Browsing by Author "Alexandre, Elisabete M. C."
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- Antimicrobial activity of pomegranate peel extracts performed by high pressure and enzymatic assisted extractionPublication . Alexandre, Elisabete M. C.; Silva, Sara; Santos, Sónia A. O.; Silvestre, Armando J. D.; Duarte, Maria F.; Saraiva, Jorge A.; Pintado, ManuelaThis study aimed to assess the effect of high pressure (300 and 600 MPa) and enzymatic extraction (pectinase and cellulase) on the phenolic compounds profile, antioxidant capacity and antimicrobial activity of extracts from pomegranate by-products. Antimicrobial activity against eight different strains of pathogenic and contaminant bacteria and against five beneficial bacteria including Lactobacillus and Bifidobacterium strains were determined. The maximum level of total phenolic content, as well as antioxidant capacity were observed at 300 MPa, however enzymatic extraction did not improve the extraction yields. Punicalagin isomers and bis-hexahydroxydiphenoyl-glucoside isomer were the most abundant phenolic compounds found in the extracts. All pomegranate peel extracts demonstrated selective antimicrobial activity against all pathogenic bacteria without affecting beneficial ones. Pressurized extracts presented lower minimum inhibitory concentration against Bacillus cereus and Pseudomonas aeruginosa and lower minimum bactericidal concentration against B. cereus, while, enzymatic extracts presented lower minimum bactericidal concentration for Staphylococcus aureus, Methicillin-resistant Staphylococcus aureus and Listeria monocytogenes. Principal component analyses reveled that antioxidant activity and phenolic compounds content were strongly related with antimicrobial activity. Pomegranate peels extracts obtained by high pressure extraction could so be used as a source of high added-value bioactive compounds for antioxidant and antimicrobial applications.
- Bioactive compounds, pigments, antioxidant activity and antimicrobial activity of yellow prickly pear peelsPublication . Castro, Luís M. G.; Alexandre, Elisabete M. C.; Pintado, Manuela; Saraiva, Jorge A.The main goal of this research was to study the effects of pressure, extraction time and ethanol concentration on antioxidant activity, total phenolics, flavonoids, anthocyanins, carotenoids and betalains compounds extraction from yellow prickly pear peels. A Box-Behnken design and Response Surface Methodology were used to evaluate the effects and estimate the optimum extraction conditions. Antimicrobial activity was evaluated against Escherichia coli and Listeria innocua. Ethanol concentration was the variable that showed the highest effect on extraction yields but high-pressure increased extraction yields between 6% and 17%. Models showed good fitting and adequacy to the experimental data and the high correlation of models indicated that it can be employed to optimise extraction conditions. The experimental and predicted values differed <10% and the extracts inhibited the growth of both bacteria. High-pressure could be a promising extraction process to improve extraction of bioactives from prickly pear peels.
- Chemical treatments impact on safety and quality of frozen red bell pepper (Capsicum annuum, L.)Publication . Alexandre, Elisabete M. C.; Santos, Dora M.; Brandão, Teresa R. S.; Silva, Cristina L. M.
- Chemical treatments impact on safety and quality of frozen red bell pepper (Capsicum annuum, L.)Publication . Alexandre, Elisabete M. C.; Santos, Dora M.; Brandão, Teresa R. S.; Silva, Cristina L. M.
- Comparison of emerging technologies to extract high-added value compounds from fruit residues: pressure- and electro-based technologiesPublication . Alexandre, Elisabete M. C.; Castro, Luís M. G.; Moreira, Sílvia A.; Pintado, Manuela; Saraiva, Jorge A.Fruit consumption has significantly increased due to their attractive sensory properties and the growing recognition of its nutritional and therapeutic values. Nevertheless, several tons of fruits are processed by the food industry for the production of different products such as juices and jams, leading to the production of a great amount of fruit waste. Until a few decades ago, fruit residues were not considered a cost neither a benefit but resulted in a significant negative impact on the environment, ending up being used as animal feed, brought to landfills or sent to composting sites. The extraction of high-added value compounds from fruit residues is usually done through conventional methods, such as Soxhlet, hydrodistillation, maceration, and enzyme-assisted extraction. Although these methods are easy to perform and cheap to operate, they present several concerns mainly due to thermo-sensible compound degradation and environment pollution. Recently, new extraction technologies have been in development to improve extraction of high-value compounds, such as high pressure, pressurized liquid extraction, instantly controlled pressure drop, pulse electric fields, and high-voltage electrical discharges, as well its combinations between each other’s. These technologies are considered environmentally friendly, allow the use of lower amounts of organic solvents and the reduction in extraction time and energetic consumption, conducting to higher yields and high-quality final extracts.
- Development of innovative non-thermal pre-treatments for frozen vegetables: a case of collaborative effort between academic research and food industryPublication . Alexandre, Elisabete M. C.; Santos, Dora M.; Brandão, Teresa R. S.; Silva, Cristina L. M.
- Development of innovative non-thermal pre-treatments for frozen vegetables: a case of collaborative effort between academic research and food industryPublication . Alexandre, Elisabete M. C.; Santos Pedro, Dora M. J.; Brandão, Teresa R. S.; Silva, Cristina L. M.
- Effect of commercial emerging nonthermal technologies on food products: microbial aspectsPublication . Alexandre, Elisabete M. C.; Inácio, R.S.; Ribeiro, A.C.; Lemos, A.; Pereira, S.; Castro, Sónia M.; Saraija, J.; Teixeira, Paula; Pintado, M. E.; Gomes, Ana M. P.
- Effect of controlled atmosphere and storage temperature on the phenolics and carotenoids of pasteurized peach puréesPublication . Oliveira, Ana; Alexandre, Elisabete M. C.; Coelho, Marta; Lopes, Cláudia; Almeida, Domingos P. F.; Pintado, M. E.
- Effect of emergent non-thermal extraction technologies on bioactive individual compounds profile from different plant materialsPublication . Moreira, Sílvia A.; Alexandre, Elisabete M. C.; Pintado, Manuela; Saraiva, Jorge A.Extraction is the first step for isolation and purification of interesting bioactive compounds, by mixing of the plant material with an adequate solvent. Those bioactive compounds are, usually, secondary metabolites, such as phenolic acids and flavonoids which are present in closed insoluble structures, making its extraction a challenge. There are many different traditional extraction methods, such as Soxhlet, heat reflux, and maceration. Nevertheless, due to several disadvantages, they are being replaced by new methods, using emergent technologies, such as high hydrostatic pressure, ultrasounds, pulsed electric fields, and supercritical fluids. The use of novel technologies allows enhancing mass transfer rates, increasing cell permeability as well as increasing secondary metabolite diffusion, leading to higher extraction yields, fewer impurities on the final extract, extractions at room temperature with thermo-sensitive structures preservation, use of different non-organic solvents, low energy consumption, short operation time, and have no significant or lower effect on the structure of bioactive compounds. This paper aims to review the effect of the main emergent extraction technologies (high hydrostatic pressure, pulsed electric fields, ultrasounds, and supercritical fluid assisted) on the individual profile of bioactive compounds from plant material.