The heat used during baking causes the flour starches to absorb liquid and swell. This process is called gelatinization. Sugar slows gelatinization by sparring with the starch for the liquid. This delay allows the sugar to tenderize the finished product and, in the case of cakes, results in excellent texture and the desired volume. It is unclear if this same effect occurs when making breads, but it is assumed that sugar’s influence on gelatinization is similar in breads with a high sugar content, resulting in a tender texture and fine crumb.