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Thesis (PhD(Agric))--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Postharvest quality of fresh table grapes is usually preserved through cooling using cold air. However, cooling efficiencies are affected by the multi-scale packaging that is commercially used for handling grapes after harvest. There is usually spatial temperature variability of grapes that often results in undesirable quality variations during postharvest handling and marketing. This heterogeneity of grape berry temperature inside multi-packages is largely due to uneven cold airflow patterns that are caused by airflow resistance through multi-package components. The aims of this study were therefore to conduct an in-depth experimental investigation of the contribution of grape multi-packaging components to total airflow resistance, cooling rates and patterns of grapes inside the different commercially used multi-packages, and to assess the effects of these multi-packages on table grape postharvest quality attributes. A comprehensive study of moisture loss from grapes during postharvest storage and handling, as well as a preliminary investigation of the applicability of computational fluid dynamics (CFD) modeling in predicting the transport phenomena of heat and mass transfer of grapes during cooling and cold storage in multi-packages were included in this study. Total pressure drop through different table grapes packages were measured and the percentage contribution of each package component and the fruit bulk were determined. The liner films contributed significantly to total pressure drop for all the package combinations studied, ranging from 40.33±1.15% for micro-perforated liner film to 83.34±2.13 % for non-perforated liner film. The total pressure drop through the grape bulk (1.40±0.01 % to 9.41±1.23 %) was the least compared to the different packaging combinations with different levels of liner perforation. The cooling rates of grapes in the 4.5 kg multi-packaging were significantly (P<0.05) slower than that of grapes in 5 kg punnet multi-packaging, where the 4.5 kg box resulted in a seven-eighths cooling time of 30.30-46.14% and 12.69-25.00% more than that of open-top and clamshell punnet multi-packages, respectively. After 35 days in cold storage at -0.5°C, grape bunches in the 5 kg punnet box combination (open-top and clamshell) had weight loss of 2.01 – 3.12%, while the bunches in the 4.5 kg box combination had only 1.08% weight loss. During the investigation of the effect of different carton liners on the cooling rate and quality attributes of ‘Regal seedless’ table grapes in cold storage, the non-perforated liner films maintained relative humidity (RH) close to 100 %. This high humidity inside non-perforated liner films resulted in delayed loss of stem quality but significantly (P ≤ 0.05) increased the incidence of SO2 injury and berry drop during storage compared to perforated liners. The perforated liners improved fruit cooling rates but significantly (P ≤ 0.05) reduced RH. The low RH in perforated liners also resulted in an increase in stem dehydration and browning compared to non-perforated liners. The moisture loss rate from grapes packed in non-perforated liner films was significantly (P<0.05) lower compared to the moisture loss rate from grapes packed in perforated liner films (120 x 2 mm and 36 x 4 mm). The effective moisture diffusivity values for stem parts packed in non-perforated liner films were lower than the values obtained for stem parts stored without packaging liners, and varied from 5.06x10-14 to 1.05x10-13 m2s-1. The dehydration rate of stem parts was inversely proportional to the size (diameter) of the stem parts. Dehydration rate of stems exposed (without liners) to circulating cold air was significantly (P<0.05) higher than the dehydration rates of stems packed in non-perforated liner film. Empirical models were successfully applied to describe the dehydration kinetics of the different parts of the stem. The potential of cold storage humidification in reducing grape stem dehydration was investigated. Humidification delayed and reduced the rate of stem dehydration and browning; however, it increased SO2 injury incidence on table grape bunches and caused wetting of the packages. The flow phenomenon during cooling and handling of packed table grapes was also studied using a computational fluid dynamic (CFD) model and validated using experimental results. There was good agreement between measured and predicted results. The result demonstrated clearly the applicability of CFD models to determine optimum table