Browsing by Subject "Fractional distillation"

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Influence of distillation parameters on the fractionation behaviour of aroma compounds in the production of Williams-Christ pear brandies and Golden Delicious apple brandies
(2025) Yagishita, Manami; Vetter, Walter
Aroma compounds are central to the sensory attributes and overall organoleptic quality of fruit brandies, yet their behavior during distillation remains insufficiently understood. The relative volatility of these compounds, a fundamental property that defines their evaporation tendency in relation to ethanol, plays a crucial role in distillation, governing their separation efficiency, distribution between vapor and liquid phases, and overall impact on the composition and sensory quality of the final product. Despite its importance, the concept of relative volatility has not been introduced in the production of fruit brandies. The aim of the first publication was to develop a quick and simple method using a basic distillation apparatus to determine the relative volatilities of flavor compounds in hydro-alcoholic solutions. This approach provides a practical alternative to the time-consuming and costly Gillespie dynamic recirculation method. Seventeen representative flavor compounds from apple and pear brandies were investigated, including unpublished data for five compounds. Relative volatilities of methanol, isobutanol, isoamyl alcohol, ethyl acetate, acetaldehyde, and 1,1-diethoxyethane were compared to reference data, showing high correlation for all compounds except 1,1-diethoxyethane. Vapor-liquid equilibrium data for an ethanol-water mixture also exhibited strong agreement with reference data. These results demonstrate that the proposed method is a reliable, fast, and cost-effective alternative to standard techniques for determining relative volatilities. The second publication investigated the impact of partial condensation in dephlegmators on the behavior of ethanol and flavor compounds, comparing setups with and without dephlegmators in both lab-scale and large-scale experiments. Lab-scale experiments demonstrated that dephlegmation led to significant enrichment of ethanol in the distillate through the selective condensation of water. The behavior of flavor compounds varied, with some showing enrichment, others depletion, and some remaining unaffected. In large-scale experiments, a distillation apparatus relying solely on dephlegmation was compared with a standard setup containing an enrichment section with three trays. The dephlegmator-based system exhibited less efficient separation of tail components, such as fusel alcohols, resulting in a lower yield of hearts fraction. Sensory triangle tests confirmed that the spirits from the two systems were distinguishable, though no clear preference emerged. This study provides the first detailed insights into the influence of dephlegmators on flavor compound behavior and separation efficiency during fruit brandy distillation, offering valuable guidance for optimizing distillation processes. The third publication explored distillation processes from the perspective of relative volatility, aiming to control behaviors of key odor-active compounds in pear brandies and enhance product quality through novel fractionation strategies. Two novel fractionation strategies were tested: one involving a high cooling water flow rate combined with a slow distillate flow, and the other employing a 12-tray distillation column. Both approaches successfully increased ethanol concentration on the top tray, altering the relative volatility of compounds in the liquid phase. Elevated ethanol concentrations reduced the relative volatility of higher alcohols, delaying their release and producing sharper, well defined peaks compared to broader profiles observed in the control distillation. This enabled selective separation of desirable compounds, such as beta-damascenone and ethyl (E,Z)-2,4-decadienoate (pear ester), from higher alcohols, resulting in an aroma-rich tails fraction. Blending this enriched tails fraction with the hearts fraction produced a final product that was significantly preferred in sensory evaluations over the standard hearts fraction. These findings demonstrate the importance of tailoring operational distillation conditions to exploit differential volatility, enabling more effective compound separation and improving the sensory quality of fruit brandies.