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This book details the basic approaches of alkaline fermentation, provides a brief history, and offers an overview of the subject. The book discusses the diversity of indigenous fermented foods involving an alkaline reaction, as well as the taxonomy, ecology, physiology, and genetics of predominant microorganisms occurring in AFFs. Presented in nine chapters, the book explains how microorganisms or enzymes transform raw ingredients into AFFs. It discusses the safety aspects of AFFs, and considers the challenges associated with the technological aspects in modernizing AFFs. It stresses the significance of the microbiological and biochemical processes in the fermentations, as well as the factors that influence the development of the characteristic microbiota, and the biochemical and organoleptic changes induced by them. It also proposes solutions, discusses the value of AFFs and related dominant microorganisms, and assesses the future of AFFs. The authors highlight commonly known foods and beverages of plant and animal origin. They provide insight into the manufacture, chemical and microbiological composition, processing, and compositional and functional modifications taking place as a result of microbial and enzyme effects. The text examines safety, legislation, traditional and industrialized processes, as well as new product development, and opportunities for developing commodities from Africa, Asia, Europe, Latin America, and the Middle East. In addition, it also assesses the value of food processing by-products, biotechnology, and engineering of solid-state processes, modern chemical and biological analytical approaches to safety, and health and consumer perception.

This book details the basic approaches of alkaline fermentation, provides a brief history, and offers an overview of the subject. The book discusses the diversity of indigenous fermented foods involving an alkaline reaction, as well as the taxonomy, ecology, physiology, and genetics of predominant microorganisms occurring in AFFs. Presented in nine chapters, the book explains how microorganisms or enzymes transform raw ingredients into AFFs. It discusses the safety aspects of AFFs, and considers the challenges associated with the technological aspects in modernizing AFFs. It stresses the significance of the microbiological and biochemical processes in the fermentations, as well as the factors that influence the development of the characteristic microbiota, and the biochemical and organoleptic changes induced by them. It also proposes solutions, discusses the value of AFFs and related dominant microorganisms, and assesses the future of AFFs. The authors highlight commonly known foods and beverages of plant and animal origin. They provide insight into the manufacture, chemical and microbiological composition, processing, and compositional and functional modifications taking place as a result of microbial and enzyme effects. The text examines safety, legislation, traditional and industrialized processes, as well as new product development, and opportunities for developing commodities from Africa, Asia, Europe, Latin America, and the Middle East. In addition, it also assesses the value of food processing by-products, biotechnology, and engineering of solid-state processes, modern chemical and biological analytical approaches to safety, and health and consumer perception.

Een aantrekkelijk alternatief voor conventionele methoden als invriezen, hittebehandeling of toevoeging van additieven

Deze natuurlijke stof fungeert als antioxidant, aroma en als conserveermiddel. Als conserveermiddel is Carvacrol niet toegestaan, wel als smaakstof

Milde proces- en conserveringsmethoden en het karakteriseren van bederfveroorzakende micro-organismen op bepaalde behandelingen. De genoomsequenties van genoemde pathogenen werden onderzocht in relatie tot hoge osmolariteit, lage temperatuur en ultra hoge druk (UHD)

Het gecombineerde proces van magnetronbehandeling en onderdompeling in kokend water is een snelle methode voor de productie van stevige aardappelschijfjes die niet bruin kleuren bij blootstelling aan de lucht

