Dados do Trabalho

Título

COATING-FORMING SOLUTION BASED ON GELATIN AND CASSAVA STARCH: RHEOLOGICAL CHARACTERIZATIONS

Introdução

Food cellulosic packaging can be coated with biopolymer films to improve its mechanical and physical proprieties. Besides, emulsions O/W incorporated with active compounds (rutin, carvacrol, and alfa-tocopherol) can be used in the coating-forming solution (CFS) to produce an active material and the knowledge of rheologic properties of the CFS is important for its application. So, the objective of this work was to study the rheologic properties of the gelatin or cassava starch CFS without (C-GCFS or C-SCFS) and with conventional emulsion (CE-GCFS or CE-SCFS).

Material e Métodos

Conventional oil-in-water (O/W) emulsions (CE) were produced with 10/90 O/W with soybean oil, Span 80 (50%) and active compounds (0.1%) as O phase, and water, Tween 80 (50%) as W phase. The CEs were prepared using an ultraturrax (15 krpm/9 min) at room temperature. The CFS were produced by heating the biopolymer at 55 °C for gelatin and 90 °C for starch. The effect of the addition of CE was studied by stationary shear flow and oscillatory essays.

Resultados e Discussão

Non-Newtonian behavior and low viscosity were observed for C-GCFS and CE-GCFS but pseudoplastic behavior was observed for C-SCFS and CE-SCFS. The effective viscosity calculated at 1% of C-SCFS decreased (1.6 to 1.3 Pa.s) with the increase of temperature (20 to 25 °C), while for CE-SCFS an important effect was not observed (1.2 - 1.3 Pa.s). The domain of linear viscoelasticity for C-GCFS and CE-GCFS was determined at 4% strain. C-GCFS and CE-GCFS were considered as a viscoelastic liquid (G’’>G’). C-SCFS and CE-SCFS were considered more resistant (G'>G''). Regarding the temperature scan test, it was observed that the addition of CE had slight effect on the test. According to the frequency scan results, C-GCFS and CE-GCFS showed presented storage module (G’) greater than the loss module (G’’) in the range of 1 to 10 Hz, this behavior being typical of viscoelastic solids. There was an intersection of G’ and G’’ curves of the C-SCFS and CE-SCFS indicating lower extensibility of the starch gel. In general, the addition of CE had little effect on the rheological properties of the gelatin and starch CFS.

Conclusão

In general, the addition of CE had little effect in the rheological properties of the gelatin coating forming solution and starch coating forming solution.