Percorrer por autor "Sousa, Sérgio"
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- Adaptation of Saccharomyces cerevisiae to high pressure (15, 25 and 35 MPa) to enhance the production of bioethanolPublication . Ferreira, Ricardo M.; Mota, Maria J.; Lopes, Rita P.; Sousa, Sérgio; Gomes, Ana M.; Delgadillo, Ivonne; Saraiva, Jorge A.Saccharomyces cerevisiae is a yeast of great importance in many industries and it has been frequently used to produce food products and beverages. More recently, other uses have also been described for this microorganism, such as the production of bioethanol, as a clean, renewable and sustainable alternative fuel. High pressure processing (HPP) is a technology that has attracted a lot of interest and is increasingly being used in the food industry as a non-thermal method of food processing. However, other applications of high pressure (HP) are being studied with this technology in different areas, for example, for fermentation processes, because microbial cells can resist to pressure sub-lethal levels, due to the development of different adaptation mechanisms. The present work intended to study the adaptation of S. cerevisiae to high pressure, using consecutive cycles of fermentation under pressure (at sub-lethal levels), in an attempt to enhance the production of bioethanol. In this context, three pressure levels (15, 25 and 35 MPa) were tested, with each of them showing different effects on S. cerevisiae fermentation behavior. After each cycle at 15 and 25 MPa, both cell growth and ethanol production showed a tendency to increase, suggesting the adaptation of S. cerevisiae to these pressure levels. In fact, at the end of the 4th cycle, the ethanol production was higher under pressure than at atmospheric pressure (0.1 MPa) (8.75 g.L−1 and 10.69 g.L−1 at 15 and 25 MPa, respectively, compared to 8.02 g.L−1 at atmospheric pressure). However, when the pressure was increased to 35 MPa, cell growth and bioethanol production decreased, with minimal production after the 4 consecutive fermentation cycles. In general, the results of this work suggest that consecutive cycles of fermentation under sub-lethal pressure conditions (15 and 25 MPa) can stimulate adaptation to pressure and improve the bioethanol production capacity by S. cerevisiae; hence, this technology can be used to increase rates, yields and productivities of alcoholic fermentation.
- Advancing circular nutrition: the development of a freeze-dried snack based on broccoli stalk powderPublication . Soares, Inês; Machado, Daniela; Vedor, Rita; Sousa, Sérgio; Orvalho, Telma; Dias, Sara; Alves, Marco; Gomes, Ana MariaAim: The upcycling of agri-food by-products presents a sustainable strategy for reducing waste and creating value-added products. This study aimed to develop a freeze-dried snack incorporating broccoli stalks, an often discarded by-product, and to characterise its nutritional composition, microbiological quality, physicochemical properties and bioactive potential. Method: Broccoli stalks were freeze-dried, milled into a powder, and incorporated into a snack formulation that was subsequently lyophilised. Nutritional profile (moisture, total protein, total fats, ash, total carbohydrates and dietary fibre) was determined using AOAC methods. Microbiological quality was assessed by enumerating mesophiles in Plate Count Agar, yeasts and molds in Potato Dextrose Agar, and enterobacteria in Violet Red Bile Glucose Agar. Physicochemical properties (pH, water activity, texture and colour) were analysed over 4-months of storage. Bioactive potential was evaluated by quantifying total phenolic content (using Folin–Ciocalteu method) and measuring antioxidant activity (via ABTS assay) and antidiabetic activity (through ?-glucosidase inhibition assay). Results: The developed snack demonstrated high dietary fibre content (33.73 g/100 g) and substantially high protein levels (24.30 g/100 g). Microbial loads remained below 10? CFU/g, indicating adequate microbiological safety. Over four months of storage, a gradual decrease in pH was observed (from 6.39 to 5.90), accompanied by an increase in water activity (from 0.21 to 0.32). Texture analysis indicated an increase in both hardness (from 11.33 kg to 14.72 kg) and crispiness (from 43.75 kg·s to 45.54 kg·s), measured by texturometer (Texture Profile Analysis). Despite the slight increase in water activity, the product became firmer and crunchier over time. The reported colour variations (0 vs. 4 months) — ?E of 15.20 on the exterior and 14.42 on the interior — were not sufficient to significantly affect the product's visual appeal. Furthermore, the snack exhibited notable total phenolic content (2.121 mg gallic acid equivalents/g), along with substantial antioxidant (6.088 ?mol Trolox equivalents/g) and antidiabetic activity (73.95% ?-glucosidase inhibition). Conclusion: The lyophilised snack developed from broccoli stalks demonstrated a favourable nutritional profile, with adequate microbiological quality and promising antioxidant and antidiabetic properties. These findings support the incorporation of vegetable by-products in the formulation of sustainable, functional foods aligned with circular economy principles.
