Effects of different levels of fat on rheological changes and microstructure of meat batters during heat processing

Summary The effect of differences in fat content (5.3% and 20.8%) on the rheological characteristics and microstructure of meat batters in the course of heating was studied. Rheological properties were assessed using nondestructive measurements (thermal scanning rigidity monitor) and structural failure (penetration test) analyses. Microstructure was studied by scanning electron microscopy (SEM). The influence of fat content on the modulus of rigidity (G) only became evident as gel structures began to form, giving higher G values for meat batters the higher the fat content of the sample. As the temperature was raised in the product (between 40 and 70° C), penetration stress and elasticity increased. The work of penetration, on the other hand, increased between 40 and 60° C, remaining steady at higher temperatures. Analysis of the results on the basis of different treatments indicates that an increase in fat content significantly raises penetration stress, elasticity and work of penetration. Increased temperature causes the formation of a matrix structure typical of heat-induced protein gels, which became compact and determine the formation of stronger, more elastic structures. Differences in microstructure caused by fat content were more evident at low temperature (40° C).

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Auswirkungen verschiedener Fettgehalte auf die rheologischen Veränderungen und Mikrostruktur von Fleischmischungen während des Erwärmungsprozesses

Zusammenfassung Es wurde die Wirkung verschiedener Fettgehalte (5,3% und 20,8%) auf die rheologischen Eigenschaften und Mikrostruktur von Fleischbräten während des Erwärmungsprozesses untersucht. Die rheologischen Eigenschaften wurden mittels nicht zerstörender Messungen (thermal scanning rigidity monitor, TSRM) und Penetrationstests bewertet. Die Untersuchungen der MikroStruktur wurde durch Raster-Elektronenmikroskopie (REM) durchgeführt. Der Einfluß des Fettgehalts auf den Festigkeitsgleitmodul (G) wird im gleichen Ausmaß ersichtlich, in welchem die Gelstrukturen beginnen, sich zu bilden. Je höher der Fettgehalt des Bräts ist, desto größer werden die G-Werte in den Bräten. Je mehr die Temperatur des Erzeugnisses gesteigert wurde (zwischen 40 °C und 70 °C), um so mehr stiegen Penetrationdruck und Elastizität an. Obwohl sich die Penetration zwischen 40 °C und 60 °C erhöhte, blieb diese bei höheren Temperaturen konstant. Die Analyse der Ergebnisse aufgrund der Behandlungen zeigt, daß ein größerer Fettgehalt den Penetrationdruck, die Elastizität und Eindringungseffekt bedeutend erhöhen. Die Erhöhung der Temperatur verursacht die Bildung von Matrix-Strukturen, die typisch für die durch Hitze herbeigeführten Proteingele sind, deren stärkere Verdichtung die Bildung von stärkeren und elastischeren Strukturen bedeutet. Die durch die Einwirkung des Fettgehalts in der Mikrostruktur entstandenen Unterschiede scheinen bei niedriger Temperatur (40 °C) klarer hervorzutreten.

     

Effect of natural fermentation on the content of inositol phosphates in lentils

The effects of natural fermentation upon phytic acid and less phosphorylated inositol phosphates ofLens culinaris var vulgaris cultivar Magda-20 were investigated. Seven fermentation runs were made following a 2² complete factorial design with three replicated centre points to study the effect of different conditions of temperature (28, 35 and 42°C) and broth concentration (79, 150 and 221 g/l). Samples were taken for each of them at daily intervals (0, 24, 48, 72 and 96 h). The pH value declined sharply in the first 24 h of fermentation, becoming stabilized from this time. The relation between lactic acid and titratable acidity presented important differences between the different fermentations, ranging from 30–80%. Phytic acid (IP ₆), inositol pentakis (IP ₅), tetrakis (IP ₄) and tris-(IP ₃) phosphates were quantitatively determined. The content of total inositol phosphates showed a maximum reduction of 63% at 72 h under the fermentation conditions of 42°C and 79 g/l.     

Rheological changes during thermal processing of low-fat meat emulsions formulated with different texture-modifying ingredients

The rheological behaviour of high-fat (22%) and low-fat (8%) meat emulsions during thermal processing in the presence (3%) of various texture-modifying non-meat ingredients, namely maltodextrin, starch, wheat flour, egg white and apple fibre, was analysed. Rheological properties of emulsions were assessed using non-destructive measurements (thermal scanning rigidity monitor, TSRM). The lower the fat content, the lower were the rigidity values of meat emulsions throughout the temperature range studied. Emulsions made with maltodextrin proved less rigid. Addition of starch and egg white favoured the formation of more rigid structures in low-fat meat emulsions at temperatures over 55 °C. Low-fat meat batters containing wheat flour and apple fibre exhibited the highest rigidity values over the given temperature range. The presence of wheat flour caused variations in the modulus of rigidity at all stages of the thermal gelation process, very similar to those observed in high-fat emulsions.     

