Browsing by Author "Alves, Vitor D."
Now showing 1 - 6 of 6
Results Per Page
Sort Options
- Antioxidants of natural plant origins: from sources to food industry applicationsPublication . Lourenço, Sofia C.; Moldão, Margarida; Alves, Vitor D.In recent years, great interest has been focused on using natural antioxidants in food products, due to studies indicating possible adverse effects that may be related to the consumption of synthetic antioxidants. A variety of plant materials are known to be natural sources of antioxidants, such as herbs, spices, seeds, fruits and vegetables. The interest in these natural components is not only due to their biological value, but also to their economic impact, as most of them may be extracted from food by-products and under-exploited plant species. This article provides an overview of current knowledge on natural antioxidants: their sources, extraction methods and stabilization processes. In addition, recent studies on their applications in the food industry are also addressed; namely, as preservatives in different food products and in active films for packaging purposes and edible coatings
- Chitin-Glucan complex hydrogels: physical-chemical characterization, stability, in vitro drug permeation, and biological assessment in primary cellsPublication . Araújo, Diana; Rodrigues, Thomas; Roma-Rodrigues, Catarina; Alves, Vitor D.; Fernandes, Alexandra R.; Freitas, FilomenaChitin-glucan complex (CGC) hydrogels were fabricated by coagulation of the biopolymer from an aqueous alkaline solution, and their morphology, swelling behavior, mechanical, rheological, and biological properties were studied. In addition, their in vitro drug loading/release ability and permeation through mimic-skin artificial membranes (Strat-M) were assessed. The CGC hydrogels prepared from 4 and 6 wt% CGC suspensions (Na51*4 and Na51*6 hydrogels, respectively) had polymer contents of 2.40 0.15 and 3.09 0.22 wt%, respectively, and displayed a highly porous microstructure, characterized by compressive moduli of 39.36 and 47.30 kPa and storage moduli of 523.20 and 7012.25 Pa, respectively. Both hydrogels had a spontaneous and almost immediate swelling in aqueous media, and a high-water retention capacity (>80%), after 30 min incubation at 37 C. Nevertheless, the Na51*4 hydrogels had higher fatigue resistance and slightly higher-water retention capacity. These hydrogels were loaded with caffeine, ibuprofen, diclofenac, or salicylic acid, reaching entrapment efficiency values ranging between 13.11 0.49% for caffeine, and 15.15 1.54% for salicylic acid. Similar release profiles in PBS were observed for all tested APIs, comprising an initial fast release followed by a steady slower release. In vitro permeation experiments through Strat-M membranes using Franz diffusion cells showed considerably higher permeation fluxes for caffeine (33.09 g/cm2/h) and salicylic acid (19.53 g/cm2/h), compared to ibuprofen sodium and diclofenac sodium (4.26 and 0.44 g/cm2/h, respectively). Analysis in normal human dermal fibroblasts revealed that CGC hydrogels have no major effects on the viability, migration ability, and morphology of the cells. Given their demonstrated features, CGC hydrogels are very promising structures, displaying tunable physical properties, which support their future development into novel transdermal drug delivery platforms.
