Simultaneous Separation of Antioxidants and Carbohydrates From Food Wastes Using Aqueous Biphasic Systems Formed by Cholinium-Derived Ionic Liquids

Abstract

The food industry produces significant amounts of waste, many of them rich in valuable compounds that could be recovered and reused in the framework of circular economy. The development of sustainable and cost-effective technologies to recover these value added compounds will contribute to a significant decrease of the environmental footprint and economic burden of this industry sector. Accordingly, in this work, aqueous biphasic systems (ABS) composed of cholinium-derived bistriflimide ionic liquids (ILs) and carbohydrates were investigated as an alternative process to simultaneously separate and recover antioxidants and carbohydrates from food waste. Aiming at improving the biocompatible character of the studied ILs and proposed process, cholinium-derived bistriflimide ILs were chosen, which were properly designed by playing with the cation alkyl side chain and the number of functional groups attached to the cation to be able to create ABS with carbohydrates. These ILs were characterized by cytotoxicity assays toward human intestinal epithelial cells (Caco-2 cell line), demonstrating to have a significantly lower toxicity than other well-known and commonly used fluorinated ILs. The capability of these ILs to form ABS with a series of carbohydrates, namely monosaccharides, disaccharides and polyols, was then appraised by the determination of the respective ternary liquid-liquid phase diagrams at 25°C. The studied ABS were finally used to separate carbohydrates and antioxidants from real food waste samples, using an expired vanilla pudding as an example. With the studied systems, the separation of the two products occurs in one-step, where carbohydrates are enriched in the carbohydrate-rich phase and antioxidants are mainly present in the IL-rich phase. Extraction efficiencies of carbohydrates ranging between 89 and 92% to the carbohydrate-rich phase, and antioxidant relative activities ranging between 65 and 75% in the IL-rich phase were obtained. Furthermore, antioxidants from the IL-rich phase were recovered by solid-phase extraction, and the IL was recycled for two more times with no losses on the ABS separation performance. Overall, the obtained results show that the investigated ABS are promising platforms to simultaneously separate carbohydrates and antioxidants from real food waste samples, and could be used in further related applications foreseeing industrial food waste valorization.

Valorization of Spent Coffee by Caffeine Extraction Using Aqueous Solutions of Cholinium-Based Ionic Liquids

“…Their biocompatible nature is usually ascribed to their similar chemical structure to the water-soluble essential nutrient cholinium chloride (also known as vitamin B4), which is found in food obtained from vegetable or animal sources and supports several biological functions [26,27]. The cholinium cation has been combined with a wide variety of organic or inorganic anions, producing ILs with different properties [28][29][30]. In the field of biomass extractions, Ribeiro et al [31] applied aqueous solutions of cholinium-based ILs as potential alternatives to imidazolium-based counterparts for the extraction of polyphenols and saponins from the leaves and aerial parts of Ilex paraguariensis (mate) and Camellia sinensis (tea).…”

“…The authors concluded that [Ch]Cl was the best solvent option for the extraction of saponins and phenolic compounds, either from mate or tea [31]. Recently, cholinium-based ILs were studied to simultaneously extract and isolate antioxidants and carbohydrates from food waste [29]. Despite all promising achievements, there is still a long path to take advantage of all the potential of more biocompatible ILs as alternative solvents to extract high-value compounds from biomass.…”

Evidences for a Null Molar Volume Contribution by Hydroxyl Groups in Ammonium Bistriflimide-Based Ionic Liquids

“…22 It was also shown that some of these ammonium bistriflimide ILs present substantially less toxicity to Caco-2 human cells than some commonly used bistriflimide-based ionic liquids. 23 The functionalization of ILs using either hydroxyl or ether groups in their chemical structure is a well-known strategy in order to tune their properties. However, quantitative analyses in which one compares the changes in properties of these types of replacements (hydroxyl or alkoxy or alkyl, all of them of comparable/similar volumetric sizes) are still lacking.…”

“…Moreover, previous work has shown the importance of adding hydroxyl groups to the ammonium cation, enhancing the hydrogen bonding ability of ILs, to produce room-temperature water-soluble bistriflimide-based ionic liquids . It was also shown that some of these ammonium bistriflimide ILs present substantially less toxicity to Caco-2 human cells than some commonly used bistriflimide-based ionic liquids …”

Rethinking the Applications of Ionic Liquids and Deep Eutectic Solvents in Innovative Nano-Sorbents

“…It has been proved that aqueous ChCl-Gly is among the most readily biodegradable and is "practically harmless" to the aquatic ecosystem (Juneidi et al, 2015). Additionally, newer generations, i.e., cholinium-derived ILs were chosen as the component of an aqueous two-phase (ATP) to simultaneously extract and recover antioxidants and carbohydrates from food waste (Neves et al, 2019). These used ILs were proven to have low toxicity toward human intestinal epithelial cells (Caco-2 cell line).…”