Methods are described for producing sugar from sugar-containing plant material with microbiological control, which includes treating a sugar-containing plant raw material and/or a component derived therefrom, and/or a medium containing the plant raw material and/or the component, with monochloramine. Monochloramine usage in the method can reduce loss of sugar from bacterial consumptions in the processing of sugar-containing plant materials, such as sugar beets, without causing adverse effects on the sugar product, such as the brightness of white sugar.