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period up to 21 days was necessary for the sponge cakes investigated by differential scanning calorimetry (DSC), because no retrogradation transition was registered up to the sixth day. The humidity and the temperature were kept constant in desiccator
from the reading ( α ), constant of the measuring system ( z = 195.5 ) and the velocity gradient ( D = 57.20 s −1 ). Shear stress: τ = α ∗ z [ mPa ] Dynamic viscosity: η = τ D [ mPa ] 2.5 Thermodynamic measurement (DSC) A Micro DSC III
The aim of the study was to select the most suitable freezing and thawing method for preserving the quality of pasta flata type Parenica cheese comparing different methods: slow, shock (circulated air) and cryogenic freezing and thawing at room temperature and in a refrigerator, respectively. To observe the effects of these methods on some cheese properties weight, pH, and dry-matter content were measured, stringiness was examined, and compression test were performed for texture analysis. Thermophysical properties were determined by DSC: unfreezable water content, onset point of melting, and latent heat. Sensory analyses were also carried out by profle analysis. Results of objective and subjective measurements showed similar trends: characteristics of cheese samples frozen in circulated air and thawed in refrigerator resembled the most to the control sample.
This study aimed to evaluate the survivability of lactobacilli cells encapsulated in calcium alginate beads coated with methacrylic acid copolymers (MAc) in high acidic foods (orange juice and mayonnaise). Lactobacilli survived well at low temperature (4 °C) for 6 wk in orange juice, 4 wk in heat-treated orange juice, 12 wk in mayonnaise, and 8 wk in heat-treated mayonnaise (P<0.05), without affecting the acidity of orange juice and mayonnaise during storage. FTIR spectra showed that the characteristic peaks of calcium alginate and MAc were not altered, designating no high affinity interaction between calcium alginate and MAc. DSC of MAc-coated alginate beads indicated an increased in melting temperature, demonstrating improvement in molecular orientation in the MAc-coated alginate beads compared to the control. Sensory evaluation revealed that panellists could detect the presence of MAc-coated alginate beads, leading to a lower acceptance score.
evaluated and completed by DSC and TG analyses. 1 Materials and methods 1.1 Materials Grated red cabbage purchased from a local farmer (Sibiu, Romania) was subjected to ovendrying at 40 °C for 12 h (Memmert 100-800) and freeze-drying at –50 °C for 24 h
Palm fat is one of the most commonly used fats in food industry. The main role of palm fat is to develop the desired texture of food products. Fat blends were developed to find the most appropriate mixture fitting the technological needs. In our work palm mid fraction (PMF) was mixed with anhydrous milk fat (AMF), goose fat (G), and lard (L) in a 1:1 ratio. Anhydrous milk fat represents fat consisting of a wide range of fatty acids. Goose fat is a soft, easily melting fat, and lard is characterized as animal fat with wide melting temperature interval. The measurements aimed to establish the miscibility of the fats and the effect of animal fats on the melting-solidification profile of palm mid fraction. SFC vs temperature curves, Differential Scanning Calorimetry (DSC) melting thermograms describe the melting profile of the samples. Isotherm crystallization by SFC vs time curves and DSC cooling thermograms were measured to characterize the solidification of pure fats and the blends. Since the SFC curves did not show crosspoints we concluded that fats blended in a 1:1 ratio were miscible. Anhydrous milk fat strongly modified the properties of palm mid fraction, the blend became similar to anhydrous milk fat. Goose fat had no strong modification effect on palm mid fraction and could be considered as a softening agent. The effect of lard was complex: melting and solidification behaviour of the blend differed from the characteristics of both parent fats.
We are synthetized thermo- and pH-sensitive gels, which are then tested as skin extenders. Our aim is the development of copolymer and composite hydrogels that, when implanted under the human skin, swell osmotically and thereby induce skin growth. During the polimerization reaction we are produced copolymers with varyable composition, which are proceed from two acrylic compounds [N- isopropyl- acrylamide (NIPAAm), and acrylamide (AAm)]. The mechanical strength and the swelling stability of the gels are enhanced by the addition of fillers [Na- montmorillonite (Na- m.) and with alkyl- ammonium ion organophilized Na- montmorillonites [(C n - m.), n = 4, 12, 18]. With this method we are synthetized composite- hydrogels. The filler content of composites varies between 1 and 25 wt%. We observed that in the case of composites synthesized with the addition of fillers, relatively low filler contents (1–5 wt%) resulted in more extensive swelling and stronger gel structure. In the course of the experiments the monomer composition of the gels (0/100–100/0 mol% NIPAAm/AAm) and in the case of composites, the quality (montmorillonite and organophilized montmorillonite) and quantity (1–25 wt%) of fillers are varied. The extent of swelling and the viscoelastic properties can be manipulated through the ratios of these parameters. In the case of certain copolymer and composite gels, values of desorption enthalpy (ΔH m ) corresponding to the actual water contents were also determined by thermoanalytical measurements (DSC). Swelling values determined by gravimetry and enthalpies calculated from DSC measurements were found to be in good correlation. Evaluation and comparison of the rheological and DSC results also allowed conclusions to be drawn concerning the types of interaction operating among the three components of the system, i.e. the polymer skeleton, the filler and water molecules. We found that water molecules within the gel matrix are bound to the 3-D polymer lattice with bonds of different strengths and the strength of these interactions are dependent on both hydrophilicity and charge conditions. In the case of hydrophobic NIPAAm composites a more extensive swelling can be achieved by applying montmorillonite fillers with hydrophobized surfaces, whereas in the case of hydrophilic AAm-based composites the use of hydrophilic montmorillonite fillers ensure more extensive swelling.
2224 2229 Aktas, N., Tülek, Y. & Gőkalp, H.Y. (1997): Determination of freezable water content of semimembranous muscle DSC study. J. Thermal Anal., 48, 259
Influence of gamma irradiation ( 60 Co-rays) with doses in the range up to 30 kGy was studied on gelatinisation of wheat starch, wheat flour and potato starch. Differential scanning calorimetry was then applied at several heating and cooling cycles for studies of the effect of irradiation with a 30 kGy dose on interaction of wheat starch with their native lipids and potato starch with admixed 1-mono-lauroyl glycerol.Amylose-lipid complex transition occurs after irradiation at decreased temperature and is accompanied by decreased enthalpy in respect to that recorded in the case of non-irradiated wheat starch, wheat flour as well as potato starch and admixed lipid. Differences between the initial and irradiated starch were easier to detect on the foregoing heating or cooling cycles than during the preceding ones and after the gels’ retrogradation. The complex was less influenced by the less advanced retrogradation taking place in the irradiated than in the non-irradiated wheat flour. Radiation-induced modification of structural properties of the complex results due to degradation of starch granules confirmed at present by essential reduction in pasting properties and by the increased amount of short molecular products leached during gelatinisation and their higher branching.
. Blaine 1994 Thermal conductivity of polymers, glasses and ceramics by modulated DSC Thermochimica Acta 243 231 – 239
