Thesis (MScAgric)--Stellenbosch University, 2008. / ENGLISH ABSTRACT: Stone fruit is susceptible to chilling injury and intermittent warming has been shown to alleviate chilling injury during cold storage. A dual temperature storage regime was developed in South Africa for plums based on the principles of intermittent warming. The regime consists of an initial period at -0.5°C, a variable duration warming period at 7.5°C, followed by -0.5°C. Refrigerated integral containers were designed to maintain product temperature and not to reduce product temperature, per se. Considering that dual temperature shipment requires significant refrigeration and effective distribution of cool air to remove sensible- and respiratory heat, the capacity of integral containers to ship plums successfully at dual temperature is questioned. The objectives of this study were, firstly, to analyse pulp temperature data and possibly identify different temperature zones within containers shipping plums at dual temperature. Secondly, to understand the underlying processes differentiating the temperature zones and thirdly, to determine the effect of container performance on fruit quality. Three processes were identified as important characteristics of pulp temperature data sets recorded during dual temperature shipping, namely cooling down, heating up and over heating in the container. The order of importance differed according to the cultivar shipped and the container’s performance. Three temperature zones were identified in dual temperature containers, where the average pulp temperature, time to heat up and time to cool down for each temperature zone increased along the length, across the width from the left to the right and up the container system. The variable temperature conditions were possibly due to a variation in delivery air temperature, poor airflow and the effect of increased respiration and, therefore, production of vital heat by the fruit. The cooling down process was identified as the most important process discriminating the temperature zones. With the exception of ‘Fortune’, variable temperature conditions found within integral containers shipping plums at dual temperature had a significant influence on the fruit firmness post-shipment, where deterioration levels increased from the front to the door end of the container due to an increase in pulp temperature. However, it was also shown that fruit firmness prior to shipment could have a determining effect on differences found. It could not be proven that variable temperature conditions resulted in significantly higher levels of internal defects within the integral container. Temperature zones could not be identified within refrigerated integral containers shipping plums at single temperature, suggesting that the containers are able to maintain the temperature well throughout the container area. A constant 2°C storage temperature could possibly replace the commercial dual temperature regime in the case of ‘Pioneer’ plums due to improved fruit firmness, similar colour development to the control and less sensible heat produced in the container resulting in a more stable container environment. However, unacceptably high levels of shrivel and internal browning were found. / AFRIKAANSE OPSOMMING: Steenvrugte is vatbaar vir koueskade en dit is bewys dat periodieke verwarming gedurende koelopberging koueskade kan verlig. Die dubbeltemperatuur opbergingsregime is in Suid- Afrika ontwikkel vir pruime en is gebaseer op die beginsels van periodieke verwarming. Die regime bestaan uit ‘n inisiële periode by -0.5°C, ‘n variërende periode by 7.5°C, gevolg deur -0.5°C. Verkoelde integrale houers is ontwerp om produktemperature te handhaaf en nie soseer om produktemperatuur te verlaag nie. Die kapasiteit van integrale houers om pruime suksesvol teen dubbeltemperatuur te verskeep word dus bevraagteken, in ag geneem dat dubbeltemperatuurverskeping betekenisvolle verkoeling en effektiewe verspreiding van koue lug vereis om die waarneembare- en respiratoriese hitte te verwyder. Die doelwitte van die studie was eerstens om die pulptemperatuurdata te analiseer en moontlik verskillende temperatuursones binne houers wat pruime teen dubbeltemperatuur verskeep te identifiseer. Tweedens, om die onderliggende prosesse wat die temperatuursones van mekaar onderskei te verstaan, en derdens om die effek van die houer se werkverrigting op vrugkwaliteit te bepaal. Drie prosesse is geïdentifiseer as belangrike eienskappe van pulptemperatuur datastelle aangeteken gedurende dubbeltemperatuurverskeping, naamlik afkoeling, opwarming en oorverhitting wat binne die houer plaasvind. Die volgorde van belangrikheid het gevarieer afhangende van die kultivar verskeep en die houer se werkverrigting. Drie temperatuursones is geïdentifiseer binne integrale houers wat pruime teen dubbeltemperatuur verskeep, waar die gemiddelde pulptemperatuur, die opwarmingstyd en die afkoelingstyd vir elke temperatuursone in die lengte, oor die wydte van links na regs en van onder na bo in die houersisteem toegeneem het. Die variërende temperatuur toestande kan moontlik toegeskryf word aan ‘n variasie in leweringstemperatuur, swak lugvloei en die effek van toenemende respirasie, en dus die produksie van hitte vrygestel deur die vrugte. Die afkoelingsproses is geïdentifiseer as die belangrikste proses wat die temperatuursones van mekaar onderskei. Behalwe in die geval van ‘Fortune, het variërende temperatuurtoestande in integrale houers wat pruime teen dubbeltemperatuur verskeep ‘n betekenisvolle invloed op die vrugfermheid na verskeping gehad, waar vrugveroudering toegeneem het van voor in die houer na die deur van die houer as gevolg van ‘n toename in pulptemperatuur. Daar is egter bewys dat die vrugfermheid voor verskeping ook ‘n bepalende effek kon hê op die fermheidsverskille. Dit kon nie bewys word dat die variërende temperatuurtoestande betekenisvol hoër vlakke van interne defekte binne die integrale houer veroorsaak het nie. Temperatuursones kon nie geïdentifiseer word binne verkoelde integrale houers wat pruime teen enkeltemperatuur verskeep het nie, wat dus impliseer dat die houers daartoe instaat is om temperatuur goed te onderhou binne die houer. ‘n Konstante 2°C opbergingstemperatuur kan moontlik die kommersiële dubbeltemperatuurregime vervang in die geval van ‘Pioneer’ pruime as gevolg van verbeterde vrugfermheid, soortgelyke kleurontwikkeling as die dubbeltemperatuurregime en minder hitte geproduseer binne die houer deur die pruime, wat ‘n meer stabiele houeromgewing veroorsaak. Onaanvaarbare hoë vlakke van verrimpeling en interne verbruining is egter gevind.