Weak organic acids such as sorbic acid, lactate, and acetic acid are widely used by the food industry as preservatives to control growth of micro-organisms. With the current trend towards milder processing of food products, opportunities arise for spore-forming spoilage and pathogenic microorganisms such as Bacillus cereus, that may survive the use of milder heating regimes. Dormant spores produced by B. cereus can survive processing conditions and their subsequent outgrowth increases the risk of premature spoilage and food safety issues. As a consequence, the use of additional preservation hurdles, such as acidification with weak organic acid additives to ensure the quality and safety of a product is important. Sorbic acid is widely used as an antimicrobial compound because of its strong inhibitory properties against bacteria and other spoilage organisms. Its effectivity has also been ascribed to its hydrophobic character, resulting in an additional mode of action not observed with other less lipophilic organic acids such as lactic acid and acetic acid. In this project the impact of sorbic acid on spore germination and outgrowth was studied at transcriptome level and was linked to the distinct phenotypic responses observed for spores exposed to different levels of sorbic acid. The various stages of spore germination and outgrowth could be recognized by distinct gene expression profiles representing either the germination phase, transition state between germination and outgrowth or outgrowing cells, respectively. A subset of genes was specifically expressed in sorbic acid-exposed germinating spores and included functions related to cell envelope, (multi) drug transporters and amino acid metabolism. At high concentrations of sorbic acid (3mM of the undisssociated form, HSA), nutrient-induced germination of B. cereus ATCC 14579 spores was completely blocked. This blockage was shown to be reversible and could be bypassed by known non-nutrient triggers that activate spores in a receptor-independent way, pointing to a possible interference of HSA with the signaling event between germinant receptors and proposed SpoVA-channels, possibly by accumulation into the spore’s inner membrane. Additional experiments with other inhibiting compounds, including organic acids and their structurally similar alcohol counterparts, showed that the lipophilic properties are an important determinant of its efficacy to block germination. Building on current knowledge on the interaction of germination-relevant protein clusters, we discuss a hypothetical model on the mode of action of sorbic acid and other short-chain lipophilic compounds in germination inhibition of B. cereus spores. In addition to the interference or even blockage of germination, sorbic acid may increase outgrowth heterogeneity when applied at lower concentrations (0.25-1.5 mM) that still allow outgrowth. The first stages of outgrowth were shown to specifically occur heterogeneously when spores were exposed to multiple stresses simultaneously. Heterogeneity effects were most pronounced for combined stress-effects where heat-treated spores were also exposed to low pH stress. Under these conditions, a large subpopulation of spores was delayed between initial germination and swelling and further outgrowth. For the food producing industry, it would be desirable to have reliable parameters to predict the behavior of surviving spores in a food product. Data presented in this thesis show that germination rate is not a good predictor for outgrowth heterogeneity when applied as a single indicator. In conclusion, the work described in this thesis strive to obtain a better understanding on the impact that preservation stresses, including (sorbic) acid stress, have on the germination and outgrowth (heterogeneity) of B. cereus spores. The results obtained in this project may contribute to the rational design of new concepts for improved food preservation and safety.

Weak organic acids such as sorbic acid, lactate, and acetic acid are widely used by the food industry as preservatives to control growth of micro-organisms. With the current trend towards milder processing of food products, opportunities arise for spore-forming spoilage and pathogenic microorganisms such as Bacillus cereus, that may survive the use of milder heating regimes. Dormant spores produced by B. cereus can survive processing conditions and their subsequent outgrowth increases the risk of premature spoilage and food safety issues. As a consequence, the use of additional preservation hurdles, such as acidification with weak organic acid additives to ensure the quality and safety of a product is important. Sorbic acid is widely used as an antimicrobial compound because of its strong inhibitory properties against bacteria and other spoilage organisms. Its effectivity has also been ascribed to its hydrophobic character, resulting in an additional mode of action not observed with other less lipophilic organic acids such as lactic acid and acetic acid. In this project the impact of sorbic acid on spore germination and outgrowth was studied at transcriptome level and was linked to the distinct phenotypic responses observed for spores exposed to different levels of sorbic acid. The various stages of spore germination and outgrowth could be recognized by distinct gene expression profiles representing either the germination phase, transition state between germination and outgrowth or outgrowing cells, respectively. A subset of genes was specifically expressed in sorbic acid-exposed germinating spores and included functions related to cell envelope, (multi) drug transporters and amino acid metabolism. At high concentrations of sorbic acid (3mM of the undisssociated form, HSA), nutrient-induced germination of B. cereus ATCC 14579 spores was completely blocked. This blockage was shown to be reversible and could be bypassed by known non-nutrient triggers that activate spores in a receptor-independent way, pointing to a possible interference of HSA with the signaling event between germinant receptors and proposed SpoVA-channels, possibly by accumulation into the spore’s inner membrane. Additional experiments with other inhibiting compounds, including organic acids and their structurally similar alcohol counterparts, showed that the lipophilic properties are an important determinant of its efficacy to block germination. Building on current knowledge on the interaction of germination-relevant protein clusters, we discuss a hypothetical model on the mode of action of sorbic acid and other short-chain lipophilic compounds in germination inhibition of B. cereus spores. In addition to the interference or even blockage of germination, sorbic acid may increase outgrowth heterogeneity when applied at lower concentrations (0.25-1.5 mM) that still allow outgrowth. The first stages of outgrowth were shown to specifically occur heterogeneously when spores were exposed to multiple stresses simultaneously. Heterogeneity effects were most pronounced for combined stress-effects where heat-treated spores were also exposed to low pH stress. Under these conditions, a large subpopulation of spores was delayed between initial germination and swelling and further outgrowth. For the food producing industry, it would be desirable to have reliable parameters to predict the behavior of surviving spores in a food product. Data presented in this thesis show that germination rate is not a good predictor for outgrowth heterogeneity when applied as a single indicator. In conclusion, the work described in this thesis strive to obtain a better understanding on the impact that preservation stresses, including (sorbic) acid stress, have on the germination and outgrowth (heterogeneity) of B. cereus spores. The results obtained in this project may contribute to the rational design of new concepts for improved food preservation and safety.

