By Harold McGee
Ice texture can vary from rocky to coarse to creamy, depending on the proportions of ingredients, how the ice is made, and the temperature at which it’s served. During the freezing process, water in the mix solidifies into millions of tiny ice crystals, which are surrounded by all the other substances in the mix: mainly leftover liquid water that forms a syrup with dissolved sugars, both from the fruit and added by the cook, as well as contents of the plant cells and cell walls. The more syrup and plant debris there are, the more the solid crystals are lubricated, the more easily they slide past each other when we press with spoon or tongue, and the softer the ice’s texture. Most ices are made with about double the sugar of ice cream (whose substantial fat and protein content helps soften the texture), between 25 and 35% by weight. Sweet fruits require less added sugar to reach this proportion, and purees rich in pectins and other plant debris (pineapple, raspberry) require less total sugar for softening. Many cooks replace a quarter to a third of the added table sugar (sucrose) with corn syrup or glucose, which helps soften without adding as much perceptible sweetness. The size of the ice crystals, and so the ice’s coarseness or creaminess, is determined by the content of sugar and plant solids, and by agitation during freezing. Sugar and solids encourage the formation of many small crystals rather than a few large ones, and so do stirring and churning. Ices served right from the freezer are relatively hard and crystalline; allowing them to warm and thus partly melt produces a softer, smoother consistency.