F. Fernández-Martín

Influence of adding Sea Spaghetti seaweed and replacing the animal fat with olive oil or a konjac gel on pork meat batter gelation. Potential protein/alginate association.

Standard and modulated differential scanning calorimetry (DSC, MDSC) and dynamic rheological thermal analysis (DRTA) were used to in situ simulate the batter gelation process. Texture profile analysis (TPA) and conventional quality evaluations were applied to processed products. Sea Spaghetti seaweed addition was highly effective at reinforcing water/oil retention capacity, hardness and elastic modulus in all formulations. Olive oil substituting half pork fat yielded a presumably healthier product with slightly better characteristics than control. A konjac-starch mixed gel replacing 70% of pork fat produced a similar product to control but with nearly 10% more water. DSC revealed the currently unknown phenomenon that Sea Spaghetti alginates apparently prevented thermal denaturation of a considerable protein fraction. MDSC confirmed that this mainly concerned non-reversing effects, and displayed glass transition temperatures in the range of 55-65°C. DRTA and TPA indicated however much stronger alginate-type gels. It is tentatively postulated that salt-soluble proteins associate athermally with seaweed alginates on heating to constitute a separate phase in a thermal composite-gelling process.

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.

Characteristics of pressurised pork meat batters as affected by addition of plasma proteins, apple fibre and potato starch

The authors thank the Comision Interministerial de Ciencia y Tecnologia (CICYT) for financial support under projects ALI97-0684 and ALI97-0759.

Pressure-assisted gelation of chemically modified poultry meat batters

Abstract Changes were induced in the characteristics of poultry meat protein using specific chemical modifiers to investigate the effect of pressurization, prior to heating, on gelation, texture and thermal behaviour of meat batters. Values of hardness and chewiness were higher in cooked meat batters treated with urea than in a salt-only sample, but cohesiveness was similar. The β-mercaptoethanol treatment produced a heat-induced gel with very similar properties to the salt-only gel. The rheological behaviours of salt-only and β-mercaptoethanol samples were very similar, but storage modulus values were higher in samples with urea, which accelerated gelation. The pressure-induced reduction of differences in the textural properties of meat batters suggests that hydrophobic interactions play an important role in heat-induced gelation. Differential scanning calorimetry showed that urea clearly destabilized chicken meat batters, while β-mercaptoethanol had very little influence on their thermal behaviour. Pressurization tended to equalize batters and final cooking definitively equalized them.

Thermal gelation of meat batters as a function of type and level of fat and protein content

The rheological behaviour of meat batters during heating was analysed as a function of protein level (10–16%), type (pork back or perirenal/peritoneal fat) and amount (10–22%) of fat used. Fat thermal behaviour was studied by differential scanning calorimetry and rheological properties of batters were assessed using non-destructive measurements (thermal scanning rigidity monitor). The higher the protein content, the higher were the rigidity values displayed by the batters, irrespective of fat type, although the magnitude of these values appeared to be dependent on the amount and characteristics of the fat. The lower the fat content, the lower were the rigidity values of the batters. This behaviour pattern was influenced by the amount of protein present. In general, samples containing perirenal/peritoneal fat exhibited lower rigidity values at high temperatures, whereas at less than 35–40 °C, the opposite appeared to be the case.

Temperature Dependence of the Vibrational Spectra of Thallium(I) Alkanoates

IR spectroscopy has been used to model the stepwise melting process of nine T1(I) n-alkanoate salts from the solid phase into the isotropic liquid. This study has provided an explanation of the thermal effect observed by differential scanning and adiabatic calorimetry as an enhancement in the normal sigmate shape heat-capacity morphology. Infrared spectra show that these salts exist at low temperature as crystals with a subcell different from orthorhombic or monoclinic formation (no factor group splitting observed). In the lowest solid-to-solid phase transitions, the alkyl chains remain, mainly, in a totally trans-planar conformation, but the concentration of nonplanar conformers increases continuously as the temperature rises, and at a particular value (different for each compound), the CH2 wagging progression bands disappear. The temperature range at which this chain “melting” takes place coincides with the final steps of the calorimetric enhancement of the heat capacity. Changes in wavenumbers of some characteristic bands are observed in the infrared spectra at several phase transitions found by calorimetry. Because of its enhanced sensitivity to conformational order, Raman spectroscopy also was used for several alkanoate salts.

