Percorrer por autor "Machado, Ana Vera"
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- Active Flexible Films for Food Packaging: A ReviewPublication . Azevedo, Ana G.; Barros, Carolina; Miranda, Sónia; Machado, Ana Vera; Castro, Olga; Silva, Bruno; Saraiva, Margarida; Silva, Ana Sanches; Pastrana, Lorenzo; Carneiro, Olga Sousa; Cerqueira, Miguel A.Active food packaging is a dynamic area where the scientific community and industry have been trying to find new strategies to produce innovative packaging that is economically viable and compatible with conventional production processes. The materials used to develop active packaging can be organized into scavenging and emitting materials, and based on organic and inorganic materials. However, the incorporation of these materials in polymer-based flexible packaging is not always straightforward. The challenges to be faced are mainly related to active agents' sensitivity to high temperatures or difficulties in dispersing them in the high viscosity polymer matrix. This review provides an overview of methodologies and processes used in the production of active packaging, particularly for the production of active flexible films at the industrial level. The direct incorporation of active agents in polymer films is presented, focusing on the processing conditions and their effect on the active agent, and final application of the packaging material. Moreover, the incorporation of active agents by coating technologies and supercritical impregnation are presented. Finally, the use of carriers to help the incorporation of active agents and several methodologies is discussed. This review aims to guide academic and industrial researchers in the development of active flexible packaging, namely in the selection of the materials, methodologies, and process conditions.
- Effect of pomegranate peels and extract in barrier, optical and mechanical properties of polylactic acid-based active packagingPublication . Andrade, Mariana; Vilarinho, Fernanda; Rodrigues, Pedro; Barros, Carolina; Cruz, Vasco; Machado, Ana Vera; Barbosa, Cássia; Ramos, Fernando; Sanches Silva, AnaBeing more than 50 % of pomegranate (Punica granatum L.) constituted by non-edible parts, namely peels (50%) and seeds (10%), pomegranate is an excellent source of by-products. Its peels and seeds present excellent antioxidant and antimicrobial activities and a high content of phenolic compounds, namely ellagitannins. This work aimed to evaluate the mechanical and optical properties of two polylactic acid (PLA)-based active packaging with 3 wt.% pomegranate peels (3PP) or 3 wt.% pomegranate peel extract (3PPE). All the samples were produced on a laboratory scale with techniques and processing conditions used in industry. The production of packaging with flexible films is mainly carried out by tubular film extrusion. With this processing method it is possible to produce samples with molecular orientation and reduced thickness equal to that of the packages currently on the market. The structural and morphological characterization of the films were evaluated by FTIR and SEM, and the color by UV-vis. Water vapor transmission and mechanical properties were also measured. The color was measured by Shimadzu UV2401PC reflectance spectrophotometer. Water vapor transmission, oxygen permeability and mechanical properties were also measured. The FTIR and SEM results indicate the incorporation of the pomegranate peels and peels extract in the PLA matrix, where PLA/3PPE showed better particle homogenization than the PLA/3PP. Regarding the color variations, the PLA/3PPE presented higher variations in terms of L*, a*, and b*. The incorporation of pomegranate derivates has a negative effect on the tensile strength and Young modulus, but a significant increase of the elongation at break for PLA/3PPE. The PLA film's water vapor barrier properties do not suffer any alteration with the incorporation of pomegranate extract.
- Extending High Fatty Foods Shelf-Life Protecting from Lipid Oxidation and Microbiological Contamination: An Approach Using Active Packaging with Pomegranate ExtractPublication . Andrade, Mariana A.; Rodrigues, Pedro V.; Barros, Carolina; Cruz, Vasco; Machado, Ana Vera; Barbosa, Cássia H.; Coelho, Anabela; Furtado, Rosália; Correia, Cristina Belo; Saraiva, Margarida; Vilarinho, Fernanda; Ramos, Fernando; Silva, Ana SanchesThe search for new forms to extend foodstuffs’ shelf-life through the use of natural compounds and extracts continues to grow among researchers and the industry. In this line of thought, the main objective of this work was to develop, characterize and evaluate the effectiveness of an active food packaging based on polylactic acid (PLA) and incorporated with natural extracts obtained from grape and/or pomegranate by-products. In vitro, antioxidant methods were applied to evaluate the antioxidant capacity of three extracts: wort extract, freeze-dried pomegranate peels extract (PPE-FD), and natural pomegranate peels (PPE-N). Punicalagin (A + B) and ellagic acid were determined in PPE-FD, PPE-N, and active films by UHPLC-DAD. New PLA-based active packaging with PPE-FD (PLA/3PPE) and pomegranate peels (PLA/3PP) were developed, and their chemical, mechanical, and barrier properties were evaluated. Moreover, the effectiveness of the new film was carried out through the study of lipid oxidation state and microbial contamination of two high-fat content foodstuffs, almonds and beef meat. PPE-FD presented high antioxidant capacity and high content in total phenolics and flavonoid compounds. The PLA/3PPE and PLA/3PP prevented the lipid oxidation of meat and presented antimicrobial activity against Staphylococcus aureus. The addition of the PPE-FD and the pomegranate peels to the PLA did not affect the morphology of the polymer. Although both PPE-FD and pomegranate peels presented punicalagin (A + B) and ellagic acid, only ellagic acid was identified and quantified in the active PLA. Active PLA films were not effective in delaying the lipid oxidation of almonds, but they showed to be significantly effective in delaying the lipid oxidation of beef meat and reducing the microbial growth in this food matrix over time.
