Abstract
The aim of this work was to analyze the potential of reverse osmosis (RO) membranes in the recovery and concentration of aroma compounds from orange juice evaporator condensate (EC) streams. Concentration experiments were performed by using three RO spiral-wound aromatic polyamide membranes (SG1812C-34D, SC1812C-34D and SE1812) with different NaCl rejections. The effect of transmembrane pressure, axial feed flowrate and volume concentration ratio (VCR) on permeate flux was studied. Rejections of the investigated membranes towards specific aroma compounds (octanol, α-terpineol, terpinen-4-ol, cis-carveol, karvon, linalool) in selected operating conditions were also evaluated. The concentrations of the aroma compounds were determined by gas chromatography coupled with mass spectrometry (GC-MS) using headspace solid-phase microextraction (HS-SPME) as a sample preparation approach. For all selected membranes, the permeate flux increased linearly by increasing the operating pressure from 5 to 25 bar; on the other hand, the feed flowrate did not have any significant effect on the permeate flux. High retention values towards aroma compounds (>80%) were measured for all selected membranes. However, the SC membrane showed the highest rejection values (>96%) and the best correlation between concentration factor of aroma compounds and VCR.
Highlights
The citrus processing industry is characterized by the production of a considerable amount of by-products of commercial value including dried pulp and molasses, juice pulps and pulp wash and d-limonene [1]
Rejections of aroma compounds were evaluated in batch concentration experiments performed in selected operating conditions
Experimental data indicated a linear dependence of pressure influence on the permeate flux due to minimal concentration polarization and fouling phenomena
Summary
The citrus processing industry is characterized by the production of a considerable amount of by-products of commercial value including dried pulp and molasses, juice pulps and pulp wash (secondary juice) and d-limonene [1] These by-products represent a serious environmental problem, since the plant material is usually prone to microbial spoilage and is commonly used in animal feed or as fertilizers. Most of these materials are enriched in bioactive compounds, such as flavonoids and phenolic acids, recognized for their beneficial implications in human health due to their antioxidant activity and free radical scavenging ability [2]. They are used by the industries in many ways, including fruit cleaning/washing, extraction/recovery of solids residual of the pulp, water replacement in the process of peel essential oil recovery, calories recovery for use in Membranes 2020, 10, 92; doi:10.3390/membranes10050092 www.mdpi.com/journal/membranes
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