MINIMIZING TURBIDITY: STRATEGY FOR ANALYZING THE ANTIOXIDANT CAPACITY OF MICROCAPSULES VIA ABTS

The methodology proposed by Re et al. (1999) for determining the antioxidant capacity by the ABTS method may have limitations when applied to samples with high turbidity, such as microcapsules. The objective of this study was to propose adaptations in the preparation of samples to minimize optical interference and allow the precise application of the method in microcapsules containing jabuticaba peel extract. The extract was obtained by ultrasound (50 min, 45 kHz, 40 °C; Elmasonic TI-H-10, Elma, Germany) and encapsulated in a 15% whey protein isolate solution, using a spray dryer (Buchi B-191, Flawil, Switzerland), with an inlet temperature of 180 °C, outlet of 45–50 °C, feeding between 20–25% and aspiration of 83–85%. Samples diluted to 5% were submitted to three different treatments for the release of antioxidant compounds with the least disruption of the protein matrix. In Test 1, the sample was stirred in a vortex for 2 minutes and centrifuged at 5000 rpm for 10 minutes (Centrifuge 5804 R, Eppendorf, Germany). In Test 2, it was subjected to ultrasound (10 min, 45 kHz, 40 °C) and then stirred in a rotary mixer (30 rpm, overnight; JOANLAB Lab 360° Disc Mixer), and then centrifuged. Test 3 consisted only of overnight rotary stirring and centrifugation under the same conditions. The supernatant was diluted (60 μL of sample to 940 μL of PA ethanol), centrifuged and analyzed in a microplate reader (Thermo Fisher Scientific) at 600 nm to determine turbidity. The values observed were: ≈0.583 (Test 1), ≈0.488 (Test 2) and ≈0.331 (Test 3)