Automated separation of tail fraction for fruit distillates by means of in‐line conductivity measurement

Abstract

The distillation cuts between head, heart and tail fraction of a fruit distillate are still done in an empirical fashion, based on the distiller's sensorial experience. There has been an unmet need for a long time to provide an objective method for determining the point of tails independent of fruit type and distillation technique. In this study, the authors provide a new method for separating the tail robustly from the heart fraction. For the first time, this is based on an in-line measurement of conductivity together with a suited algorithm for differentiating the conductivity increase before and after the point of tails. The method has been validated with three different fruit mashes of different sugar content, distilled applying different levels of rectification due to different settings of the dephlegmator of the still. Verification with sensory analysis confirmed the validity of the method.

Monitoring of Carboxylic Acids by In-Line Conductivity Measurement to Determine Optimum Distillation Strategy for Distilling Apple Spirits

“…To minimize the disturbance from this variation for the determination of the cut point of tails, a smoothing of the conductivity data in terms of introducing a moving average over 120 s was applied. Finally, the sensorial analysis revealed expected aroma deficits with runs #2 and #5 as higher ethanol fortification yielded cleaner distillates, which are less complex and less rich in aroma compounds confirming earlier results. , Therefore, another distillation strategy was tested in a second experimental setting (runs #3 and #4), where the reflux conditions of run #1 and thus ethanol fortification were kept at a similar level like described in Section . Ethanol concentration c EtOH (hearts), distillation speed, as well as vapor temperature T (start) of these runs were therefore quite comparable (Table ).…”

“…The distillation equipment and process conditions as described hereafter are similar to that used for other studies before. , …”

“…The distillation equipment and process conditions as described hereafter are similar to that used for other studies before. 4,12 The distillation of the five mash aliquots was performed using a 100 L batch still (Figure 1) with a 300 mm reflux column (A) containing three trays and a dephlegmator (B) manufactured by Arnold Holstein GmbH, Markdorf Germany. Run parameters and results are shown in Table 1.…”

“…The determination of the cut point of tails however is difficult, as there are less volatiles in these fractions and the congeners differ between different fruit types and even cultivars of the same kind of fruit. With regard to a more parametric determination of the cut point of tails, vapor temperature or ethanol concentration (bulk concentration of alcohols) is utilized; however, Liebminger et al showed that these methods do not work under any conditions. Instead, they proposed a new procedure of an in-line conductivity measurement as a robust way to determine the cut point of tails, especially during countercurrent distillation when different reflux conditions are considered.…”

Production of Coffee Cherry Spirits from Coffea arabica Varieties

“…In contrast, the stainless-steel distillation equipment was neither particularly professional nor of high-quality, but it was sufficient for this first pilot experiment. To improve the flavour quality of distillates, an automated tail separation by means of in-line conductivity measurement could be a possibility [ 39 , 40 ]. A higher quality copper still should also be considered to create cleaner and high-grade coffee pulp spirits.…”