The Determination of Low-Level Water in Transdermal Dosage Forms as Tyvek Laminates with an Evaporator Oven

An assay of water in adhesive monolithic transdermal drug dosage forms ('patches'), using lamination to Tyvek, and gaseous extraction in an evaporator oven into a Karl Fischer titrator, is described. The method is simple, linear, accurate, specific and more sensitive than alternatives.     

On a non-linear formulation for curved Timoshenko beam elements considering large displacement/rotation increments

An incremental Total Lagrangian Formulation for curved beam elements that includes the effect of large rotation increments is developed. A complete and symmetric tangent stiffness matrix is obtained and the numerical results show, in general, an improvement over the standard formulation where the assumption of infinitesimal rotation increments is made in the derivation of the tangent stiffness matrix.     

Industrial trials on coadjuvants for olive oil extraction

Industrial scale experiments were performed in an olive oil production factory to assess the effect of different physical acting coadjuvants on oil extraction and oil quality. Up to 120,000 kg olives were processed. Talc and calcium carbonate, with different particle sizes, were assayed at concentrations ranging from 0.3% to 1% by weight. Both coadjuvant types are food grade and are recognized as food additives by EU regulations (E-170 as calcium carbonate and E-553b as talc). Industrial trials were performed at room temperature with no added water, thus avoiding volatile compound loss and hydrosoluble compound content decrease. As a consequence, the obtained oils were more aromatic and their positive attributes more intense, in comparison to other olive oils produced in different operational conditions. In addition, energy requirements were decreased (releasing a lesser amount of carbon dioxide into the atmosphere) and water uptake was kept to a minimum.     

Supramolecular solvent-based microextraction of Sudan dyes in chilli-containing foodstuffs prior to their liquid chromatography-photodiode array determination

A supramolecular solvent made up of reverse micelles of decanoic acid was proposed for the simple and rapid extraction of Sudan I, II, III and IV from chilli-containing foodstuffs. The procedure involved the extraction of minute quantities (0.5–1 g) of homogenised food sample with an aqueous solution containing 10% THF and 200 mg of decanoic acid, conditions under which the supramolecular solvent (around 330 μL) formed in situ and instantaneously. The overall sample treatment took about 30 min and several samples could be simultaneously treated using conventional lab equipment. No clean-up or solvent evaporation were required before determination of Sudan dyes by liquid chromatography and photometric detection. Extractions were independent of salt addition (up to 1 M), the temperature (up to 60 °C) and the pH (below 4) rendering the method robust. The detection limits of the method were 4.2, 2.7, 6.5 and 7.4 μg kg⁻¹ for Sudan I, II, III and IV, respectively. Recoveries obtained by applying this approach to the analysis of six chilli-containing sauces fortified with Sudan dyes at the μg kg⁻¹ level were in the interval 86–108% with relative standard deviations between 2% and 7%.     

Effect of hydroxypropyl-β-cyclodextrin on the aggregation of (E)-resveratrol in different protonation states of the guest molecule

The aggregation state of (E)-resveratrol was studied in the presence and absence of hydroxypropyl-β-cyclodextrin (HP-β-CD) using absorption and steady-state fluorescence at different pH values. The results revealed that this potent antioxidant shows a monomer/aggregate equilibrium which is dependent on the protonation state of (E)-resveratrol. This equilibrium can be modified by the presence of HP-β-CD, which reduces the aggregation of the (E)-resveratrol molecules, producing individual molecules of the solute and preventing side effects due to aggregation phenomena. At pH values higher than the pK_a1 of (E)-resveratrol, the coexistence of different protonated/deprotonated forms of this antioxidant does not permit the fluorimetric determination of the complexation constant (K_F) of (E)-resveratrol with HP-β-CD. However, when the Hildebrand–Benesi equation was used to calculate this constant at physiological pH, this problem was resolved, with a K_F value of 14490 ± 723 M⁻¹ and the stoichiometry of the complexation process 1:1 for all the cases tested. The results obtained in this paper resolve the contradictory data published about the complexation process of (E)-resveratrol by cyclodextrins.