半纖維素的主要成分為木糖以β-1,4 鍵結形成之聚木醣 (xylan),聚木醣水解可得到木寡糖,屬於功能性寡醣,除了像一般醣類能夠作為甜味劑,木寡糖對於熱和酸亦具有良好的穩定性。此外,已有學者研究發現木寡糖可以活化腸道有益菌,改善腸道功能,及維持糞便的柔軟度(Okazaki and otehrs 1990a; 1990b; Suntory Ltd 1997)。研究指出木寡糖可減少罹患結腸癌的風險並且能降低血中膽固醇和增加礦物質的吸收,並可當做益生質,促進腸內益生菌如比菲德氏菌和乳酸菌的菌數或活力增加,進而使人體健康。 木寡糖透過化學方法,如:熱液處理,可以進行酶解或水解,而透過一系列的純化步驟,則可以解決產生之木寡糖品質粗糙的問題,以生產至少含有75~90%木寡糖的高純度木寡糖(More et al., 2006; Vazquez et al., 2000)。木寡醣並且成為近年來國內新興的一種功能性食品添加劑。 木寡糖因其結構特性,故在酸性條件下表現相對穩定且具有益生質的特性,可調整腸道益菌生態,讓益生菌種取得絕對的生長優勢。木寡糖不易被「有害菌」利用,又不會為胃酸所分解,所以能有效到達大腸,幫助維持、提升腸道營養吸收機能。由於人體內70%免疫細胞來自於腸道,若能使腸道內有益菌增生,便得以壓抑壞菌數量,進而有助提升腸道營養吸收機能、促進腸道蠕動,使得排便順暢。
Xylooligosaccharides(XOS) are chains of xylose molecules linked via β 1-4 bonds with degree of polymerization ranging from 2 to 10. The currently available xylooligosaccharides, resulted from hydrolysis of xylan, is a functional oligosaccharide. Like ordinary sugar it can serve as a sweetener. XOS also has good resistance to heat and acid. In addition, it has found that xylooligosaccharides can stimulate the proliferation of intestinal bacteria and improve bowel function, and to maintain soft feces. The study shows that XOS can reduce blood cholesterol and increase the absorption of minerals, and can be as beneficial biomass to promote intestinal probiotics such as bifidobacteria and lactobacilli by increasing viable counts or energy, and thus enhance human health. Xylan can be hydrolyzed either by enzymatic or by chemical methods (hydrothermal treatments) and, furthermore, a combination of both. The resulting crude XOS solutions require a sequence of purification steps to yield high purity XOS containing at least 70-90% XOS. XOS has become a new functional food additive in the early 1990s. XOS is very unique, because of its structural characteristics, being resistant to heat and acid. Its biomass characteristics are to stimulate the growth of probiotics and strong affect the intestinal bacteria ecology. The XOS is difficult to be consumed by harmful bacteria and to be subjected gastric acid decomposition. XOS can effectively reach the large intestine, helping to maintain and enhance intestinal nutrients absorption. The 70% of immune cells from the human body are from the intestinal tract. If microbial proliferation in the intestine can be readily ruled by XOS ingestion, leading to suppression of bad bacteria, to enhance intestinal nutrient absorption and to promote the intestinal peristalsis to defecation.