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- 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.
- Edible films as carrier for lactic acid bacteriaPublication . Pereira, Joana Odila; Soares, José; Sousa, Sérgio; Madureira, Ana Raquel; Gomes, Ana M. P.; Pintado, M. E.The use of edible coatings and films formulated with bioactive compounds in food products in order to convey new functionalities or extend shelf-life opens new possibilities as a carrier for functional lactic acid bacteria. In this work the main objective was to study the stability of probiotic microorganisms, viz. Bifidobacterium animalis Bb-12® and Lactobacillus casei-01, in edible film formulations based on whey protein isolate (WPI). The results demonstrated a loss of bacterial cell viability of ca. 3 log cycles (reaching 106 CFU/g film) until 60 d at both 23 and 4 C, noting that the most marked decrease was at 23 C for both strains. Bifidobacterium animalis Bb-12® remained viable for a longer period of time and with less decrease in its cell numbers (108 CFU/g film). Physical properties, namely color, water activity, thickness, young’s modulus, tensile strength, elongation at break and the molecular structure of WPI films were maintained stable throughout the storage period at both temperatures tested. Edible films incorporated with probiotics can be good carriers for these to be ingested together with food products.
- Influence of L-cysteine, oxygen and relative humidity upon survival throughout storage of probiotic bacteria in whey protein-based microcapsulesPublication . Rodrigues, D.; Sousa, Sérgio; Santos, Nathália Baptista T.; Silva, J.P.; Lobo, J. M. Sousa; Costa, P; Amaral, Gustavo Henrique De Oliveira; Pintado, M.M.E; Gomes, Ana Maria; Malcata, F. Xavier; Freitas, Ana CThe survival rates of Lactobacilus acidophilus Ki, Lactobacillus paracasei L26 and Bifidobacterium animalis BB-12 were studied after whey protein microencapsulation via spray-drying, with or without L-cysteine-HCl, and storage up to 6 months at 5 degrees C and 22 degrees C, with variation in relative air humidity and oxygen levels. Lb. paracasei L26 was the least susceptible to storage conditions: above 10(6) cfu g(-1) were recorded by 180 d at 22 degrees C, irrespective of relative humidity, and the presence/absence of oxygen and L-cysteine. Higher relative humidity, higher temperature and longer storage periods were deleterious to survival of both B. animalis BB-12 and Lb. acidophilus Ki; the effect of L-cysteine-HCl was dependent on the probiotic strain. The effect of overhead oxygen was not significant upon any probiotic strain studied. Whey protein microcapsules containing L-cysteine-HCl protected probiotic cultures from simulated gastrointestinal 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.
- In vitro digestibility and fermentability of fructo-oligosaccharides produced by Aspergillus ibericusPublication . Nobre, C.; Sousa, S.C.; Silva, S.P.; Pinheiro, A.C.; Coelho, E.; Vicente, A.A.; Gomes, A.M.P.; Coimbra, M.A.; Teixeira, J.A.; Rodrigues, L.R.The bifidogenic potential of fructo-oligosaccharides (FOS) produced by a newly isolated strain – Aspergillus ibericus was studied. Their activity was compared to FOS produced by Aureobasidium pullulans and to a nonmicrobial commercial FOS sample (Raftilose® P95). FOS fermentability by a number of probiotic bacteria and their hydrolytic resistance to the simulated harsh conditions of the digestive system was evaluated. Aspergillus ibericus FOS sample effectively promoted probiotic bacteria growth. Overall, microbial-derived FOS promoted greater cellular growth compared to the commercial sample. FOS fermentation was both substrate and strain specific. The FOS structural differences identified may explain their distinct assimilation by the probiotics. [Fru (2→6)Glc] (possibly blastose) and a reducing trisaccharide (possibly [Fru(β2→6)Glc(α1↔β2)Fru], neokestose) were only found in microbial-derived FOS samples, while Raftilose® P95 was richer in inulobiose/inulotriose. 1- Kestose and nystose were only slightly hydrolyzed in the presence of gastric and intestinal fluid. FOS synthesized by Aspergillus exhibited great potential as food ingredients with likely prebiotic features.