grape packaging and cooling procedures. / AFRIKAANSE OPSOMMING: Naoes kwaliteit van vars tafeldruiwe word gewoonlik behou deur middel van verkoeling van die produk met koue lug. Ongelukkig word die effektiwiteit van dié verkoeling beïnvloed deur die multivlakverpakking wat kommersieel gebruik word vir die naoes hantering van druiwe. Daar is gewoonlik ruimtelike variasie in die temperatuur van die druiwe wat ongewenste variasie in die kwaliteit van die druiwe veroorsaak tydens naoes hantering en bemarking. Die heterogene druiwetemperature binne die multivlakverpakkings word grootliks veroorsaak deur onegalige lugvloeipatrone van die koue lug as gevolg van die weerstand wat die verskillende komponente van die multivlakverpakkings teen lugvloei bied. Die doel van hierdie studie was dus om ‘n indiepte eksperimentele ondersoek te doen om die bydrae van multivlakverpakking op totale lugvloeiweerstand, verkoelingstempo’s en –patrone van druiwe binne kommersieël gebruikte multivlakverpakkings te ondersoek, asook die effek van die multivalkverpakking op die naoes kwaliteit van druiwe te bepaal. ‘n Omvattende studie van vogverlies van druiwe tydens naoes opberging en hantering, asook ‘n voorlopige ondersoek na die bruikbaarheid van ‘n berekende vloei dinamika (BVD) model om die bewegingsfenomeen van hitte en massa oordrag van druiwe tydens verkoeling en koelopberging in multivlakverpakkings te voorspel, was ook by die studie ingesluit. Die totale drukverskil deur verskillende tafeldruif verpakkingssisteme is gemeet en die persentasie wat deur elke verpakkingskomponent en die vruglading bygedra is, is bereken. Van al die verpakkingskombinasies wat gemeet is, het die voeringfilms betekenisvol tot die totale drukverskil bygedra, en het gewissel van 40.33±1.15% vir die mikro geperforeerde voeringfilm tot 83.34±2.13 % vir die nie-geperforeerde voeringfilm. Die totale drukverskil oor die druiflading (1.40±0.01 % to 9.41±1.23 %) was die minste in vergelyking met die verskillende verpakkingskombinasies met die verskillende vlakke van voeringperforasies. Die verkoelingstempos van die druiwe in die 4.5 kg multiverpakking was betekenisvol (P<0.05) stadiger as vir die druiwe in die 5 kg handmandjie (‘punnet’) multiverpakking. Die 4.5 kg karton het ‘n seweagstes verkoelingstyd van 30.30-46.14% en 12.69-25.00% langer, respektiewelik, as oop-vertoon en toeslaan-‘punnet’ multiverpakkings gehad. Na 35 dae van koelopberging by -0.5°C het druiwetrosse in die 5 kg ‘punnet’-kartonkombinasies (oop-vertoon en toeslaan-’punnet’) ‘n massaverlies van 2.01 – 3.12% gehad, terwyl die trosse in die 4.5 kg kartonkombinasie slegs ‘n 1.08% massaverlies gehad het. In die ondersoek na die effek van verskillende kartonvoerings op die verkoelingstempo en kwaliteitseienskappe van ‘Regal seedless’ tafeldruiwe tydens koelopbering, het die nie-geperforeerde kartonvoerings ‘n relatiewe humiditeit (RH) van byna 100 % gehandhaaf. Hierdie hoë humiditeit in die nie-geperforeerde voeringfilms het ‘n verlies in stingelkwaliteit vertraag, maar het die voorkoms van SO2-skade en loskorrels betekenisvol (P < 0.05) verhoog in vergelyking met geperforeerde voerings. Die geperforeerde voerings het vrugverkoelingstempos verbeter, maar het die RH betekenisvol (P ≤ 0.05) verlaag. Die lae RH in die geperforeerde voerings het gelei tot ‘n verhoging in stingeluitdroging en –verbruining in vergelyking met die nie-geperforeerde voerings. Die vogverliestempo uit druiwe verpak in nie-geperforeerde voeringfilms was betekenisvol (P<0.05) stadiger in vergelyking met druiwe verpak in geperforeerde voeringfilms (120 x 2 mm and 36 x 4 mm). Die effektiewe vogdiffusiewaardes vir stingelgedeeltes verpak in nie-geperforeerde voeringfilms was stadiger as vir stingelgedeeltes wat verpak is sonder verpakkingsvoerings, en het gevarieer van 5.06x10-14 – 1.05x10-13 m2s-1. Die uitdrogingstempo van stingelgedeeltes was omgekeerd eweredig aan die grootte (deursnit) van die stingelgedeeltes. Die uitdrogingstempo van stingels wat blootgestel was (sonder voerings) aan sirkulerende koue lug was betekenisvol (P<0.05) hoër as die uitdrogingstempos van stingels wat verpak was in nie-geperforeerde voeringfilms. Empiriese modelle is gebruik om die uitdrogingskinetika van die verskillende stingelgedeeltes te beskryf. Die potensiaal van koelkamer humidifisering in die vermindering van die uitdroging van druifstingels is ondersoek. Humidifisering het stingeluitdroging vertraag en het die tempo van stingeluitdroging en -verbruining verminder, maar dit het die voorkoms van SO2-skade op die tafeldruiftrosse verhoog en het die verpakkings laat nat word. Die bewegingsfenomeen tydens verkoeling en hantering van verpakte tafeldruiwe is ook ondersoek deur gebruik te maak van ‘n BVD model en is bevestig met eksperimentele resultate. Daar was goeie ooreenstemming tussen gemete en voorspelde resultate. Die resultaat demonstreer duidelik die toepaslikheid van BVD-modelle om die optimum tafeldruifverpakkings- en verkoelingsprosedures te bepaal. / PPECB and Postharvest Innovation Programme (PHI-2) for their financial support

