Chitosan and crosslinked chitosan nanoparticles: Synthesis, characterization and their role as Pickering emulsifiers.

Chitosan has been modified in order to produce nanoparticles with promising characteristics in diverse food applications, e.g. Pickering emulsions. Chitosan deprotonation and ionic crosslinking with tripolyphosphate were assessed in this work. Chitosan nanoparticles produced by these two methods were characterized according to surface charge, particle size distribution, chemical structure, wettability and microstructure imaging. The nanoparticles' performance in the formation of oil-in-water Pickering emulsions was studied by physicochemical and rheological assays. Chitosan nanoparticles produced by amino deprotonation were larger and resulted in emulsions with larger oil droplets, with rheological behavior of the emulsions being greatly affected by increasing concentration of chitosan, which formed a network structure in the continuous phase. On the contrary, the tripolyphosphate-crosslinked chitosan nanoparticles were smaller and produced emulsions with smaller droplets, which remained less viscous even when chitosan concentration was increased and showed evidences of Pickering stabilization when analyzed by microscopy techniques.

Oxidative stability of soybean oil added to coffee husk extract (Coffea arabica L.) under accelerated storage conditions

Abstract Several plants have been studied as potential sources of natural antioxidants for use in the food industry, especially polyphenols. The aim of this study was to evaluate the effects of hydroalcoholic extract from coffee husk on the oxidative stability of soybean oil when stored in an oven. Samples were maintained at a temperature of 60 °C and their oxidative stability was evaluated once every 5 days for a period of 20 days through the Rancimat equipament and analysis of peroxide value, conjugated dienes and tocopherols retention. The oxidation rate in terms of mass gain was evaluated once every 24 hours for a period of 24 days. Although the antioxidant TBHQ showed a better efficiency in the inhibition of oxidation, coffee husk extract showed a synergistic effect when used with the synthetic, delaying the appearance of degradation products. In addition, the freeze-dried extract showed the ability to reduce the mass-gain rate when used alone as well as when used in combination with the synthetic antioxidant butyl hydroxyanisole (BHA), noting a synergistic effect on oxidative stability between the extract and the BHA. Therefore, coffee husk extract could be considered a source of natural antioxidants for synthetic antioxidants substitution.