Ml. Fishman et al., PECTIN STARCH/GLYCEROL FILMS - BLENDS OR COMPOSITES/, Journal of macromolecular science. Pure and applied chemistry, A33(5), 1996, pp. 639-654
The miscibility of pectin (P), starch (S), and glycerol (G) in films w
as investigated by dynamic mechanical analysis (DMA), tensile measurem
ents, scanning electron microscopy (SEM), Fourier transform infrared s
pectroscopy (FT-IR), and film dissolution studies. DMA revealed that P
/S/G films exhibit up to three thermodynamic transitions prior to film
degradation when heated. Transitions appear to be induced or enhanced
by the addition of glycerol. The lowest transition occurred below -50
degrees C, the second above room temperature and below 100 degrees C,
and the third above 100 degrees C. DMA and SEM on P/S/G films contain
ing starch solubilized for various lengths of time revealed that a ten
fold difference in the particle size of starch produced no more than a
20% difference in the dynamic moduli. Tensile measurements revealed t
hat changes in glycerol content or relative humidity induced greater c
hanges in mechanical properties than time of starch solubilization (ge
latinization). FT-IR spectra of P/S/G films revealed that the microstr
ucture around ester and carboxylic acid side chains of pectin was chan
ged significantly by the level of glycerol and relatively little by va
rying the starch level. Results from dissolution studies were consiste
nt with the idea that P/S/G films are highly compatible composites of
starch in pectin.