The effects of caffeine and sodium L-glutamate (MSG) on the rheological properties of corn starch paste samples (3.00 wt%) were studied by steady and dynamic viscoelasticity, DSC measurements, and microscopic observation. The concentrations of caffeine and MSG were varied in the respective ranges of 0 and 2.3 wt% and between 0 and 18 wt%. The viscosity of the paste samples was not affected by adding caffeine when the concentration was below 1.8 wt%, but was increased by adding caffeine above 1.8 wt%. Excessive caffeine (above 2.6 wt%) led to the aggregation of caffeine. There was no interaction between corn starch and caffeine. The viscosity of the paste samples was also not affected by adding MSG when the concentration was below 9 wt%, but was decreased by adding MSG above 9 wt%. The gelatinization temperature of starch with MSG was increased with increasing MSG concentration, while the gelatinization enthalpy was increased with increasing MSG concentration up to 9 wt%, but was decreased with increasing MSG concentration above 9 wt%. It is concluded that MSG inhibited the swelling of the starch granules and then led to the precipitation of starch when excessively added (above 20 wt%).