- Effects of encapsulation on the viability of probiotic strains exposed to lethal conditionsPublication . Borges, Sandra; Barbosa, Joana; Camilo, Rute; Carvalheira, Ana; Silva, Joana; Sousa, Sérgio; Gomes, Ana M.; Pintado, Maria M.; Silva, José P.; Costa, Paulo; Amaral, Maria H.; Teixeira, Paula; Freitas, Ana C.The effect of microencapsulation on the viability of Lactobacillus casei, L. paracasei, L. acidophilus Ki and Bifidobacterium animalis BB-12 during exposure to lethal conditions (25% NaCl, pH 3.0 and 55–60 ºC) was evaluated. Results demonstrated that survival of probiotic strains to the imposed lethal stress conditions was strain dependent. With the exception of exposure to 25% (w ⁄ v) NaCl, L. acidophilus Ki (free and encapsulated cells) demonstrated the highest survival rates through exposure to lethal conditions of temperature and pH. For this probiotic strain exposed to heat, microencapsulated cells expressed a higher heat tolerance at 55 ºC than free cells. For the other tested bacteria, in general, encapsulation had no positive effect on survival through the tested lethal conditions.
- Ultrasound and heat treatment effects on Staphylococcus aureus cell viability in orange juicePublication . Tahi, Akila Amir; Sousa, Sérgio; Madani, Khodir; Silva, Cristina L. M.; Miller, Fátima A.Ultrasounds are being considered an excellent alternative technology in juice preservation. Yet, when combined with heat treatment, the process seems to be further intensified. This work aimed to evaluate and compare the impact of ultrasounds and heat treatments, when applied alone or in combination, on Staphylococcus aureus survival in orange juice. Inoculated commercial pasteurized orange juice was treated at different times at 20, 30, 40, 50 and 60 °C. SEM analyses were applied to identify morphological changes in S. aureus cells appearance. The microbial inactivation data were fitted using two mathematical models, depending on the behaviour observed. Sonication at 20, 30, and 40 °C induced 4.02 ± 0.52, 3.80 ± 0.49 and 4.30 ± 0.74 log cycles reduction of S. aureus after treatments of 90, 60 and 60 min, respectively. The heat treatments at the same temperatures had no impact on S. aureus survival. When 50 and 60 °C were applied, more than 5-log reductions were attained for both thermosonication and heat treatments alone. A synergistic effect was observed between sonication and high temperatures. At 50 °C, the thermosonication reduced the treatment time from 60 to 35 min and the microbial load from 5.14 ± 0.08 to 10.76 ± 0.28 log cycles reduction, compared to heat treatment alone. Results from SEM images showed that cells undergo membrane damage during sonication exposure. This was observed by collapsed cells, cell disruption, and holes in the cell's membrane. Thermosonication proved to be a viable alternative to thermal pasteurization of orange juice since milder treatments can be safely applied, improving the final product quality.
- Development of a rice-based fermented probiotic beverage with lactobacillus spp. and streptococcus thermophilusPublication . Gomes, Ana Maria; Ramalhosa, Francisco; Sousa, Sérgio; Rodrigues, Dina; Freitas, Ana Cristina
- 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.
- Lactobacillus reuteri growth and fermentation under high pressure towards the production of 1,3-propanediolPublication . Mota, Maria J.; Lopes, Rita P.; Sousa, Sérgio; Gomes, Ana M.; Delgadillo, Ivonne; Saraiva, Jorge A.Lactobacillus reuteri is a lactic acid bacterium able to produce several relevant bio-based compounds, including 1,3-propanediol (1,3-PDO), a compound used in food industry for a wide range of purposes. The performance of fermentations under high pressure (HP) is a novel strategy for stimulation of microbial growth and possible improvement of fermentation processes. Therefore, the present work intended to evaluate the effects of HP (10–35 MPa) on L. reuteri growth and glycerol/glucose co-fermentation, particularly on 1,3-PDO production. Two different types of samples were used: with or without acetate added in the culture medium. The production of 1,3-PDO was stimulated at 10 MPa, resulting in enhanced final titers, yields and productivities, compared to 0.1 MPa. The highest 1,3-PDO titer (4.21 g L−1) was obtained in the presence of acetate at 10 MPa, representing yield and productivity improvements of ≈ 11 and 12%, respectively, relatively to the same samples at 0.1 MPa. In the absence of acetate, 1,3-PDO titer and productivity were similar to 0.1 MPa, but the yield increased≈26%. High pressure also affected the formation of by-products (lactate, acetate and ethanol) and, as a consequence, higher molar ratios 1,3-PDO:by-products were achieved at 10 MPa, regardless of the presence/absence of acetate. This indicates a metabolic shift, with modification of product selectivity towards production of 1,3-PDO. Overall, this work suggests that HP can be a useful tool to improve of 1,3-PDO production from glycerol by L. reuteri, even if proper process optimization and scale-up are still needed to allow its industrial application. It also opens the possibility of using this technology to stimulate other glycerol fermentations processes that are relevant for food science and biotechnology.
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