Browsing by Author "Pereira, Diogo"
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- Exploring the potential of pineapple waste parts in agar film production: characterization and performance analysisPublication . Varghese, Nivin; Costa, Carlota; Marques, Bruno; Pereira, Diogo; Sousa, Clara; Melo, Adma; Ramos, Inês; Silva, Cristina L. M.; Brandão, TeresaAim: Agar films have gained attention as biodegradable packaging materials due to their sustainability and versatility. This study explores the potential use of pineapple waste parts (rind, core, and crown) as a renewable source for agar film production. The aim is to investigate the characteristics and performance of agar films incorporating powdered pineapple subproducts for enhanced packaging applications. Method: Control agar films were prepared by boiling and stirring a mixture of water, agar (2% w/v), and glycerol (10% w/w of the agar). Pineapple waste parts, including rind, core, and crown, were freeze-dried, ground, sieved (particles with diameter < 250 μm were used), and then incorporated into the film forming solutions by substituting 25% of the agar weight. Each sample film was obtained by pouring 20 g of the solutions into petri dishes (diameter of 9 cm) and dried at 35 °C for approximately 20 hours. The films were kept under ambient conditions and characterized in terms of color (Lab* coordinates), thickness, pH, water activity, moisture content, mechanical properties (tensile strength and elongation at break), and contact angle (for wettability assessment). Additionally, Fourier Transform Infrared Spectroscopy (FTIR) analyses were conducted for further characterization and films comparison. Results: When pineapple waste was added to the formulations, color differences increased, especially noticeable in those with crown powder, resulting in darker, more opaque films. Thickness was consistent across all films (0.134 ± 0.096 mm), except for crown-derived ones, significantly thicker (0.322 ± 0.198 mm). Films were equivalent in terms of water activity (0.515 ± 0.013) and moisture content (14.86 ± 0.66%). However, there was variation in pH; agar-control (6.75 ± 0.01) and crown-based films (5.71 ± 0.02) exhibited significantly higher pH values compared to the others (3.73 ± 0.03). Films with pineapple subproducts showed reduced tensile strength and elongation at break compared to the control. Contact angle differences were not significant, suggesting similar wetting behavior. FTIR analysis indicated varied compositions, which may justify the mechanical performance diferences. Conclusion: Agar films enriched with pineapple subproducts exhibit promising characteristics for potential packaging applications. However, further exploration into their water vapor and oxygen barrier properties is warranted.
- Exploring the potential of pineapple waste parts in agar film production: characterization and performance analysisPublication . Varghese, Nivin; Costa, Carlota; Marques, Bruno; Pereira, Diogo; Sousa, Clara; Melo, Adma; Ramos, Inês; Silva, Cristina L. M.; Brandão, Teresa R. S.Introduction: The excessive use of non-biodegradable plastics in food packaging significantly contributes to environmental pollution and resource depletion. The use of food processing by-products in developing bioplastics and organic films represents a promising strategy for reducing waste and creating value-added products. Pineapple waste, for instance, is rich in fibers and bioactive compounds, making it an ideal candidate for incorporation into biopolymer films. Objectives: o explore the potential of utilizing pineapple waste parts (core, rind, and leaves) to produce biodegradable packaging films using agar-agar as the primary binding matrix. To characterize the films' physical, chemical, and mechanical properties through various tests including colour, thickness, pH, water activity, moisture content, wettability, tensile strength, elongation at break, and Fourier Transform Infrared Spectroscopy (FTIR) analysis for comprehensive comparison. Main achievements: Different parts of pineapple waste impart different properties of agar-based films. The developed films can be customized for specific applications by adjusting their composition, which allows for enhanced stability. This adaptability lays the groundwork for further optimization to meet targeted needs. Future research on water and oxygen permeability should be conducted to fully realize the potential of these films across diverse packaging applications.
- Peer feedback : online model for developing metacognitive skills in studentsPublication . Pereira, António; Araújo, Beatriz; Matias Alves, José; Pereira, Diogo; Príncipe, Fernanda