Thesis (MScAgric)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Quality of certain Leucospermum and Leucadendron cultivars after approximately 21 days shipping has been reported to be substandard due to ‘drying out’ of leaves and, in the case of Leucadendrons, involucral leaves. The nature of the symptoms of this ‘drying out’ and the conditions under which they form, viz. long exposures to low temperatures, has led us to hypothesize that these are symptoms of chilling injury (CI). Chilling injury, as far as we are aware, has not been documented on Leucospermums or Leucadendrons. Typical CI symptomology is discussed and shown for Leucospermum ‘Gold Dust’, ‘High Gold’ and ‘Succession’ and for Leucadendron ‘Chameleon’, ‘Laurel Yellow’ and ‘Safari Sunset’. The nature of CI symptoms for Leucospermums and Leucadendrons was generally membranous breakdown that manifested in some cases as a ‘water soaked’ appearance which, at a more advanced stage, was generally visible as ‘dried out’ patches on the leaves. In the case of the Leucadendrons CI was also visible on the immature involucral leaves which are more sensitive to chilling conditions than mature leaves. Dark discoloration of especially immature involucral leaves is also a symptom of CI. As water uptake of shoots with chilling injury is hindered the styles of the Leucospermums wilt. As can be expected, the lower the temperature below the threshold temperature and the longer the exposure the more severe the symptoms. CI was recorded on cut flower shoots of Leucospermum ‘Gold Dust’, ‘High Gold’, ‘Rigoletto’, ‘Succession’ and ‘Vlam’ after 21 and 24 days storage at 1ºC. After 24 days storage the chilling injury was more severe than after 21 days storage in most cases. Each cultivar was pulsed with 5 ml per stem of a 2% (w/v) sugar solution of either lactulose, sucrose, glucose, fructose or mannose before storage. After storage, CI was recorded on day 0, 3, 7 and 10 of the vase phase. Of the cultivars tested ‘Vlam’ and especially ‘Rigoletto’ were more prone to chilling injury development. ‘High Gold’ and ‘Vlam’ shoots were pulsed with 0 (control), 1.5, 3 or 4% (w/v) solutions of either mannose or fructose. The best control of CI for both cultivars was achieved with 1.5% (w/v) solution. Lower concentrations of mannose and fructose were tested on ‘High Gold’ shoots, with a 1% (w/v) solution giving the best control for both. At high concentrations signs of toxicity became evident directly after pulsing. ‘High Gold’ shoots were pulsed with 1% (w/v) solutions of mannose and fructose and sugar analyses were performed on shoots at different stages of storage and after 10 days in the vase. A slight increase in mannose and fructose was detectable in the stems of the shoots directly after pulsing but not in the leaves or the inflorescences. This is due to the low concentrations being used. The levels of all the carbohydrates decreased during the 21 days storage and more so during the vase phase of the flowering shoots. The fact that such low concentrations were effective in controlling chilling injury suggests that the sugars may have an effect other than on the osmotic potential. Cut ‘flower’ shoots of Leucadendron ‘Chameleon’, ‘Laurel Yellow’ and ‘Safari Sunset’ were stored for 14, 21 and 28 days, at 1º, 3º and 5ºC and CI development recorded during the subsequent 10 day vase phase. ‘Laurel Yellow’ and ‘Safari Sunset’ showed signs of chilling injury on the leaves after 28 days storage at 3ºC or lower and ‘Safari Sunset’ stored for 21 days developed chilling injury during the vase phase. Immature involucral leaves were more sensitive to chilling injury than leaves. CI increased with longer exposure times and lower storage temperatures for all three cultivars evaluated. ‘Chameleon’ was the most chilling tolerant of the cultivars up to 21 days. At 5ºC chilling injury was low irrespective of cold storage duration but longer exposures to 1º and 3ºC resulted in increased chilling injury development during the vase phase. All three cultivars were pulsed with 5 ml per stem of a 1% (w/v) solution of lactulose, sucrose, glucose, fructose or mannose and stored for 14, 21 and 28 days at 1ºC. The sugars reduced chilling injury on the leaves for ‘Safari Sunset’ when stored for 28 days and, to a lesser extent, in ‘Chameleon’. The sugars failed to reduce chilling injury of the involucral leaves of ‘Chameleon’ and ‘Laurel Yellow’ whereas there was some control especially after 28 days for ‘Safari Sunset’. In some cases the sugar pulse exacerbated chilling injury. Chilling injury generally increased rapidly after storage during the first three days in the vase and then at a lower rate for the next seven days. Leucadendron ‘Chameleon’, ‘Laurel Yellow’ and ‘Safari Sunset’ ‘cut flower’ shoots were pulsed with a 1% (w/v) glucose solution. Expressed on a dry weight basis, an increase in glucose concentration was not detected. The reduction in chilling injury of leaves by a sugar pulse is speculated, as for the Leucospermums, to be as a result of their presence in the apoplast and not the symplast and that their presence there protects the membranes against chilling conditions in some way. / AFRIKAANSE OPSOMMING: Die kwaliteit van sekere Leucospermum en Leucadendron kultivars na ongeveer 21 dae verskeping is waargeneem as substandaard as gevolg van die uitdroog van blare en, in die geval van Leucadendrons, die ‘involucral’ blare. Die aard van die simptome van hierdie uitdroging en die toestande waaronder dit plaasvind nl. lang periodes van blootstelling aan lae temperature, het ons tot die hipotese gebring dat hierdie simptome van koueskade is. Sover as wat ons bewus is, is koueskade nog nie gedokumenteer op Leucospermums of Leucadendrons nie. Tipiese koueskade simptomologie word bespreek en gewys vir Leucospermum ‘Gold Dust’, ‘High Gold’ en ‘Succession’ en vir Leucadendron ‘Chameleon’, ‘Laurel Yellow’ en ‘Safari Sunset’. Die koueskade simptome vir Leucospermums en Leucadendrons was oor die algemeen membraan afbraak wat ‘n water deurdrenkte voorkoms tot gevolg gehad het wat in ‘n meer gevorderde stadium sigbaar was as uitgedroogde kolle op die blare. In die geval van Leucadendrons was koueskade ook sigbaar op die onvolwasse ‘involucral’ blare wat meer sensitief is vir koue toestande as volwasse blare. Donker verkleuring van veral onvolwasse ‘involucral’ blare is ook ‘n simptoom van koueskade. Aangesien wateropname van stele met koueskade verhinder word, verwelk die ‘styles’ van die Leucospermums. Soos verwag kan word hoe laer die temperature onder die drempel temperatuur en hoe langer die blootstelling, hoe meer ernstig die simptome. Koueskade is aangeteken op gesnyde blomstele van Leucospermum ‘Gold Dust’, ‘High Gold’, ‘Rigoletto’, ‘Succession’ en ‘Vlam’ na 21 en 24 dae opberging by 1°C. Na 24 dae opberging was die koueskade meer ernstig as na 21 dae opberging in meeste gevalle. Elke kultivar het 5ml per steel van ‘n 2% (g/v) suiker oplossing van laktolose, sucrose, glucose, fruktose of mannose voor opberging opgeneem. Na opberging is koueskade aangeteken op dag 0, 3, 7 en 10. Van die kultivars wat getoets