Edible films obtained by extrusion. Influence of xanthan gum and potassium sorbate incorporation on mechanical behavior

S. K FLORES; D. COSTA; F. YAMASHITA; L. N. GERSCHENSON; M. V. GROSSMANN

ANAHEIM, CALIFORNIA, USA

Congreso; IFT 2009 ANNUAL MEETING + FOOD EXPO; 2009

Institutte of Food Technologists

Edible films (EF) are biopolymers based materials. The knowledge of mechanical properties in relation to film composition is important to characterize them for different applications in food industry. The objective of this research was to study the effect of xanthan gum (XG) and potassium sorbate (KS) incorporation on the mechanical behavior of tapioca starch-glycerol EF. Films were obtained by extrusion (blowing). The glycerol:starch proportion (1:4.5) was maintained constant and the formulations included: 2–4% (w/w) of KS and 0–5–10% (w/w) of XG. An Instron Universal Testing Machine was used to determine the Elastic Modulus (Ec, kPa), Stress at Break (sr, kPa) and Strain at Break (er, %). Results showed that at 4% KS, an increment from 0 to 5% of XG did not modify the stress-strain response, but with 10% XG a significantly higher Ec (253357 kPa), sr (5032 kPa) and er (9,8%) were observed. When KS was 2%, Ec and sr were higher as XG content increased. At a constant XG level, KS increase promoted, in general, lower Ec and sr, and higher er. The maximum solid character was observed for films with 2% KS and 10% XG (Ec: 488814 kPa, sr: 10435 kPa y er: 4,6%); films with 4% KS and without gum were the most ductile (Ec: 104968 kPa, sr: 4004 kPa y er: 106%). Stress-strain curves of films with 10% XG and both KS levels, showed a yielding zone. In general, differences were observed between the mechanical properties parallel to and perpendicular to the flow direction, revealing anisotropy. Results suggest that KS acts as a plasticizer and XG produces stronger films. Characteristics of the product to which the EF will be applied and the goal of film application will determine the formulation that is convenient to be used.