Pretreatment methods for analyzing steviol glycosides in diverse food samples

Steviol glycosides are well-known food sweeteners; their consumption has steadily increased over time. A pretreatment method was developed and validated to better separate rebaudioside A and stevioside from various protein-rich and fatty foods for quantification. This method was applied to soy sauce in liquid type and fish cake and coffee in solid type. Parameters such as linearity, limit of detection (LOD), limit of quantification (LOQ), accuracy, and precision were calculated. Calibration curves were linear in the working range of 5-100 mg/l, with coefficients of determination ≥0.99. The LOD and LOQ were in the ranges of 0.16-0.39 and 0.52-1.28 mg/kg, respectively. The percentage recoveries of the fortified samples were in the 88.01%-103.09% range, and the relative standard deviation was <10%. Method validation predicted a desirable accuracy, linearity, and precision. Therefore, the developed method can be practically applied for the quantitation of steviol glycosides in various foods, including soy sauce in liquid type and fish cake and coffee in solid type.