De voordelen van het toepassen van een conventionele verhitting met daaraan toegevoegd een elektromagnetische verhitting

Nieuwe technologieën voor het langer houdbaar maken van voedsel staan op het punt om door te breken in de zuivelindustrie. Vooral het gebruik van hoge druk en pulserende elektrische velden zijn veelbelovend voor niche producten, meent dr. Paul Bartels.

Optimalisatie van de procesvoering die gericht is op de produkteigenschappen en niet voornamelijk op omgevingsfactoren. Enkele voorbeelden zijn gegeven van kleine doelgerichte IT-systemen voor de groente- en fruitsector

Momenteel is alleen het gebruik van nisine als conserveermiddel toegestaan

Het meten van biochemische parameters voor het vaststellen van de versheid van schol, tong en haring

Het verbeteren van de efficientie van de produktie door het veranderen van de genetische aanleg van de varkens

Bacillus cereus is a food spoilage microorganism and a pathogen. Growth of B. cereus can be prevented or delayed by adding growth limiting compounds to the food product or by altered storage conditions. Combinations of growth limiting factors can show synergy, or be multiplicative without synergy (gamma hypothesis). For food safety management, it is important to understand if combinations are synergistic or not, to avoid making faildangerous or overly fail-safe predictions. Therefore, the aim of this PhD project was to validate the gamma hypothesis for specific combinations of hurdles commonly used in food production. Since the relationship between growth and toxin production of B. cereus is little understood, a second aim was to investigate the production of the emetic toxin cereulide in more detail. Several new lines of research were set-up to deliver on these aims. For growth data collection to quantify hurdle effects and to study combinations of hurdles, the relative rate to detection method was found to be preferred over two other methods evaluated. The gamma hypothesis was validated for combinations of pH and undissociated acid. For combinations of pH and water activity lowering solutes, the gamma hypothesis could neither be validated nor rejected. The validity of the gamma hypothesis appeared to be dependent on the models chosen for the single hurdle effects, which are subsequently combined into the gamma model. A systematic way of model selection is therefore advocated. Investigating cells in the transition from lag phase (λ) to exponential growth phase, it was found that trends in physiological processes could be observed for different culture conditions, independent of the duration of λ. Esterase activity and electron transport chain activity were found to be useful quantitative markers for this transition phase. A new method to produce synthetic cereulide showing biological activity was developed, allowing accurate quantification of cereulide in samples. The use of valinomycin as a standard, the current procedure, underestimates the amount of cereulide by approximately 10 %. Considering the onset of emetic toxin production, LCMS analysis of B. cereus F4810/72 grown in BHI showed that cereulide production does not start before cells are in mid to late stationary phase, although significant variation was noted possibly related to variability in the growth parameters maximum specific growth rate (μmax) and λ. Addition of salt to the growth medium delayed the production of cereulide. This research has been able to deliver several new insights and tools that are useful for food safety management of the emetic toxin producer B. cereus.

