Browsing by Author "Freitas, A. C."
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- Akkermansia muciniphila antimicrobial susceptibility profilePublication . Barbosa, J. C.; Machado, D.; Almeida, D.; Andrade, J. C.; Freitas, A. C.; Gomes, A. M.
- Antibacterial and antioxidant potential of aqueous extracts of bio-residues from agrocybe cylindracea and pleurotus ostreatus myceliumPublication . Sousa, A. S.; Marçal, S.; Costa, C.; Ferreira, I.; Barros, J.; Nunes, J.; Freitas, A. C.; Morais, A. M. M. B.; Pintado, M.The production of fresh mushrooms results in a large quantity of bio-residues, which may account for more than 20% of a crop volume and contributes to production costs and environmental impact, if not used. These products consist mainly of stalks, mushrooms of irregular dimensions and shape and basal material. Thus, the main objective of MicoBioExtract project is the valorisation of these bio-residues and the development of add-value by-products with bioactive compounds such as polysaccharides and phenolic compounds produced by mushrooms. In the present work, the aqueous extracts from Agrocybe cylindracea byproducts (ACB) and Pleurotus ostreatus mycelium (POM) were evaluated for potential antioxidant and antimicrobial activities. Water soluble substances were extracted from mushrooms according to two different methods. In method 1 it was performed a hot extraction (extract 1A; 90 °C; 1 h; 500 rpms). In method 2, the biomass was submitted to an extraction at room temperature (extract 2B) and the resulting residue was extracted with hot water (extract 2C; 90 °C; 1 h; 500 rpms). The aqueous extracts from POM were obtained only by method 1. Extracts were lyophilized and their bioactivity evaluated measuring the antioxidant (ABTS, DPPH and ORAC) and antimicrobial (determination of the minimum inhibitory concentration – MIC) activities. The mutagenicity was also tested (Ames assay with and without S9). Moreover, it was determined the total phenolics content of the extracts and α and β – glucans (Folin Ciocalteu and Beta-Glucan Assay methods, respectively). The results obtained from antioxidant methods showed that all extracts from both mushrooms are a potential source of natural antioxidant and phenolic compounds. According to ABTS, extract 2B from ACB showed the best value with 8.48±0.33 mg ascorbic acid equivalent (AAE)/g dry extract and 4.14±0.52 mg AAE/g dry extract for POM. Regarding the antimicrobial activity, MIC results showed that ACB and POM extracts inhibited the growth of Gram- (Salmonella enteritidis) and Gram+ (Bacillus cereus and Listeria monocytogenes). Concerning the mutagenicity, the results showed no toxic effect except for extract 1A from ACB. Regarding the β-glucan content, the extracts from ACB presented higher content of β-glucan than the C extracts from POM. Thus, aqueous extracts from mushroom bio-residues showed potential antioxidant and antimicrobial properties and to develop a circular bioeconomy approach.
- Antioxidative peptides: trends and perspectives for future researchPublication . Freitas, A. C.; Andrade, J. C.; Silva, F. M.; Rocha-Santos, T. A. P.; Duarte, A. C.; Gomes, Ana M. P.In recent years, much attention has been given to dietary antioxidants, especially polyphenols. Several peptides derived from protein molecules have also been found to show antioxidant capacity along with other biological properties and thus there is an increasing interest in these compounds as health promoters. This review summarizes and discusses the main sources of antioxidative peptides with focus on food-derived peptides (animal, plant and marine sources), methods of preparation, antioxidant capacity evaluation as well as their proposed mechanisms of action. A discussion of the potential health effects and comments on the different applications for these antioxidants and their potential research interest are also subject of this review.
- Biodegration of microplastics by marine fungiPublication . Silva, A.A.; Bastos, A.S.V.; Paço, A.; Costa, J.P.; Santos, P.; Duarte, K.; Rocha-Santos, T.; Freitas, A. C.