- Akkermansia muciniphila encapsulated in calcium-alginate hydrogelated matrix: viability and stability over aerobic storage and simulated gastrointestinal conditionsPublication . Machado, Daniela; Fonseca, Mariana; Vedor, Rita; Sousa, Sérgio; Barbosa, Joana Cristina; Gomes, Ana MariaAkkermansia muciniphila is considered a next-generation probiotic to be incorporated in new food and pharmaceutical formulations. Effective delivery systems are required to ensure high probiotic viability and stability during product manufacture, shelf-life, and post-consumption, namely, throughout digestion. Hydrogelated matrices have demonstrated promising potential in this dominion. Hence, this work aimed to evaluate the effect of a calcium-alginate hydrogelated matrix on A. muciniphila viability during 28-days refrigerated aerobic storage and when exposed to simulated gastrointestinal conditions, in comparison with that of free cells. Akkermansia muciniphila was successfully encapsulated in the calcium-alginate matrix via extrusion (60% encapsulation yield). Furthermore, encapsulated A. muciniphila exhibited high stability (a loss in viability lower than 0.2 log-cycle) after 28-days of refrigerated aerobic storage, maintaining its viability around 108 CFU/g. Prominently, as the storage time increased, encapsulated A. muciniphila revealed higher viability and stability regarding in vitro gastrointestinal conditions than free cells. This suggests that this encapsulation method may attenuate the detrimental effects of prolonged aerobic storage with a subsequent gastrointestinal passage. In conclusion, encapsulation via extrusion using a calciumalginate hydrogelated matrix seems to be a promising and adequate strategy for safeguarding A. muciniphila from adverse conditions encountered during refrigerated aerobic storage and when exposed to the gastrointestinal passage.
- Anti-obesity potential of a yogurt functionalized with a CLNA-rich pomegranate oilPublication . Machado, Manuela; Sousa, Sérgio; Rodriguez-Alcalá, Luís M.; Gomes, Ana Maria; Pintado, ManuelaPomegranate oil is rich in conjugated linolenic acids, compounds which have attracted attention due to their potential applicability in obesity management as they are capable of modulating leptin and adiponectin secretion and regulate fatty acids storage and glucose metabolism. Among the possible bioactive foodstuffs capable of delivering these bioactive compounds yogurts have shown potential. Thus, the purpose of this work was to develop functional yogurts through the addition of pomegranate oil either in its free or encapsulated (used as a protective strategy against oxidation and gastrointestinal tract passage) forms. To that end, the pomegranate oil (free and encapsulated) was incorporated in yogurt and the functional yogurt capacity to modulate hepatic lipid accumulation, adipocyte metabolism (in terms of lipolysis, and adipokines secretion) and immune response was evaluated. The results obtained showed that the pomegranate oil's incorporation led to an improvement in the yogurts' nutritional values, with a reduction in its atherogenic and thrombogenic indexes (more than 78% for atherogenic and 76% for thrombogenic index) and an enhancement of its hypocholesterolemic/hypercholesterolemic ratio (more than 62%) when compared to the control yogurt. Furthermore, data also showed for the first time how these functional yogurts promoted modulation of metabolic processes post GIT as they were capable of reducing by 40% triglycerides accumulation in steatosis-induced Hep G2 cells and by 30 % in differentiated adipocytes. Moreover, samples also showed a capacity to modulate the leptin and adiponectin secretion (56 % of increase in adiponectin) and reduce the IL-6 secretion (ca 44%) and TNF-α (ca 12%) in LPS-stimulated cells. Thus, the CLNA-rich yogurt here developed showed potential as a viable nutraceutical alternative for obesity management.