- Mono and multilayer active films containing green tea to extend food shelf lifePublication . Vieira, Dalila M.; Andrade, Mariana; Vilarinho, Fernanda; Sanches Silva, Ana; Rodrigues, Pedro; Castro, M. Cidália; Machado, Ana VeraAn active packaging film made of one and two-layers structure based on low-density polyethylene (LDPE) was produced with the incorporation of green tea extract (GTE) at different amounts by blown film extrusion. Film structure, optical, mechanical, antioxidant and barrier properties were characterized. The films revealed homogeneous film surface, the presence of GTE increases the tensile properties, improves friction coefficient and reduces LDPE films transparency. Moreover, the antioxidant capacity and barrier properties (water and oxygen) were enhanced, even at low concentrations. This study demonstrates the benefits of GTE incorporation into LDPE matrix, mainly in coextruded films, and its potential to develop an active and sustainable food packaging film at industrial scale.
- Pla Films Loaded with Green Tea and Rosemary Polyphenolic Extracts as an Active Packaging for Almond and BeefPublication . Andrade, Mariana; Barbosa, Cássia; Cerqueira, Miguel; Azevedo, Ana Gabriela; Barros, Carolina; Machado, Ana Vera; Coelho, Anabela; Furtado, Rosália; Belo Correia, Cristina; Saraiva, Margarida; Vilarinho, Fernanda; Sanches Silva, Ana; Ramos, FernandoAbstract: The antioxidant capacity and the phenolic compounds of extracts from Green Tea and Rosemary was determined. RE presented a higher antioxidant capacity and higher content of TPC and flavonoids than GTE. While the main phenolic compounds identified in RE were carnosic acid, carnosol and rosmarinic acid, in GTE were catechin, epigallocatechin gallate, epicatechin, rutin and gallic acid. Active PLA films were prepared by the incorporation of GTE and RE at different percentages, followed by the evaluation of their properties. Afterwards, almonds and beef were selected as model foodstuff and packaged with active PLA films.PLA with 4 % of GTE presented a higher WVP and opacity, while PLA with 4% (w/w) of RE presented the highest O2 permeability. PLA with 2 and 4 % (w/w) of GTE presented the highest DPPH inhibition percentage and the highest total content in phenolic compounds and flavonoids at the end of 10 days (at 40 °C), in contact with a fatty food simulant. Regarding the almond packaged with the active films, PLA films with 2 and 4 % of RE were the most effective in the reduction of oxidation, allowing to obtain the lowest malonaldehyde (MDA) content and the lowest peroxides, at the end of 60 days of storage at room temperature. In addition, PLA with GTE and RE inhibited the formation of MDA content in beef stored for 11 days at 4 °C. This study shows that these PLA active packages can contribute for delaying lipid oxidation in foodstuffs with high fat content.
- Whey protein active films incorporated with a blend of essential oils: Characterization and effectivenessPublication . Ribeiro-Santos, Regiane; de Melo, Nathália Ramos; Andrade, Mariana; Azevedo, Gabriela; Machado, Ana Vera; Carvalho-Costa, Denise; Sanches-Silva, AnaWhey protein concentrate (WPC) films incorporated with a blend of Cinnamomum cassia, Cinnamomum zeylanicum, and Rosmarinus officinalis essential oils were characterized and evaluated for their effectiveness as an antioxidant for food applications. The effect of the incorporation of essential oils (EOs) at different concentrations (1, 2, 2.7, and 5% w/w) in WPC were studied by measuring their physical, optical, mechanical, and microstructural properties, in order to evaluate their behavior as a food packaging. The effectiveness of these active WPC films as a packaged was evaluated using a fatty food model (salami). The state of the salami oxidation was measured by the TBARs and hexanal assays during 180 days of storage. A yellowish characteristic color and opacity of WPC‐based films tend to increase with the increase of the EO concentration in the film formulation. While films containing 1 and 2% of EOs showed to be the most hydrophobic and present the lowest moisture content and solubility in water, films with higher EOs % (2, 2.7, and 5%, w/w) presented the highest water vapor transmission rate. The developed WPC active films showed to be heterogeneous, presenting cracks and pores due to the weakening of the polymer chain interaction forces by the EOs, which affected their mechanical behavior. WPC films incorporated with EOs may retard lipid oxidation induced by UV light in food. Besides, they showed to be very effective in the reduction of lipid oxidation in a previous assay with salami, with a longer storage time.