Relationships among the composition and physicochemical properties of starches with the characteristics of their films.
The physical, molecular, and functional properties of corn, cassava, and yam starches were related to the film properties of these starches. Corn, cassava, and yam starches contained 25%, 19%, and 30% amylose, respectively. Amylose from yam starch showed the smallest molecular weight among the starches and amylopectin from corn starch the smallest molecular weight. Cassava starch presented a higher amylopectin content, and its gels and films were less strong, more transparent, and more flexible than corn and yam films. Plasticized films of the three starches were more flexible, with a higher strain and lower stress at break when the glycerol content increased. Unplasticized films were brittle and had water vapor permeability values ranging from 6.75 x 10(-10) to 8.33 x 10(-10) g m(-1) s(-1) Pa(-1). These values decreased when the glycerol content reached 20 g/100 g of starch because a more compact structure was formed. Then, at a glycerol content of 40 g/100 g of starch, the WVP increased because the film matrixes became less dense.
Mali
Suzana
S
Departamento de Tecnologia de Alimentos e Medicamentos, Centro de Ciências Agrárias, Universidade Estadual de Londrina, Caixa Postal 6001, CEP 86051-990, Londrina, Brazil. smali@sercomtel.com.br
Karam
Laura Beatriz
LB
Ramos
Luiz Pereira
LP
Grossmann
Maria Victória E
MV
D000687:Amylopectin / Q000032:analysis; D000688:Amylose / Q000032:analysis; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D027742:Dioscorea / Q000737:chemistry*; D018857:Food Packaging / Q000295:instrumentation*; D002365:Manihot / Q000737:chemistry*; D010968:Plasticizers; D011108:Polymers / Q000737:chemistry; D013213:Starch / Q000737:chemistry*; D003313:Zea mays / Q000737:chemistry*
D010968:Plasticizers; D011108:Polymers; D013213:Starch; D000688:Amylose; D000687:Amylopectin