Improving of Gelling Capacity of Cooked Crab Meat Proteins

Cooked crab meat subjected to a cutting process can aggregate again, forming weak gels. The objective of this work was to determine the effect of two mixing methods, combined with the addition of the microbial enzyme TGase (MTGase) on the mechanical and functional properties of gels from washed or unwashed blue crab (Callinectes sapidus) meat. Live crabs were obtained from Laguna Madre, Tamaulipas, Mexico, and cooked at 120°C for 20 min before hand-picking the meat from the shell. Cooked meat was processed by mixing and cut at temperatures of 25 or 60°C, without (control) or 0.5% of MTGase. Then cooked at 90°C for 15 min. Changes in texture profile analysis, percentage of extractable water, and color were evaluated. The mixing method at 60°C allowed increasing the textural properties of the gels, and the addition of MTGase significantly improved the mechanical properties. The results allowed stablishing a viable technique to obtain restructured gels from cooked crab meat with no need to extract the soluble compounds responsible for their distinctive odor and taste which often affect the mechanical properties.

The Influence of the Addition of Nuts on the Thermal and Rheological Properties of Wheat Flour

The aim of the study was to assess the influence of replacing wheat flour with hazelnuts or walnuts, in various amounts, on the thermal and rheological properties of the obtained systems. The research material were systems in which wheat flour was replaced with ground hazelnuts (H) or walnuts (W) in the amount of 5%, 10%, and 15%. The parameters of the thermodynamic gelatinization characteristics were determined by the differential scanning calorimetry method. In addition, the pasting characteristics were determined with the use of a viscosity analyzer and the viscoelastic properties were assessed. Sweep frequency and creep and recovery tests were used to assess the viscoelastic properties of the tested gels. It was found that replacing wheat flour with nuts increased the values of gelatinization temperature, gelatinization, and retrogradation enthalpy, and the degree of retrogradation. The highest viscosity was characteristic of the control sample (2039 mPa·s), and the lowest for the paste with 15% addition of walnuts (1120 mPa·s). Replacing the flour with nuts resulted in a very visible reduction in the viscosity of such systems. In addition, gels based on the systems with the addition of H and W were weak gels (tan δ = G″/G′ > 0.1), and the values of G′ and G″ parameters decreased with the increased share of nuts in the systems. Creep and recovery analysis indicated that the systems in which wheat flour was replaced with hazelnuts were less susceptible to deformation compared to the systems with the addition of W.

Rheological behavior and texture of corn starch gels (Zea mays), arrowroot (Maranta arundinaceaea L.) and cassava (Manihote sculenta Crantz)

The main energy reserve in plants is starch. It is unique among polysaccarides for being in the form of granules. Starch granules are heterogeneous mixtures of amylose and amylopectin. Gelatinization and retrogradation of starch depend on the ratio of amylose to amylopectin, type of crystallinity, along with the sizes and structure of starch granules. The present work determined the rheological behavior in a dynamic state, in terms of sweeping frequency, time and temperature, in addition to the extrusion of corn starch gels and arrowroot and cassava starches. The rheological study demonstrated that in all samples analyzed, whether in a non-gelatinized liquid mixture or in the form of gels, behaved as non-Newtonian fluids independent of time. Non-gelatinized mixtures showed properties of dilating non-Newtonian fluids and the gels of pseudoplastic non-Newtonian fluids. Gels were classified as elastic, as it was found that the storage module is larger than the dissipation module with the storage module decreasing with increasing temperature, and thus temperature dependent. With increased temperature, the gels showed low stability which is characteristic of weak gels. The more elastic the gel, the greater its resistance and the corn starch gel was the most resistant when compared to arrowroot and cassava starch.

Tuning Gel State Properties of Supramolecular Gels by Functional Group Modification

The factors affecting the self-assembly process in low molecular weight gelators (LMWGs) were investigated by tuning the gelation properties of a well-known gelator N-(4-pyridyl)isonicotinamide (4PINA). The N―H∙∙∙N interactions responsible for gel formation in 4PINA were disrupted by altering the functional groups of 4PINA, which was achieved by modifying pyridyl moieties of the gelator to pyridyl N-oxides. We synthesized two mono-N-oxides (INO and PNO) and a di-N-oxide (diNO) and the gelation studies revealed selective gelation of diNO in water, but the two mono-N-oxides formed crystals. The mechanical strength and thermal stabilities of the gelators were evaluated by rheology and transition temperature (Tgel) experiments, respectively, and the analysis of the gel strength indicated that diNO formed weak gels compared to 4PINA. The SEM image of diNO xerogels showed fibrous microcrystalline networks compared to the efficient fibrous morphology in 4PINA. Single-crystal X-ray analysis of diNO gelator revealed that a hydrogen-bonded dimer interacts with adjacent dimers via C―H∙∙∙O interactions. The non-gelator with similar dimers interacted via C―H∙∙∙N interaction, which indicates the importance of specific non-bonding interactions in the formation of the gel network. The solvated forms of mono-N-oxides support the fact that these compounds prefer crystalline state rather than gelation due to the increased hydrophilic interactions. The reduced gelation ability (minimum gel concentration (MGC)) and thermal strength of diNO may be attributed to the weak intermolecular C―H∙∙∙O interaction compared to the strong and unidirectional N―H∙∙∙N interactions in 4PINA.

Effects of heating and calcium and phosphate mineral supplementation on the physical properties of rennet-induced coagulation of camel and cow milk gels

The physical properties of rennet-induced coagulation of preheated camel and cow milk gels (50 and 70 °C for 10 min) enriched with calcium chloride (CaCl2) and hydrogen phosphate dihydrate (Na2HPO42H2O) were evaluated using the dynamic low amplitude oscillatory shear analysis. The storage modulus (Gʹ) and loss modulus (Gʺ) of camel milk gels showed significant (P < 0·05) lower values than those of cow milk gels. The preheating of camel milk at 50 °C affected negatively the gelation properties, while the preheating at 70 °C prevented the formation of rennet-induced milk gels. No effect was observed on the gelation properties of cow milk gels. The CaCl2 added at 10 and 20 mM to preheated camel and cow milk reduced significantly (P < 0·05) the gelation time and increased the gel firmness. In contrast, Na2HPO42H2O added at 10 and 20 mM induced the formation of weak gels for preheated camel and cow milk at 50 °C, and even no gelation for preheated camel milk at 70 °C.