Xylitol

Key takeaways

Xylitol belongs to mathematics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Xylitol to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Xylitol from memory before moving on to harder problems.

Reference excerpt

Xylitol is an organic compound with the formula HOCH(CH(OH)CH2OH)2. Two other isomeric sugar alcohols exist. It is a colorless or white crystalline solid. It is classified as a polyalcohol and a sugar alcohol, specifically an alditol. Of the common sugar alcohols, only sorbitol is more soluble in water. It is sometimes also called birch sugar as it can be extracted from birch wood. It should not be confused with birch syrup, which is made from birch sap and contains only trace amounts of xylitol. The name derives from Ancient Greek: ξύλον, xyl[on] 'wood', with the suffix -itol used to denote it being a sugar alcohol. Xylitol is used as a food additive and sugar substitute. Its European Union code number is E967. Replacing sugar with xylitol in food products may promote better dental health, but evidence is lacking on whether xylitol itself prevents dental cavities. In the United States, xylitol is used as a common sugar substitute, and is considered to be safe for humans. Xylitol can be toxic to dogs and ferrets.

History Emil Fischer, a German chemist, and his assistant Rudolf Stahel isolated a new compound from beech wood chips in September 1890 and named it Xylit, after the Greek word for wood. The following year, the French chemist M. G. Bertrand isolated xylitol syrup by processing wheat and oat straw. Sugar rationing during World War II led to an interest in sugar substitutes. Interest in xylitol and other polyols became intense, leading to their characterization and manufacturing methods.

Structure, production, commerce Xylitol is one of three 5-carbon sugar alcohols. The others are arabitol and ribitol. These three compounds differ in the stereochemistry of the three secondary alcohol groups.

Xylitol occurs naturally in small amounts in plums, strawberries, cauliflower, and pumpkin; humans and many other animals make trace amounts during metabolism of carbohydrates. Unlike most sugar alcohols, xylitol is achiral. Most other isomers of pentane-1,2,3,4,5-pentol are chiral, but xylitol has a plane of symmetry. Industrial production starts with lignocellulosic biomass from which xylan is extracted; raw biomass materials include hardwoods, softwoods, and agricultural waste from processing maize, wheat, or rice. The mixture is hydrolyzed with acid to give xylose. The xylose is purified by chromatography. Purified xylose is catalytically hydrogenated into xylitol using a Raney nickel catalyst. The conversion changes the sugar (xylose, an aldehyde) into the primary alcohol, xylitol. Xylitol can also be obtained by industrial fermentation, but this methodology is not as economical as the acid hydrolysis/chromatography route described above. Fermentation is affected by bacteria, fungi, or yeast, especially Candida tropicalis. According to the US Department of Energy, xylitol production by fermentation from discarded biomass is one of the most valuable renewable chemicals for commerce, forecast to be a US $1.41 billion industry by 2025.

Uses Xylitol is used as a sugar substitute in such manufactured products as drugs, dietary supplements, confections, toothpaste, and chewing gum, but is not a common household sweetener. Xylitol has negligible effects on blood sugar because its assimilation and metabolism are independent of insulin. It is approved as a food additive and sugar substitute in the United States. Xylitol is also found as an additive to saline solution for nasal irrigation and has been suggested to be effective in improving symptoms of chronic sinusitis. However the evidence surrounding the effectiveness of xylitol for nasal irrigation remains doubtful. Xylitol can also be incorporated into fabrics to produce a cooling fabric. When moisture, such as sweat, comes into contact with the xylitol embedded in the fabric, it produces a cooling sensation.

Food properties

Nutrition, taste, and cooking Humans absorb xylitol more slowly than sucrose, and xylitol supplies 40% fewer calories than an equal mass of sucrose. Xylitol has about the same sweetness as sucrose, but is sweeter than similar compounds like sorbitol and mannitol. Xylitol is stable enough to be used in baking, but, because xylitol and other polyols are more heat-stable, they do not caramelise as sugars do. Sugars and polyols lower the freezing point of foods such as ice-cream, but xylitol does so excessively, requiring thickeners to keep the ice-cream from being too soft.

Food risks Normal levels of consumption by humans have not been shown to pose serious health risks in most humans. The European Food Safety Authority has not set a limit on daily intake of xylitol. Due to the adverse laxative effect that all polyols have on the digestive system in high doses, xylitol is banned from soft drinks in the European Union. Similarly, due to a 1985 report by the E.U. Scientific Committee on Food which states that "ingesting 50 g a day of xylitol can cause diarrhea", tabletop sweeteners (as well as other products containing xylitol) are required to display the warning "Excessive consumption may induce laxative effects".

Metabolism Xylitol has 2.4 kilocalories of food energy per gram (10 kilojoules per gram) according to U.S. and E.U. food-labeling regulations. The real value can vary depending on metabolic factors. The liver primarily metabolizes absorbed xylitol. The main metabolic route in humans occurs in the cytoplasm via nonspecific NAD-dependent dehydrogenase (polyol dehydrogenase), which transforms xylitol to D-xylulose. Specific xylulokinase phosphorylates it to D-xylulose-5-phosphate, which then goes into the pentose phosphate pathway for further processing. About 50% of ingested xylitol is absorbed via the intestines. In humans, 50–75% of the xylitol not absorbed in the gut is fermented by gut bacteria into short-chain organic acids and gases, potentially leading to flatulence. Any remnant unabsorbed xylitol that escapes fermentation is excreted unchanged, mostly in feces; less than 2 g of xylitol out of every 100 g ingested is excreted via urine. Xylitol ingestion also increases motilin secretion, which may be related to the ability of xylitol to cause diarrhea. The less-digestible but fermentable nature of xylitol also contributes to constipation-relieving effects.

Health effects

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Xylitol

Start with the simplest possible case. Write down what Xylitol claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In mathematics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Xylitol before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Xylitol ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Xylitol

In research: Xylitol appears in mathematics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Xylitol in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Xylitol is common in secondary-school and first-year university syllabi. It links to neighbouring topics Chewing gum, E-number additives, Excipients, so understanding it makes those chapters shorter.
In everyday life: Look for Xylitol outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Xylitol in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Xylitol means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Xylitol out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Xylitol in simple terms?

Xylitol is an organic compound with the formula HOCH(CH(OH)CH2OH)2. Two other isomeric sugar alcohols exist.

Why does Xylitol matter?

Because it connects several mathematics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Xylitol?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Xylitol.