Poly(citrate glyceride): a hyperbranched polyester for starch plasticization

Abstract

Hyperbranched polyesters (HBPETs), terminated with either hydroxyl or carboxyl groups, were prepared from citric acid and glycerol in simple one-step syntheses. The HBPET structure and degree of branching were investigated using Fourier transform infrared and 1 H NMR spectroscopies and gel permeation chromatography. The HBPET plasticizers were combined with a maize starch via cooking and film formation. The mechanical, thermal, paste and structural properties of the plasticized starch composites were studied in detail using differential scanning calorimetry, thermogravimetric analysis, rapid viscosity analysis and X-ray diffraction. The HBPETs reduced the pasting viscosity but slightly increased the pasting temperature of the starch. The smaller breakdown and setback values of the plasticized starch pastes relative to those of native starch suggested weaker retrogradation. Compared with glycerol/starch plasticized films, HBPET/starch composite films had lower crystallinity, lower glass transition temperature and better mechanical and thermal properties. The properties of the plasticized starch samples strongly depended on the terminal groups and the molecular weight of the HBPET plasticizers.

Effect of hyperbranched poly(citric polyethylene glycol) with various polyethylene glycol chain lengths on starch plasticization and retrogradation

“…Besides, starch would preferentially associate with the plasticizers with stronger eletrophilicity or nucleophilicity comparing with water. Then molecular chain spreading of starch into the water would be suppressed . The decreasing [PT] of CA/MS, PCPEG/MS and PEG/MS is coincident with the declining nucleophilicity of oxygen atoms in those plasticizers and the declining hydrogen bond formability.…”

“…They were named as PCPEG200, PCPEG300 and PCPEG400, correspondingly. The molecular weight and degree of branching of PCPEG were determined according to our previous report and the characteristic values for PCPEG are listed in Table .…”

“…Addition of plasticizers can modify the brittleness and improve the flexibility and extensibility of starch film . An ideal plasticizer should reduce the intermolecular forces and recrystallization of starch, increase the mobility of starch chains, decrease the moisture absorption and be compatible with starch . So far, the most used starch plasticizers are small molecules with polar groups, such as OH, COOH and NH 2 , which tend to migrate and aggregate in starch materials, leading to starch retrogradation after several days of storage …”

“…In our previous study, several kinds of CHP were proved to be good plasticizers of starch, but the mechanism remains unknown . The random structure and low functional group accessibility of CHPs lead to great difficulty in the structure–performance study of hyperbranched polymer plasticizers.…”

Aging properties and hydrophilicity of maize starch plasticized by hyperbranched poly(citrate glyceride)

“…Accordingly, we prepared a type of hyperbranched polyesters with GLY and citric acid, two popular eatable, low price additives in the food industry. After a series of structural characterizations of the hyperbranched poly(citrate glyceride)s (HBPETs), they were used to plasticize starch films. On the basis of the principle mentioned previously, the synthesized HBPETs were expected to modify the retrogradation and water vapor permeability (WVP) of starch films, which is the goal of our research.…”