Fouling Behavior of Camel and Cow Milks Under Different Heat Treatments

Using a developed laboratory-scale device, different heat treatment conditions were applied on camel and cowmilks. After each fouling experiment, photos of stainless steel plates were taken and dry deposit weights were determined. The thermal behavior of camel and cow proteins was studied by electrophoresis (sodium dodecyl sulphate polyacrylamide gel electrophoresis, SDS-PAGE), differential scanning calorimetry (DSC), and free thiol group concentration evolution. The obtained results have shown that heating both camel and cow milks at 70 °C for 2 h generates deposit formation. The fouling rate was more important when heating camel milkthan after heating cow milk for all heat conditions except at 90 °C for 2 h. Electrophoresis patterns indicated that after heating camel milk at 90 °C, α-lactalbumin (α-la), camel serum albumin (CSA), and κ-casein bands decreased. Bovine serum albumin (BSA) disappeared from the electrophoresis patterns after heating cow milk at 70 °C while β-lactoglobulin (β-lg) and α-la bands disappeared only at 90 °C. DSC thermograms of camel milk showed that the denaturation temperature of camel proteins is 77.8 °C, lower than that of cow proteins which is 81.7 °C. The results of free thiol group evolution versus temperature and heating time showed that camel protein denaturation starts between 70 and 80 °C. However, for cow milk, the whole denaturation phenomenon happens after heat treatment at 70 °C for 30 min

Micelles obtained by aggregation of gemini surfactants containing the CCK8 peptide and a gadolinium complex

Two gemini surfactants, [C18CysL5CCK8]2 and [C18CysDTPAGlu]2, containing, respectively, the CCK8 peptide and the DTPAGlu chelating agent or its gadolinium complex have been prepared by linking lipophilic chains through a disulfide bond between two cysteine residues. The two surfactants aggregate in water solution forming pure or mixed micelles, with a critical micellar concentration in the 5 9 10-6–5 9 10-5 mol kg-1 range, as measured by fluorescence spectroscopy. As indicated by small-angle neutron scattering, the shape and size of the micelles are influenced by the temperature: increasing temperature leads to progressive reduction of the size of the supramolecular aggregates. Cylindrical structures found at lower temperatures (10–40 C) evolve into ellipsoidal micelles at 50–80 C. Furthermore, the surface-exposed CCK8 peptide changes its conformation above a transition temperature of approximately 45 C, going from a beta-sheet to a random-coil structure, as indicated by circular dichroism measurements. The mixed aggregate obtained by coaggregation of the two gemini-based amphiphilic compounds, [C18CysDTPAGlu(Gd)]2 and [C18CysL5CCK8]2 in 70:30 molar ratio, represents the first example of a peptide-containing gemini surfactant as a potential target-selective contrast agent in MRI. In fact, it presents a high relaxivity value of the gadolinium complex, 21.5 mM-1 s-1, and the CCK8 bioactive peptide exposed on the external surface is therefore capable of selective targeting of the cholecystokinin receptors