Dados do Trabalho

Título

ARRHENIUS KINETICS OF OXIDATIVE STABILITY FOR THE EVALUATION OF DIFFERENT METHODS OF EXTRACTION OF BRAZIL NUTS OIL

Introdução

This study examined Arrhenius kinetics for lipid oxidation of three variations of Brazil nut oils (Bertholletia excelsa): commercial (extracted by mechanical cold pressing) and residual oils extracted from cake using hexane and bioethanol from sugar cane.

Material e Métodos

Residual oil was extracted via reflux at 70 °C with a solid:solvent ratio of 1:15 (g:mL) for 8 hours, followed by rotary evaporation at 50 °C under vacuum. The oxidation induction time (OIT) of the samples was determined through accelerated lipid oxidation using the Rancimat equipment at 110 °C, 120 °C, and 130 °C, and the activation energy (Ea) and Q10 were calculated from these results.

Resultados e Discussão

For all temperatures, bioethanol-extracted oil showed OIT two to three times greater than the other oils, followed by hexane-extracted and commercial oils. At 110 °C, the OIT were 24.70±0.45 h, 9.68±0.08 h, and 7.54±0.08 h, respectively; at 120 °C, these decreased to 9.56±0.14 h, 4.21±0.09 h, and 3.67±0.04 h; and at 130 °C, 4.27±0.24 h, 2.33±0.23 h, and 1.51±0.04 h. Bioethanol-extracted oil also showed the highest Ea (113.22 kJ/mol, R²=0.9989), followed by the commercial oil (103.53 kJ/mol, R²=0.9944) and hexane-extracted oil (91.94 kJ/mol, R²=0.9944). Between 120 °C and 130 °C, the commercial oil presented Q10=0.3 suffering less influence of temperature on lipid oxidation than the hexane-extracted oil with Q10=0.6. This explains the higher Ea for commercial oil despite its lower overall OIT values. Both oils exhibit Q10=0.6 between 110 °C and 120 °C. Bioethanol-extracted oil presented a Q10=0.7 in both temperature ranges. This last oil possibly contains more antioxidant compounds (e.g.: polyphenols and tocols), which explains its greater oxidative stability and also its higher influence by the increase in temperature, indicating probable loss or degradation of these compounds.

Conclusão

Therefore, Ea describes the dependence of the lipid oxidation on temperature, but its absolute value when compared does not answer which has higher OIT value. Bioethanol emerges as a promising solvent for Brazil nut oil extraction, adding greater oxidative stability.