Aroma compounds, recovery

Souchon, I., Afhes, V., Pierre, F.X. and Marin, M. (2004) Liquid-liquid extraction and air stripping in membrane contactor application to aroma compounds recovery. Desalination, 163, 39. 

Aroma compound recovery PDMS Temperature effects are studied [112]... 

Organic-water mixture Membrane made of elastomeric or hydrophobic polymeric material Modeling studies and application aroma compound recovery [114]... 

Aroma compounds recovery of tropical fruit juice by pervaporation... 

Karls son HOE, Loureiro S, and Tragardh G. Aroma compound recovery with pervaporation-temperature effects during pervaporation of Muscat wine. J. Food Eng. 1995 26 177. 

Karlsson HOE and Tragardh G. Pervaporation dilute organic-water mixtures A literature review on modeling studies and application to aroma compound recovery. J. Memb. Sci. 1993 76 121. 

Pereira CC, Rufino JRM, Habert AC, Noberga R, Cabral LMC, and Borges CP. Aroma compounds recovery of tropical fruit juice by pervaporation Membrane material selection and process evaluation. J. Food Eng. 2005 66(l) 77-87. 

Raisi A, Aroujalian A. 2011. Aroma compound recovery by hydrophobic pervaporation The effect of membrane thickness and coupling phenomena. Sep. Purif. Technol. 82 53-62. 

Karlsson HOE and Tragardh G (1993), Pervaporation of dilute organic-waters mixtures. A literature review on modelling studies and applications to aroma compound recovery , 7 Membr Sci, 76,121-146. 

Solvent extraction is an excellent choice for aroma-compound isolation from foods when applicable. Unfortunately, many foods contain some lipid material, which limits the use of this technique since the lipid components would be extracted along with the aroma compounds. Alcohol-containing foods also present a problem in that the choice solvents (e.g. dichloromethane and diethyl ether) would both extract alcohol from the product, so one obtains a dilute solution of recovered volatiles in ethanol. Ethanol is problematic since it has a high boiling point (relative to the isolated aroma compounds), and in concentration for analysis, a significant proportion of aroma compounds would be lost with the ethanol. As one would expect, the recovery of aroma compounds by solvent extraction is dependent upon the solvent being used, the extraction technique (batch or continuous), and the time and temperature of extraction. 

As mentioned in the introduction to this section, there is the opportunity to recover aroma compounds from baking or roasting exhaust gases. The patent literature contains numerous references to the recovery of aroma compounds using this approach, most commonly from cocoa, coffee, or tea processing. Aroma compounds from the roaster exhaust gases are either condensed in cryogenic traps [29-32] or collected on absorbents (e.g. charcoal [33]) and then solvent-extracted to obtain a concentrated aroma extract. The concentrated extract may be used to aromatise a similar product (e.g. soluble coffee) or may be used to flavour other products (e.g. coffee-flavoured ice creams). 

A similar apparatus has been used for recovery of aroma compounds from cacao during processing [34]. In this process, water and acetic acid are removed from the aroma-laden gas stream by the initial traps and then the gas is passed through traps of the same design as those described by Cams and Tuot [29]. The aroma isolate so provided is suggested to be useful for the flavouring of soluble cocoa beverages, cake mixes, and confectionery products. 

If one is considering the recovery of aroma compounds from waste gas streams, one should investigate the pollution-control literature. There are a large number of patents and scientific articles that deal with this issue. The techniques used are generally aimed at the removal of trace volatiles in air streams and are potentially suited to aroma recovery. The primary consideration is whether the techniques yield an isolate safe for human consumption. 

In comparison with adsorptive/absorptive techniques for aroma recovery from bioconversions, the disadvantage of pervaporation is the fact that both sorption and diffusion determine the overall selectivity. While the sorption selectivity is very high (equal to that of adsorptive/absorption), the diffusion selectivity favours water owing to the simple fact that water is a smaller molecule than aroma compounds and thus sterically less hindered during diffusion (Table 19.1). The overall (perm)selectivity P=SD) is therefore lower than in strictly sorption controlled processes, although it is still favourable compared with that for evaporation. This shortcoming compares, however, with operational advantages of pervaporation as outlined before. 

Recovery of aroma compounds from diluted aqueous streams (we are excluding from this discussion the recovery of aromas from vapour streams) may be of industrial interest under different circumstances recovery of complex aroma profiles and/or target aroma compounds from active biocatalytic processes recovery of complex aroma profiles and/or target aroma compounds from natural extracts and industrial process water (or effluent) streams. 

Most research on aroma recovery by organophilic pervaporation has been conducted using aqueous aroma model solutions [25-28], although in recent years significant interest has been devoted to the recovery of aroma compounds from natural complex streams, such as fruit juices [29-31], food industry effluents [32] and other natural matrixes [33]. The increasing demand for natural aroma compounds for food use, and their market value, opens a world of possibilities for a technique that allows for a benign recovery of these compounds without addition of any chemicals or temperature increase. However, in most situations, dedicated requests by industrialists are formulated in cooperation with marketing departments, which translate into the need for a correct public perception. 

Pierre, F.X., Souchon, I. and Marin, M. (2001) Recovery of sulfur aroma compounds using membrane-based solvent-extraction. Journal of Membrane Science, 187, 239. 

Bitteur and Rosset (23) have applied solid phase extraction for the recovery of black currant aroma compounds from waste water. They passed solutions of known compounds in water through three different extraction columns, eluted each with either ethanol or dichloromethane and then analyzed the eluant to determine extraction efficiency. While this study was aimed at the recovery of aroma compounds on a commercial basis, their results demonstrated that reverse phase polymers can effectively be employed in the recovery of aroma compounds from dilute aqueous systems. 

Processes for production of ethanol and acetone-butanol-ethanol mixture from fermentation products in membrane contactor devices were presented in Refs. [88,89]. Recovery of butanol from fermentation was reported in Ref. [90]. Use of composite membrane in a membrane reactor to separate and recover valuable biotechnology products was discussed in Refs. [91,92]. A case study on using membrane contactor modules to extract small molecular weight compounds of interest to pharmaceutical industry was shown in Ref. [93]. Extraction of protein and separation of racemic protein mixtures were discussed in Refs. [94,95]. Extractions of ethanol and lactic acid by membrane solvent extraction are reported in Refs. [96,97]. A membrane-based solvent extraction and stripping process was discussed in Ref. [98] for recovery of Phenylalanine. Extraction of aroma compounds from aqueous feed solutions into sunflower oil was investigated in Ref. [99]. 

Recovery of aroma compounds PDMS on polyetherimide from wine-must fermentation... 

Recovery of aroma compounds (l-octene-3-ol, ethyl acetate/butyrate/hexanoate) Recovery of picolines from aqueous solutions Recovery of aroma compounds... 

Scale-up of pervaporation for the recovery of natural aroma compounds in the food industry. Part 2 Optirrrization and integration... 

Generally, alcohols showed higher separation factors when present in model multicomponent solutions than in binary systems with water. On the other hand, aldehydes showed an opposite trend. The acmal tea aroma mixmre showed a rather different behavior from the model aroma mixmre, probably because of the presence of very large numbers of unknown compounds. Overall, the PDMS membrane with vinyl end groups used by Kanani et al. [20] showed higher separation factors and fluxes for most of the aroma compounds. Pervaporation was found to be an attractive technology. However, as mentioned above the varying selectivities for the different aroma compounds alter the sensory prohle and therefore application of PV for recovery of such mixmres needs careful consideration on a case-by-case basis. 

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