Microencapsulation of grape skin phenolics for pH controlled release of antiglycation agents.

Grape skin (GS) phenolics can prevent structural damage of proteins due to reducing sugars or dicarbonyl compounds, which is the leading cause of hyperglycaemia damage and is involved in inflammatory diseases. In this study, alginate hydrogel was used to encapsulate GS phenolics as a pH dependent releasing system. Microbeads were obtained by a vibrating nozzle method using calcium chloride as hardening agent. Encapsulation efficiency for total phenolics was 68%. At pH 1.4, the alginate microbeads remained intact and only 13% of total phenolic compounds of the microbeads was released. The percent release depended on the compound: procyanidin B1 release was 74%, catechin and epicatechin release was ~ 50%, while anthocyanin and flavonol release was less than 11%. At pH 7.4, the microbeads were dissolved and formed a viscous solution that showed ability to protect bovine serum albumin from glycation induced by both fructose and methylglyoxal. The antiglycation activity was 246 mmol catechin equivalents (CE)/kg of dry microbeads in the fructose model system and 78 mmol CE/kg of dry microbeads in the methylglyoxal model system. These values corresponded to 68% and 62% of the expected activity, probably due to interaction between phenolics and the alginate carrier. Despite the recovery of antiglycation activity was incomplete, results of this study confirmed the efficiency of alginate to act as a pH controlled released system for GS phenolics. This functionalized polymer could be applied in the prevention of advanced-glycation-endproducts related diseases.

Modelling the stability of maltodextrin-encapsulated grape skin phenolics used as a new ingredient in apple puree.

Highly soluble maltodextrin-encapsulated grape skin phenolics comprising anthocyanins and less hydrophilic flavonoids were added as an ingredient to apple puree. Upon formulation, heat treatments were applied to achieve 3-14 decimal reductions (D) of the target microorganism (Alicyclobacillus acidoterrestris). A storage study was performed at 15-35°C for 1month. Monomeric anthocyanins were retained at 100% after the 3 D treatment, while anthocyanin retention decreased to 72% with increasing heating intensity until 14 D. During storage, the concentration of monomeric anthocyanins decreased following first-order kinetics (k25°C=34.4d(-1), activation energy=51.0kJ/mol). The flavanols were more stable than the monomeric anthocyanins. The hydroxycinnamic acid, dihydrochalcone and flavonol contents did not change. The fortified puree had a two-fold higher reducing capacity with respect to apple puree. Overall, this ingredient could meet the industrial demand for sustainable colouring agents and health promoting compounds.

Grape skin phenolics as inhibitors of mammalian α-glucosidase and α-amylase--effect of food matrix and processing on efficacy.

Type-2 diabetes is continuously increasing worldwide. Hence, there is a need to develop functional foods that efficiently alleviate damage due to hyperglycaemia complications while meeting the criteria for a sustainable food processing technology. Inhibition of mammalian α-amylase and α-glucosidase was studied for white grape skin samples recovered from wineries and found to be higher than that of the drug acarbose. In white grape skins, quercetin and kaempferol derivatives, analysed by UPLC-DAD-MS, and the oligomeric series of catechin/epicatechin units and their gallic acid ester derivatives up to nonamers, analysed by MALDI-TOF-MS were identified. White grape skin was then used for enrichment of a tomato puree (3%) and a flat bread (10%). White grape skin phenolics were found in the extract obtained from the enriched foods, except for the higher mass proanthocyanidin oligomers, mainly due to their binding to the matrix and to a lesser extent to heat degradation. Proanthocyanidin solubility was lower in bread, most probably due to formation of binary proanthocyanin/protein complexes, than in tomato puree where possible formation of ternary proanthocyanidin/protein/pectin complexes can enhance solubility. Enzyme inhibition by the enriched foods was significantly higher than for unfortified foods. Hence, this in vitro approach provided a platform to study potential dietary agents to alleviate hyperglycaemia damage and suggested that grape skin phenolics could be effective even if the higher mass proanthocyanidins are bound to the food matrix.

Protective ability of phenolics from white grape vinification by-products against structural damage of bovine serum albumin induced by glycation.

