Thermo- and photosensitivity of Euterpe oleracea Mart. (Arecaceae) fruit pulp: Consequences for its antioxidant activity under basic storage conditions in the Amazon

Abstract

Anthocyanins are chemically unstable, casting doubt on the antioxidant activity (AA) of Euterpe oleracea Mart. (Arecaceae) fruit pulp during storage. In this study, AA, total monomeric anthocyanin (TMAC), total flavonoid (TFC), and total phenolic contents (TPC) of this preparation after 24 h and 5 days at ambient temperature/ambient light-dark (AT/AL), ambient temperature/continuously dark (AT/CD), and under refrigeration/continuously dark (UR/CD) were compared to those of the fresh preparation. A FRAP and a DPPH assay, and a pH differential, an AlCl3 colorimetric, and Folin-Ciocalteu’s method were used. Associations between pairs of variables were determined by Pearson correlation coefficient (r). Student’s t test and one-way ANOVA with Tukey HSD were used to evaluate the data for statistically significant differences (p < 0.05). FRAP and DPPH IC50 values of the fresh preparation were 116 ± 3 μM Fe2+ equivalents/100 μg, and 57 ± 12 μg/mL, respectively. They were hardly affected after 24 h, but had decreased 4-fold and increased 2-fold, respectively, after 5 days, the least at UR/CD. TMAC, TFC, and TPC of the fresh preparation were 21 ± 4 mg Cy3GE/mg, 25 ± 4 μM RE/100 μg, and 67 ± 2 μM GAE/100 μg. The loss of AA after 5 days was accompanied by a 3- to 5-fold TMAC and TFC degradation, and a 1.5-fold TPC decrease. AA correlated better with TMAC and TFC (r ±0.7 - ±1.0) than with TPC (r ±0.4 - ±0.9). These observations are important for communities with only basic facilities for preparing and storing E. oleracea fruit pulp.