Maltose, also called malt sugar, is a sugar made of two glucose units joined together. It forms naturally when starch is broken down, for example in sprouting grain, and is produced commercially from starch using enzymes, often sold as a thick maltose syrup. It is clearly less sweet than table sugar.
Maltose syrup has a long history in East Asian sweets. It gives a gentle sweetness, a glossy look and a soft, chewy texture, and like other sugars it helps slow the firming of starch-based doughs as they age. That makes it a useful partner for mochi, where the rice dough wrapper should stay soft.
Wall’s Vanilla and Milk Flavoured Ice Cream in Chewy Mochi lists maltose among its ingredients, next to sugar, whole milk powder, cream, coconut oil and butter. Maltose itself contains no common allergen, although the milk ingredients in that snack do.
