# Concentrations of Beetroot (_Beta vulgaris_ L.) Peel and Flesh Extracts by Reverse Osmosis Membrane
## 4 Discussion  
In the case of membrane filtration, CRs of betalains in final retentates of beetroot peel were 3.69 for BC, 4.99 for BX, and 4.16 for TBC, whereas beetroot flesh filtrates exhibited CRs of 5.22 for BC, 6.04 for BX, and 5.52 for TBC. The superiority of CR for flesh concentrate, compared to peel, can be explained by the variation of dry matter, vitamin, mineral, and other biomolecules in different parts of beetroot [25]. Additionally, the superior amount of TPC was in concentration of peel extract, compared to concentration of flesh extract. Amounts of betalains, phenolics, and antioxidants depend upon the variety of beetroot and their sources [26]. The CR of phenolics in beetroot flesh retentate outweighed the CR of beetroot peel filtrates (from 8.8 to 9.4) at the end of the filtration. The nature of beetroot, as earlier discussed, might have influenced the efficiency of the membrane performance, leading to the differences in VRR and CR. In terms of CR for antioxidants, beetroot peel extract exhibited 3.8, which is significantly lower than the CR for beetroot flesh concentrates (CR 11.6). The detected huge amounts of antioxidants in the final concentrates of flesh-water extracts imply the presence of antioxidant-rich water-soluble compounds, which are accumulated in the cytoplasm [27].  
With increase of VRR, the concentrations of TBC, TPC, and AA were increased. The flux behavior of peel extract showed regular reduction with increasing VRR. The accumulation of the compounds on the membrane surface led to the flux declination due to membrane fouling and concentration polarization [28]. Being regarded as non-porous, formation of cake layer on RO membrane surface was more rapid [29]. The accumulation of foulants, cake formation, and pore plugging on/in the membrane layers might be responsible for the resistance to permeation [30]. In membrane filtration, fouling starts with the interaction between the solute and the membrane material by developing the chemical bonds and the van der Waals forces [31]. The extent of adsorption is determined by several factors, such as the membrane material, type, concentration of solutes, ionic strength, and pH of feed solution [32]. The filtration processes of beetroot peel and flesh extracts by RO membrane succeeded in retaining the mentioned compounds at -99% in the concentrates. Likewise, approximately 98% of betalains were retained by loose RO membrane [33]. TSS of crude beetroot flesh extract was improved from 0.02 to 4%, while TSS of peel extract went up to nearly 3% more than the initial feed (0.1%). According to [PERSON] and coworkers [34], the concentrations of phenolics, anthocyanin, vitamin C, and cyanidin-3-glucoside were increased by 3.2, 6.5, 7, and 4.5 times, respectively, by R25A polyamide RO membrane. Furthermore, the membrane filtration has some influence on the tonality of extracts, and the variations depend upon type of extract, whether it is peel or flesh.  
After the membrane filtration, the improvements in t\({}_{1/2}\) values were observed with higher retention values in peel extracts. In the peel extracts, CR of betalains went down significantly after 15 min of heating time, whereas the CR of respective betalains in the beetroot's flesh extracts dramatically reduced within 30 to 45 min of heating. [PERSON] and coworkers [35] claimed that the degradation of betalains from beet leaves after heat in touch was 60 min. Furthermore, it has been reported that thermal treatment at 45 \({}^{\circ}\)C for 6 days affects the stability of betalains in the blanching wastewater of beetroot processing [36].