is, was ‘Vlam’ en veral ‘Rigoletto’ meer geneig tot koueskade ontwikkeling. ‘High Gold’ en ‘Vlam’ stele is geplaas in oplossings van 0 (kontrole), 1.5, 3 of 4 % (g/v) oplossings van mannose of fruktose. Die beste beheer van koueskade vir beide kultivars is deur die 1.5 (g/v) oplossing behaal. Laer konsentrasies van mannose en fruktose is getoets op ‘High Gold’ stele met ‘n 1% (g/v) mannose oplossing wat die beste beheer gegee het. Met hoë konsentrasies het tekens van toksisiteit sigbaar geword direk na opneem van die oplossing. ‘High Gold’ stele is geplaas in 1% (g/v) oplossings van mannose of fruktose en suiker analises is uitgevoer op stele by verskillende stadiums van opberging en na 10 dae in die vaas. ‘n Effense toename in mannose en fruktose is waargeneem in die stele van die blomme direk na opname van die oplossing, maar nie in die blare of die blomme nie. Dit is as gevolg van die lae konsentrasies wat gebruik is. Die vlakke van al die koolhidrate het afgeneem gedurende die 21 dae opberging en nog meer so gedurende die vaas periode van die blommende stele. Die feit dat sulke lae konsentrasies effektief is in die beheer van koueskade dui daarop dat die suikers ‘n effek het anders as op die osmotiese potensiaal. Snyblomme van Leucadendron ‘Chameleon’, ‘Laurel Yellow’ en ‘Safari Sunset’ is opgeberg vir 14, 21 en 28 dae, by 1º, 3º en 5°C en koueskade ontwikkeling is aangeteken gedurende die opvolgende 10 dae vaas periode. ‘Laurel Yellow’ en ‘Safari Sunset’ het tekens gewys van koueskade op die blare na 28 dae opberging by 3°C of laer en ‘Safari Sunset’ opgeberg vir 21 dae het koueskade ontwikkel gedurende die vaas periode. Onvolwasse ‘involucral’ blare was meer sensitief vir koueskade as die blare. Koueskade het toegeneem met langer blootstellingstye en laer opbergins temperature vir al drie kultivars geëvalueer. ‘Chameleon’ was die mees koueverdraagsaam van die drie kultivars tot op 21 dae. By 5°C was laag ongeag van die koue opberging tydperk, maar langer blootstellings aan 1º en 3°C het gelei tot toename in koueskade ontwikkeling gedurende die vaas periode. Al drie kultivars is voorsien met 5ml per steel van ‘n 1% (g/v) oplossing van lactulose, sucrose, glucose, fruktose of mannose en opgeberg vir 14, 21 en 28 dae by 1°C. Die suikers het koueskade verminder op die blare van ‘Safari Sunset’ wanneer opgeberg vir 28 dae en, tot ‘n mindere mate, in ‘Chameleon’. Die suikers het egter nie koueskade verminder van die ‘involucral’ blare van ‘Chameleon’ en ‘Laurel Yellow’ nie, waar daar egter wel in ‘n mate beheer was veral na 28 dae vir ‘Safari Sunset’. In sommige gevalle het die voorsiening van suiker die koueskade vererger. Koueskade het oor die algemeen vinnig toegeneem na opberging gedurende die eerste drie dae in die vaas en dan teen ‘n laer tempo vir die volgende sewe dae. Leucadendron ‘Chameleon’, ‘Laurel Yellow’ en ‘Safari Sunset’ snyblom stele is voorsien van ‘n 1% (g/v) glukose oplossing. Uitgedruk op ‘n droëmassa basis is ‘n toename in glukose konsentrasie nie waargeneem nie. Die afname in koueskade van blare deur die voorsiening van ‘n suiker oplossing is gespekuleer vir die Leucospermums, om ‘n resultaat te wees van hulle teenwoordigheid in die apoplas en nie die simplas nie, en dat die teenwoordigheid daar die membrane op ‘n manier beskerm teen koue toestande.

Orientador: Barbara Janet Teruel Mederos, Paulo Ademar Martins Leal / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agrícola / Made available in DSpace on 2018-08-20T03:40:17Z (GMT). No. of bitstreams: 1 Tinini_RodolphoCesardosReis_M.pdf: 2113855 bytes, checksum: bf35d4b21243161421a237dd2edcc622 (MD5) Previous issue date: 2012 / Resumo: A hortaliça folhosa mais consumida e produzida no Brasil é a alface (Lactuca sativa L.) e seu consumo vem crescendo a cada ano devido a uma tendência da população mundial em adquirir hábitos de vida mais saudáveis. Existem diferentes métodos de resfriamento para conservação pós-colheita, já utilizados e aplicados em olerícolas, porém não se tem conhecimento sobre seus efeitos e benefícios para a alface. O objetivo deste estudo foi avaliar a aplicação de diferentes métodos de resfriamento e sua adequação para diferentes variedades de alface. Os tipos de alfaces analisadas foram a repolhuda crespa ou americana, a solta crespa, a repolhuda lisa e a solta lisa, adquiridas de um produtor da região de Campinas-SP. Foram avaliados três métodos de resfriamento seguidos de acondicionamento em câmara fria a 5ºC: resfriamento com ar forçado (com controle da umidade relativa do ar e sem controle da umidade relativa do ar), resfriamento evaporativo em túnel (nebulização e ventilador-meio poroso) e resfriamento com água fria (imersão e aspersão), sendo que o controle consistiu apenas no acondicionamento do produto em câmara fria a 5ºC, e os parâmetros físico-químicos (pH, ácido ascórbico, clorofila e perda de massa). O delineamento experimental foi inteiramente casualizado (DIC) com cinco repetições por tratamento, observando-se a interação entre os métodos de resfriamento e tempo de armazenamento, e estes parâmetros foram submetidos à análise estatística multivariada aplicando-se a análise de componentes principais. Conclui-se que o melhor método para o resfriamento de alface é o do ar forçado com umidificação, pois equilibra eficiência de resfriamento e menor degradação do produto. O resfriamento da alface pelo método evaporativo apresenta uma lenta retirada de calor especifico, desfavorecendo a manutenção da vida útil do produto, assim como o método por água fria que causa acúmulo de água no interior do produto facilitando as reações de deterioração. Com relação à análise de custo energético, o resfriamento de alface pelo método ar forçado se torna mais interessante em termos de aplicabilidade e manutenção da qualidade do produto, mesmo apresentando um maior custo se comparado ao resfriamento de alface pelo método evaporativo / Abstract: The leafy vegetable most consumed and produced in Brazil is the lettuce (Lactuca sativa L.) and its consumption is growing up every year due a tendency of world population to acquire healthier lifestyle. There are different cooling methods for post-harvest quality, already used and applied in vegetable crops, but there is no knowledge about yours effects and benefits for lettuce. The objective of this study was evaluating the application of different cooling methods and their suitability for different varieties of lettuce. The types of lettuce analyzed were "repolhuda crespa" ou "americana", a "solta crespa", a "repolhuda lisa" e a "solta lisa", acquired from a region producer in Campinas-SP. We evaluated three cooling methods followed to a storage in cold chamber at 5 ° C: forced air cooling (with relative humidity control and no relative humidity control), evaporative cooling tunnel (misting and porous-fan) and hydroccoling (immersion and spray), and control consisted in the product cold storage at 5°C, was evaluate the physic-chemical parameters (pH, ascorbic acid, chlorophyll and weight loss). The experimental design was completely randomized, with five replicates per treatment, observing the interaction between cooling methods and storage time, and these parameters were subjected to multivariate statistical analysis with applying the principal component analysis. It is concluded that the best method for cooling lettuce is forced air with humidification it balances cooling efficiency and less degradation of the product. The cooling of the lettuce by evaporative method has a slower specific heat removed, which does not favor the maintenance product shelf-life, as well as the hydrocooling causes water accumulation in the product facilitates the degradation reactions. Regarding the analysis of cost energy, the cooling lettuce by forced air method becomes more interesting in terms of applicability and maintenance at product quality, even with a higher cost compared to the cooling of lettuce evaporative method / Mestrado / Tecnologia Pós-Colheita / Mestre em Engenharia Agrícola