Bacillus cereus is a food spoilage microorganism and a pathogen. Growth of B. cereus can be prevented or delayed by adding growth limiting compounds to the food product or by altered storage conditions. Combinations of growth limiting factors can show synergy, or be multiplicative without synergy (gamma hypothesis). For food safety management, it is important to understand if combinations are synergistic or not, to avoid making faildangerous or overly fail-safe predictions. Therefore, the aim of this PhD project was to validate the gamma hypothesis for specific combinations of hurdles commonly used in food production. Since the relationship between growth and toxin production of B. cereus is little understood, a second aim was to investigate the production of the emetic toxin cereulide in more detail. Several new lines of research were set-up to deliver on these aims. For growth data collection to quantify hurdle effects and to study combinations of hurdles, the relative rate to detection method was found to be preferred over two other methods evaluated. The gamma hypothesis was validated for combinations of pH and undissociated acid. For combinations of pH and water activity lowering solutes, the gamma hypothesis could neither be validated nor rejected. The validity of the gamma hypothesis appeared to be dependent on the models chosen for the single hurdle effects, which are subsequently combined into the gamma model. A systematic way of model selection is therefore advocated. Investigating cells in the transition from lag phase (λ) to exponential growth phase, it was found that trends in physiological processes could be observed for different culture conditions, independent of the duration of λ. Esterase activity and electron transport chain activity were found to be useful quantitative markers for this transition phase. A new method to produce synthetic cereulide showing biological activity was developed, allowing accurate quantification of cereulide in samples. The use of valinomycin as a standard, the current procedure, underestimates the amount of cereulide by approximately 10 %. Considering the onset of emetic toxin production, LCMS analysis of B. cereus F4810/72 grown in BHI showed that cereulide production does not start before cells are in mid to late stationary phase, although significant variation was noted possibly related to variability in the growth parameters maximum specific growth rate (μmax) and λ. Addition of salt to the growth medium delayed the production of cereulide. This research has been able to deliver several new insights and tools that are useful for food safety management of the emetic toxin producer B. cereus.

DCS-bewaring is uitgegroeid tot een toepasbaar laag zuurstofbewaarsysteem. Met dit systeem van Food & Biobased Research behoudt de bewaarder niet alleen kwaliteit in de lange bewaring, maar blijft de hardheid vooral in de uitstalperiode op peil. Specifiek voor Elstar is voordeel te behalen in de vorm van minder schilvlekjes.

Deze schimmels vormen in de voedingsindustrie een steeds terugkerend probleem. Ze kunnen pasteurisatie overleven

