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Keywords:

  • Antioxidant activity;
  • drying;
  • fruits

Summary

This study investigates the drying kinetics of residue of acerola, in a fixed-bed dryer, analysing the effect of the process variables on the antioxidant properties of the residue. A complete factorial design 32 has been performed, where the independent variables studied were as follows: air velocity (0.5, 1.0 and 1.5 m s−1) and air-drying temperature (40, 50 and 60 °C). The bioactive compounds studied were L-ascorbic acid, total phenolic, total flavonoids and antioxidant activity (expressed as IC50) was determined using free radical DPPH. Both independent variables studied have shown to be statistically significant. The content of ascorbic acid was the highest at 60 °C and 1.0 m s−1 (126.2 ± 0.004 mg 100 g−1) while for the fresh residue 16.12 ± 0.003 mg 100 g−1, whereas the total phenolic showed the highest content at 50 °C and 1.5 m s−1 (46.2 ± 0.003 mg gallic acid.100 g−1) while for the fresh residue 12.59 ± 0.001 mg gallic acid.100 g−1. The drying conditions play an important role in determining the final quality of the product mainly in terms of antioxidant activity.