Thesis (M.Sc. (Horticulture)) -- University of Limpopo, 2022 / Cold storage is commonly used to prolong papaya fruit storability. Furthermore, the optimal recommended storage temperature is below 10℃ for export and distant market. However, chilling injury (CI) occurs at 10℃ or lower during prolonged cold storage. This condition hampered consumer acceptance, resulting in economic losses for producers and exporters. Therefore, the study aimed to investigate the potential of postharvest polyamine dips and storage conditions to improve the quality and shelf life of ‘Solo’ papaya fruit. The experiment was conducted as 4 x 2 factorial arranged in a completely randomised design (CRD) with eight replications. The fruits were treated with putrescine (PUT) (0 (control), 1, 2 and 3 mM) before storage for 21 days at 7.5 and 13℃ plus 5 days storage at ambient temperature. Additionally, the PUT effect on quality attributes and shelf-life were studied. The results showed that physiological and pathological disorders increased with progressive storage, irrespective of storage temperature. However, PUT treatment reduced the incidence of chilling injury and anthracnose at both 7.5 and 13℃. Additionally, the interaction of treatment and cold storage temperature significantly affected ‘Solo’ papaya fruit physical and biochemical quality attributes. Furthermore, treatment with 2 and 3 mM PUT concentration reduced changes in colour, mass, firmness, TA, and TSS compared to control. In conclusion, postharvest PUT improved ‘Solo’ papaya fruit quality and prolonged shelf-life. / AgriSETA (Agricultural Sector Training Authority)

Thesis (PhD(Agric))--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The development and application of science-based tools for determining optimum fruit maturity and postharvest handling protocols to maintain quality and reduce losses during postharvest handling and marketing is essential to maintain the competitiveness of the emerging pomegranate industry in South Africa. Currently, there are no quality standards for the South African pomegranate industry, neither is there a general consensus on the optimal harvest maturity indices for fruit cultivars. These information are important to ensure the delivery of good quality fruit to consumers, particularly for long supply chains. The overall aims of this study were (a) to develop science-based management tools for determining optimum maturity indices and storage performance of pomegranate fruit cultivars grown in South Africa, and (b) to characterise the physico-chemical and pharmacological properties of selected cultivars relevant to postharvest handling and industrial applications. In Section II, seasonal studies on pomegranate (‘Baghwa’ and ‘Ruby’) fruit growth and the evolution of maturity indices during development were conducted. Significant increases in total soluble solids (TSS), sugars (glucose and fructose) and anthocyanin composition, coupled with significant decline in titratable acidity (TA), organic acids and total phenolics (TP) occurred with advancing fruit maturity. Fruit at advanced maturity stages were characterized by intense pigmentation of peel and aril, which coincided with maximum accumulation of anthocyanins. Among all the major maturity indices investigated, TSS, BrimA and anthocyanins did not show significant (p<0.05) seasonal variability, and strong correlations were found among the indices. In combination, these indices accounted for fruit juice sugar content, acidity and colour and could serve as reliable markers to determine optimal maturity for both pomegranate cultivars. The studies in Section III focused on characterization of postharvest quality including nutritional, medicinal and antioxidant properties of fruit parts. Quality attributes of eight commercial cultivars were analysed by cluster analysis, which enabled the cultivars to be separated into two clusters (cluster 1 = ‘Ruby’, ‘Arakta’ and ‘Ganesh’; cluster 2 = ‘Bhagwa’, ‘Acco’ and ‘Herskawitz’) and two ungrouped cultivars (‘Molla de Elche’ and ‘Wonderful’) based on important quality attributes (size, texture, colour, soluble solids, acidity, juiciness and phenolics). Furthermore, pomegranate fruit peel extracts were studied to highlight their potential for value-adding in pharmaceutical and other industrial applications. The results showed that fruit peels of the investigated cultivars possess strong antibacterial, antioxidant and antityrosinase activities, and hence could be exploited as potential sources of natural antimicrobial and antioxidant agents, as well as a potential tyrosinase inhibitor. The research reported in Section IV investigated the effects of harvest maturity and storage conditions on postharvest quality and nutritional value of ‘Bhagwa’ and ‘Ruby’ cultivars. Fruit harvested at commercial maturity were stored at 5±0.3°C, 7±0.5°C and 10±0.4°C with 92±3% RH and at room temperature (20±2.2°C, 65±5.5% RH) for 16 weeks. Fruit physiological responses and quality were affected by storage condition, with the maximum levels of respiration occurring at higher temperature and extended storage duration. Fruit colour and antioxidant capacity varied slightly among storage temperatures, with total soluble solids and titratable acidity decreasing gradually over time at different temperatures. Considering that fruit stored at 5°C and 92% RH had significantly reduced weight loss, low incidence of physiological disorders and best results in maintaining flavour attributes (TSS and TA, TSS:TA ratio), the investigated cultivars may be stored at 5°C and >92% RH for 8 - 12 weeks. In paper 9 (Section IV), the research investigated the relationships between instrumental and sensory measurements of pomegranate fruit at different harvest maturities during storage and shelf life. Mature ‘Bhagwa’ fruit harvested at different times could not be discriminated by sensory attributes assessed by a trained panel. However, TSS (R2 = 0.677) and juice content (R2 = 0.512) were the two most decisive quality attributes at shelf life related to harvest maturity status. For ‘Ruby’, however, a combination of instrumental and sensory attributes appeared to be influential in discriminating mature fruit harvested at