A rapid dialysis method for the analysis of stevioside SS and rebaudioside A RS in foods was developed. Minced samples 10 g were packed into 30 cm net length dialysis tubing with 30 methanol to increase the dialysis efficiency. The dialysis tubing was put in a 100 mL centrifuge tube, and the total fluid volume was made up to 100 mL with 30 methanol. Dialysis was done with shaking while heating at 50 . The dialysis times were reduced from 48-72 hr in the conventional method to 2 hr under these conditions. The dialysate was loaded on a C18 solid-phase extraction cartridge, and the cartridge was washed with 40 methanol. SS and RS were eluted from the cartridge with 80 methanol, and separated by reversed-phase HPLC. Recovery yields of SS and RS, spiked at 0.02 g/kg in various foods, were 83.0-105.1 and the relative standard deviations were mostly less than 5 .

A quantitative analysis by HPLC of α-glucosyltransferase-treated stevia in foods was considered. This analysis is the way which hydrolyzed α-glucosyltransferase-treated stevia in the stevioside (SS) and the rebaudioside A (RS) using a glucoamylase. Recovery (%) of α-glucosyltransferase-treated stevia, spiked at 200 mg/kg in various foods, were more than 80% and the relative standard deviations were less than 5.0% as SS and RS for the rate of collection. A qualitative analysis by LC-MS/MS was performed 36 products of commercial foods containing stevia. We quantified of 11 products in which α-glucosyltransferase-treated stevia was detected. Quantitative value was at most 180 mg/kg as SS, at most 70 mg/kg as RS.

No abstract

MS-based screening method was developed for stevia sweetener in processed foods. After extraction of stevia sweetener from processed foods by dialysis, the dialysate was diluted with water, and stevia sweetener was measured by LC-MS/MS. Recovery from 5 kinds of processed foods spiked with 10 mg/kg of stevioside SS , 10 mg/kg of rebaudioside A RS , or 100 mg/kg of α -glucosyltransferase-treated stevia Gts product was excellent, and no interfering peak was observed. Thirty-six commercial processed foods indicated as containing stevia were analyzed using this established method. Among them, 33 contained SS, 33 contained RS, and 11 contained Gts. Five products contained both stevia extract and Gts.