The invention provides methods of purifying Rebaudioside D from the Stevia rebaudiana Bertoni plant extract along with Rebaudioside A. The methods are useful for producing high purity Rebaudioside D and Rehaudioside A. The invention further provides a low-calorie soy sauce containing the purified Rebaudioside D and a process for making the low-calorie soy sauce containing the purified Rebaudioside D.