Influence of drying on in vitro gastric digestion of beetroot: evaluation of the microstructure

Abstract

To better understand the influence of processing on the bioaccessibility of bioactive compounds during digestion, the microstructure of  beetroot samples was observed prior to and after 180 min of in vitro digestion, by using scanning electron microscopy. Beetroot samples were subjected to convective drying at 60 ºC and 2 m/s and freeze-drying at -50 ºC and 30Pa. Dried beetroots were rehydrated prior to digestion by immersion in distilled water at 37 ºC during 90 min. To extract quantitative information related to cell size from the visual texture of beetroot, grey level granulometric methods from mathematical morphology were applied. Keywords: freeze drying; convective drying; scanning electron microscopy; image analysis; image texture analysis.