INVESTIGADORES
BERTUZZI Maria Alejandra
artículos
Título:
Mechanical Properties of High Amylose Starch Based Films Gelatinized at Low Temperature
Autor/es:
BERTUZZI, MARÍA ALEJANDRA; ARMADA, MARGARITA; GOTTIFREDI, JUAN C.
Revista:
Brazilian Journal of Food Technology
Editorial:
Instituto de Tecnologia de Alimentos ITAL
Referencias:
Lugar: Campinas; Año: 2012 vol. 15 p. 219 - 227
ISSN:
1981-6723
Resumen:
In the present study, a better knowledge of the influence of plasticizer
content, storage relative humidity and film thickness on the mechanical properties
of high amylose corn starch based films gelatinized at low temperature, is
presented. The mechanical properties, tensile strength and percentage of
elongation at break of high amylose corn starch films plasticized with glycerol
were evaluated using tension tests. The films exhibited an increase in elongation
and a decrease in tensile strength with increasing plasticizer concentration.
When the glycerol level was high, some fissures were detected in the dry films,
possible due to phase separation (starch-glycerol) phenomena. Film crystallinity
is related to the reorganization capacity of the polymer chain, and thus the relative
film crystallinity should increase with plasticizer content (glycerol and water).
The mechanical properties were found to be strongly dependent on the water
content due to the hydrophilic nature of starch films. The influence of moisture
sorption on tensile strength was similar to that of plasticization with glycerol. The
relationship between polymer chain mobility and water content explained this
behavior. Elongation suffered a different effect and maximum values were reached
at 45% relative humidity. The final drop in elongation was due to a softening of the
structure at high relative humidity. The thicker the film the longer the drying time
required, leading to greater relative crystallinity due to the corresponding increase
in the possibility for chain reorganization. As a consequence, linear increases in
tensile strength and elongation were observed with film thickness over the whole
range studied (30 to 100 µm).