Bacillus cereus is a ubiquitous Gram-positive organism, which frequently causes foodborne illnesses. The widespread prevalence of B. cereus makes it a common contaminant in fresh foods where it also can cause spoilage. To prevent food-borne diseases and food spoilage, foods are often processed and/or preserved. In recent years, consumers’ preferences have directed to fresher and tastier foods and this has acted as a driver for food industry to use milder processing and preservation techniques. Examples of hurdles that can be applied to preserve foods are low pH and the addition of organic acids. B. cereus may overcome these adverse conditions by displaying an adaptive stress response. The response of B. cereus upon exposure to these hurdles was investigated using two model strains, ATCC 14579 and ATCC 10987. Comparative analysis revealed numerous strain-specific genes and differences in metabolic capacities, including a urease encoding gene cluster in ATCC 10987 and a nitrate respiration cluster in ATCC 14579. A survey including ATCC 10987 and 48 environmental and outbreak-associated isolates revealed urease activity, i.e., the conversion of urea in ammonia and carbon dioxide, to be present in 10 isolates. However, the activity appeared to be too low to contribute to acid resistance in the strains tested. To search for other acid resistance mechanisms, comparative phenotype and transcriptome analyses of strains ATCC 14579 and ATCC 10987 cells exposed to organic and/or inorganic acid shocks were performed. Upon exposure to low pH with or without the addition of lactic acid or acetic acid, common acid resistance mechanisms and induction of the nitrate reductase cluster in the more acid resistant strain ATCC 14579 were revealed. Furthermore, a major oxidative response was displayed, which included the induction of several oxidative stress related genes and the production of inactivation-associated reactive oxygen species (ROS), such as hydroxyl radicals, peroxynitrite, and superoxide. ROS were detected using fluorescent probes in combination with flow cytometry, including a newly developed method using a specific probe that enables superoxide detection in Grampositive and Gram-negative bacteria. The formation of ROS was also shown upon exposure to heat and was found to be oxygen dependant. Correspondingly, assessment of B. cereus stress survival capacity revealed increased heat- and acid-resistance with cells grown and exposed to stresses in the absence of oxygen. The excess ROS may originate from stressinduced dysfunction of the aerobic electron transfer chain, which was indicated by the induction of alternative electron transfer chain components upon exposure to organic and inorganic acid shocks. Upon exposure to stress, superoxide is generated through the premature leakage of electrons to oxygen at sites in the electron transfer chain at elevated rates. Subsequently, superoxide may promote the formation of other ROS, which can cause cellular damage leading to cell death. The induction of oxidative stress related genes has been reported in numerous other studies involving a wide range of bacteria exposed to different adverse conditions. However, a clear relation between the formation of ROS and the applied environmental stress was up to now not established. Secondary oxidative responses, including the formation of ROS, are possibly common bacterial responses to severe stresses under aerobic conditions. This thesis describes genomic differences between B. cereus strains and the acid stress response of these strains on transcriptome and phenotype levels, including measurements of intracellular ROS. The findings in this study can contribute to further understanding of bacterial stress responses and secondary oxidative responses. Furthermore, the results obtained may aid to optimize and select (combinations of) stresses to apply in hurdle technology, thus enabling design of safe, milder food processing and preservation techniques.

They set themselves ambitious goals: to maintain food texture, improve shelf life, and reduce energy consumption during preservation processes. The EU-funded ‘NovelQ’ consortium, consisting of 36 research partners from across Europe, is co-ordinated by the Agrotechnology and Food Sciences Group (AFSG) of Wageningen UR. Halfway through the five-year term, Wageningen Update examines the state of affairs and the experiences thus far.

Bacillus cereus is a ubiquitous Gram-positive organism, which frequently causes foodborne illnesses. The widespread prevalence of B. cereus makes it a common contaminant in fresh foods where it also can cause spoilage. To prevent food-borne diseases and food spoilage, foods are often processed and/or preserved. In recent years, consumers’ preferences have directed to fresher and tastier foods and this has acted as a driver for food industry to use milder processing and preservation techniques. Examples of hurdles that can be applied to preserve foods are low pH and the addition of organic acids. B. cereus may overcome these adverse conditions by displaying an adaptive stress response. The response of B. cereus upon exposure to these hurdles was investigated using two model strains, ATCC 14579 and ATCC 10987. Comparative analysis revealed numerous strain-specific genes and differences in metabolic capacities, including a urease encoding gene cluster in ATCC 10987 and a nitrate respiration cluster in ATCC 14579. A survey including ATCC 10987 and 48 environmental and outbreak-associated isolates revealed urease activity, i.e., the conversion of urea in ammonia and carbon dioxide, to be present in 10 isolates. However, the activity appeared to be too low to contribute to acid resistance in the strains tested. To search for other acid resistance mechanisms, comparative phenotype and transcriptome analyses of strains ATCC 14579 and ATCC 10987 cells exposed to organic and/or inorganic acid shocks were performed. Upon exposure to low pH with or without the addition of lactic acid or acetic acid, common acid resistance mechanisms and induction of the nitrate reductase cluster in the more acid resistant strain ATCC 14579 were revealed. Furthermore, a major oxidative response was displayed, which included the induction of several oxidative stress related genes and the production of inactivation-associated reactive oxygen species (ROS), such as hydroxyl radicals, peroxynitrite, and superoxide. ROS were detected using fluorescent probes in combination with flow cytometry, including a newly developed method using a specific probe that enables superoxide detection in Grampositive and Gram-negative bacteria. The formation of ROS was also shown upon exposure to heat and was found to be oxygen dependant. Correspondingly, assessment of B. cereus stress survival capacity revealed increased heat- and acid-resistance with cells grown and exposed to stresses in the absence of oxygen. The excess ROS may originate from stressinduced dysfunction of the aerobic electron transfer chain, which was indicated by the induction of alternative electron transfer chain components upon exposure to organic and inorganic acid shocks. Upon exposure to stress, superoxide is generated through the premature leakage of electrons to oxygen at sites in the electron transfer chain at elevated rates. Subsequently, superoxide may promote the formation of other ROS, which can cause cellular damage leading to cell death. The induction of oxidative stress related genes has been reported in numerous other studies involving a wide range of bacteria exposed to different adverse conditions. However, a clear relation between the formation of ROS and the applied environmental stress was up to now not established. Secondary oxidative responses, including the formation of ROS, are possibly common bacterial responses to severe stresses under aerobic conditions. This thesis describes genomic differences between B. cereus strains and the acid stress response of these strains on transcriptome and phenotype levels, including measurements of intracellular ROS. The findings in this study can contribute to further understanding of bacterial stress responses and secondary oxidative responses. Furthermore, the results obtained may aid to optimize and select (combinations of) stresses to apply in hurdle technology, thus enabling design of safe, milder food processing and preservation techniques.