Grape skins recovered from white grape vinification processes were studied as possible anti-glycation agents. Total phenolics were characterised by the Folin Ciocalteu assay, proanthocyanidins by depolymerisation with n-butanol/HCl, flavonols by HPLC-DAD, reducing capacity by ferric ion reducing antioxidant power assay (FRAP) and anti-glycation activity by a bovine serum albumin (BSA)/fructose model system. Structural modifications of BSA were investigated by 2D isoelectric focusing sodium dodecyl sulfate polyacrylamide gel electrophoresis (IEF/SDS-PAGE) and fluorescence measurements. Both pI and Mr. of BSA were modified upon glycation reaction. These changes attributable to the involvement of free amino groups in Maillard-type reactions were inhibited by the white grape skin extracts. The anti-glycation activity ranged between 250 and 711mmol aminoguanidine Eq/kg. These results raise the interest in the potential health benefits of by-products of white grape vinification that could have a secondary use as an ingredient for new functional foods targeting wellbeing of diabetic and elderly people.

Use of winemaking by-products as an ingredient for tomato puree: the effect of particle size on product quality.

Formulations of tomato puree with grape skin fibres (Chardonnay variety) having varying particle sizes were studied. The contents of flavonoids (by HPLC-DAD) and proanthocyanidins (n-butanol/HCl assay), reducing capacity (ferric ion reducing antioxidant power, FRAP) and anti-glycation activity by a bovine serum albumin (BSA)/fructose model system were analysed in vitro. A liking test was performed with consumers. Stabilization was carried out by either an intensive autoclave treatment or an optimised microwave-treatment achieving 6D-reduction of the target microorganism (Alicylobacillus acidoterrestris). In the fortified tomato purees, the solubility of proanthocyanidins decreased, but was partly restored by autoclave treatment, which also caused deglycosylation of flavonol glycosides. Microwave treatment did not show any effect on phenolics. The reducing capacity and ability to inhibit protein glycation greatly increased in the fortified purees. The particle sizes of solids in the formulations played a major role with respect to the consumers' liking, with the smallest fraction showing maximum ratings.

Characterization of phenolics, in vitro reducing capacity and anti-glycation activity of red grape skins recovered from winemaking by-products.

Red grape skins recovered from ten winemaking processes were analyzed for total phenolic content (Folin Ciocalteu assay), proanthocyanidins (n-butanol/HCl assay), individual phenolics (UPLC-DAD-MS), in vitro ferric ion reducing capacity and anti-glycation activity by bovine serum albumin/fructose and bovine serum albumin/methylglyoxal model systems. The aim was to assess if these by-products have potential as dietary anti-glycation agents, to prevent the glyco-oxidative stress associated with type-2 diabetes. Variability was observed in total phenolics (12.1-53.6g gallic acid Eq/kg), proanthocyanidins (7.2-51.1g/kg), anthocyanins (2.5-13.8 g malvidin 3-O glucoside Eq/kg), flavonols (0.3-2.6g quercetin 3-O glucoside Eq/kg) and reducing capacity (103-511 mmol Fe(II) Eq/kg). For all samples, the anti-glycation effectiveness was higher than that of commercial nutraceutical preparations. Hence, in spite of differences in cultivar, location of the vineyard and winemaking procedures, these by-products could be used as a source of cost-effective anti-glycation agent either as a food ingredient or as a nutraceutical preparation.

Phytochemical stability in dried tomato pulp and peel as affected by moisture properties.

Phytochemical stability was studied in dried tomato pulp and dried tomato peel stored at 30 °C with various water activity (a(w)) levels and related to glass transition temperature (T(g)) and water mobility. At a(w) < 0.32, the values for T(g) were >30 °C for both the pulp and peel, indicating that they were in the glassy state, with little molecular mobility. At a(w) = 0.56, T(g) was <30 °C, indicating the samples were in the rubbery state, with decreased viscosity and increased molecular mobility. The hydrophilic antioxidants (hydroxycinnamic acids and naringenin) were stable for samples in the glassy state, but were unstable for samples in the rubbery state. In contrast, the lipophilic antioxidants lycopene and α-tocopherol were mostly unstable for samples in the glassy state. These results could be used to optimize phytochemical contents in tomato products that must be dried prior to further processing.