different times, with TSS:TA ratio being the most decisive (R2 = 0.654) in distinguishing different fruit harvests, followed by sweet taste (R2 = 0.474) and hue angle (R2 = 0.431). The results showed that to ensure the best post-storage quality of ‘Bhagwa’, the optimum harvest maturity was between 167 - 175 DAFB (H2 and H3) when fruit reached maximum TSS level (>16°Brix; H3) and juice content (>65 mL/100 g aril; H2). However, for ‘Ruby’, this study indicated that the optimum harvest date was at 143 DAFB (H2) when TSS:TA ratio was >55, which coincided with significantly higher sensory rating for sweet taste after shelf life of fruit at H2 than H1 and H3, respectively. The results from this thesis provide new understanding and better insights on fruit characteristics of major pomegranate cultivars grown in South Africa. Overall, the study provides new knowledge on science-based tools for assessing fruit readiness for harvest as well as storage conditions to maintain fruit postharvest quality and reduce losses. It also provides scientific information on phytochemical contents and antioxidant compounds in fruit to promote value-adding of pomegranate as a good raw material with potential applications in health food products and other industrial applications such as pharmaceuticals and cosmetics. / AFRIKAANSE OPSOMMING; Die ontwikkeling en toepassing van wetenskapgegronde instrumente vir die bepaling van optimale vrugrypheid en naoes-hanteringsprotokolle om gedurende die naoes-hantering en -bemarking van vrugte gehalte te behou en verliese te verminder, is noodsaaklik om die mededingendheid van die ontluikende granaatbedryf in Suid-Afrika te verseker. Tans is daar nie enige gehaltestandaarde vir die Suid-Afrikaanse granaatbedryf óf algemene eenstemmigheid oor die optimale oesrypheidsaanwysers vir vrugtekultivars nie. Hierdie inligting is belangrik om die naoes-lewering van uithalervrugte aan verbruikers te verseker, veral vir lang verskaffingskettings. Die oorkoepelende doelwitte van hierdie studie was (a) om wetenskapgegronde bestuursinstrumente te ontwikkel vir die vasstelling van optimale rypheidsaanwysers en bergingsprestasie van granaatkultivars wat in Suid-Afrika verbou word, en (b) om die fisiko-chemiese eienskappe en farmakologiese kenmerke van gekose kultivars te tipeer. In deel II is seisoenale studies oor granaatgroei en die ontwikkeling van rypheidsaanwysers gedurende groei onderneem. Namate vrugte ryp geword het, is beduidende toenames in totale oplosbare vaste stowwe (TSS), suikers (glukose en fruktose) en antosianien-samestelling opgemerk, sowel as ’n beduidende afname in titreerbare suur (TA), organiese suur en totale fenol (TP). Vrugte in gevorderde stadia van rypheid is gekenmerk deur intense pigmentasie van die skil en aril, wat met maksimum opbou van antosianien verband gehou het. Van ál die belangrike rypheidsaanwysers wat ondersoek is, het TSS, BrimA en antosianien onbeduidende (p<0.05) seisoenale veranderlikheid getoon, en is sterk verbande tussen die aanwysers opgemerk. Gesamentlik sou die aanwysers kon rekenskap gee van sapsuikerinhoud, -suurgehalte én -kleur, en sou dit dus as betroubare rypheidsmerkers kon dien om optimale rypheid vir albei granaatkultivars te bepaal. Die studies in deel III het gekonsentreer op die tipering van die naoes-kenmerke, onder meer die voedings-, medisinale en antioksidant-kenmerke van vrugtedele. Kenmerke van agt kommersiële kultivars is deur middel van groepsontleding bestudeer, waarvolgens die kultivars op grond van belangrike kenmerke (grootte, tekstuur, kleur, oplosbare vaste stowwe, suurgehalte, sappigheid en fenol) in twee groepe (groep 1 = ‘Ruby’, ‘Arakta’ en ‘Ganesh’; groep 2 = ‘Bhagwa’, ‘Acco’ en ‘Herskawitz’) en twee niegegroepeerde kultivars (‘Molla de Elche’ en ‘Wonderful’) ingedeel is. Ten einde die toegevoegde waarde van granaatskille vir farmaseutiese en kosmetiese doeleindes te bevorder, is skilekstrakte ook bestudeer. Die resultate toon dat die vrugteskille van die bestudeerde kultivars oor sterk antibakteriese, antioksidant- en antitirosinase- eienskappe beskik. Daarom kan die skil van die granaatkultivars as moontlike bron van natuurlike antimikrobiese en antioksidant-agense sowel as ’n moontlike tirosinase-inhibitor ontgin word. Die navorsing in deel IV het ondersoek ingestel na die uitwerking van oesrypheid en bergingsomstandighede op die naoes-gehalte en -voedingswaarde van die kultivars ‘Bhagwa’ en ‘Ruby’. Vrugte wat op kommersiële rypheid geoes is, is vir 16 weke by 5±0.3 °C, 7±0.5 °C en 10±0.4 °C met 92±3% RH, sowel as by kamertemperatuur (20±2.2 °C, 65±5.5% RH) geberg. Die bergingsomstandighede het die fisiologiese reaksies en gehalte van die vrugte beïnvloed: Maksimum vlakke van respirasie het teen hoër temperature en met verlengde berging voorgekom. Die kleur en antioksidantvermoë van die vrugte het effens tussen bergingstemperature verskil, en totale oplosbare vaste stowwe en titreerbare suur het mettertyd geleidelik by verskillende temperature afgeneem. Gedagtig daaraan dat die vrugte wat teen 5 °C en 92% RH geberg is beduidend minder gewigsverlies, ’n lae voorkoms van fisiologiese afwykings en die beste resultate in blywende geurkenmerke (TSS en TA, TSS:TA-verhouding) getoon het, kan die bestudeerde kultivars vir 8 tot 12 weke teen 5 °C en >92% RH geberg word (navorsingstuk 8). In navorsingstuk 9 (deel IV) is daar ondersoek ingestel na die verhouding tussen instrument- en sintuiglike metings van granate in verskillende stadia van oesrypheid gedurende berging en raklewe. Geen verskil in sintuiglike kenmerke kon bespeur word by ryp ‘Bhagwa’- vrugte wat op verskillende tye geoes is nie. Tog was TSS (R2 = 0.677) en sapinhoud (R2 = 0.512) die twee bepalendste gehaltekenmerke wat betref oesrypheidstatus gedurende raklewe. By ‘Ruby’ kon ’n kombinasie van instrument- en sintuiglike kenmerke egter wél tussen stadia van oesrypheid onderskei, met die TSS:TA-verhouding die bepalendste (R2 = 0.654) in die onderskeid tussen verskillende vrugteoeste, gevolg deur ’n soet smaak (R2 = 0.474) en skakeringshoek (R2 = 0.431). Die resultate toon dat die beste nabergingsgehalte vir ‘Bhagwa’ verkry word by ’n optimale oesrypheid van 167–175 DAFB (H2 en H3), wanneer vrugte die maksimum TSS-vlak (>16°Brix; H3) en sapinhoud (>65 mL/100 g aril; H2) bereik het. Vir ‘Ruby’ dui hierdie studie op ’n optimale oesdatum van 143 DAFB (H2) met ’n TSS:TA-verhouding van >55, wat verband gehou het met ’n beduidend hoër telling vir soet smaak by H2 eerder as by H1 en H3 ná raklewe. Die resultate van hierdie tesis bied ’n beter begrip van, en insig in, die vrugtekenmerke van granaatkultivars wat in Suid-Afrika verbou word. Oor die algemeen bied die studie wetenskaplike inligting om moontlik die toegevoegde waarde van granate as ’n goeie bron van minerale elemente sowel as farmaseutiese, kosmetiese en antioksidant-verbindings te bevorder. Dit bied ook kennis oor die ontwikkeling van wetenskapgegronde instrumente vir die vasstelling van optimale vrugrypheid en naoes-hanteringsprotokolle om gedurende die naoes-hantering en -bemarking van granate vruggehalte te behou en verliese te verminder.

