Cold extraction of minimally processed Stevia UEM‐13 leaves: Amylase inhibition and increased bioaccessibility of bioactive compounds by microencapsulation

Abstract

Sweeteners and other bioactives present in the leaves of Stevia rebaudiana have shown functional and nutritional benefits in several pathologies. The number of consumers of teas and plant extracts has grown significantly, but little is known about cold extraction, especially of Stevia. Thus, the objectives of this study were to perform a semi-continuous cold percolation extraction of minimally processed Stevia UEM-13 leaves and to microencapsulate this extract with maltodextrin by Spray Dryer, in order to evaluate possible functional effects of the free and microencapsulated extract. The extract had 25.27 g/100 g of steviol glycosides, quantified by HPLC (11.9% rebaudioside A and 10.2% stevioside) and 72.36 μgGAE/mg of total phenolic compounds. The antioxidant capacity was 50.2% for DPPH radical and 28.4% for ABTS·+. The microencapsulation presented efficiency of 70.59%, with well-defined spheres by visualization through scanning electron microscopy. The free and microencapsulated extract (0.5 mg/ml) decreased the enzymatic activity of α-amylase with possible non-competitive or mixed inhibition in a dose-independent manner and also showed good acceptance in the preliminary sensory test with little bitter and herbaceous residual. The bioaccessibility of bioactive compounds (sweeteners, total phenolics, antioxidant activity for DPPH and ABTS·+ radicals) was evaluated by simulating in vitro digestion and those that were microencapsulated showed higher bioaccessibility for all conditions (mouth, gastric, and intestinal conditions). Thus, it is suggested the direct use or application in food of the microencapsulated extract obtained in cold of Stevia leaves, for the preservation of bioactive compounds and possible functional activities. Novelty impact statement Cold extraction of Stevia leaves shows similar yields to hot extraction and contains significant contents of phenolic compounds and antioxidant activity. The cold extract 0.5 mg/ml contains possible antidiabetic property presenting α-amylase enzyme inhibition. The microencapsulation of the crude stevia extract preserves the bioactive compounds and antioxidant activity on simulated in vitro digestion.