New types of hydrogels have been obtained starting from high bloom purified gelatin A, alone or in mixtures with hyaluronan and with a hyaluronan derivative bearing primary amino groups, by transglutaminase-catalyzed cross-linking. The reticulation process, carried out adopting two different temperature protocols, and the ensuing materials have been characterized in terms of rheologically estimated gel times, equilibrium swelling in water and in phosphate buffer solution (PBS), and rigidity modulus. Main structural and conformational factors governing the physicochemical properties and the possible application of the new hydrogels are discussed.

Hydrophilic networks based on functionalized hyaluronic acid and on partially acetylated chitosan, respectively, have been obtained. In the case of hyaluronic acid (HA), primary amino functionalities have been introduced along the polysaccharide chains. The ensuing derivatives, i.e., HA-lysine (HA-K), HA-diamino pentane (HA-DAP), and HA-glycine-lysine (HA-GK), have been characterized by high field NMR spectroscopy. NMR 2D-DOSY experiments have allowed us to optimize the purification procedure. Chitosan was made soluble in water by partial acetylation. Cross-linking reactions have been performed using glutaraldehyde. The obtained networks have been qualitatively characterized by means of (13)C CP-MAS NMR technique. The hydrogels have been characterized also in terms of water uptake.

The chemical composition of coffee has been widely investigated, focusing the attention both on main components and trace compounds. Most of these studies have been performed by using liquid and gas chromatography, eventually combined with mass spectroscometry. These techniques, although straight and effective, are time demanding due to the sample pretreatments. Here, we propose high‐resolution‐magic‐angle spinning nuclear magnetic resonance spectroscopy (HR‐MAS NMR), a system capable of acquiring highly resolved NMR spectra of gel‐like and suspension samples. This approach allowed us to determine the chemical composition of coarsely ground coffee beans of two varieties: Arabica and Robusta. Variation of the concentration of relevant species was monitored as a function of roasting temperature, from green beans to completely roasted. The HR‐MAS NMR tool demonstrated to be very powerful for quick chemical composition determination, opening up possibilities for novel applications of this approach in food quality control. PRACTICAL APPLICATIONS Food quality control needs novel and press‐button applications. High‐resolution‐magic‐angle spinning nuclear magnetic resonance contains such requirements, since it can analyze suspension and gel‐like samples, providing a chemical characterization with minor, or, in most cases, no chemical and physical pretreatment operations. The application proposed here concerns the examination of relevant molecules in coffee beans as a function of the roasting temperature. This can be used for a quality check of the final product, and such approach has a general suitability, being functional for almost all foodstuff, fresh and transformed.

No abstract

Methylprednisolone steroid esters of hyaluronan differing in degree of functionalization and molecular weight were investigated in aqueous solution. Conformation and aggregation phenomena were elucidated by means of circular dichroism, viscometry, rheology, and nuclear magnetic resonance, mainly by (1)H pulsed field gradient (PFG) NMR, which allows the determination of the diffusion coefficient of the species under investigation. The functionalization of hyaluronan with the steroid induces a reduction of the molecular volume, as a consequence of intramolecular hydrophobic interactions. For concentrated samples we have observed the coexistence of unimolecular collapsed chains and of aggregates, the latter disappearing upon dilution. The methylprednisolone ester of lower molecular weight hyaluronan has a larger molecular volume than its higher molecular weight analogue, even though still smaller than the underivatized polymer. This effect can be explained with the reduced flexibility of the polymer backbone probably impairing intramolecular interactions.