Thesis (PhD(Agric))--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The aim of this study was to develop non-destructive methods to predict external and internal quality of citrus fruit. A critical review of the literature identified presymptomatic biochemical markers associated with non-chilling rind physiological disorders. The prospects for the use of visible to near infrared spectroscopy (Vis/NIRS) as non-destructive technology to sort affected fruit were also reviewed. Initial studies were conducted to determine the optimum condition for NIRS measurements and to evaluate the accuracy of this technique and associated chemometric analysis. It was found that the emission head spectroscopy in diffuse reflectance mode could predict fruit mass, colour index, total soluble solids, and vitamin C with high accuracy. Vis/NIRS was used to predict postharvest rind physico-chemical properties related to rind quality and susceptibility of ‘Nules Clementine’ to RBD. Partial least squares (PLS) statistics demonstrated that rind colour index, dry matter (DM) content, total carbohydrates, and water loss were predicted accurately. Chemometric analysis showed that optimal PLS model performances for DM, sucrose, glucose, and fructose were obtained using models based on multiple scatter correction (MSC) spectral pre-processing. The critical step in evaluating the feasibility of Vis/NIRS was to test the robustness of the calibration models across orchards from four growing regions in South Africa over two seasons. Studies on the effects of microclimatic conditions predisposing fruit to RBD showed that fruit inside the canopy, especially artificially bagged fruit, had lower DM, higher mass loss, and were more susceptible to RBD. The study suggested that variations in microclimatic conditions between seasons, as well as within the tree canopy, affect the biochemical profile of the rind, which in turn influences fruit response to postharvest stresses associated with senescence and susceptibility to RBD. Principal component analysis (PCA) and PLS discriminant analysis (PLS-DA) models were applied to distinguish between fruit from respectively, inside and outside tree canopy, using Vis/NIRS signal, suggesting the possibility of using this technology to discriminate between fruit based on their susceptibility to RBD. Results from the application of optical coherence tomography (OCT), a novel non-destructive technology for imaging histological changes in biological tissues, showed promise as a potential technique for immediate, real-time acquisition of images of rind anatomical features of citrus fruit. The study also demonstrated the potential of Vis/NIRS as a non-destructive tool for sorting citrus fruit based on external and internal quality. / AFRIKAANSE OPSOMMING: Die studie het ten doel gestaan om nie-destruktiewe meeting metodes te toets en ontwikkel wat die interne en eksterne-kwaliteit van sitrusvrugte kan voorspel. In ʼn litratuuroorsig is biochemies verandering in die skil en wat geassosieer word met die ontwikkeling van fisiologies skildefekte geïdentifiseer, asook is die moontlikheid ondersoek om Naby Infrarooi spektroskopie (NIRS) as ‘n nie-destruktiewe tegnologie te gebruik om vrugte te sorteer. Eerstens was die optimale toestande waarby NIRS meetings van sitrusvrugte geneem moet word asook die akkuraatheid van die toerusting en chemometrika data-ontleding beproef. Daar is gevind dat die uitstralings-kop spektrofotometer in diffusie-weerkaatsings modus vrugmassa, skilkleur, totale opgeloste stowwe asook vitamien C akkuraat kan voorspel. Daarna van NIRS gebruik om na-oes fisies-chemiese eienskappe wat verband hou met skilkwaliteit en vatbaarheid vir skilafbraak van ‘Nules Clementine’ mandaryn. Deur gebruik te maak van “Partial least squares” (PLS) statistieke was gedemonstreer dat die skilkleur, droë massa (DM), totale koolhidrate en waterverlies akkuraat voorspel kon word. Chemometriese analises het ook getoon dat optimale PLS modelle vir DM, sukrose, glukose en fruktose verkry kan word deur modelle te skep wat gebaseer is op “Multiple scatter correction” (MSC) spektrale voor-verwerking. ʼn Belangrike stap in die ontwikkeling van NIRS gebaseerde indeling is om die robuustheid van die kalibrasiemodelle te toets en was gedoen deur vrugte te meet en sorteer van vier boorde en oor twee seisoene. ʼn Verder eksperiment om die impak van mikroklimaat op die skil se vatbaarheid vir fisiologiese defekte te ontwikkel het getoon dat vrugte wat binne in die blaardak ontwikkel (lae vlakke van sonlig) ʼn laer DM, hoër gewigsverlies het en was ook meer vatbaar vir skilafbraak. Die resultate dui daarop dat verskille in mikroklimaat oor die seisoen asook in die blaardak die skil se biochemiese profiel beïnvloed, wat lei tot ʼn negatiewe reaksie op na-oes stres en verhoogde voorkoms van fisiologiese skilafbraak. Die ontwikkelde “Principal component analysis” (PCA) en PLS-diskriminant analise modelle was daarna suksesvol toegepas om vrugte te skei na NIRS meetings, op die basis van vrugpossies in die blaardak. Nuwe, nie-destruktiewe tegniek, nl. “Optical coherence tomography” (OCT) was suksesvol getoets as manier om ʼn fotografiese beeld te skep van histologiese veranderinge in die skil. Die resultate dui op die potensiaal van die onontginde tegnologie om intak biologiese-materiaal te analiseer. Hierdie studie het getoon dat daar wesenlike potensiaal is om NIRS verder te ontwikkel tot ʼn tegnologie wat gebruik kan word om vrugte te sorteer gebaseer op eksterne (skil) asook interne (pulp) eienskappe

Thesis (MSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Grapes are lost annually due to spoilage by Botrytis cinerea. Botrytis cinerea is currently controlled using fungicides and SO2 fumigation in storage rooms but with limited success. Although these techniques have been used for decades they have been associated with numerous of disadvantages. Fungicides are restricted from being used during storage due to legislation and toxicity of the fungicides present on the surface of the berries. SO2 fumigation does not kill the dormant infections present inside the grape tissue and if the SO2 concentration is too high the berries are damaged. During this study two different polymer nanofibrous platforms was synthesized in an attempt to prevent the rotting effect of B. cinerea. The first polymer was modified to yield a polymer with a positively charged quaternized nitrogen moiety, which was subsequently reacted with sodium metabisulfite through an ion exchange process. The modified polymer was electrospun into nanofibrous mats for the benefit of the nanofibers’ high available surface area. A further functionalization was done to increase the quantity of sodium metabisulfite on the surface of the polymer nanofibers. Sodium metabisulfite salt released SO2 gas upon reaction with water vapour