Resultaten van een studie naar de mogelijkheden van verwerking van varkensvlees, runderhart en zwoerd met een cooking-extruder. De grondstoffen werden bij een watergehalte van 40-75 procent behandeld. Kenmerkende produktparameters als watersorptie-index, wateroplosbaarheid, eiwitdispersibiliteit, viscositeit en textuureigenschappen worden gemeten en bediscussieerd

De invloed van deze technologie op vitamines, kleur, smaak en textuur. Enzymen en micro-organismen kunnen geinactiveerd worden, terwijl vitamines, kleur en smaak intact blijven

De proceedings van dit congres zijn verkrijgbaar bij TNO Voeding te Zeist. Info: 030-6944144

Gegevens van een enquete zijn behandeld. Naar aanleiding hiervan wordt op 24 juni een workshop gehouden te Wageningen met als titel: "Thermische processen met behulp van dielektrische technieken". informatie hierover bij Miriam Algera, ATO-DLO, 0317-475024

Bij de productie van veel soorten vleeswaren wordt nitriet gebruikt voor het verkrijgen van een door de consument gewenste stabiele roze kleur, voor de smaak en voor de microbiologische stabiliteit. Over de toepassing van nitriet bij de bereiding van biologische vleeswaren bestaat al jaren een discussie. Om deze discussie te ondersteunen is er een experimentele studie uitgevoerd, waarin het effect op de kleur en de kleurstabiliteit tijdens de bewaring van biologische vleeswaren, geproduceerd met een verlaagde hoeveelheid nitriet, werd onderzocht. Daarnaast zijn challengetesten met vleeswaren uitgevoerd, met als doel de ontwikkelingsmogelijkheden van Clostridium botulinum in vleesproducten met verlaagd nitrietgehalte te bestuderen. Geconcludeerd wordt dat de kans op de ontwikkeling van C. botulinum bacteriën en de vorming van botuline toxien relatief klein is voor gepasteuriseerde vleesproducten zonder nitriet die gekoeld bewaard worden en qua productsamenstelling lijken op de in het onderzoek onderzochte modelvleesproducten

In this book, scientists from various disciplines address the advances in seafood research with respect to quality, safety, consumer’s demands and processing of wild and farmed fish. The nutritional properties of marine lipids and lipid oxidation from model systems to seafood are presented. Several contributions on the effects of natural anti-oxidants to prevent oxidation are also included. Effects of dietary factors on muscle tissue quality, pre-rigor processing and brining of farmed cod are covered. The development of rigor mortis and the quality of muscle in relation to commercial and experimental slaughter techniques are also discussed. Consumer’s knowledge, perception and need for information about seafood are discussed. Topics such as shelf life and microbial quality of seafood are covered in a range of contributions. Inactivation of micro organisms or biopreservation of seafood are included. Attention is paid to the development of the Quality Index Method for the evaluation of the quality of fresh fish and products. The characterisation and the quality of processed by-products are also presented. The presence of trace elements and organic contaminants in variety of seafood products is highlighted. Finally, several contributions regarding advanced methodologies to determine the quality of seafood are presented.

