9 pages, 4 figures, 4 tables, Chondroitin sulfate (CS) is a sulfated glycosaminoglycan with diverse biological activities, which are influenced by molecular weight (Mw) and sulfation pattern. In the present work, we take advantage of the characteristic high Mw of fish CS (51–70 kDa) to obtain lower Mw fragments with hyaluronidase and chondroitinase ABC. With this aim, we present a pseudo-mechanistic model capable of reproducing the decrease in Mw of CS from five different fish species over 24 h at four enzyme to substrate ratios. The fitting parameters of the model for each species allow to establish conditions of reaction to produce CS of the desired Mw. Furthermore, the main features of the sulfation pattern of fish CS remain in the depolymerized fragments, highlighting the feasibility of the proposed approach, This study was financed by projects IBEROS (0245_IBEROS_1_E, POCTEP 2015), CVMar+I (0302_CVMAR_I_1_P, POCTEP 2015), BLUEHUMAN (EAPA_151/2016, UE-INTERREG Atlantic Area Programme) and Xunta de Galicia (Grupos de Potencial Crecimiento, IN607B 2018/19). M.R.G thanks RTI2018-093560-J-I00 (MCIU/AEI/FEDER, UE), Peer reviewed

13 pages, 3 tables, 4 figures, Mechanistic models based on chemical properties of metals and body size have received substantial attention for their potential application to various metals and to different conditions without required calibration. This advantage has been demonstrated for a number of metals, such as Cd and Ag. However, the capacity of metal-specific chemical properties to explain variations in the accumulation for platinum-group elements (PGEs) has not been investigated yet, although emission of these metals is of increasing concern. Once being released, PGEs exist in the environment in mixtures with other metals. The present study attempted to model the accumulation of Pd and Pt in mixtures with Ag and Cd in the zebra mussel (Dreissena polymorpha) from the aqueous phase; and to investigate the potential application of mechanistic models to Pd and Pt. The present study showed statistically insignificant differences in metal accumulation among size groups in a narrow range of shell length (16–22 mm). Kinetic models could simulate well the accumulation of Cd, Ag, and Pt when metal-specific responses of zebra mussels are taken into consideration. These responses include enhanced immobilisation as a detoxifying mechanism and exchange between soft tissues and shells via the extrapallial fluid. Environmental conditions, e.g. the presence of abiotic ligands such as chloride, might also play an important role in metal accumulation. Significant relationships between the absorption efficiency and the covalent index indicate the potential application of mechanistic models based on this chemical property to Pt, T.T.Y.L was granted with funding from the Deutsche Forschungsgemeinschaft (DFG), Germany (LE 3716/2-1). M.R.G. acknowledgements financial funding to RTI2018-093560-J-I00 (MCIU/AEI/FEDER, UE), Peer reviewed

11 pages, 5 figures, 6 tables, Smart active packaging is an innovative packaging system that combines the benefits of measuring, estimating or predicting different aspects of food quality or safety with the release of an active substance that extends product shelf life. Nevertheless, in its typical configuration, the active packaging and the smart packaging are not connected, and the information provided is not exploited to design the release of the active substance.

In this work, we demonstrate how smart active packaging systems using predictive mathematical models allow the automatic optimisation of food packaging design and the prediction of the expected shelf life along the food chain. On the one hand, the system calculates the best design of the active packaging and the concentration of the active substance in the different layers that maximise food quality and safety. On the other hand, the model allows to calculate and update shelf life values along the food chain under unexpected changes in the storage conditions. Shelf life estimations and prediction will help distributors and sellers to adjust the product market prices. For example, prices can be lowered to avoid food losses when the product is close to its use-by date.

Hake (Merluccius merluccius) represents an example of a highly relevant and perishable food that can be conserved using natural antimicrobials. Therefore, the case study selected to illustrate the proposed methodology consists of the smart active packaging of hake using carvacrol as the active substance (antimicrobial). Besides, different polymers are considered as possible active packaging materials. The Matlab™ codes required to perform the simulations of the models described in this work as well as the optimisations for packaging design are available at https://doi.org/10.5281/zenodo.3244153, C.V. acknowledges funding received from the European Union's Horizon 2020 research and innovation programme under grant agreement no. 723575 (CoPro project). M.M.I. belongs to the Galician Competitive Research Group (ED431C 2017/029) and the CRETUS strategic partnership (AGRUP2017/01), co-funded by FEDER (EU). M.R.G. acknowledges financial support through the projects IMMICRO (201870E134) and ControlAR (RTI2018-093560-J-I00, MCIU/AEI/FEDER, UE), Peer reviewed

