Caracterização durante o tempo de armazenamento da xantana sintetizada por Xanthomonas arboricola pv. pruni modificada quimicamente por desacetilação e reticulação

Abstract

Xanthan gum is a biopolymer produced from Xanthomonas by fermentation from a natural source. The properties of gum are affected by their chemical composition, structure and molecular mass, being widely used in the food, pharmaceutical and oil industry. In this work were produced from the fermentation process of Xanthomonas arborícolas pv pruni strain 106 and commercial xanthan (Jungbunzlauer®) used as control. The post-fermentation, deacetylation and cross-linking chemical modifications were carried out, and the behavior during the storage time under different temperature conditions (25 °C and 45 °C) was analyzed. The gums were characterized in relation to the analysis of the process yield, moisture content, salt content, morphology through MEV images and finally characterization of the functional groups from the FTIR. After that, the content of acetyl and pyruvate, the degree of swelling and the rheological properties of the gums were analyzed during the storage period. From these analyzes we can observe an average yield in the fermentation process of xanthan pruni of 11.03 g L-1. In relation to the chemical modification the deacetylation process for xanthan pruni presented low yield (58.7%) when compared to the deacetylation process of commercial xanthan (82.7%). The crosslinking process with glutaraldehyde showed high yields of 90.7% for xanthan pruni and 81.5% for commercial xanthan. The xanthanes stored at 45 °C showed a mean reduction of 60% of moisture content at the end of storage. Natural pruni xanthan showed high potassium content (44.2 mg g-1) compared to natural commercial xanthan (0.8 mg g-1). With the scanning electron microscopy (SEM) of the xanthan powder, surface differences between the natural and modified xanthans were observed. From the analyzes of FTIR, it was verified a change in the functional groups present in the gums, thus proving the insertion of new active groups, due to the post-fermentative chemical modifications that were performed. The natural commercial xanthan in its chemical composition showed high acetyl content (4.97%) in relation to natural pruni xanthan (1.33%). The pyruvate content was not altered with thermochemical deacetylation. The behavior of swelling degree in almost all xanthans, except for reticulated xanthan pruni, showed an increase of swelling degree with the course of the analysis time. For the crosslinked xanthan pruni, a reduction of swelling degree (less than 40%) and viscosity was observed, stating that glutaraldehyde cross-linking directly affects the solubility of xanthan. Finally, it is concluded that the viscosity of pruni and commercial xanthan are directly influenced by the chemical modifications and the storage temperature.