Thermodynamics of thallium alkanoates III. Heat capacity and thermodynamic functions of thallium(I) n-tetradecanoate from 7 to 450 K

The thermal behavior of thallium(I) n-dodecanoate was studied by adiabatic calorimetry from 6 to 350 K and by d.s.c. from 230 through 470 K. The agreement between the results (temperature and thermal functions of transitions and heat capacity) from both methods was within the experimental error over the common temperature range. Several phases were observed in the sample. Four of the five solid-to-solid transitions appeared in the common temperature range of both techniques. The two lowest-temperature transitions appear as a bifurcated pair (at 282.65 and 284.8 K) with (Cp,mR) ≈ 250 and 450, respectively. The third and fourth occur at 293.1 and 312.1 K with (CpmR) ≈ 250 and 14000. Above 350 K three more transitions were measured by d.s.c.: solid-to-solid, solid-to-mesophase, and mesophase, and mesophase-to-isotropic-liquid transformations at 356.6, 400.1, and 471.5 K. The corresponding values of ΔtrsSmoR for the seven transitionswere 0.910, 1.111, 0.710, 2.075, 0.69, 1.64, and 0.50. Smoothed thermodynamic values are tabulated at selected temperatures through the “clearing” point.

A thermophysical study of the melting process in alkyl chain metal n-alkanoates: The thallium (I) series

The peculiar thermal behavior of the thallium(I) n-alkanoates series (consisting in several transitions between polymorphic and mesomorphic phases) in comparison with other metallic n-alkanoates series is stated. The allowance of highly accurate adiabatic heat capacity data permits a study of the CH2 contributions to the lattice heat capacity curve at low temperature. Moreover, in this series an anomalous gradual enhancement of the lattice heat capacity has been interpreted from vibrational spectroscopy results as a noncooperative effect due to the internal hindered rotation of the alkyl chain (formation of gauche defects, even in the solid state). The thermodynamics of the “stepwise melting process” from the totally ordered solid at low temperature to the isotropic liquid is based on a revised lattice heat-capacity curve. This was used to evaluate the energy and entropy not only of the clear first order transitions present in the series but also of the described noncooperative effect. The CH2 enthalpy an...

Thermophysics of thallium alkanoates IV. Heat capacity and thermodynamic functions of thallium(I) n-dodecanoate from 7 to 470 K

The thermal behavior of thallium(I) n-dodecanoate was studied by adiabatic calorimetry from 6 to 350 K and by d.s.c. from 230 through 470 K. The agreement between the results (temperature and thermal functions of transitions and heat capacity) from both methods was within the experimental error over the common temperature range. Several phases were observed in the sample. Four of the five solid-to-solid transitions appeared in the common temperature range of both techniques. The two lowest-temperature transitions appear as a bifurcated pair (at 282.65 and 284.8 K) with (Cp,mR) ≈ 250 and 450, respectively. The third and fourth occur at 293.1 and 312.1 K with (CpmR) ≈ 250 and 14000. Above 350 K three more transitions were measured by d.s.c.: solid-to-solid, solid-to-mesophase, and mesophase, and mesophase-to-isotropic-liquid transformations at 356.6, 400.1, and 471.5 K. The corresponding values of ΔtrsSmoR for the seven transitionswere 0.910, 1.111, 0.710, 2.075, 0.69, 1.64, and 0.50. Smoothed thermodynamic values are tabulated at selected temperatures through the “clearing” point.

DSC thermophysics on some medium chain thallium(I) n-alkanoates: Phase transitions, thermal functions and heat capacity

Abstract Four members of the series of anhydrous thallium(I) n -alkanoates with medium chain-length ( n -octanoate, n -nonanoate, n -undecanoate and n -tridecanoate) have been prepared, purified, and studied by differential scanning calorimetry between 200 and 500 K. Their polymorphic and mesomorphic behaviour has also been investigated by polarization microscopy. The temperatures and enthalpy changes for the phase transitions have been measured and the corresponding entropy changes calculated. Heat capacity measurements by DSC between 300 and 500 K are also reported.