Physical characterization of cassava starch biofilms with special reference to dynamic mechanical properties at low temperatures

Biofilms based on cassava starch and containing glycerol as a plasticizer were characterized with respect to the effect of potassium sorbate concentration and pH on color, crystallinity and mechanical performance al low temperature. It could be observed that a lower pH resulted in lower values of yellow index and tan delta and higher crystallinities. Crystallinity decreased with sorbate addition, which also resulted, in general, an increase in yellow index and moisture content and a decrease of storage modulus for temperatures higher than the glycerol glass transition. Increase in sorbate content displaced the glass transition temperature of a glycerol-rich phase toward lower temperatures and increased the difference between the value that E ' took in the glassy region and the value that it took in the rubbery region. It is concluded that the physical properties of edible films can be affected by the antimicrobial agent, sorbate potentially compromising biofilm performance. (c) 2006 Elsevier Ltd. All rights reserved.