Abstract: The technology disclosed in this specification pertains to pectin containing cellulosic materials. The cellulosic material is modified so that it can form strong gels when dispersed in aqueous solution. Also disclosed are methods for modifying the cellulosic materials, including, at least in some embodiments, methods to monitor changes in the infrared spectrum of the cellulosic material that happen during a modification reaction to control the reaction and obtain end products capable of making gels having the desired gel strength.