thumb|right|260px|Amylase reaction consisting of hydrolyzing amylose, producing maltose

Maltose ( or ), also known as maltobiose or malt sugar, is a disaccharide formed from two units of glucose joined with an α(1→4) bond. In the isomer isomaltose, the two glucose molecules are joined with an α(1→6) bond. Maltose is the two-unit member of the amylose homologous series, the key structural motif of starch. When beta-amylase breaks down starch, it removes two glucose units at a time, producing maltose. An example of this reaction is found in germinating seeds, which is why it was named after malt. Unlike sucrose, it is a reducing sugar.

History

Maltose was discovered by Augustin-Pierre Dubrunfaut, although this discovery was not widely accepted until it was confirmed in 1872 by Irish chemist and brewer Cornelius O'Sullivan. Its name comes from malt, combined with the suffix '-ose' which is used in names of sugars.

It has a sweet taste, but is only about 30–60% as sweet as sugar, depending on the concentration. A 10% solution of maltose is 35% as sweet as a 10% solution of sucrose.

Sources and absorption

thumb|right|Maltose syrup

Maltose is a malt component, a substance obtained when the grain is softened in water and germinates. It is also present in highly variable quantities in partially hydrolyzed starch products like maltodextrin, corn syrup and acid-thinned starch.

Outside of plants, maltose is also (likely) found in honey.

In humans, maltose is broken down by various maltase enzymes, providing two glucose molecules that can be further processed: either broken down to provide energy, or stored as glycogen. The lack of the sucrase-isomaltase enzyme in humans causes sucrose intolerance, but complete maltose intolerance is extremely rare because there are four different maltase enzymes.

Culinary uses

Maltose syrup is a key ingredient for char siu, a Cantonese-style barbecued pork, and is also used in other roasted meat marinades. In 1960s Hong Kong, maltose syrup sandwiched between two saltine cracker was a common street food due to its simplicity and low cost. In the present day, it is considered a nostalgic food and is mostly found at traditional food stalls in Hong Kong, Macau and Taiwan.

References

  • Maltose, Elmhurst College Virtual Chembook.