- 背景資料
半乳甘露聚醣，又稱聚半乳甘露醣，其分子結構以甘露聚醣為主鏈<甘露糖以β-(1,4)醣苷鍵鍵結而成>，並加上單一的半乳糖作為支鏈<甘露聚醣的第6號碳上接出>。此外，不同來源的半乳甘露聚醣其支鏈上所含的半乳糖數量亦會有所不同，半乳糖數量之多寡，會影響半乳甘露聚醣之溶解度，當半乳糖數量越多，則溶解度也隨之增加。
植物材料或食品中，常見的半乳甘露聚醣有下列幾種:
備註:產品名稱 (植物)中文名稱 (植物)英文名稱 (植物)學名 半乳糖(GAL):甘露糖(Man)比例 決明子；草決明 Cassia Seed Cassia tora Linn. 19 : 81 刺槐豆膠(Carob bean gum) 刺槐豆 Carob (locust bean) Ceratonia siliqua 22 : 78 關華豆膠(Guar gum) 關華豆 Guar Cyamopsis tetragonolobus 38 : 62 紫花苜蓿草 Lucerne (alfalfa) Medicago sativa L. 48 : 52 葫蘆巴；希臘草 Fenugreek Trigonella foenum-graecum L. 48 : 52
1️⃣刺槐豆膠、關華豆膠被歸類為食品添加物，類別為 (十二) 粘稠劑（糊料）和 (十六) 乳化劑
2️⃣決明子、紫花苜蓿草、葫蘆巴為可供食品使用之原料，次分類為草、木本植物類(2)可供直接食用
- 方法(METHOD)
1. Mill seed sample or seed fraction (e.g. carob seed) to pass a 0.5 mm screen using a Tecator® Cyclotec mill (or equivalent). Commercial galactomannan flours do not require milling.
2. Accurately weigh approx. 100 mg of milled sample into a glass, round-bottomed test tube (16 x 120 mm). Tap the tube to ensure all of the sample falls to the bottom of the tube.
3. Add 5 mL of 80% (v/v) aqueous ethanol to each tube, stir on a vortex mixer and incubate at 85-90°C for approx. 5 min. Add a further 5 mL of aqueous ethanol, again stir on a vortex mixer and centrifuge at 1,500 g for 10 min. Carefully decant the supernatant solution (discard this solution).
NOTE: This solution contains galactosyl-sucrose oligosaccharides.
4. Resuspend the pellet in 5 mL of aqueous ethanol as in Step 3, and repeat the operations in Step 3. Again, discard the supernatant after centrifugation and allow excess liquid to drain from the tubes by inverting on absorbent paper.
5. Resuspend the pellet in 8 mL of 100 mM sodium acetate buffer (pH 4.5) (Buffer B) and stir vigorously on a test-tube stirrer to effect complete dispersion. Immediately place the tube in a boiling water bath. After 30 sec, remove the tube and stir it vigorously on a vortex mixer. Return the tube to the boiling water bath for a further 30 sec and again remove it and stir on a vortex mixer. Return the tube to the boiling water bath for 4 min. Remove the tube, stir it vigorously on a vortex mixer and place it in a water bath at 40°C.
NOTE: These operations are performed to ensure thorough suspension and even hydration of the polysaccharide. Formation of “lumps” of partially hydrated and swollen galactomannan will hinder the ability of β-mannanase to penetrate and depolymerise the polymer.
6. After 5 min at 40°C, add 10 μL of β-mannanase suspension (suspension 3) and stir the tube vigorously on a vortex mixer for 30 sec. Incubate the tubes at 40°C for 60 min with intermittent vigorous stirring (about 2-3 times on a vortex mixer).
7. Quantitatively transfer the solution to a 25 mL volumetric flask using a water wash bottle and adjust to volume with distilled water. Mix the flask contents thoroughly.
8. Filter an aliquot of the solution (Whatman® No. 1 filter paper) or centrifuge at 1,500 g for 10 min.
9. Use this solution in the assay described below.
NOTE: At this stage, the solution is either analysed directly, or diluted based on the predicted galactomannan content as well as the D-galactose/ D-mannose ratio of the galactomannan, e.g. for a sample of carob flour containing approx 30% (w/w) galactomannan with a D-galactose/D-mannose ratio of 22:78, the solution is analysed directly; however for a guar flour sample with a similar galactomannan content, but with a D-galactose/D-mannose ratio of 38:62, the solution is diluted 2-fold with water before analysis.
- 操作流程(PROCEDURE)
商品特色
商品規格
- 商品規格 100 檢測反應
Bottle 1:
Buffer (25 mL, pH 8.6) plus sodium azide (0.02% w/v) as a preservative (Buffer A).
Stable for > 2 years at 4°C.
Bottle 2:
NAD+.
Stable for > 5 years below -10°C.
Bottle 3:
β-Mannanase suspension (A. niger; 1.1 mL).
Stable for > 4 years at 4°C.
Bottle 4:
α-Galactosidase (guar seed) plus β-mannanase (A. niger) suspension, 2.2 mL.
Stable for > 4 years at 4°C.
Bottle 5:
β-Galactose dehydrogenase (2.4 mL).
Stable for > 4 years at 4°C.
Bottle 6:
D-Galactose standard solution (5 mL, 0.4 mg/mL in 0.02% sodium azide).
Stable for > 4 years; store sealed at 4°C.
Bottle 7:
Control carob galactomannan flour sample (with galactomannan content as stated on the vial label).
Stable for > 5 years at room temperature.