Master of Science / Department of Agricultural Economics / Vincent Amanor-Boadu / Food insecurity affects 16 percent of the population in northern Ghana, making food security a major focus for many of the development programs in the country. A major initiative to overcome food insecurity may involve the development of effective storage systems to help farmers control the flow of their production to markets and, thus, have higher control over the price they receive. While the poor storage infrastructure in the region is known, there is lack of knowledge about the factors motivating farmers to utilize storage in spite of these conditions. The purpose of this paper is to increase understanding about storage behavior of smallholder maize farmers in northern Ghana. A review of the literature indicates credit plays a large role in storage behavior. The purpose of this thesis is to bridge the gap between literature on storage as a bank, and on storage as a way to ensure food security. Specific objectives include: i) estimating formal and informal credit’s effects on storage behavior of smallholder maize growers, and ii) examining the effect of credit at various levels of storage. This analysis is based on data collected on 527 farmers in Ghana’s four northernmost regions obtained from an agricultural production survey conducted in 2013 and 2014 by USAID-METSS – a project funded by the Economic Growth Office of the USAID mission in Ghana. Ordinary Least Squares modeling was employed to determine the marginal effects of formal and informal credit on storage. Additionally, quantile regression modeling estimated the marginal effects at different levels of storage, including the median. The results indicate that formal credit and on-farm storage had statistically significant negative effects on maize storage at both the mean and median, but only farm output proved to be statistically significant at different levels across the storage distribution. On-farm storage had a statistically significant negative effect on storage when compared to storing off-farm at facilities like local store rooms. Carryover storage from the previous year tested to have statistically significant negative effects on storage. Under the conceptual framework utilized for this study, the results suggest that using formal credit increases a household’s food security.

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Made available in DSpace on 2017-07-10T17:37:43Z (GMT). No. of bitstreams: 1 Karine_Zachow.pdf: 505370 bytes, checksum: d13cb696c6352796268e8e885343e6aa (MD5) Previous issue date: 2011-08-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Tomato (Lycopersicon esculentum Mill) is subject to chilling injury during cold storage. The application of calcium and plant growth regulators in post-harvest may help to reduce a number of physiological disorders on fruits. In this work were verified the influence of the application in post-harvest of the five treatments: control, without heat shock; only heat shock; heat shock + Ca 2 %; heat shock + GA3 100 mg L-1; and heat shock + Ca 2 % + GA3 100 mg L-1, associated with hydrothermal treatment (45 °C) for 12 min of immersion in the response of tomato to the "chilling" and check the physical and chemical composition, the bioactive compounds and enzyme activity of the fruit. The fruits were stored at 5 °C and relative humidity of 80 % for a period of ten days. The evaluations were made ten days after removal of the fruits of the cooling conditions. The design was completely randomized with five treatments and five repetitions, each repetition being characterized by a fruit. Was applied to the ANOVA results, and when the parameter was significant, the averages were compared by Tukey test, at 5 % probability. The use of heat shock treatment was effective in reducing pathogens in tomato fruits after cold storage. Treatment with heat shock + Ca 2 % + GA3 100 mg L-1 was the best among the rest, because it provided a higher concentration of ascorbic acid, as well as β-carotene and total phenols in the fruits treated and caused a reduction in the incidence of pathogens. The use of GA3 showed better results compared