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.

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.

Properties of tomato powders as additives for food fortification and stabilization.

The antioxidant activities of two freeze-dried tomato powders as additives for food fortification and stabilization were studied. The two tomato powders were obtained from the whole fruit and from the pulp after "serum" separation, respectively. The antioxidant activity was studied by measuring (a) the inhibition of the singlet oxygen-catalyzed oxidation of alpha-linolenic acid, in the presence or absence of copper ions, as a model of the oxidative processes occurring in foods, and (b) the inhibition of xanthine oxidase (XOD)- and myeloperoxidase (MPO)-catalyzed reactions and copper-induced lipid peroxidation. The partial separation of "serum" decreased the freeze-drying time by 50%. The partially fractionated tomato powder had a 60% lower phenolic content and an 11-fold higher lycopene content than the whole tomato powder, on a dry weight basis. Ascorbic acid was almost completely removed by fractionation. Both the powder obtained from the whole tomato and that obtained from the partially fractionated tomato had antioxidant activity in all the model systems used. Based on these results, we conclude that tomato powders have multifunctional properties, which could address the prevention of oxidative degradations both in foods and in vivo. Therefore, tomato can be regarded as source of food additives for fortification and stabilization, even if it is submitted to technological processes that can cause the loss of the more labile hydrophilic antioxidants.