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Physiologie après récolte --- Postharvest physiology --- Vegetables --- Technologie alimentaire --- Food technology --- Physiologie végétale --- Plant physiology --- 664.843 --- 631.56 --- 632.167 --- Vegetables preserved by particular methods --- Preparation of produce. Treatment after harvesting. Postharvest --- Physiological diseases during storage --- 632.167 Physiological diseases during storage --- 631.56 Preparation of produce. Treatment after harvesting. Postharvest --- 664.843 Vegetables preserved by particular methods --- Food crops --- Horticultural crops --- Horticultural products

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Consumenten hechten belang aan de beschikbaarheid van verse groenten en fruit doorheen het gehele jaar. Tuinbouwgewassen zijn echter bederfelijk van aard. Vandaar dat er diverse methoden zijn ontwikkeld voor het verhogen van de bewaarbaarheid. Doorgaans wordt bewaring onder een gewijzigde bewaaratmosfeer (Controlled Atmospheres, CA) toegepast om processen als ademhaling, ethyleenproductie, afrijping en veroudering tegen te gaan. Hierbij wordt de temperatuur verlaagd en de atmosfeersamenstelling aangepast door het zuurstofniveau te verlagen en het koolstofdioxideniveau te verhogen. Een dergelijke CA bewaring is product specifiek en niet per definitie succesvol. Het optreden van fysiologische gebreken is dan ook niet altijd te voorkomen.   Peren van de variëteit ‘Conference’ zijn gevoelig aan het optreden van bruinverkleuring en holtevorming indien deze niet correct worden bewaard. Deze bewaarafwijking is vermoedelijk het gevolg van een gebrekkige ademhaling die vervolgens een lawine van metabolische processen op gang brengt. Eerdere studies hebben zich voornamelijk gericht op de rol van gastransportprocessen en het antioxidantmetabolisme bij het induceren van deze bewaarafwijking maar hebben daarbij belangrijke biochemische aspecten grotendeels verwaarloosd. In deze thesis wordt bruinverkleuring en holtevorming in ‘Conference’ peer bestudeerd vanuit een breder perspectief middels een holistische studie van het proteoom. Het primaire doel van deze doctoraatsstudie is inzicht te verkrijgen in de fysiologische achtergrond van bruinverkleuring en holtevorming gebruik makend van eiwitanalysetechnieken. Om bruinverkleuring en holtevorming in ‘Conference’ peer te bestuderen was het noodzakelijk geschikte technieken voor eiwitextractie, twee-dimensionale gelelektroforese (2-DE) en data-analyse te optimaliseren. Eiwitextractieopbrengst werd geoptimaliseerd door toepassing van extractiebuffer met hoge zuurtegraad en hoge concentraties aan dithiothreitol. Een eerste 2-DE studie gericht op het karakteriseren van al dan niet aangetast weefsel toonde aan dat zowel de ademhaling als ook de eiwitsynthese, het antioxidantmetabolisme en de ethyleenbiosynthese was aangetast. In bruin weefsel was celdood aantoonbaar aanwezig. Een terugkerend probleem bij gelgebaseerde eiwitdata is de aanwezigheid van ontbrekende waarden. Deze vormen een uitdaging voor een correcte statistische data-analyse en interpretatie. In deze thesis werd dit probleem succesvol opgelost door op grond van Bayesiaanse principale component analyse waarden toe te kennen aan de ontbrekende observaties. Het lange termijneffect van CA bewaarcondities op het metabolisme van peer werd bestudeerd. De verschillende combinaties van zuurstof en koolstofdioxide induceerde verschillen op het niveau van zowel de ademhaling als ook de eiwitsynthese, het antioxidantmetabolisme en de ethyleenbiosynthese Tenslotte werd het korte termijneffect van CA bewaarcondities op het metabolisme van peer weefselstukjes bestudeerd. Deze resultaten bevestigde goeddeels de resultaten verkregen voor het lange termijneffect. Voor wat betreft het ademhalingsmetabolisme werden slechts subtiele effecten waargenomen, uitgezonderd de inductie van de pentose-fosfaat-route bij afwezigheid van zuurstof. Vergelijkbaar aan het lange termijneffect van een verlaagd zuurstofgehalte werden diverse allergenen en andere beschermingseiwitten gereguleerd. Er werden echter geen significante verschillen waargenomen voor de glutathion-ascorbaat-route wat ons doet vermoeden dat bruinverkleuring pas zichtbaar wordt wanneer deze metabole route wordt aangetast. Op grond van de proteoomstudie in deze thesis werd het mogelijk een aantal kandidaatbiomerkers te selecteren voor een vroegtijdige signalering van het optreden van bruinverkleuring en holtevorming tijdens de bewaring van ‘Conference’ peer. Consumers demand fresh fruits and vegetables throughout the whole year. Horticultural crops are very perishable. Thus, strategies to control and extend their storage life are mandatory. Commonly, controlled atmosphere (CA) conditions are applied to retard respiration, ethylene production, ripening and senescence. The temperature is reduced and the air atmosphere composition is modified by reducing the oxygen content and by increasing the carbon dioxide composition. This CA strategy is commodity specific; inappropriate conditions may cause physiological disorders. When improperly stored, pears of the variety ‘Conference’ are very susceptible to develop core breakdown which is characterized by flesh browning and cavities. This disorder is supposed to be the consequence of an impaired respiration triggering a cascade of metabolic events. Previous studies have mainly focused on understanding this disorder by gas transport and antioxidant system studies, thereby ignoring many biochemical aspects. In this dissertation, core breakdown has been studied in a broader perspective by using a holistic proteomics approach. The main objective of this work was to understand the physiological background of core breakdown disorder by using proteomics tools. To start the study of core breakdown in ‘Conference’ pears it was necessary to fine tune protein extraction, two-dimensional electrophoresis (2-DE) and data analysis protocols. Subsequently a complete 2-DE study aiming at characterizing tissue either or not affected by core breakdown revealed impairment of respiration, protein synthesis and antioxidant and ethylene biosynthesis pathways. Cell death was also evident in brown tissue. One common problem associated to gel based proteomics data is the presence of missing values. Missing values present a challenge not only in terms of how to deal with them but also in the interpretation of the data. It was shown that missing values in gel-based proteomics data can be treated satisfactorily by means of the Bayesian Principal Component imputation method. The effect of long term exposure to different CA conditions on the metabolism of stored pears was studied. Different combinations of oxygen and carbon dioxide concentrations induced differences at the level of respiration, protein synthesis, antioxidant and ethylene pathways. Finally, the short term effect of extreme CA conditions on the metabolism of pear slices was studied. Results partially confirmed the findings for the long term exposure of pears. Only subtle changes in respiration pathways were observed except for the pentose phosphate pathway which was activated under anoxia. Similarly to long term exposure of intact pears to anoxia, allergens and other defense related enzymes were regulated. No significant changes in the glutathione-ascorbate pathway were found leading us to suspect that browning development appears as soon as this pathway collapses. This proteomic approach allowed the selection of potential candidate markers for the early-stage detection and tracking of core breakdown during storage of pears. Consumers demand fresh fruits and vegetables throughout the whole year. Horticultural crops are very perishable. Thus, strategies to control and extend their storage life are mandatory. Commonly, controlled atmosphere (CA) conditions are applied to retard respiration, ethylene production, ripening and senescence. The temperature is reduced and the air atmosphere composition is modified by reducing the oxygen content and by increasing the carbon dioxide composition. This CA strategy is commodity specific; inappropriate conditions may cause physiological disorders. When improperly stored, pears of the variety ‘Conference’ are very susceptible to develop core breakdown which is characterized by flesh browning and cavities. This disorder is supposed to be the consequence of an impaired respiration triggering a cascade of metabolic events. Previous studies have mainly focused on understanding this disorder by gas transport and antioxidant system studies, thereby ignoring many biochemical aspects. In this dissertation, core breakdown has been studied in a broader perspective by using a holistic proteomics approach. The main objective of this work was to understand the physiological background of core breakdown disorder by using proteomics tools. Protein extraction, two-dimensional electrophoresis (2-DE) and data analysis protocols were optimized for further characterization of brown tissue and tissue exposed to different CA conditions. Neglected issues in gel-based proteomics such as experimental setup, handling of missing values and mixed spots were addressed aiming for a sound biological interpretation of the generated data. This proteomics approach revealed that respiration pathways, antioxidant and other defense related mechanisms and the ethylene biosynthesis pathway are involved in core breakdown development. This proteomics approach allowed the selection of potential candidate markers for the early-stage detection and tracking of core breakdown during storage of pears. Several allergen isoforms revealed as potential markers for core breakdown might be involved in conferring some sort of protection when pears are exposed to stressful CA conditions.

