Where is maltose found?

Maltose, also called malt sugar, is seldom a disaccharide present naturally in foods, while it is added to many products: it is often present in products commercialized as sugar free, in which it is referred as malt (it should be noted that maltose and sucrose have the same caloric content) and may be used as sweetener as well, with a sweetness equal to 33% of sucrose.
It consists of two units of glucose linked together by α-(1→4) glycosidic bond.

Maltose in germinating seeds

In seeds, during germination, it is synthesized in a reaction catalyzed by the enzyme diastase (amylase) that hydrolyzes starch to the disaccharide for the new plant. Diastase is used commercially as well to hydrolyze starch to maltose (malt) in the brewing of beer.
As vegetable diastase also pancreatic α-amylase is able to cleave starch into molecules ofthe disaccharide (in addition to maltose, maltotriose, a trisaccharide, and small oligosaccharides are released from its action on starch).

Enzymatic cleavage

The disaccharide, both coming from pancreatic α-amylase action on starch or added to commercialized foods, by the action of the multifunctional enzyme sucrase-isomaltase (see sucrose), undergoes the hydrolysis of the α-(1→4) glycosidic bond between the two molecules of glucose that form it releasing them (α-(1→4)-glicosidasic reaction).

References

Arienti G. “Le basi molecolari della nutrizione”. Seconda edizione. Piccin, 2003

Belitz .H.-D., Grosch W., Schieberle P. “Food Chemistry” 4th ed. Springer, 2009

Bender D.A. “Benders’ Dictionary of Nutrition and Food Technology”. 8th Edition. Woodhead Publishing. Oxford, 2006

Cozzani I. and Dainese E. “Biochimica degli alimenti e della nutrizione”. Piccin Editore, 2006

Giampietro M. “L’alimentazione per l’esercizio fisico e lo sport”. Il Pensiero Scientifico Editore, 2005

Mahan LK, Escott-Stump S.: “Krause’s foods, nutrition, and diet therapy” 10th ed. 2000

Mariani Costantini A., Cannella C., Tomassi G. “Fondamenti di nutrizione umana”. Prima edizione. Il Pensiero Scientifico Editore, 1999

Shils M.E., Olson J.A., Shike M., Ross A.C. “Modern nutrition in health and disease” 9th ed., by Lippincott, Williams & Wilkins, 1999

Stipanuk M.H., Caudill M.A. Biochemical, physiological, and molecular aspects of human nutrition. 3rd Edition. Elsevier health sciences, 2013 [Google eBooks]