Effect of branched 1,4-butanediol citrate oligomers with different molecular weights on toughness and aging resistance of glycerol plasticized starch.

The thermoplastic starch with glycerol is easy to retrograde and sensitive to hygroscopicity. In this study, branched 1,4-butanediol citrate oligomers with different molecular weights (P1, P2, and P3) are synthesized, and then mixed with glycerol (G) as the co-plasticizers to prepare thermoplastic starch (CS/PG). The results show that the molecular weight and branching degree of the branched 1,4-butanediol citrate oligomers increase as reaction time prolongs. Compared with glycerol plasticized starch, the thermoplastic starch films with branched 1,4-butanediol citrate oligomers/glycerol (10 wt%/20 wt%) have a better toughness, transmittance, and aging resistance, and have a lower crystallinity, hygroscopicity, and thermal stability. The toughness, transmittance, and aging resistance of CS/PG films are positively correlated with the molecular weight of the branched 1,4-butanediol citrate oligomers. These are due to the fact that the branched 1,4-butanediol citrate oligomer with a high molecular weight could form a stronger hydrogen bond and the more stable cross-linked structure with starch chains than that with a lower molecular weight. The elongation at break of CS/P3G film stored for 3 and 30 d are 98.0 % and 88.1 %, respectively. The mixture of branched butanediol citrate oligomers and glycerol, especially P3/G, has a potential application in the preparation of thermoplastic starch.

Preparation and release characteristic of quercetin loaded poly(lactic acid) ultrafine fibers.

In this study, poly(lactic acid) (PLA) ultrafine fibers have been prepared by electrospinning method using mix-solvent. The results showed that the variation of solvent ratio (N,N-dimethylformamide (DMF)/Dichloromethane (DCM)) could change the surface morphology of PLA nanofibers. By adjusting the solvent ratio, the quercetin release rate from the fiber membranes could be controlled. Furthermore, by adjusting the PLA concentration, the nanofibers without beads could be obtained. After addition of quercetin to polymer solution, the spindle-shaped beads on the fiber disappeared, but surface morphology of the fiber changed little with increase in quercetin dosage, and the release rate of quercetin increased with increase of quercetin dosage.

Synergistic effects of sodium adipate/triethylene glycol on the plasticization and retrogradation of corn starch.

Starch retrogradation resulted in bad performance and taste of starch products. In this study, the corn starch films modified by sodium adipate and triethylene glycol were prepared by solution casting. The retrogradation of modified starch films were studied by FT-IR, XRD, SEM, tension test and UV-Vis. The results showed that sodium adipate was more effective than triethylene glycol in inhibiting the short-term retrogradation of starch, and triethylene glycol was more effective than sodium adipate in inhibiting the long-term retrogradation of starch. However, the mixture of sodium adipate and triethylene glycol, especially 15% adipic acid and 10% triethylene glycol, showed synergistic effects on the short-term and long-term retrogradation of starch. The starch film with 15% adipic acid and 10% triethylene glycol had the highest elongation at break, the best transmittance, the lowest change rate of elongation at break, and the lowest moisture content among all the recipes.

Effect of sodium citrate/polyethylene glycol on plasticization and retrogradation of maize starch.

Maize starch was plasticized by mixtures of sodium citrate and polyethylene glycol 200 (PEG200) at varied weight ratios (citric acid/PEG200, 25/0, 20/5, 15/10, 10/15, 5/20 and 0/25). The structure and pasting, aging, moisture absorption and thermal properties of the plasticized starches were studied by means of Fourier transformed infrared, X-ray diffraction, rapid viscosity analysis, tension test and thermogravimetric analysis. Comparing with single plasticizer, co-plasticizers with appropriate proportions are more effective in hindering the retrogradation of starch paste and film. The results also showed that the mechanical property and humidity sensitivity of the starch film worsen after the introduction of PEG200 compared with sodium citrate plasticized starch, but the thermal stability and anti-aging property increase. This is consistent with the association ability of plasticizers with starch observed from FTIR. In addition to the simple additive effect of components on some properties, special formulations also show some synergistic effects, such as the co-plasticizer of 20% citric acid and 5% PEG200 has a better comprehensive property for plasticizing the maize starch bulk than sodium citrate or PEG200 alone. The mixture of sodium citrate and PEG200 can be used as a candidate plasticizer for preparing thermoplastic starch for food and packaging industries.

Effects of lipid chain length on the surface properties of alkylaminomethyl rutin and of its mixture with model lecithin membrane.

Three model flavonoid-based bioactive molecules with different lipid chain lengths (RuCn: n=8, 12, 18) were newly synthesized. The surface properties [surface pressure (π)-area (A), surface potential (ΔV)-surface pressure (π) and dipole moment (u(⊥))-surface pressure (π)] of pure RuCn and the lecithin membrane compounds had been investigated by using the Langmuir monolayer technology. The results suggested that the distinctive monolayer behavior of RuCn is strongly dependent on the lipid chain length. The great differences in the monolayer properties brought by the lipid chain length could be attributed to two major factors: (i) the ionization degree of the bulky hydrophilic head group (including hydroxyl and NH groups) alters its local field solely via the surface potential; (ii) tring molecular (or dipole) packing density within monolayers. The excess Gibbs energy (ΔG((ex))) calculated for the RuCn-lecithin mixed monolayers infers that higher stability of the mixed monolayer can be strengthened as the lipid chain length decreases. And the addition of RuCn into lecithin membrane may increase the total u(⊥) of the binary mixed monolayers, which could inhibit the hydration of the lecithin's hydrophilic head groups. The shorter the lipid chain length of RuCn (e.g., RuC8) is, the higher the surface activity can be. Our findings provide a molecular basis for the application of such class of biomolecules in the functional food, cosmetics and medicine.