• 作者： 鄭丹楓;張為憲
• 作者服務機構： 國立台灣大學食品科技研究所
• 中文摘要： 甜菊萃取液之甜菊糖含量，約佔總萃取乾物之30%，其餘70%為有機與無機雜質。這些非甜菊糖雜質影響甜菊糖之純化、結晶操作甚鉅，因此本研究之目的在於瞭解這些雜質之成份及性質，裨助於甜菊糖之純化方法改進及產品品質之提高。 研究結果發現，甜菊水萃取液之色素有chlorophyll a、chlorophyll b、xanthophyll、β-carotene及其他兩種尚未確認之色素。為了甜菊糖純化過程中品質管制之方便，萃取液之色素含量可使用420nm 及670nm兩波長之吸光度來判定。膠質含量約佔總萃取乾物之15%，膠質種類以植物性粘質物（plant mucilages）為主，其餘有阿拉伯膠（arabic gum）及刺梧桐樹膠（karaya gum）。無機物約佔總萃取乾物之13%，其中無機離子主要為鹼性陽離子，以鉀含量最高。有機酸主要為酒石酸，其次為甲酸及檸檬酸。 從非甜菊糖成份之去除試驗結果發現，利用消石灰可除去部分膠質及色素，強酸性陽離子交換樹脂可進一步除去膠質、色素及無機物等，強鹽基性陰離子交換樹脂可以除去色素、無機物及有機酸等，最後再用陽陰離子混合交換樹脂可更進一步除去膠質、色素、無機物及有機酸等，而且對所萃取的甜菊糖只造成20~25%的損失，尚具商業價值。
• 英文摘要： About 30% of the total solids of Steviaextracts are steviosides, and the remaining70% are impurities of either organic orinorganic nature. These impurities willnot only affect the processes of purificationand crystalization of steviosides from theseextracts, but also affect the purity of theproducts obtained. The purpose of this studywas to investigate the nature of these im-purities, in order to improve the quality ofsteviosides products and also to revise thepurification processes· In this study we found that the pigmentspresent in Stevia extracts were chlorophyllsa and b, xanthophyll, β-carotene and twounidentified pigments. It was recommendedto use the absorbance at 420 nm and 670 nmwavelengths as measures of pigments contentsof Stevia extracts for the purpose of qualitycontrol during steviosides purification pro-cesses. The content of gums was about 7~15% of the total extracted solids; the maingums are found to be plant mucilages; arabicgum and Karaya were also found. Thecontent of inorganic matters was about 13%of the total extracted solids; the main com-ponents were found to be alkaline cations,with K as the predominant one. Tartaric acidwas the major organic acid in Stevia extracts,and the next important was formic and citricacids. In a study to remove the non-steviosidecontaminants from Stevia extracts it was foundthat gums and pigments were partly nemovedby Ca (OH) treatment. Gums, pigmentsand inorganic impurities were found tobe removed by strong acid cation exchangeresin. Pigments, inorganic matter and organicacids could be removed by strong base anionexchange resin. Gums, pigments, inorganicmatter and organic acids could be furtherremoved by treatment with a mixed bed ofweak acid cation exchange resin and weakbase anion exchange resin. The loss of totalsteviosides during the above processes was20~25%, indicating that these processes havean economical value.
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