Industries of the food sector have made a great effort to control SARS-CoV-2 indirect transmission, through objects or surfaces, by updating cleaning and disinfection protocols previously focused on inactivating other pathogens, as well as food spoilage microorganisms. The information, although scarce at the beginning of the COVID-19 pandemic, has started to be sufficiently reliable to avoid over-conservative disinfection procedures. This work reviews the literature to propose a holistic view of the disinfection process where the decision variables, such as type and concentration of active substances, are optimised to guarantee the inactivation of SARS-CoV-2 and other usual pathogens and spoilage microorganisms while minimising possible side-effects on the environment and animal and human health, This research was funded by RTI2018-093560-J-I00 (MCIU/AEI/FEDER, UE), IN606A2020/028 (Xunta de Galicia predoctoral grant) and EIT Food RIS Fellowships., Peer reviewed

11 pages, 3 figures, 4 tables.-- This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY), Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) are standard indexes for determining disinfection effectiveness. Nevertheless, they are static values disregarding the kinetics at sub-MIC concentrations where adaptation, growth, stationary, and death phases can be observed. The understanding of these dynamic mechanisms is crucial to designing effective disinfection strategies. In this study, we studied the 48 h kinetics of Bacillus cereus and Escherichia coli cells exposed to sub-MIC concentrations of didecyldimethylammonium chloride (DDAC). Two mathematical models were employed to reproduce the experiments: the only-growth classical logistic model and a mechanistic model including growth and death dynamics. Although both models reproduce the lag, exponential and stationary phases, only the mechanistic model is able to reproduce the death phase and reveals the concentration dependence of the bactericidal/bacteriostatic activity of DDAC. This model could potentially be extended to study other antimicrobials and reproduce changes in optical density (OD) and colony-forming units (CFUs) with the same parameters and mechanisms of action, This study was funded by the projects RTI2018-093560-J-I00 (MCIU/AEI/FEDER, UE), RYC2019-028006-I/AIE/10.13039/501100011033, 20213AT001, and the Xunta de Galicia Grants IN606A-2020/028 and IN607B-2021/11, Peer reviewed

26 pages, 6 tables, 1 figure.-- This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license, Fish freshness can be considered as the combination of different nutritional and organoleptic attributes that rapidly deteriorate after fish capture, i.e., during processing (cutting, gutting, packaging), storage, transport, distribution, and retail. The rate at which this degradation occurs is affected by several stress variables such as temperature, water activity, or pH, among others. The food industry is aware that fish freshness is a key feature influencing consumers’ willingness to pay for the product. Therefore, tools that allow rapid and reliable assessment and prediction of the attributes related to freshness are gaining relevance. The main objective of this work is to provide a comprehensive review of the mathematical models used to describe and predict the changes in the key quality indicators in fresh fish and shellfish during storage. The work also briefly describes such indicators, discusses the most relevant stress factors affecting the quality of fresh fish, and presents a bibliometric analysis of the results obtained from a systematic literature search on the subject, We thanks the grants RTI2018-093560-J-I00 funded by MCIN/AEI/10.13039/501100011033, “ERDF A way of making Europe”, the CSIC grant 20213AT001 and Project Pescando4.0 (ref. 202178002) funded by NextGenerationEU funds in the framework of the Plan de Recuperación, Transformación y Resiliencia (PRTR) managed by the Ministerio de Agricultura, Pesca y Alimentación through the RD685/2021, Peer reviewed

14 pages, 3 figures, 1 table.-- This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license, Unravelling the mechanisms of action of disinfectants is essential to optimise dosing regimes and minimise the emergence of antimicrobial resistance. In this work, we examined the mechanisms of action of a commonly used disinfectant—benzalkonium chloride (BAC)—over a significant pathogen—L. monocytogenes—in the food industry. For that purpose, we used modelling at multiple scales, from the cell membrane to cell population inactivation. Molecular modelling revealed that the integration of the BAC into the membrane requires three phases: (1) the approaching of BAC to the cellular membrane, (2) the absorption of BAC to its surface, and (3) the integration of the compound into the lipid bilayer, where it remains at least for several nanoseconds, probably destabilising the membrane. We hypothesised that the equilibrium of adsorption, although fast, was limiting for sufficiently large BAC concentrations, and a kinetic model was derived to describe time–kill curves of a large population of cells. The model was tested and validated with time series data of free BAC decay and time–kill curves of L. monocytogenes at different inocula and BAC dose concentrations. The knowledge gained from the molecular simulation plus the proposed kinetic model offers the means to design novel disinfection processes rationally., We acknowledge the funding received from the MCIN/AEI/10.13039/501100011033 (grant RTI2018-093560-J-I00, “ERDF A way of making Europe”), from CSIC (grant 20213AT001) and Xunta de Galicia (grant GAIN IN607B 2020/03)., Peer reviewed

