Aroma recovery

Concentration and Aroma Recovery. Most of the citms juice sold and transported internationally is as frozen concentrate, usually 60—65 °Brix. Because single-strength citms juices generally are 7—12 °Brix solutions, a fivefold or greater concentration has occurred, making the concentrate a more economical product to freeze, store, and transport. 

Concentration and Aroma Recovery. Concentration of juice from deciduous fmit is best carried out using an evaporator that causes as httle thermal degradation as possible and that permits recovery of volatile materials important to the aroma of the fresh fmit, ie, essence. Evaporators that use a high temperature for a short time and operate under a vacuum, such as the APV Crepaco falling film plate evaporator or the Alfa Laval centrifugal... 

There are two methods available for aroma recovery. In one method, a portion of the water is stripped from the juice prior to concentration and fractionally distilled to recover a concentrated aqueous essence solution. Apple juice requires 10% water removal, peach 40%, and Concord grape 25—30% to remove volatile flavor as an essence. Fractional distillation affords an aqueous essence flavor solution of 100—200-fold strength, which means the essence is 100 to 200 times more concentrated in flavor than the starting juice. A second method of essence recovery is to condensate the volatiles from the last effect of the evaporator they are enriched in volatile flavor components (18). 

H. O. E. Karlsson, G. Tragadh. Pervaporation of dilute organic waters mixtures A literature review on modeling studies and applications to aroma recovery. J Membr Sci 75 121, 1993. 

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. 

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. 

Pervaporation may certainly play an important role for replacement of evaporative techniques as well as aroma-recovery processes based on solvent extraction, in particular when the labelling natural is considered crucial. Some of the most relevant technical challenges discussed herein have to be addressed in order to render organophilic pervaporation a competitive process (Fig. 19.4). In particular, the way of capturing the target aromas from the permeate stream has to be reanalysed in terms of minimising energy consumption and labour-intensive operations. 

If sample does not contain fat or oil, the duration of the extraction should not exceed 1 hr. If it contains fats one must verify the extraction time that is necessary for an efficient aroma recovery. Depending on the matrix, one must also verify the appropriate extraction time, prior to beginning. Generally, this time does not exceed 1 hr. Solvent injection and quantification by GC/MS after the SDE is usually used to verify the minimum extraction time needed. 

By use of selective membranes, water can be removed by filtration from the juice in order to effect its concentration. Depending upon the molecular size of the compounds and the cut-off value of the membrane used, there is likely to be some loss of flavour components. These may be recovered from the permeate by distillation and returned to the juice concentrate. Concentration by these methods is less effective in terms of folding than other methods but can provide advantages in specific cases for example, capital costs associated with hyperfiltration are around 10-30% less than for evaporative systems with aroma recovery equipment. 

VOC thermal stability. Separation of VOCs from water by pervaporation generally requires heating the feed water to only 50-70 °C. This is significantly lower than the temperatures involved in distillation or steam stripping, a considerable advantage if the VOCs are valuable, thermally labile compounds. This feature is important in applications such as flavor and aroma recovery in the food industry. 

T. Schafer J. G. Crespo, Aroma Recovery by Organophilic Pervaporation. In Flavours and Fragrances Chemistry, Bioprocessing and Sustainability R. G. Berger, Ed. Springer-Verlag Berlin, 2007 pp 427-438. 

Pervaporation have been considered an interesting alternative process for the current industrial options for aroma recovery, distillation, partial condensation, solvent extraction, adsorption, or a combination thereof. It is considered a basic unit operation with significant potential for the solution of various environmental and energetic processes (moderate temperatures). This separation process is based on a selective transport through a dense membrane (polymeric or ceramic) associated with a recovery of the permeate from the vapour phase. A feed liquid mixture contacts one side of a membrane the permeate is removed as a vapour from the other side. Transport through... 

All the above mentioned evaporators can be equipped with aroma recovery units which for better heat balance can be integrated directly into the evaporator stages. Apple juice evaporators are designed in such a way that the de-aromatised juice can be taken out of the evaporator with approx. 50°C for clarification. The clarified juice is fed back to the next evaporator stage at the same temperature. The evaporation process is not interrupted and the evaporator can operate smoothly and uniformly. 

The Centritherm-Evaporator (27) is very popular for the concentration of passion fruit juice. This is a one-stage rotary thin film evaporator which can be fitted with or without aroma recovery. Originally developed by Alfa Laval for concentrating sensitive products in the pharmaceutical industry, this machine is now sold and serviced by FLAVOURTECH Pty. Ltd (27). For the very efficient recovery of the aroma FLA-VOURTECH can also offer a so-called Spinning Cone Column which has been successfully applied for the recovery of difficult-to-recover aromas such as coffee aroma. 

While producing juices and concentrates it is recommended to recover the aroma of the juice separately in order to add it back at a later time. For this purpose aroma recovery units have been developed which are constantly improved [7-12], Basically there are two different methods ... 

Recovery in especially developed separate aroma recovery units. 

Hochberg, U., Progresses in Aroma Recovery, Fllissiges Obst, 3, (1987)... 

Dimitriou, M., Concentration Plants with Aroma Recovery, Operation Experience and New Developments, Fltissiges Obst, 4, (1986)... 

Apart from the taste oils, the aqueous essences synonymously called aroma, water-phase, waterphase aroma or essence waterphase are also retained as part of the aroma recovery during juice concentration. Their flavouring potential is mainly used in reconstituted fmit juices. On the one hand, the watery environment exerts a negative... 

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