Effect of sugar addition on glass transition temperatures of cassava starch with low to intermediate moisture contents.
This work studies how sucrose (S) addition modifies the thermal properties of cassava starch (CS). Neat CS and CS-S blends with 4, 6 and 8% sugar contents (CS-S-4%, CS-S-6% and CS-S-8%) were prepared and analyzed by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA), in a wide range of moisture levels (2-20%). In equilibrated samples with moisture contents lower than 10%, twoendothermic steps were observed during first DSC heating scans and two corresponding relaxation maxima in tan δ were detected by DMTA. The first transition, detected at around 45-55°C by both DSC and DMTA, is frequently found in starchy foods, while the second observed at higher temperatures is associated to the glass transition temperature of the blends. At higher moisture contents, only one thermal transition was observed. Samples analyzed immediately after cooling from the melt (i.e., after erasing their thermal history), exhibited a single glass transition temperature, regardless of their moisture content. Addition of sugar promotes water plasticization of CS only at high moisture contents. In the low moisture content range, anti-plasticization was observed for both neat and sugar-added CS samples. Addition of sugar decreases the moisture content needed to achieve the maximum value of the glass transition temperature before plasticization starts. The results of this work may be valuable for the study of texture establishment in low moisture content extruded food products.
Departamento de Tecnología de Procesos Biológicos y Bioquímicos, Universidad Simón Bolívar, Aptdo. 89000, Caracas 1080-A, Venezuela; Grupo de Polímeros USB, Departamento de Ciencia de los Materiales, Universidad Simón Bolívar, Aptdo. 89000, Caracas 1080-A, Venezuela.
Yetzury
Y
Figueroa
Departamento de Tecnología de Procesos Biológicos y Bioquímicos, Universidad Simón Bolívar, Aptdo. 89000, Caracas 1080-A, Venezuela; Grupo de Polímeros USB, Departamento de Ciencia de los Materiales, Universidad Simón Bolívar, Aptdo. 89000, Caracas 1080-A, Venezuela.
Marvilan
M
Guevara
Departamento de Tecnología de Procesos Biológicos y Bioquímicos, Universidad Simón Bolívar, Aptdo. 89000, Caracas 1080-A, Venezuela; Grupo de Polímeros USB, Departamento de Ciencia de los Materiales, Universidad Simón Bolívar, Aptdo. 89000, Caracas 1080-A, Venezuela.
Adriana
A
Pérez
Departamento de Tecnología de Procesos Biológicos y Bioquímicos, Universidad Simón Bolívar, Aptdo. 89000, Caracas 1080-A, Venezuela.
Aura
A
Cova
Departamento de Tecnología de Procesos Biológicos y Bioquímicos, Universidad Simón Bolívar, Aptdo. 89000, Caracas 1080-A, Venezuela. Electronic address: asandova@usb.ve.
Aleida J
AJ
Sandoval
Grupo de Polímeros USB, Departamento de Ciencia de los Materiales, Universidad Simón Bolívar, Aptdo. 89000, Caracas 1080-A, Venezuela; POLYMAT and Polymer Science and Technology Department, Faculty of Chemistry, University of the Basque Country UPV/EHU, Paseo Manuel de Lardizabal 3, 20018 Donostia/San Sebastián, Spain; IKERBASQUE, Basque Foundation for Science, Bilbao, Spain. Electronic address: alejandrojesus.muller@ehu.es.
Alejandro J
AJ
Müller
Anti-plasticization; Cassava starch; DMTA; DSC; Glass transition temperature; Plasticization; Sugar; Water partition