Isothermal crystallization of concentrated amorphous starch systems measured by modulated differential scanning calorimetry

Biocomposites of cellulose reinforced starch: improvement of properties by photo-induced crosslinking

In the present study, the composite films have been prepared from the aqueous dispersions of starch with microcrystalline cellulose using glycerol as plasticizer and irradiated under ultraviolet (UV) light using sodium benzoate as photo-sensitizer. Photo-crosslinking was characterized by measuring the water absorption under 100% relative humidity, swelling degree and gel fraction in dimethylsulphoxide (DMSO), upon irradiation time. Both, the incorporation of cellulose and photo-irradiation were found to decrease the water absorption, swelling in DMSO and increase the gel fraction. Thermal transitions indicated the anti-plasticization of amylopectin chains at the fiber/matrix interface. With increasing content of cellulose and photo-irradiation time, the tensile modulus and strength were found to improve. It is summarized that the combination of cellulose reinforcement and photo-crosslinking of matrix has improved the physical and mechanical properties.

Structural features of non-granular spherulitic maize starch

Complementary analyses of the internal structure of spherulites crystallized from high-amylose maize starch were obtained using light, electron and atomic force microscopy. Radially oriented crystalline lamellae were observed in transmission and scanning electron microscopy, as well as AFM. Internal structures consistent with the central hilum region of starch granules were observed. Spherulites were composed largely of linear or lightly branched starch polymers. Degradation of amylopectin at gelatinization temperatures of 180 degrees C was evident, but iodine binding suggested a high molecular weight (>100 DP) for the spherulitic polymers.

Amylopectin as a subcoating material improves the acidic resistance of enteric-coated pellets containing a freely soluble drug

The effect of an aqueous amylopectin subcoating on the acidic resistance and dissolution behaviour of enteric-coated pellets was studied. Freely water-soluble riboflavin sodium phosphate (RSP) was used as a model drug, and microcrystalline cellulose (MCC) and lactose as fillers in the pellet cores. The pellets were subcoated with 5% aqueous amylopectin solution or with 5% hydroxypropyl methylcellulose (HPMC) solution, and subsequently film-coated with aqueous dispersion of cellulose acetate phthalate (CAP). Drug release of enteric-coated pellets was investigated by confocal laser scanning microscopy (CLSM). Dissolution tests showed that amylopectin subcoating improved the acidic resistance of the enteric-coated pellets in 0.1 N hydrochloric acid (HCl) compared with HPMC subcoating. As the amylopectin subcoating load was increased to 4% and the aqueous CAP coating load to 35%, the coated pellets resisted in 0.1 N HCl solution for approximately 1 h (the amount of drug released was below 10%), and they dissolved in the SIF without enzymes in less than 10 min. Confocal microscopy images and profiles of mean fluorescence intensities of RSP (obtained in the range of the interface of the pellet core and the film and the film coating surface) showed consistent results with dissolution tests. It seems that amylopectin subcoating can prevent the influx of the dissolution medium into the pellet core, and thus decrease the premature dissolution and release of the drug from the enteric-coated pellets in 0.1 N HCl solution. The drug release mechanism appeared to be osmotically driven release, and followed by diffusion through the polymer film.

The use of modulated temperature differential scanning calorimetry for the characterisation of food systems

Modulated temperature Differential Scanning Calorimetry (MTDSC) is used to characterise food systems. It is shown that by splitting the total heat flow into reversing (related to heat capacity) and non-reversing contributions, overlapping thermal events can be separated. The combination of excellent sensitivity and high resolution provides more accurate results for weak and/or broad transitions. The thermal transitions of maltotriose, maltohexaose and thermoplastic starch are treated as examples. It is also shown that MTDSC is very useful to follow in situ slow crystallisation processes. These structural changes are detected by measuring the heat capacity in the quasi-isothermal mode. The (quasi-)isothermal crystallisation of pregelatinized waxy corn starch is given as an example.