c. sugar

Caster sugar, also known as superfine sugar, baker's sugar, or castor sugar, is a refined sucrose product derived from sugar cane or sugar beets with crystals finer than standard granulated sugar but coarser than powdered sugar. The name derives from its traditional packaging in a caster (a small container with a perforated top for sprinkling). The crystal structure—typically 0.35 to 0.5 mm in diameter—dissolves rapidly in liquids and incorporates into batters and doughs more uniformly than larger granules, producing a superior texture in baked goods and providing better integration in cold preparations.\n\nCaster sugar is chemically identical to granulated sugar (both are sucrose) and differs only in granule size. The refining process involves crystallization, centrifugation, and sieving to achieve the smaller, uniform particle distribution. It is white, free-flowing, and hygroscopic, readily absorbing moisture from humid environments.

Caster sugar is the preferred sweetener in baking, particularly in cakes, cookies, meringues, and pastries, where its rapid dissolution produces lighter crumb structures and smoother batters. It is indispensable in the preparation of whipped egg white-based desserts such as pavlovas and soufflés, where quick incorporation and even distribution prevent grittiness. In confectionery, caster sugar creates finer-grained fondants, glazes, and caramels. Beyond baking, it is used to sweeten beverages, preserve fruits (in syrups and jams), and prepare desserts requiring smooth, lump-free textures. It is particularly valued in British and Commonwealth baking traditions and is standard in pastry shops worldwide.