What is an unfermentable sugar, isomeric with glucose, found in the ripe berries of the rowan tree, or sorb, and extracted as a sweet white crystalline substance; -- called also mountain-ash sugar called?

sorbin — An unfermentable sugar, isomeric with glucose, found in the ripe berries of the rowan tree, or sorb, and extracted as a sweet white crystalline substance; -- called also mountain-ash sugar. (Webster's 1913.)

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