仙草凝膠物質之莘取及其凝膠性質之研究

Abstract

仙草(Mesona procumbens Hemsi.)是一種含有具凝膠性多糖類物質之草本植物，其經過適當鹼量添加與熬煮所得之萃取液，在添加2％澱粉時，會有韌性極強之凝膠特性。本研究比較仙草萃取時，添加0.05、0.1、0.3、0.5、0.7、l.0、1.2、1.4％碳酸鈉、碳酸氫鈉對仙草多糖類物質萃出之影響，結果顯示碳酸鈉處理之乾物抽出率與全可溶性固形物分別在19.32至44.85％與1.8至4.6ºBrix間，添加碳酸氫鈉萃取處理之乾物抽出率、全可溶性固形物則分別在13.90至38.95％與1.3至4.9ºBrix間，此顯示兩種鹼類皆有助於使仙草組織崩解並釋出其中之多糖類物質，而碳酸鈉處理較碳酸氫鈉處理對仙草植物中多糖類物質有更佳之抽出效果。又添加愈高量之碳酸鈉、碳酸氫鈉處理，會有愈多之仙草多糖類物質被抽出。綜合所製成仙草凍之凝膠品質、風味及口感，顯示以添加0.3至0.5％之碳酸鈉濃度進行萃取為最佳。 為比較碳酸鈉與碳酸氫鈉處理所得萃取液之凝膠性質，將此兩種鹼類處理所得之萃取液分別稀釋為含0.6、0.8、1.0、1.2、1.4％固形物之仙草溶液，再分別添加2.0、2.5、3-4.0％之小麥澱粉，各處理均顯示添加0.3％或0.5％碳酸鈉、碳酸氫鈉之萃取處理有最高之凝膠強度，其凝膠強度分別在42.0至130.0克／平方公分與36.3至110.6克／平方公分間，顯示以碳酸鈉處理所得之萃取液有較佳的凝膠品質；提高澱粉濃度有使仙草凝膠強度增加之趨勢，濃度以2.0-3.0％澱粉處理較宜，因添加4.0％小麥澱粉處理仙草凍之質感較差。 Hsian-tsao gel is a jello-type dessert popularly consumed in the Far East countries. The gel is prepared from the alkaline extract of Hsian-tsao (Mesona procumbensHemsl.) herb with the addition of approximately 2 % starch at boiling temperature. A dark-brownish gel will be formed after the solution is cooled. Extraction of Hsian-tsao gelling constituents using sodium carbonate and sodium bicarbonate at concentration ranged from 0.05 % to 1.4 % for 3 hours resulted in the total solids recoveris of 19.3 to 44.8 % and 13.9 to 39.0 %, respectively. These results are significantly higher than 12.2 % total solid srecovery of the herb extracted with distilled water. The higher concentration of sodium carbonate or sodium bicarbonate solution the more total solids is yielded. Hsian-tsao gels prepared from 1.0 Brix 0.3 % or 0.5 % sodium carbonate or sodium bicarbonate extracts with 2.0 % wheat starch added resulted in the most acceptable gel strength of 80 g/cm2. The higher the concentration of extract and the higher the starch added to the extract formed the greater gel strength of the gel.