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Repositório Institucional da Universidade Católica Portuguesa
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Nitrite reduction in cooked ham: an organoleptic and food safety concern?
Publication . Nunes, Maria J. M.; Pereira, Rui C.; Noronha, Lúcia; Cruz, Inês; Komora, Norton; Barbosa, Joana Bastos; Monteiro, Maria João P.; Ribas, Tânia C. F.; Mesquita, Raquel B. R.; Rangel, António O. S. S.; Carvalho, Fátima; Brandão, Teresa R. S.; Teixeira, Paula
Cooked meat products, particularly ham, are widely consumed, and reducing nitrite levels has become a priority due to health concerns and regulatory pressure. This study evaluated the microbiological safety, technological performance, physicochemical properties, and sensory attributes of whole cooked ham formulated with reduced nitrite (from 150 to 80 ppm) during shelf life. Microbiological analyses were conducted every 15 days, including total viable counts (TVC), lactic acid bacteria (LAB), Enterobacteriaceae, Staphylococcus aureus and Escherichia coli. TVC and LAB remained below the safety threshold (<104 CFU/g), while all other parameters were below detection limits. Sulphite reducing Clostridium spores, Salmonella spp. and Listeria monocytogenes were absent from all samples. Challenge testing with L. monocytogenes and Clostridium sporogenes was performed to assess the product's ability to inhibit pathogen growth under simulated storage conditions (up 35 and 90 days, respectively) and temperature abuse conditions (8 °C). The reduced-nitrite ham formulation effectively inhibited the growth of C. sporogenes and delayed the growth of L. monocytogenes. Technological assessments included colour measurements, water retention capacity, and texture profile analysis (TPA), with no significant differences observed between the standard and nitrite reduced formulations (P > 0.05). Physicochemical parameters such as pH (6.0–6.2), water activity (aw, 0.9669–0.9482), and residual nitrite content (4 to 1 mg/kg) were evaluated at 0, 45 and 90 days. These findings demonstrate that reducing nitrite levels to 80 ppm can ensure the product safety and quality, as evidenced by stable physicochemical properties and the preservation of sensory characteristics such as appearance, odour, texture, and flavour.
Distance backbones optimize spreading dynamics and centrality ranks in the sparsification of complex networks
Publication . Pereira, Bernardo; Costa, Felipe Xavier; Rocha, Luís M.
Detailed network models of social, biological and other complex systems are often dense, which increases their computational complexity in simulations and analysis. To address this challenge, graph sparsification is used to remove edges while preserving desired network properties. Distance backbones of weighted graphs, which remove edges that break a generalized triangle inequality for any given path-length measure, preserve all shortest paths of weighted graphs. They have been shown to typically sparsify graphs more, as well as preserve community structure and spreading dynamics better than alternative state-of-the-art methods. Here, We show that they significantly best preserve node centrality ranks, as well as local and global dynamics in spreading phenomena. This is done by introducing the distance backbone synthesis (DBS) to progressively sparsify weighted graphs according to a general family of nested distance backbones, whereby each edge is associated with the smallest distance backbone in which it appears. DBS provides a principled and natural method to sweep all degrees of sparsification possible while preserving connectivity, allowing us to precisely study (directed and undirected) weighted graph sparsification under multi-objective criteria. It provides an algebraically-principled explanation of edge importance by revealing the precise topological space associated with each edge. The theory is demonstrated with a battery of social contact networks obtained from real-world social activity in different scenarios. Our study also shows that the optimal preservation of node centrality and spreading dynamics happens for the distance backbone obeying the generalized triangle inequality for the path-length measure g(x, y) = (?3 x + ?3 y) 3 , which removes more than half of the edges from the empirical networks studied.
Digital twins for circular cities: planning for positive energy districts
Publication . Marante, Claudia Antunes; Rezazadeh, Arash; Bohnsack, René
Positive energy districts (PEDs) address the energy issues of unsustainable urban development by producing more renewable energy than they consume. However, the transformation of PEDs face challenges that require the application of new technologies. This article focuses on the role of digital twins and generative AI to explore how these technologies can support the development of PEDs in line with circular economic principles. Based on a case study of an EU Horizon R&D project, this article develops a framework for implementing generative AI-assisted digital twins for PEDs and provides decision support for their integration into 9R circular economic strategies.
Development, characterization, and evaluation of chitosan nano/microcapsules with Bacillus subtilis extract and their effect on tomato (Solanum lycopersicum) seed germination
Publication . Díaz-Herrera, René; Gómez-García, Ricardo; Duarte, Rafael; Vasconcelos, Marta W.; Alvarez-Pérez, Olga B.; Arredondo-Valdés, Roberto; Ventura-Sobrevilla, Janeth; Pintado, Manuela
The use of chemical fertilizers has led to significant environmental pollution. An alternative to these fertilizers is the use of natural compounds, such as phytohormones, which promote germination and crop development. However, environmental factors can affect natural compounds, reducing their effectiveness. Therefore, increasing their stability without decreasing their activity to improve crop quality is essential. This study produced and characterized chitosan and sodium tripolyphosphate (TPP) nano-microparticles (NMP) loaded with Bacillus subtilis extract and evaluated their impact on tomato seed germination. We employed two experimental designs (Box–Behnken and Box–Hunter–Hunter) to determine the optimal production conditions and characterized the NMP using DLS, SEM, and FTIR. The optimal treatment consisted of 8 min of homogenization, followed by 8 min of ultrasound at a 70% amplitude, resulting in a particle size of 330.7 nm, a polydispersity index of 0.25, a zeta potential of 34.3 mV, and an encapsulation efficiency of 68.8%. The NMP loaded with bacterial extract was applied to tomato seeds as a 50% dilution pretreatment. NMP achieved the best results, with a 72% germination rate (1.6 seeds per day) and an average germination time of 3.8 days. It is concluded that the experimental designs helped improve particle properties and that the chitosan and TPP coating enhances the stability and activity of the bacterial extract, potentially benefiting agronomic applications.