The potential of aroma recovery by combining absorption with distillation is shown by calculating the aroma folding factor (AF), defined here as the times the aroma vapour stream fed to the condenser is more concentrated in the aroma compounds than the feed. AF can be calculated from:
equation(2)
Turn MathJaxon
where ae is the fraction of aroma evaporated, fe is the fraction of feed evaporated, ana and wvna are the fractions of aroma and water vapour respectively non-absorbed by the hygroscopic solution.
Eq. (2) gives the number of times the condensate will be more concentrated in the aroma compounds than the feed if all the aroma compounds in the vapour phase that are not absorbed by the hygroscopic solution in the absorber, are condensed in an efficient condenser. The absorber increases the aroma folding by a factor equal to ana/wvna. For example, for an absorber in which 10% of an aroma compound and 80% of water vapour are absorbed by the hygroscopic solution, the AF will be 4.5 times higher than in the simple distillation.
4. Conclusions
It was demonstrated that a vapour stream rich in aroma compounds can be produced by passing the vapour over a hygroscopic solution, such as LiBr solution, where most of the water vapour is absorbed, while aroma compounds are absorbed to a less extend. Compounds of low relative volatility, i.e. methanol, ethanol, were absorbed in LiBr solution to a significant amount. Compounds of higher relative volatility i.e. ethyl acetate, methyl butyrate and ethyl butyrate were only slightly absorbed. When distillation was combined with partial absorption of water vapour to the LiBr solution, the relative concentration of each aroma compound in the condensate was 1.8–2.8 times higher than in the condensate obtained with simple distillation.
The potential of aroma recovery by combining absorption with distillation is shown by calculating the aroma folding factor (AF), defined here as the times the aroma vapour stream fed to the condenser is more concentrated in the aroma compounds than the feed. AF can be calculated from:
equation(2)
Turn MathJaxon
where ae is the fraction of aroma evaporated, fe is the fraction of feed evaporated, ana and wvna are the fractions of aroma and water vapour respectively non-absorbed by the hygroscopic solution.
Eq. (2) gives the number of times the condensate will be more concentrated in the aroma compounds than the feed if all the aroma compounds in the vapour phase that are not absorbed by the hygroscopic solution in the absorber, are condensed in an efficient condenser. The absorber increases the aroma folding by a factor equal to ana/wvna. For example, for an absorber in which 10% of an aroma compound and 80% of water vapour are absorbed by the hygroscopic solution, the AF will be 4.5 times higher than in the simple distillation.
4. Conclusions
It was demonstrated that a vapour stream rich in aroma compounds can be produced by passing the vapour over a hygroscopic solution, such as LiBr solution, where most of the water vapour is absorbed, while aroma compounds are absorbed to a less extend. Compounds of low relative volatility, i.e. methanol, ethanol, were absorbed in LiBr solution to a significant amount. Compounds of higher relative volatility i.e. ethyl acetate, methyl butyrate and ethyl butyrate were only slightly absorbed. When distillation was combined with partial absorption of water vapour to the LiBr solution, the relative concentration of each aroma compound in the condensate was 1.8–2.8 times higher than in the condensate obtained with simple distillation.
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The potential of aroma recovery by combining absorption with distillation is shown by calculating the aroma folding factor (AF), defined here as the times the aroma vapour stream fed to the condenser is more concentrated in the aroma compounds than the feed. AF can be calculated from:
equation(2)
Turn MathJaxon
where ae is the fraction of aroma evaporated, fe is the fraction of feed evaporated, ana and wvna are the fractions of aroma and water vapour respectively non-absorbed by the hygroscopic solution.
Eq. (2) gives the number of times the condensate will be more concentrated in the aroma compounds than the feed if all the aroma compounds in the vapour phase that are not absorbed by the hygroscopic solution in the absorber, are condensed in an efficient condenser. The absorber increases the aroma folding by a factor equal to ana/wvna. For example, for an absorber in which 10% of an aroma compound and 80% of water vapour are absorbed by the hygroscopic solution, the AF will be 4.5 times higher than in the simple distillation.
4. Conclusions
It was demonstrated that a vapour stream rich in aroma compounds can be produced by passing the vapour over a hygroscopic solution, such as LiBr solution, where most of the water vapour is absorbed, while aroma compounds are absorbed to a less extend. Compounds of low relative volatility, i.e. methanol, ethanol, were absorbed in LiBr solution to a significant amount. Compounds of higher relative volatility i.e. ethyl acetate, methyl butyrate and ethyl butyrate were only slightly absorbed. When distillation was combined with partial absorption of water vapour to the LiBr solution, the relative concentration of each aroma compound in the condensate was 1.8–2.8 times higher than in the condensate obtained with simple distillation.
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