Academic collection --- 631.56 --- 632.167 --- 634.13 --- 577.1 --- Preparation of produce. Treatment after harvesting. Postharvest --- Physiological diseases during storage --- Pears. Pyrus communis --- Chemical bases of life. Biochemistry and bio-organic chemistry generally --- Theses --- 577.1 Chemical bases of life. Biochemistry and bio-organic chemistry generally --- 634.13 Pears. Pyrus communis --- 632.167 Physiological diseases during storage --- 631.56 Preparation of produce. Treatment after harvesting. Postharvest

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Focusing on the great variety of research being done in the field of postharvest pathology, this volume presents a collection of topics concerning the diseases of harvested fruits and vegetables. Each chapter represents a separate unit which taken together create a better understanding of the whole subject. Topics include the causal agents of postharvest diseases of fruits and vegetables, their sources and their ways of penetration into the host; factors that may accelerate the development of the pathogen in the host - and those that suppress them; a list of the main pathogens of fruits

Fruit --- Vegetables --- Fruits --- Pomology --- Food --- Food crops --- Horticultural crops --- Horticultural products --- Plants --- Postharvest diseases and injuries. --- 631.56 --- 632.167 --- 632.938 --- 632.938 Immunology. Plants resistant to diseases and pests. Immunization of plants --- Immunology. Plants resistant to diseases and pests. Immunization of plants --- 631.56 Preparation of produce. Treatment after harvesting. Postharvest --- Preparation of produce. Treatment after harvesting. Postharvest --- 632.167 Physiological diseases during storage --- Physiological diseases during storage --- Postharvest diseases and injuries

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634 --- 634 Horticulture generally --- Horticulture generally --- Fruit processing --- Ripening --- 631.576 --- 631.547.6 --- 632.167 --- -Fruit --- -Fruit processing --- Fruits --- Pomology --- Horticultural products --- Fruits. Parts of fruit --- Ripening. Maturing. Artificial ripening --- Physiological diseases during storage --- Fruit processing. --- Ripening. --- 632.167 Physiological diseases during storage --- 631.547.6 Ripening. Maturing. Artificial ripening --- 631.576 Fruits. Parts of fruit --- 577.1 --- Fruit --- 577.1 Chemical bases of life. Biochemistry and bio-organic chemistry generally --- Chemical bases of life. Biochemistry and bio-organic chemistry generally --- Food --- Food crops --- Horticultural crops --- Plants --- Composition --- Phytochemistry. Phytobiochemistry --- Nutritionary hygiene. Diet --- Composition. --- Fruit - Composition --- Fruit - Ripening