan, although it helped stabilise the formed gel at high temperatures (80 °C).

Evidence of an active laccase-like enzyme in deepwater pink shrimp (Parapenaeus longirostris)

This paper demonstrates the presence of an active laccase-like enzyme from deepwater pink shrimp (Parapenaeus longirostris) using polyacrylamide gel electrophoresis. This enzyme was found in all anatomical parts of the deepwater pink shrimp, but particularly in the cephalothorax, and became active during the course of storage. Gel staining with laccase-specific substrates such as ADA, DMP and DAB was used to characterize a protein of around 44kDa as containing laccase activity. The enzyme was inhibited by a specific inhibitor, CTAB. 4-Hexylresorcinol, a specific inhibitor of polyphenoloxidase (PPO), did not inhibit the laccase-like enzyme. Low concentrations of antioxidants ascorbic acid or sodium metabisulphite were sufficient to inhibit the laccase-like enzyme. ABTS and DMP were subsequently used to characterize the enzyme. Given the evidence of this enzyme in deepwater pink shrimp, new melanosis-inhibiting compounds that are suitable for consumption need to be found to complement specific inhibitors of PPO activity.

Ultrastructural and rheological changes during the gelation of giant squid (Dosidicus gigas) muscle

The giant squid or dosidicus (Dosidicus gigas) is normally shipped frozen from the coasts of America. During the period prior to freezing-when conditions are not always optimum-and during frozen storage, the functional capacity of the muscle proteins declines, rendering the material useless for certain processes such as conversion to gel. This paper examines the reasons for the lack of a good gel-forming capacity as measured both rheologically (breaking force, breaking deformation and gel strength) and in terms of ultrastructure (scanning microscopy). The study was carried out at four different temperatures known to be critical for fish muscle protein gel formation, and at two salt concentrations. At 35°C the structure was spongier in gels made with 1.5% NaCl, although a true gel was still not formed, as shown by rheological measurements. Above 30°C, the ultrastructure became more cellular, particularly in samples made with 2.5% NaCl, at which concentration gel strength values were higher. However, at neither salt concentration nor at any of the experimental temperatures was the mesh as spongy as in other fish gels reported in the literature. The values of rheological analysis and folding test were correspondingly low.

Behaviour of egg white and starch in gelation of sardine muscle (Sardina pilchardus)

Response surface methodology was used to determine the role played by egg white and starch in gelation of minced and washed sardine muscle. There was no detectable interaction, either positive or negative, between the effects of the two ingredients. Both egg white and starch significantly affected gel strength. Egg white had a direct, positive influence on hardness and adhesiveness. Starch had a direct, positive influence on cohesiveness and the ability to retain water.

Influence of added salt and non-muscle proteins on the rheology and ultrastructure of gels made from minced flesh of sardine (Sardina pilchardus)

Abstract A study of rheological and ultrastructural properties of gels made from sardine was undertaken in order to examine the effects of adding non-muscle proteins (egg white, soy protein, casein and gluten) at different gelling temperatures. The highest values for gel strength, breaking force and breaking deformation were obtained with 2.5% salt content, which produced a more homogeneous gel matrix. Suwari gels containing soy protein exhibited greater gel strength, while for gels cooked at 90 °C the gel strength was highest in those containing egg white and a true three-dimensional network was displayed.

Preparation and molecular characterization of chitosans obtained from shrimp (Litopenaeus vannamei) shells.

Four chitosan samples were prepared from shrimp shells without deproteination and decoloration steps, by a deacetylation process at 2 reaction times (2 and 4 h) and with/without using a reducing agent (R.A.). Variations in the physicochemical properties of the final products were analyzed. Viscosity average molecular weight (Mw) determinations demonstrated the protective action of the R.A. on the molecular oxidative degradation. Oppositely, an increase on the reaction time produced samples with low Mw. Deacetylation degrees (DDs) were chemically evaluated by the nitrogen content and by spectroscopic techniques as infrared and nuclear magnetic resonance. The existing differences in crystallinity were studied by X-ray diffraction. Differential scanning calorimetry and thermogravimetry were used to demonstrate the dehydration and thermal degradation processes of the different chitosans. A novel method from calorimetric profiles is presenting for DD determinations of chitosan, which achieved highly satisfactory results (linear fit and Pearsons correlation coefficient) and is proposed to be generally extended to complex curves application.

Anti-Inflammatory, Antioxidant, and Antimicrobial Effects of Underutilized Fish Protein Hydrolysate

ABSTRACT Antimicrobial, anti-inflammatory, and antioxidant activities of protein hydrolysates from Argentine croaker (Umbrina canosai) protein isolate (CPI) or Argentine croaker myofibrillar protein with different degrees of hydrolysis (DH: 10–20%) prepared using Alcalase or Protamex were determined. Results showed that an increase in the DH resulted in higher content of hydrophobic and aromatic amino acids (AAAs) and in a decrease in molecular weight (MW) distribution for all hydrolysates obtained. Furthermore, the enzyme and raw material used influenced the amino acid content and MW determined. Hydrolysates from CPI with a 20% DH by Alcalase had higher 2,2ʹ-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) radical scavenging activity, metal chelation, and ferric-reducing antioxidant power (p < 0.05). All hydrolysate samples decreased the pro-inflammatory capacity. In all the evaluated microorganisms, only seven were inhibited, most being Gram-positive. Alcalase was found to exert a considerable influence on antibacterial activity. These hydrolysates are an alternative as natural antimicrobials, anti-inflammatory, and antioxidant compounds.