When evaluating the effect of SR addition on ascorbic acid bioaccessibility, it is noteworthy that this compound remained
undetected in the dialysed fraction of the 2.5% SR beverage. In the intestinal phase, SR may exert a negative effect over the ascorbic acid stability. This can be due to interferences between the steviol glycosides with the ascorbic acid structure at basic conditions, as in previous steps no significant differences were detected with respect to the formulation involved. No study has been published up to date showing these possible interferences. Interaction between stevioside and ascorbic acid was investigated by Kroyer (2010), but he observed a protective effect of stevioside on the degradation of ascorbic acid. However, the pH used in his study is not specified. Interestingly, Šic Zˇlabur et al. (2013) obtained a decrease in the ascorbic acid content when apple purees were sweetened with stevia and pasteurised. However, they attribute this loss to the heat treatment and not to the stevia addition. According to Vallejo et al. (2004), ascorbic acid was the metabolite that showed the greater decrease (91% loss) after intestinal digestion. As ascorbic acid is a thermosensitive compound, in fruit
and vegetables it has been used as an indicator of the loss of other vitamins (Zulueta et al., 2007). Consequently, the decrease in bioaccessibility observed for this bioactive compound may also be observed in other similarly alike thermosensitive vitamins, such as vitamin B group, although further studies are necessary.