present in the atmosphere which resulted in the inhibition of conidial germination of B. cinerea. The second polymer was synthesized and then electrospun into polymer nanofibrous mats followed by chemical modification of the electrospun polymer nanofibers. This post-electrospun modification resulted in the covalent attachment of a fungicide-derivative to the surface of the polymer nanofibers. The fungicide-derivative showed excellent inhibition of B. cinerea mycelium growth. Anti-fungal studies were conducted using the two modified polymer nanofibrous mats against B. cinerea to evaluate these nanofibrous surfaces as B. cinerea inhibiting membranes. Results indicated that B. cinerea conidial germination and mycelium growth were successfully inhibited. / AFRIKAANSE OPSOMMING: Druiwe bederf jaarliks weens die verrottende effek van die fungi Botrytis cinerea. Botrytis cinerea word tans beheer deur gebruik te maak van swamdoders en swaweldioksied (SO2) besproeiings in stoorkamers, maar met beperkte sukses. Alhoewel hierdie tegnieke al vir dekades in gebruik is, word dit geassosieer met verskeie probleme. Die gebruik van swamdoders word in stoorkamers verbied, weens die moontlike skadelike inname daarvan deur die mens aangesien die swamdoders op die druiwe se oppervlakte teenwoordig is. SO2-gasbesproeiings maak nie dormante infeksies binne-in die druiwe self dood nie en indien SO2 -konsentrasies te hoog is kan dit die druiwe beskadig. Tydens hierdie studie is twee verskillende polimeer-nanoveselplatforms gesintetiseer met die doel om die verrottende effek van B. cinerea te voorkom. Die eerste polimeer is aangepas met ’n primêre amienverbinding met die doel dat dit deur ‘n opvolgende modifikasiereaksie verander om sodoende ’n polimeer met ‘n kwatenêre ammoniumgroep te verkry. Die doel van die kwatenêre eienskap is dat ioniese uitruiling plaasvind tussen die anioon van die polimeer en die natruimmetabisulfiet-anioon van die sout. Die voorbereide kopolimeer is geëlektrospin in nanoveselmatte deur middel van die enkelnaald-en-enkelbal-elektrospintegniek om SMI-qC12 nanovesels te lewer wat gefunksionaliseer is. Die nanoveselmatte is na die elektrospinproses verder aangepas om die hoeveelheid natruimmetabisulfiet op die oppervlak van die nanovesels te verhoog. Die natruimmetabisulfiet stel SO2-gas vry sodra dit in aanraking kom met waterdamp in die lug wat ’n beperkende effek op spoorontkieming van B. cinerea tot gevolg het. Die tweede polimeer is voor en na die elektrospinproses gefunksionaliseer met gesintetiseerde organiese verbindings (swamdoder). Die aanpassing van die polimeer met die organiese verbindings het plaasgevind op ‘n kovalente wyse om te verhoed dat die organiese verbinding vrygelaat word tydens gebruik. Die organiese verbindings het effektiewe beperking van miselium-groei getoon. Anti-swamstudies is uitgevoer tussen die twee gefunksionaliseerde polimeer platforms en B. cinerea om die oppervlaktes van die gefunksionaliseerde polimeer/nanovesels te evalueer as B. cinerea beperkende platforms. Resultate het aangetoon dat spoorontkieming en miselium groei van B. cinerea suksesvol beperk is.

Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The export of South African fruit to some of its biggest international markets may be rejected if the phytosanitary pest, Phlyctinus callosus (Coleoptera: Curculionidae) is found in fruit consignments. An alternative to methyl bromide fumigation is needed and one of the most promising of the alternative treatments is phytosanitary irradiation as it is environmentally friendly, does not leave residues on food or in the environment and it is effective against a wide variety of insects. Field-collected weevils were treated with five doses of gamma irradiation (5, 10, 20, 40 and 80 Gy) and the fecundity and fertility of mating crosses of treated males and females with treated and untreated individuals of the opposite sex, were determined to evaluate the effect on P. callosus reproductive ability post-treatment. Results indicated that irradiation treatment did not affect fecundity, but fertility was significantly affected, decreasing as the irradiation dose increased. Females were more susceptible to the irradiation treatment than males, and after treatment with 80 Gy, eggs laid by females and mated with either treated or untreated males, did not hatch. A generic dose of 400 Gy for all insect pests except tephritid fruit flies and pupae and adult Lepidoptera is currently approved by USDA-APHIS (United States Department of Agriculture – Animal and Plant Health Inspection Services) for use on certain commodities. Results from the present study support the development of a species-specific dose for P. callosus, as well as the development of a group generic dose for the Curculionidae that is lower than 400 Gy. Effective phytosanitary irradiation treatments are only feasible if the treatment does not adversely affect fruit quality and the marketability of export fruit. Therefore, an investigation of the effects of irradiation disinfestations treatments on the quality of the new pluot cultivar, ‘Flavor Fall’ was made. Packed cartons were treated with three doses of gamma irradiation: 400 Gy, 900 Gy and 1400 Gy. After treatment fruit underwent a PD 7 dual temperature cold storage regime for 42 days and a shelf-life simulation for 7 days. The impact of insect-proof bags, sometimes required by importing countries to keep insects off packaged fruit, was also investigated. Respiration rate of the fruit was measured throughout and fruit quality evaluations were done after cold storage and after shelf-life. The results indicated that quality parameters measured at the end of cold storage, which would be after the fruit arrives at the export markets, were above the minimum standards for overseas markets. Gel breakdown was unacceptably high after the higher temperature exposure of shelf-life for fruit treated with the 900 and 1400 Gy doses. The insect-proof bags reduced shrivel, but resulted in higher incidence of gel breakdown. The use of irradiation, together with the use of the insect-proof bag, has potential as an alternative postharvest mitigation treatment for plums. Lastly, an investigation into potential rearing methods for P. callosus, including recommendation for the future, was made as the availability of a sustainable rearing method that ensures a consistent supply of high quality P. callosus adults would enable continuous research with greater numbers of this pest. The information generated in this study provides a greater understanding of the radiation biology of, not only this curculionid species, but the Curculionidae as a group, and is valuable in advancing the development of alternative postharvest control measures against this phytosanitary pest. / AFRIKAANSE OPSOMMING: Suid Afrikaanse vrugte uitvoere na van die grootste