# Concentrations of Beetroot (_Beta vulgaris_ L.) Peel and Flesh Extracts by Reverse Osmosis Membrane
## 1 Introduction  
Reverse osmosis (RO) is a pressure-driven process, whereby a semipermeable membrane rejects dissolved constituents present in the feed stream. This rejection is due to size exclusion, charge exclusion, and physicochemical interactions between solute, solvent, and membrane [1]. The process efficiency depends on operational parameters, and on the properties of membrane and feed. The most commercially available modules are spiral-wound and hollow fiber. The latter has an extremely high packing density, and thus offers high permeation rate but is more prone to fouling. RO membranes can be either asymmetric, containing one polymer layer, or a composite of two or more layers [2].  
The RO process is used in chemical and environmental engineering for the removal of inorganics and organic pollutants present in wastewater [3]. It is seen from the literature review that RO processes have been widely used for the separation and concentration (recovery) of solutes in many fields. The uses of RO in the treatment of various effluents from chemicals, petrochemical, electrochemical, food, paper, and tanning industries, as well as for the treatment of municipal wastewaters, have been reported in several articles [4, 5, 6]. Applications of RO have been known to be crucial for the concentration of fruit and vegetable juices, sea salts, dairy products, and removal of alcohol from alcoholic beverages [7, 8, 9]. Fundamentally, RO is combined with other filtration techniques, such as microfiltration [9], ultrafiltration [10], and nanofiltration [11]. This has led to improve the quality of product [3].  
Beetroots (_Beta vulgaris_ L.) are herbaceous bieneninals of the Chenopodiaceae family with high sugar content (7.7%), mostly sucrose, and trace amounts of fructose and glucose [12; 13]. The alternative names are red beet, sugar beet, garden beet, white beet, sea beet, spinach beet, and chard. Aside from compacting with biopigment, known as betalains, beetroots are rich in nitrate (NO\({}_{3}\)\({}^{-}\)), which plays a role in the cardiovascular system. Betalains are composed of red-color-giving betacyanin (BC) and yellow-color-giving betaxanthin (BX) compounds. Betalains associated with their antioxidant activity (AA) have been claimed as having anticancer, antiproliferative, anti-inflammatory, and antimicrobial activities [14; 15]. Daily consumption of beetroot juice can regulate blood pressure, and has vasoprotective effects [12; 13]. According to the findings of [PERSON] et al. [16], beetroots contain sodium (4.17 mg), potassium (13.82 mg), magnesium (5.91 mg), phosphorous (11.57 mg), copper (0.21 mg), and iron (26.46 mg) per 100 g. The chemical composition of the beetroot peel is presented as follows: moisture content (30.88%), ash content (10.58%), crude fat (3.29%), crude fiber (6.98%), protein (4.1%), and carbohydrate (44.17%), along with the mineral composition of sodium (4.17%), iron (26.46%), copper (0.21%), magnesium (5.91%), potassium (13.82%), and phosphorous (11.57%) [16].  
In the articles of [PERSON] et al. [17; 18], the application of nano and RO membranes have been exploited in the concentration of the ethanolic, as well as aqueous, extracts of beetroot's peel. In this particular research, betalains, phenolics, and antioxidants from the aqueous extract of peel, and flesh of beetroot were concentrated by thin-film composite-type RO membrane (X20). Furthermore, thermo-instability of betalains (color compounds) has been investigated.