Secagem híbrida do resíduo de acerola em secador roto-aerado com infravermelho e extração de compostos bioativos

Abstract

Brazil is the third biggest producer and exporter of fruits in the world, it produces more then 41 million of tons per year. Approximately 47% of these productions are used in the manufacturing of pulps and juices. It is also estimated that 40% of the processed fruit volume become residues, which are rich in nutrients such as vitamins, phenolic compounds and minerals, and could be reused to mitigate its social, environmental, and economic impact. However, this material has a high level of moisture, what hinders its handling and reduces the useful life of the product. Drying is an alternative that’s continually evolving to enable reusing these materials. Accordingly, it has been developed in FEQUI/UFU a new dryer called roto-aerated. This dryer provides a better fluid-particle contact than the conventional rotatory dryer, due to a new form of drying air arrangement, increasing the heat and mass transferring coefficients, reducing the energy consumption. In order to increase moisture reduction, a pre-drying system with infrared lamps has been installed on the infeed conveyor. This work addressed the acerola residue characterization, showing that it has satisfactory minerals, proteins, fibers and antioxidant compounds concentrations. It has been shown that antioxidant compounds extraction using ultrasound and micro-waves are more efficient than the conventional method (vortex). These methods also allow the utilization of non-toxic solvents, like ethanol in place of methanol. The optimal levels determined to ultrasound extraction are 67.5%, 13.6 min, 80.9ºC e 59.8 mL/g of solvent concentration, time, temperature and liquid-solid ratio, respectively. This condition presented a maximal TPC (931.2 ± 40.1 mg GAE/100 g), TFC (4.8 ± 0.3 mg de rutin/100 g) and minimal IC50 (5.6 ± 0.3 μg /mL). The extraction time of the micro-wave extraction has been reduced in 70.6% and 96.1% compared to ultra-sound and conventional (agitation with methanol), respectively. The content of total phenolics compounds and total flavonoids were 186.9% and 75.6% greater than the obtained in the conventional extraction, and 65.9% and 17,1% greater than the determined in the ultra-sound extraction, respectively. The IC50 presented reductions of 92.4% and 87.3% compared to the conventional and ultra-sound extractions, respectively. The drying time using the roto-aerated vary from 12 to 16 minutes, it’s possible to reduce the material moisture from 78.7 to 24.9 g/100 g d. w. The content of total phenolic compounds and the total titratable acidity have shown up to 23.6% and 20% of reduction, respectively. In contrast, the content of total flavonoids and ascorbic acid presented an increase of 84.6% and 830.2%, respectively. The drying with ethanol pulverization on the acerola residue allowed an increase of up to 72% of the moisture reduction. Therefore, the hybrid drying method combined with the pre-treatment with ethanol is an alternative to reuse the acerola residue.