internasionale markte mag weg gewys word as die fitosanitêre pes, Phlyctinus callosus (Coleoptera: Curculionidae) in die versending gevind word. ‘n Alternatief vir metiel bromied beroking word benodig en een van die mees belowende alternatiewe behandelings is fitosanitêre bestraling aangesien dit omgewings vriendelik is, nie residue op kos of in die omgewing los nie, en effektief is teen ‘n wye verskeidenheid van insekte. Veldversamelde kalanders is behandel met vyf dosisse gamma bestraling (5, 10, 20, 40 en 80 Gy) waarna die vrugbaarheid van paringskruisings bepaal is deur kruisings tussen behandelde manlike en vroulike kalanders met behandelde en nie-behandelde individue van die teenoorgestelde geslag te maak, en so die na-behandelings effek op die voortplantings vermoeë van P. callosus te evalueer. Die resultate het getoon dat die bestralings behandeling geen invloed gehad het op die hoeveelheid eiers wat gelê is nie, maar dat die uitbroei van eiers aanduidend geaffekteer is deur die behandeling. Die hoeveelheid eiers wat uitgebroei het, het minder geraak soos die bestralings behandeling toegeneem het. Vroulike kalanders was meer sensitief vir die behandeling en na 80 Gy, of hul gekruis is met behandelde of niebehandelde mannetjies, het geen eiers uitgebroei nie. ‘n Generiese dosis van 400 Gy vir alle insekte, uitsluitend tephritiese vrugte vlieë en papies en volwasse Lepidoptera is huidiglik goedgekeur deur die USDA-APHIS (United States Department of Agriculture – Animal and Plant Health Inspection Services) vir sekere kommoditeite. Die resultate van die huidige studie ondersteun die ontwikkeling van ‘n spesie-spesifieke dosis vir P. callosus, so ook die ontwikkeling van ‘n generiese groep dosis vir Curculionidae wat laer as 400 Gy is. Effektiewe fitosanitêre bestralings behandeling is slegs moontlik indien die behandelings dosis nie nadelig vir vrugkwaliteit en die bemarking van uitvoer vrugte is nie. Dus is die effek wat bestralings bestryding behandeling op die kwaliteit van ‘n nuwe pluot kultivar, ‘Flavor Fall’ ondersoek. Vrugte verpak in kartonne is met drie dosisse gamma bestraling behandel: 400 Gy, 900 Gy en 1400 Gy. Na behandeling is die vrugte deur ‘n PD 7 dubbel temperatuur koelopbergings regime van 42 dae en rak-lewe simulasie vir 7 dae gesit. Die impak van insek-bestande sakke wat insekte van die verpakte vrugte weg hou en soms deur invoerende lande ‘n vereiste is, is ook ondersoek. Respirasie tempo van die vrugte is getoets en vrugkwaliteit evaluasies is gedoen na koelopberging en rak-lewe. Die resultate het getoon dat die kwaliteits maatstawwe wat getoets is na koelopberging (wat tipies is wanneer die vrugte by die uitvoer mark arriveer), almal bo die minimum standaarde van die uitvoer markte was. Gel-afbraak was onaanvaarbaar hoog na blootstelling aan die hoër temperature tydens rak-lewe vir vrugte wat behandel is met 900 en 1400 Gy. Die insek-bestande sakke het verrimpeling verminder, maar die voorkoms van gel-afbraak vermeerder. Die gebruik van bestraling, tesame met die insek-bestande sakke, het potensiaal as alternatiewe na-oes behandeling vir pruime. Laastens is ‘n ondersoek ingestel vir moontlike teeltegnieke vir P. callosus en aanbevelings gemaak vir toekomstike studies. Die beskikbaarheid van ‘n volhoubare teeltegniek wat konstante, hoë kwaliteit P. colossus individue verskaf sal aaneenlopende navorsing met groter getalle van die pes moontlik maak. Die inligting wat deur hierdie studie gegenereer is help om die bestralings biologie, nie net van hierdie curculionid spesie nie, maar die Curculionidae as ‘n groep te verstaan, en is kosbaar in die bevordering van ontwikkeling van alternatiewe na-oes beheer meganismes teen hierdie fitosanitêre pes.

Neofabraea is a genus of an important plant pathogenic fungi having worldwide appearance. Four Neofabraea species are responsible for bull's eye rot of pome fruits. The aim of this thesis was to investigate which of these species occur in the Czech Republic. 81 isolates were collected during a two- year period and they were identified using PCR fingerprinting (primers ERIC 1R and M13-core) and DNA sequencing (ITS, mtSSU and tub2). The results showed that species N. alba, N. perennans and Cryptosporiopsis kienholzii occur in the Czech Republic. According to available information, this is the second record of C. kienholzii in Europe. One isolate (KP4) failed to be identified as any of the species. KP4 is very close to C. kienholzii, but it can be distinguished both biologically and genetically. Furthermore, the aggressiveness of individual species was compared.N. perennans and strain KP4 proved to be most aggressive, the least aggressive is C. kienholzii. Two N. alba strains (KP36 and KP37) isolated from healthy apple fruit and leaf are pathogenic for apple fruits. Keywords: aggressiveness, Cryptosporiopsis kienholzii, Dermateaceae, Helotiales, apple tree, Malus, PCR fingerprinting, postharvest diseases Powered by TCPDF (www.tcpdf.org)

<p>Maize is a major calorie source for people living in Sub-Sahara Africa. In this region, <i>Aspergillus flavus</i> causes ear rot diseases in maize, contributing to food insecurity due to aflatoxin contamination. The biological control principle of competitive exclusion has been applied in both the United States and Africa to effectively reduce aflatoxin levels in maize at harvest by introducing atoxigenic strains that out-compete toxigenic strains. The goal of this study was to determine if the efficacy of preharvest biocontrol treatments carry over into the drying period, which is often delayed in Sub-Sahara Africa by the complexities of postharvest drying practices and lack of modern drying machinery. Maize was collected from fields in Texas and North Carolina that were treated with commercial biocontrol, and control fields that were untreated. To simulate moisture conditions similar to those experienced by farmers during drying in Sub-Sahara Africa, we adjusted the grain to 20% moisture content and incubated it at 28 ℃ for 6 days. Although the initial number of infected kernels in most samples were high, less than 24% of kernels were infected with <i>Aspergillus flavus</i> and aflatoxin levels were low (<4ppb). Both toxigenic and atoxigenic strains increased and spread through the grain over the incubation period, and aflatoxin levels increased, even in samples from biocontrol-treated fields. Our molecular analysis suggests that applied biocontrol strains from treated fields migrate to untreated fields. The results also indicate that the population of toxigenic <i>A. flavus</i> in the harvested grain will grow and produce aflatoxin during the drying period when moisture is high. Therefore, any potential postharvest reduction in aflatoxin accumulation will depend on how effective the biocontrol strain was at displacing the toxigenic populations prior to harvest.</p>