- Antioxidant properties of sterilized yacon (Smallanthus sonchifolius) tuber flourPublication . Sousa, Sérgio; Pinto, Jorge; Rodrigues, César; Gião, Maria; Pereira, Cláudia; Tavaria, Freni; Malcata, F. Xavier; Gomes, Ana; Pacheco, M. T. Bertoldo; Pintado, ManuelaThe objective of this research work was to investigate the antioxidant properties of sterilized yacon tuber flour. The results revealed for the first time the high antioxidant activity of sterilized yacon flour. The best extract obtained by boiling 8.9% (w/v) of yacon flour in deionised water for 10 min exhibited a total antioxidant capacity of 222 ± 2 mg (ascorbic acid equivalent)/100 g DW and a total polyphenol content of 275 ± 3 mg (gallic acid equivalent)/100 g DW associated to the presence of four main phenolic compounds: chlorogenic acid, caffeic acid, coumaric acid and protocatechuic acid, as well as the amino acid tryptophan. The most abundant was chlorogenic acid, followed by caffeic acid. Biological assays revealed that the extract had indeed antioxidant protection, and no pro-oxidant activity. In conclusion, sterilized yacon tuber flour has the potential to be used in the food industry as a food ingredient to produce functional food products.
- Breaking the silica barrier: optimising carotenoid extraction from diatomsPublication . Rocha, Helena R.; Coelho, Marta; Sousa, Sérgio; Morais, Rui M. S. C.; Pintado, Manuela; Gomes, Ana M.Introduction: Diatoms are microalgae rich in bioactive carotenoids with antioxidant and health-promoting potential (1,2,3,4). However, their rigid silica frustules limit solvent penetration, hindering efficient carotenoid extraction and concealing their true content (5). This study investigates physical and chemical treatments to disrupt the silica structure of Chaetoceros calcitrans, Nannofrustulum shiloi, and Cylindrotheca fusiformis. The aim is not only to enhance carotenoid recovery while preserving pigment integrity, but also to understand how each extraction technique affects the silica frustule at the structural and chemical levels. By linking extraction efficiency to silica modifications, this work contributes to the development of sustainable strategies that unlock the full potential of diatom-derived carotenoids for use in functional foods, nutraceuticals, and natural colourants. Objectives: This study aimed to: To evaluate the effect of physical and chemical treatments on silica removal and carotenoid recovery efficiency; To assess structural and chemical alterations in the silica frustule caused by different extraction methods using SEM and FTIR analyses; To identify optimal treatment conditions that maximise carotenoid yield while preserving pigment integrity.
- Characterization of freezing effect upon stability of, probiotic loaded, calcium-alginate microparticlesPublication . Sousa, Sérgio; Gomes, Ana M.; Pintado, Maria M.; Silva, José P.; Costa, Paulo; Amaral, Maria H.; Duarte, Armando C.; Rodrigues, Dina; Rocha-Santos, Teresa A. P.; Freitas, Ana C.Microencapsulation, utilizing different techniques and polymers, has been studied with the objective of maintaining probiotic viability in food matrices, protecting the cells from their detrimental environment, storage conditions andthe passage of gastrointestinal tract (GIT). The main objective of this study was to assess the effect of freezing at−20◦C upon probiotic alginate-calcium microparticles’ integrity and functionality through parameters such as size,morphology and structure of microparticles as well as to assess cell resistance to simulated gastrointestinal tractconditions upon storage. In order to study the effect of freezing upon the stability of the microparticles, calcium-alginate microparticles, with or without probiotic cells (Lactobacillus casei-01, Lactobacillus paracasei L26, Lactobacillusacidophilus KI and Bifidobacterium animalis BB-12), were characterized at production time and after 60 days storage at−20◦C. An increase in particle size, loss of the spherical shape and porous net damages were observed after 60 daysof storage at −20◦C. In accordance, encapsulation in alginate was not able to exert protection to the encapsulatedprobiotic cells stored at −20◦C for 60 days, especially from acid and particularly bile salts. B. animalis BB-12 revealedto be the most resistant probiotic strain, to both the microencapsulation process and to GIT simulated conditions.
