The impact of high intensity ultrasound (US, 45 and 20 kHz) on a purified macromolecular fraction (more than 85% of polymeric procyanidins) from grape seed extract was investigated. Matrix-Assisted Laser Desorption/Ionisation (MALDI-TOF), Reverse Phase High Performance Liquid Chromatography (RP-HPLC) and Fourier-transform infrared spectroscopy (FTIR) revealed a modification in the chemical structure of these macromolecules treated by US and, particularly, bath US produced a considerable increase of up to 49, 41 and 35%, respectively, of catechins and oligomeric and polymeric procyanidin contents of the treated purified fraction. Bath US also produced an important increase in the number of procyanidins with higher molecular mass (up to decamers) and an overall increase in the mass signal intensities in most of the detected B-type procyanidin series, as well as an important increase of the antioxidant activity of the macromolecular fraction of procyanidins. These results could be ascribed to a certain disaggregation of procyanidins linked to other biopolymers, such as proteins and/or polysaccharides, indicating that US is an efficient technology to modify the chemical structure and hence the bioactivity of tannins.

The hydrolysis of plant glucosinolates by myrosinases (thioglucosidases) originates metabolites with chemopreventive properties. In this study, the ability to hydrolyze the glucosinolate sinigrin by cultures or protein extracts of Lactiplantibacillus plantarum WCFS1 was assayed. This strain possesses myrosinase-like activity as sinigrin was partly hydrolyzed by induced cultures but not by protein extracts. The 11 glycoside hydrolase GH1 family proteins, annotated as 6-phospho-β-glucosidases, were the proteins most similar to plant myrosinases. The activity of these proteins was assayed against sinigrin and synthetic glucosides. As expected, none of the proteins assayed possessed myrosinase activity against sinigrin or the synthetic β-thio-glucoside derivative or against the β-glucoside. However, all 11 proteins were active on the phosphorylated-β-glucoside derivative. Moreover, only eight of these proteins were active on phospho-β-thioglucose. These results supported that, in L. plantarum WCFS1, glucosinolates may undergo previous phosphorylation, and GH1 proteins are the glycosidases involved in the hydrolysis of phosphorylated glucosinolates.

To improve flavor profiles, three cyclodextrin glucosyltransferases (CGTases) from different bacteriological sources, Paenibacillus macerans, Geobacillus sp. and Thermoanaerobacter sp., were used with an extract of steviol glycosides (SVglys) and rebaudioside A (RebA) as acceptor substrates in two parallel sets of reactions. A central composite experimental design was employed to maximize the concentration of glucosylated species synthesized, considering temperature, pH, time of reaction, enzymatic activity, maltodextrin concentration and SVglys/RebA concentration as experimental factors, together with their interactions. Liquid chromatography coupled to a diode-array detector (LC-DAD), liquid chromatography-mass spectrometry (LC-ESI-MS) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) were used to characterize and identify the chemical structures obtained along the optimization. To assess the impact on the sensory properties, a sensory analysis was carried out with a group of panelists that evaluated up to 16 sensorial attributes. CGTase transglucosylation of the C-13 and/or C-19 led to the addition of up to 11 glucose units to the steviol aglycone, which meant the achievement of enhanced sensory profiles due to a diminution of bitterness and licorice appreciations. The outcome herein obtained supposes the development of new potential alternatives to replace free sugars with low-calorie sweeteners with added health benefits.