Concentrations of Beetroot (<i>Beta vulgaris</i> L.) Peel and Flesh Extracts by Reverse Osmosis Membrane

The objective of this investigation was to concentrate betalains, phenolics, and antioxidants from the extract of peel and flesh of beetroot (Beta vulgaris L.). Thin-film composite reverse osmosis (RO) membrane composed of the thick polyamide barrier layer, microporous polysulfone interlayer, and polyester support web was used in membrane module. In a later exercise, thermo-instability of betalain color compounds was investigated with different temperatures. After the filtration of the aqueous extract of flesh, betacyanins, betaxanthins, and total betalains were increased by 5.2, 6.1, and 5.5 times, respectively. Likewise, the mentioned bioactive compounds were increased by 3.7, 4.9, and 4.2 times after filtration of the aqueous extract of peel. The amounts of total betalains measured in the final flesh extract were two times lower (14.33 ± 0.15 mg·g−1 dm) compared to the peel concentrate (30.02 ± 0.28 mg·g−1 dm). The superior amount of phenolic was shown in the final flesh extract (34.47 ± 0.19 mg GAE·g−1 dm) compared to peel extract (12.74 ± 0.42 mg GAE·g−1 dm). The antioxidant activity in final beetroot peel extract and flesh extract were 24.65 ± 1.42 mg ASE·g−1 dm and 11.6 ± 0.1 mg ASE·g−1 dm, respectively. The recovery of thermo-sensitive bio-colorants was achieved by membrane filtration with the least thermal degradation