to Ca, when combined with heat shock, the fruits response to the effects of cold storage, requiring further investigation in this direction / O tomate (Lycopersicon esculentum Mill) está sujeito a danos causados pelo frio ( chilling ) durante o armazenamento refrigerado. A aplicação, em pós-colheita, de cálcio e reguladores vegetais, bem como do uso de tratamento hidrotérmico, pode contribuir para reduzir vários tipos de desordens fisiológicas nos frutos. Neste trabalho, verificou-se a influência da aplicação, pós-colheita, de cinco tratamentos, sendo eles: controle, sem choque térmico; apenas choque térmico; choque térmico + Ca 2 %; choque térmico + GA3 100 mg L-1; e choque térmico + Ca 2 % + GA3 100 mg L-1, associada ao tratamento hidrotérmico (45 ºC) por 12 min de imersão, na resposta do tomate ao chilling , verificando a composição físico-química, os compostos bioativos e atividade enzimática dos frutos. Os frutos foram armazenados a 5 ºC e umidade relativa de 80 % por um período de dez dias. As avaliações foram efetuadas dez dias após a retirada dos frutos das condições de refrigeração. O delineamento utilizado foi inteiramente casualizado, com cinco tratamentos e cinco repetições, sendo cada repetição caracterizada por um fruto. Aos resultados aplicou-se ANOVA, e quando o parâmetro foi significativo, suas médias foram comparadas pelo Teste de Tukey, ao nível de 5 % de probabilidade. O uso do tratamento com choque térmico foi eficiente na redução de patógenos nos frutos de tomate após o armazenamento com frio. O tratamento com choque térmico + Ca 2 % + GA3 100 mg L-1 foi o melhor entre os demais, pois proporcionou maior concentração de ácido ascórbico, bem como de β-caroteno e fenóis totais nos frutos tratados e proporcionou redução da incidência de patógenos. O uso do GA3 apresentou melhores resultados comparado ao Ca, quando combinados ao choque térmico, na resposta dos frutos aos efeitos do frio durante a armazenagem, necessitando de maiores investigações neste sentido

This Project identified the relationships between storage conditions, dry matter losses (DMLs) caused by Fusarium species in cereal grains and mycotoxin contamination and assessed novel control strategies for post-harvest grain management including chemical control and ozone. F. graminearum, F. verticillioides and F. langsethiae were inoculated on wheat, maize and oats and stored under environmental conditions where marginal to optimum spoilage and mycotoxin contamination can occur. DMLs were calculated from the CO2 produced and were significantly correlated with deoxynivalenol (DON), zearalenone (ZEA), fumonisins (FUMs) and T-2 and HT-2 toxins respectively. Mycotoxin levels in wheat and maize exceeded the EU legislative limits with 0.9-1% DMLs. Therefore, CO2 monitoring during storage can indicate the level of contamination in a stored batch. Using CO2 production data at different water activity (aw) and temperature conditions, the environmental regimes at which F. langsethiae can grow and contaminate oats with T-2 and HT-2 toxins were identified for the first time. Five acids were examined in vitro and little effect was observed on Fusarium growth, in the aqueous form, while the effect on mycotoxin production varied. Dissolved in ethanol, adipic, fumaric and ferulic acids inhibited fungal growth and controlled DON and FUMs, but T-2 toxin was stimulated by the ethanol. Two garlic essential oils, propyl-propylthiosulfinate (PTS) and propyl propylthiosulfonate (PTSO) were studied for the first time. In vitro, 200 ppm reduced fungal growth (50-100%) and mycotoxin production by >90%. The efficacy was species-dependent. In naturally contaminated oats of 0.93 aw stored for 20 days, 16 ppm PTSO reduced T-2 and HT-2 toxins by 66% and ochratoxin A (OTA) by 88%, while 200 ppm PTS reduced OTA by 95%. In wheat, 100 ppm PTS reduced DON and ZEA and 300 ppm PTS reduced fumonisins by 40-80%. PTSO:PTS (1:1) at 400 and 600 ppm was very effective against DON and ZEA in wheat of 0.92 aw. Ozone (O3) exposure at 200 ppm for 30 min delayed Fusarium spore germination on media of 0.98 aw and inhibited germination at 0.94 aw. O3 was more effective against fungal spores than mycelium and little effect was observed on growing cultures. In vitro, mycotoxin production after exposure depended on the stage of life of the fungi. O3 reduced fungal populations in grains. Mycotoxin production in wet grains treated with 100-200 ppm O3 for 60 min and stored for up to 30 days was reduced or completely inhibited, depending on the species and the exposure system. Simultaneous drying of the grain due to the O3 passage was observed.