- Development of probiotic tablets using microparticles: viability studies and stability studiesPublication . Sousa e Silva, J. P.; Sousa, Sérgio C.; Costa, Paulo; Cerdeira, Emília; Amaral, Maria H.; Lobo, José Sousa; Gomes, Ana M. P.; Pintado, Maria M.; Rodrigues, Dina; Rocha-Santos, Teresa; Freitas, A. C.Alternative vectors to deliver viable cells of probiotics, to those conferring limited resistance to gastrointestinal conditions, still need to be sought. Therefore the main goal of the study was to develop tablets able to protect entrapped probiotic bacteria from gastric acidity, thus providing an easily manufacturing scale-up dosage form to deliver probiotics to the vicinity of the human colon. Whey protein concentrate microparticles with Lactobacillus paracasei L26 were produced by spray-drying and incorporated in tablets with cellulose acetate phthalate and sodium croscarmellose. The viability of L. paracasei L. 26 throughout tableting as well as its gastric resistance and release from the tablets were evaluated. Storage stability of L. paracasei L26 tablets was also performed by evaluation of viable cells throughout 60 days at 23 degrees C and 33% relative humidity. A decrease of approximately one logarithmic cycle was observed after the acid stage and the release of L. paracasei L26 from the tablets occurred only after 4 h in the conditions tested. Microencapsulated L. paracasei L26 in tablets revealed some susceptibility to the storage conditions tested since the number of viable cells decreased 2 log cycles after 60 days of storage. However, the viability of L. paracasei L26 after 45 days of storage did not reveal significant susceptibility upon exposure to simulated gastrointestinal conditions. The developed probiotic tablets revealed to be potential vectors for delivering viable cells of L. paracasei L26 and probably other probiotics to persons/patients who might benefit from probiotic therapy.
- Effect of ripening time and the combination of ewe and goat milk on the microflora of Picante cheesePublication . Freitas, A. C.; Malcata, F. X.
- Effect of storage conditions on stability of free and encapsulated in plain- or cysteine-supplemented alginate, Bifidobacterium animalis BB-12®Publication . Sousa, S. C.; Costa, E. A.; Gomes, A. M.; Pintado, M. M.; Malcata, F. X.; Silva, J. P.; Lobo, J. M. Sousa; Costa, P.; Amaral, M. H.; Bahia, M. F.; Rocha-Santos, T.; Rodrigues, D.; Freitas, A. C.The main objective of this research work was to study the viability of Bifidobacterium animalis BB-12® as free and calcium alginate-encapsulated cells, with or without cysteine, throughout storage, at four different temperatures. Extrusion by aerodynamically assisted flow was used to produce alginate and calcium alginate supplemented with L-cysteine·HCl microcapsules, containing B. animalis BB-12®. The microcapsules were suspended in Ringer solution in a 1:9 (g/mL) ratio, and stored at 21, 4, -20 and -80 ºC throughout six months, respectively. In parallel, the viability of free cells in cell suspension, was subjected to the same storage conditions and the corresponding viability assessed. Results showed that at 21, 4 and -20 ºC, the encapsulation did not have a protective effect—free cells maintained their viability throughout longer periods than encapsulated counterparts. At -80 ºC, encapsulation protected B. animalis BB-12® in comparison to the behavior of free cells. However, this effect was only observed in calcium alginate microcapsules supplemented with L-cysteine.HCl. After 180 days storage at -80 ºC, a 2 log cycle difference, in viable cells was observed between microcapsules with or without cysteine. The viable numbers of B. animalis BB-12® in microcapsules without cysteine was similar to that of free cells. In conclusion, alginate encapsulation revealed a protective effect on viability of B. animalis BB-12® stored at -80 ºC when supplemented with L-cysteine.HCl.