10 pages, 5 figures, 1 table.-- Under a Creative Commons license, Food preservatives exhibit a weak antimicrobial effect that is difficult to describe mathematically. Preservatives are commonly added below the Minimum Inhibitory Concentration (MIC) to avoid organoleptic rejection and may exhibit very different antimicrobial effects. In most cases, they inhibit bacteria growth in the first hours, reduce the stationary phase and increase the final death phase. Mathematical descriptions of these dynamics are complex but critical to understanding and optimising food preservation, such as in the case of active packaging.
In this work, we propose a new mathematical model to describe bacteria dynamics with preservatives along the exponential, stationary and death phases. We demonstrate that unknown model parameters can be estimated from measurements of bacterial growth curves at different preservative concentrations (identifiability analysis) and find a closed-form solution of the model that allows us to infer the MIC as well as the bacteriostatic (inhibition of growth rate) and bactericidal (increase on death rate) effects.
To illustrate and validate the model capabilities, we experimentally measure 48 hours growth kinetics of Escherichia coli and Bacillus cereus bacterial strains exposed to carvacrol, a preservative and flavouring agent widely employed in the food industry. We show how the model describes the measured trend during the exponential, stationary and death phases in the log-scaling of bacterial counts and can be used to analyse the antimicrobial properties of carvacrol, We thank the grants RTI2018-093560-J-I00 funded by MCIN/AEI/10.13039/501100011033, “ERDF A way of making Europe”, the CSIC grant 20213AT001 and the Xunta de Galicia, Spain grants IN606A-2020/028 and IN607B-2021/11, Peer reviewed

5 pages.-- This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license, Several factors influence consumers’ choices of food products. While price remains the main criterion, quality, pleasure, convenience, and health are also important driving factors in food market evolution. Food enterprises are making significant efforts to manufacture products that meet consumers’ demands without compromising on safety standards. Additionally, the food industry also aims to improve the efficiency of transformation and conservation processes by minimizing energy consumption, process duration, and waste generation. However, foods are highly complex systems in which: (i) non-linear dynamics and interactions among different temporal and spatial scales must be considered; (ii) a wide range of physical phenomena (such as evaporation, mechanical changes, thawing, energy/mass transport, and color changes) occur; (iii) different food matrices (such as meat, vegetables, cereal, milk, and juices) with different microstructures and properties are involved; and (iv) the number of quality and safety indicators (such as bacteria, total volatile basic nitrogen, color, texture, odor, and sensory characteristics) is substantial. Mathematical modeling and simulation are key elements that allow us to gain a deeper understanding of food processes and enable the use of tools such as optimization and real-time control to improve their efficiency. This special issue aims to gather research on the development of dynamic mathematical models that describe the relevant factors in food processes from the perspectives of food safety (chemical or microbiological), food quality (organoleptic or nutritional), or resource consumption. Additionally, the development of model-based tools to improve food processes is also considered. This includes decision-making and optimization tools, the characterization of uncertainty/variability in model predictions, model simulation techniques, software sensors, and software development. The contributions published in this Special Issue can be grouped into two categories according to their main research topic: the evolution of safety and quality indicators in unprocessed food systems, and transformation and preservation processes, We acknowledge receipt of the following grants: RTI2018-093560-J-I00, funded by Spanish Ministerio de Ciencia e Innovación MCIN/AEI/10.13039/501100011033 “ERDF—A way of making Europe”; Project Pescando4.0 (ref. 202178002), funded by NextGenerationEU within the framework of the Plan de Recuperación, Transformación y Resiliencia (PRTR) and managed by the Ministerio de Agricultura, Pesca y Alimentación through the RD 685/2021; and Project MODELSANO, funded by the Spanish MINECO (grant number PID2019-104212RB-I00/AEI/10.13039/501100011033), Peer reviewed

Unravelling the mechanisms of action of disinfectants is essential to optimise dosing regimes and minimise the emergence of antimicrobial resistance. In this work, we examined the mechanisms of action of a commonly used disinfectant—benzalkonium chloride (BAC)—over a significant pathogen—L. monocytogenes—in the food industry. For that purpose, we used modelling at multiple scales, from the cell membrane to cell population inactivation. Molecular modelling revealed that the integration of the BAC into the membrane requires three phases: (1) the approaching of BAC to the cellular membrane, (2) the absorption of BAC to its surface, and (3) the integration of the compound into the lipid bilayer, where it remains at least for several nanoseconds, probably destabilising the membrane. We hypothesised that the equilibrium of adsorption, although fast, was limiting for sufficiently large BAC concentrations, and a kinetic model was derived to describe time–kill curves of a large population of cells. The model was tested and validated with time series data of free BAC decay and time–kill curves of L. monocytogenes at different inocula and BAC dose concentrations. The knowledge gained from the molecular simulation plus the proposed kinetic model offers the means to design novel disinfection processes rationally., Agencia Estatal de Investigación | Ref. RTI2018-093560-J-I00, Centro Superior de Investigaciones Científicas | Ref. 20213AT001, Xunta de Galicia | Ref. GAIN IN607B 2020/03