- Chemical and structural characterization of Pholiota nameko extracts with biological propertiesPublication . Rodrigues, Dina; Freitas, Ana C.; Sousa, Sérgio; Amorim, Manuela; Vasconcelos, Marta W.; Costa, João P. da; Silva, Artur M. S.; Rocha-Santos, Teresa A. P.; Duarte, Armando C.; Gomes, Ana M. P.Edible mushrooms including Pholiota nameko are excellent sources of extractable bioactive compounds with much to explore. Enzymatic extractions with Cellulase and Viscozyme were responsible for highest extraction yields (67-77%). No strong antioxidant activity was observed although extracts were able to scavenge ABTS(+) and OH(+). Potential prebiotic activity was observed in all extracts, some increasing 1.4-2 Log cycles of Lactobacillus acidophilus La-5 and Bifidobacterium animalis BB12. 30-50% α-glucosidase inhibition was observed in ultrasound, Flavourzyme and Cellulase extracts. Flavourzyme and Cellulase extracts are richer in macro (Mg, K and P) and micro elements (Zn, Mn and Fe) in comparison to mushroom. Monosaccharides content and profile varied slightly among both extracts with predominance of glucose, galactose and mannose with no uronic acids detection; Flavourzyme extract reported higher free amino acids content. Presence of α and β-glycosidic structures such as glucans and glucan-protein complexes are among the polysaccharides found in both extracts.
- A chemical study of yoghurt produced under isostatic pressure during storagePublication . Vieira, Patrícia; Pinto, Carlos A.; Goodfellow, Brian James; Gomes, Ana M.; Sousa, Sérgio; Machado, Manuela; Delgadillo, Ivonne; Saraiva, Jorge A.Yoghurt fermented under sub-lethal high pressure (10, 20, 30 and 40 MPa at 43 °C), and afterward placed under refrigeration (4 °C for 23 days) was studied and compared with yoghurt fermented at atmospheric pressure (0.1 MPa). For a deeper analysis, metabolite fingerprinting by nuclear magnetic resonance (NMR), sugars and organic acids assessment by high performance liquid chromatography (HPLC), total fatty acids (TFA) determination and quantification by gas chromatography with a flame ionization detector (GC-FID) were performed. Metabolomic analyses revealed that only 2,3-butanediol, acetoin, diacetyl and formate vary with the increase of pressure and probable relation with pressure influenced diacetyl reductase, acetoin reductase and acetolactate decarboxylase. Yoghurts fermented at 40 MPa had the lowest content in lactose (39.7 % of total sugar reduction) and the less content in TFA (56.1 %). Further research is of interest to understand more about fermentation processes under sub-lethal high pressure.
- Combined effect of pressure and temperature for yogurt productionPublication . Lopes, Rita P.; Mota, Maria J.; Sousa, Sérgio; Gomes, Ana M.; Delgadillo, Ivonne; Saraiva, Jorge A.Fermentation under non-conventional conditions has gained prominence in the last years, due to the possible process improvements. Fermentation under sub-lethal pressures is one of such cases, and may bring novel characteristics and features to fermentative processes and products. In this work, the effect of both pressure (10–100 MPa) and temperature (25–50 °C) on yogurt production fermentation kinetics was studied, as a case-study. Product formation and substrate consumption were evaluated over fermentation time and the profiles were highly dependent on the fermentation conditions used. For instance, the increase of pressure slowed down yogurt fermentation, but fermentative profiles similar to atmospheric pressure (0.1 MPa) were obtained at 10 MPa at almost all temperatures tested. Regarding temperature, higher fermentative rates were achieved at 43 °C for all pressures tested. Moreover, the inhibitory effect of pressure increased when temperature decreased, with complete inhibition of fermentation occurring at 50 MPa for 25–35 °C, contrasting to 43 °C where inhibition occurred only at 100 MPa. Therefore, an antagonistic effect seems to occur, since yogurt fermentation was slowed down by pressure increasing, on one hand, and by temperature decreasing, on the other hand. Additionally, some kinetic parameters were calculated and fermentation at 43 °C presented the best results for yogurt production, with lower fermentation times and higher lactic acid productivities. Interestingly, fermentation at 10 MPa/43 °C presented the optimal conditions, with improved yield and lactic acid production efficiency, when compared to fermentation at 0.1 MPa (efficiency of 75% at 10 MPa, against 40% at 0.1 MPa). As the authors are aware, this work gives the first insights about the simultaneous effect of pressure and temperature variation on a microbial fermentation process, which can be combined to modulate the metabolic activity of microorganisms during fermentation in order to improve the fermentative yields and productivities of the desired product.