- Effects of different ripening procedures on the final characteristicsPublication . Freitas, A. C.; Malcata, F. X.Picante da Beira Baixa (or Picante) cheese is a hard, piquant, salted traditional cheese manufactured in Portugal from raw sheep’s and goat’s milks. The purpose of this work was to quantitatively assess the influence of various ripening procedures on the final characteristics of Picante cheese. Two alternative ripening protocols were considered, the traditional one and another with controlled environmental conditions via use of maturation chambers set at different preselected temperatures. The experimental cheeses were characterised in terms of microbiological, physicochemical, biochemical, sensorial and textural properties. Ripening time and temperature were statistically significant parameters for all microflora. The two ripening methods led to statistically significant differences in all physicochemical and biochemical parameters, especially the moisture content and the soluble nitrogen fractions (i.e. water loss was slower and proteolysis was faster in cheeses ripened via the traditional method). Differences in microbiological, physicochemical and biochemical properties were probables implicated in differences in textural and sensorial properties, especially cheese hardness and flavour. It was concluded that the standard ripening method was closest to the traditional one in terms of final cheese characteristics when the ripening temperature was above 11.5 7C.
- Effects of encapsulation on the viability of probiotic strains exposed to lethal conditionsPublication . Borges, S.; Barbosa, J.; Camilo, R.; Carvalheira, A.; Sousa, S.; Gomes, A. M.; Pintado, M. M.; Silva, J. P.; Costa, P.; Amaral, M. H.; Silva, J.; Teixeira, P.; Freitas, A. C.The effect of microencapsulation in an alginate matrix on the viability of several potential probiotic strains (Lactobacillus paracasei LAFTI® L26, L. acidophilus Ki and Bifidobacterium animalis BB-12®), in the presence and absence of L-cysteine, during the exposure to lethal conditions of temperature (55 ºC for L. acidophilus Ki and 60 ºC for L. paracasei and B. animalis BB-12®, during 60 min), pH (3.0 during 6h) and salt (25% during 24h), was evaluated. The microcapsules were prepared via extrusion by aerodynamically-assisted flow. The effect of the disintegration of the microcapsules by mixing with sodium citrate in the enumeration of survivors was also evaluated. The lethal treatments were performed in whey protein concentrate medium and the survivors were enumerated accordingly. In general, the microencapsulated cells were more sensitive to the lethal conditions. The addition of L-cysteine to growth medium did not increase the viability of the tested strains except for B. animalis BB-12®. Furthermore, the disintegration in sodium citrate did not affect the viability. The survival of the probiotic strains was dependent on the lethal stress being imposed and planktonic cells were more resistant to the tested lethal conditions. Encapsulation of these probiotic bacteria did not improve their survival through lethal conditions.
- Encapsulation protective effect upon viability of probiotic bacteria throughout storage and gastrointestinal tractPublication . Rodrigues, D.; Sousa, S.; Rocha-Santos, T.; Gomes, A. M.; Pintado, M. M.; Malcata, F. X.; Silva, J. P.; Lobo, J. M. S.; Costa, P.; Amaral, M. H.; Freitas, A. C.Microcapsules (MC) with fresh cultures of potential probiotic strains (Lactobacillus paracasei LAFTI® L26, L. acidophilus Ki and Bifidobacterium animalisBB-12®) were produced by spray-drying using whey protein concentrate (WPC50) with or without L-cysteine (0.5 g/L). After microencapsulation, the MC were stored, in duplicate, at 5ºC over a period of 6 months during which the number of viable cells (VC) were evaluated. After 15, 60 and 120 days of storage, their resistance throughout gastrointestinal conditions was evaluated. In MC without L-cysteine, the VC numbers of L. acidophilus Ki and B. animalis BB-12® after 6 months of storage decreased from 108 to 106 cfu/g whereas no decrease was observed for L. paracasei. The presence of L-cysteine revealed a positive effect, especially for L. acidophilus Ki after 90 days of storage accounting for more than one logarithm cycle increase in viability. Encapsulation had a protective effect on the three probiotic strains when exposed to the gastrointestinal conditions in comparison to their free cells. This effect was particularly significant for L. acidophilus Ki in conditions similar to those of ileum/duodenum including the presence of pancreatin and bile salts. Storage time did not affect the resistance of the three probiotic strains to the gastrointestinal conditions.