Antioxidant concentration effect on stability of Brazil nut (Bertholletia excelsa) crude oil.

Shelled and broken Brazil nuts easily lose quality, if not properly stored. Pressing is an alternative use of these nuts and the crude oil stability was studied. Our previous studies demonstrated that TBHQ (200 mg kg-1) was very efficient to prevent rancidity development in oils bottled in brown and clear glass. As TBHQ has higher price than other phenolic antioxidants like BHT and BHA, an oven test (at 63 degrees C) was conducted to determine the economical and best concentration of TBHQ for Brazil nut crude oil. An assay at ambient temperature was conducted in brown and clear glass flasks with and without the economical concentration of TBHQ calculated (83 mg kg-1) for 90 days. Acid, peroxide, and iodine indices and the absorptivity at 232 nm were determined. TBHQ, even at this low dosage, was very efficient in both brown and clear glass flasks. Peroxide value increased from 11.5 meq O2 kg-1 to average 15 and 35, in TBHQ and control samples after 90 days. The absorptivity at 232 nm remained at 1.3 in samples with TBHQ while the control increased to 1.6.