The Effect of Microwave Treatment on The Esterification in Kaoliang Spirit.

New distilled kaoliang spirit must undergo aging process in order to reduce the pungent taste after drinking ,remove the off-flavor and make the aroma more attractive to consumers. Esters are the key com-pound of alcohol beverages aroma because their low threshold and distinctive flavor. Not only the esters in alchol beverages increase their content via esterifition ,esters and other compounds also reach equi-librium state during the aging process. Aging process is a time and space-consuming operation. Reducing the aging time via other treatment means lowering the production cost. Microwave irradiation has been utilized in many organic synthesis reac-tion because it can accelerate the reaction rate in short time by inducing compounds to vibrate. The aim of this master thesis is to shorten the aging process time in order to reduce the production cost. Kaoliang spirit is the sample in this experiment because it is one of the most character-istic alcohol beverages and the concentration changes ofethyl acetate -the main aromatic compound in kaoliang spirit is the indicator of the effect of microwave treatment. The results of batch-microwave treatment shows that microwave treatment can accelerate the esterification reaction rate about 3.35 times without containing ethyl acetate at the beginning. However, because micro- wave improve the forward and reverse reaction rate simul-tane-ously ,the esterification rate gets slower while the ethyl acetate concen-tration accumulated. It is reasonable to doubt that the way to affect the concentration of ethyl acetate and acetic acid is not mainly via esterifi-cation because of the unequal change between ethyl acetate and acetic acid in the continuous experiment. Therefore, the forward and reverse reaction rate are raised while applying continuous operation system and microwave treatment to new distilled kaoliang spirit ,causing the dif-ferent concentration change between ethyl acetate and acetic acid. But the equilibrium constant of reaction turned down from 4.57 to 3.43 after microwave treatment. It reveals that microwave treatment can urge the reaction to equilibrium. In conclusion, although that the continuous operation system used in this experiment can help the reaction reach equilibrium quickly but is not an appropriate operation way to increase the ethyl acetate concen-tration. However, the flavor quality of aged Chinese spirit would be a harmonization of many compounds, could not just rely on the concen-tration of a particular compound. Hence, a sensory experiment is needed in order to check the effect of continuous microwave treatment on kao-liang spirit in the future.新製好的酒品需經陳化處理，使新酒原先入口後的刺激感降低，雜味消除讓香味醇正，並使酒香更加誘人。而酯類由於其使人類感受到的閾值濃度低，且又帶有特殊香氣，往往是影響酒香的主要關鍵成分。在陳化過程中，酒液中的酯類能再藉由酯化反應增加含量，並與其他物質達成平衡而使整體風味更加圓熟。 不過陳化步驟耗時且占空間，如果可利用其他處理方式來縮短陳化所需的時間即可降低生產成本。微波因為能使分子快速震動，可在短時內提高反應速率，已利用在促進多種有機合成反應中。本實驗希望藉由微波處理來縮短陳化處理所需要的時間，以達節省酒類生產製作成本。並以亞洲華人地區的特色酒品－高粱酒為樣品，並以高粱酒主要香氣成分的乙酸乙酯含量變化，作為微波加速陳化操作效果之指標。 實驗先以批式操作模擬酒液來探討微波操作對於正向酯化反應的促進效果。由實驗結果可得知，在樣品起始無乙酸乙酯存在下，微波操作可以提升酯化反應速率達3.35倍。但隨乙酸乙酯含量增加，微波同時也促進逆向反應進行，而降低乙酸乙酯生成速率。實驗最後以新酒進行實驗，由連續式實驗中乙酸乙酯與醋酸的濃度改變趨勢不一致可合理懷義，影響酒液中乙酸乙酯濃度變化的因素眾多，應非只由乙醇與醋酸行正逆酯化反應而已。因此以本實驗的循環攪拌系統搭配微波處理，會同時加速多種反應進行，而使乙酸乙酯與醋酸濃度產生不一致的變化。而雖然新酒中乙酸乙酯濃度在連續式微波處理後降低，但以酯化反應平衡常數而言，經微波處理後樣品的反應平衡常數從4.57下降至3.43，較未處理前接近老熟酒的反應平衡常數3.0352。由此可知微波處理可以促進反應到達平衡狀態。 綜合實驗結果：若針對提高酒液內乙酸乙酯含量，則本實驗所採用之連續式微波系統並非是合適的操作方式。但事實上陳化酒的香氣品質優劣，可能需請品酒師品評，感受酒液內芳香物質的整體協調性而決定，並非以單一香氣成分濃度高低而決定。因此，未來可搭配品評試驗來確認連續式微波處理對高粱酒品質之影響。表目錄 III 圖目錄 IV 中文摘要 V Abstract VI 第一章、前言 1 第二章、文獻回顧 2 一、高粱酒 2 (一)酒精飲料簡介 2 (二)酒精飲料分類 2 (二)酒類呈味影響因素 5 (三)高粱酒製程 9 二、微波 11 (一)微波簡介 11 (二)微波原理 11 (三)微波應用實例 12 第三章、材料與方法 14 一、實驗材料 14 (一)試藥 14 (二)樣品 14 二、實驗器材 14 三、實驗方法 19 1.批式微波酯化反應 19 2.連續式酯化反應 19 2-1溫度效應 19 2-2濃度效應 20 2-3新酒連續式處理 20 四、分析方法 22 (一) Ethyl acetate乙酸乙酯濃度測定 22 (二) Acetic acid醋酸濃度測定： 22 第四章、結果與討論 24 一、模擬酒液模型建立 24 二、確立高粱酒陳化指標 26 三、批式微波操作對於乙酸乙酯生成速率之影響 28 (一)結果與討論 28 (二)小結 30 四、連續式微波處理對於乙酸乙酯生成速率之影響 38 (一) 結果與討論 38 (二) 小結 40 五、連續式微波處理對於新酒中酯類濃度之影響 46 (一) 結果與討論 46 (二) 小結 48 第五章、總結 53 參考文獻 54 一、中文參考書目 54 二、英文參考書目 5