- Concentration of tea extracts by osmotic evaporation: optimisation of process parameters and effect on antioxidant activityPublication . Marques, Marisa P.; Alves, Vitor D.; Coelhoso, Isabel M.In this work, the concentration process of three different tea extracts (medicinal Rosil No. 6, Black, and Forest Fruit teas) using the osmotic evaporation (OE) process, was studied. The effect of the OE process on the content of phenolic compounds and antioxidant activity was evaluated. The concentration process was carried out in a hollow-fibre membrane contactor with an effective surface area of 0.54 m2. The tea extract was circulated through the shell side of the contactor, while a concentrated osmotic solution (CaCl2 5 M) was circulated inside the fibres. The flux, the driving force, and the mass transfer coefficient were evaluated. A decrease of the water flux over time was observed and was attributed only to the decrease of the driving force, caused by the dilution of the osmotic solution. Using a surface area/feed volume ratio of 774 m2 m3, it is possible to reach a tea concentration of 40% (w/w) in 5 h, with a constant water flux and without losing the phenolic content and antioxidant potential in most teas
- Exopolysaccharides enriched in rare suggars: bacterial sources, production and applicationsPublication . Roca, Christophe; Alves, Vitor D.; Freitas, Filomena; Reis, Maria A.M.Microbial extracellular polysaccharides (EPS), produced by a wide range of bacteria, are high molecular weight biopolymers, presenting an extreme diversity in terms of chemical structure and composition. They may be used in many applications, depending on their chemical and physical properties. A rather unexplored aspect is the presence of rare sugars in the composition of some EPS. Rare sugars, such as rhamnose or fucose, may provide EPS with additional biological properties compared to those composed of more common sugar monomers. This review gives a brief overview of these specific EPS and their producing bacteria. Cultivation conditions are summarized, demonstrating their impact on the EPS composition, together with downstream processing. Finally, their use in different areas, including cosmetics, food products, pharmaceuticals, and biomedical applications, are discussed
- Fucose-containing exopolysaccharide produced by the newly isolated Enterobacter strain A47 DSM 23139Publication . Freitas, Filomena; Alves, Vitor D.; Torres, Cristiana A.V.; Cruz, Madalena; Sousa, Isabel; Melo, Maria João; Ramos, Ana M.; Reis, Maria A.M.Enterobacter strain A47 (DSM 23139) was found to produce a fucose-containing exopolysaccharide (EPS). The EPS is composed of fucose, galactose, glucose, pyruvate, succinate and acetate in the molar ratios 1.6:1.3:1.1:1.2:0.7:1.5. It is a high molecular weight (5.8×106) homogeneous biopolymer, as indicated by the low polydispersity value (1.3). The steady shear flow properties of the EPS aqueous solutions are similar to guar gum and fucogel, and its viscoelastic properties indicate the formation of viscous aqueous solutions with entangled polymer chains. Additionally, the EPS has demonstrated good flocculating and emulsion stabilizing capacities, comparable to some commercially available products. These functional propertiesmakethe fucose-containing EPS a good alternative tomanysynthetic polymers, as well as other natural polysaccharides, in several applications in the food, pharmaceutical, cosmetic, textile, paper and petroleum industries.
- Kinetics of production and characterization of the fucose-containing exopolysaccharide from Enterobacter A47Publication . Torres, Cristiana A.V.; Marques, Rodolfo; Antunes, Sílvia; Alves, Vitor D.; Sousa, Isabel; Ramos, Ana Maria; Oliveira, Rui; Freitas, Filomena; Reis, Maria A.M.A fucose-containing exopolysaccharide (EPS) was produced by the bacterium Enterobacter A47 using glycerol byproduct from the biodiesel industry. The analysis of kinetic data suggested a partially growth associated EPS synthesis model. Although the EPS was composed of fucose, galactose and glucose at all cultivation stages, their relative proportion has varied considerably during the run. At the beginning (24 h), glucose was the main component (82.4 wt.%), being fucose and galactose minor components (5.0 wt.% and 10.9 wt.%, respectively), while at the end (96 h) it was composed of 26.0 wt.% fucose, 28.9 wt.% galactose and 43.7 wt.% glucose. The acyl groups content and composition have also changed, reaching their maximum content (19.2 wt.%) at the end of the run. Moreover, the molecular weight has increased linearly during the run (from 8 × 105 to 5 × 106). The changes observed in EPS composition and molecular weight have also had an impact upon the polymer’s intrinsic viscosity, as shown by its linear increase from 3.95 to 10.72 dL g−1. The results suggest that the culture might have synthesized at least two distinct EPS, with different sugar composition and average molecular weight, which predominated at different cultivation stages