Pulsed electric fields (PEF) is a novel, non-thermal pasteurization method which uses short, high electric field pulses to inactivate microorganisms. The advantage of a pasteurization method like PEF compared to regular heat pasteurization is that the taste, flavour, texture and nutritional value are much less affected. At the moment, the PEF process faces several challenges, to which microtechnology could be an aid. The small electrode distance in microtechnological reactors enables the use of relatively low voltages and therefore a better control of the pulses. Secondly, the temperature can be controlled because of the high surface-to-volume ratio. It is therefore possible to separate the electric field inactivation kinetics and heat inactivation kinetics. This thesis describes the design of a PEF microreactor, inactivation experiments on several model systems combined with a comparison to a single cell electroporation microtechnological chip and the conceptual design of anupscaledPEF microreactor.

In this book, scientists from various disciplines address the advances in seafood research with respect to quality, safety, consumer’s demands and processing of wild and farmed fish. The nutritional properties of marine lipids and lipid oxidation from model systems to seafood are presented. Several contributions on the effects of natural anti-oxidants to prevent oxidation are also included. Effects of dietary factors on muscle tissue quality, pre-rigor processing and brining of farmed cod are covered. The development of rigor mortis and the quality of muscle in relation to commercial and experimental slaughter techniques are also discussed. Consumer’s knowledge, perception and need for information about seafood are discussed. Topics such as shelf life and microbial quality of seafood are covered in a range of contributions. Inactivation of micro organisms or biopreservation of seafood are included. Attention is paid to the development of the Quality Index Method for the evaluation of the quality of fresh fish and products. The characterisation and the quality of processed by-products are also presented. The presence of trace elements and organic contaminants in variety of seafood products is highlighted. Finally, several contributions regarding advanced methodologies to determine the quality of seafood are presented.

Pulsed electric fields (PEF) is a novel, non-thermal pasteurization method which uses short, high electric field pulses to inactivate microorganisms. The advantage of a pasteurization method like PEF compared to regular heat pasteurization is that the taste, flavour, texture and nutritional value are much less affected. At the moment, the PEF process faces several challenges, to which microtechnology could be an aid. The small electrode distance in microtechnological reactors enables the use of relatively low voltages and therefore a better control of the pulses. Secondly, the temperature can be controlled because of the high surface-to-volume ratio. It is therefore possible to separate the electric field inactivation kinetics and heat inactivation kinetics. This thesis describes the design of a PEF microreactor, inactivation experiments on several model systems combined with a comparison to a single cell electroporation microtechnological chip and the conceptual design of anupscaledPEF microreactor.

Bij de productie van veel soorten vleeswaren wordt nitriet gebruikt voor het verkrijgen van een door de consument gewenste stabiele roze kleur, voor de smaak en voor de microbiologische stabiliteit. Over de toepassing van nitriet bij de bereiding van biologische vleeswaren bestaat al jaren een discussie. Om deze discussie te ondersteunen is er een experimentele studie uitgevoerd, waarin het effect op de kleur en de kleurstabiliteit tijdens de bewaring van biologische vleeswaren, geproduceerd met een verlaagde hoeveelheid nitriet, werd onderzocht. Daarnaast zijn challengetesten met vleeswaren uitgevoerd, met als doel de ontwikkelingsmogelijkheden van Clostridium botulinum in vleesproducten met verlaagd nitrietgehalte te bestuderen. Geconcludeerd wordt dat de kans op de ontwikkeling van C. botulinum bacteriën en de vorming van botuline toxien relatief klein is voor gepasteuriseerde vleesproducten zonder nitriet die gekoeld bewaard worden en qua productsamenstelling lijken op de in het onderzoek onderzochte modelvleesproducten