Thesis (MScAgric)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: Protea cut flowers are exported worldwide but the vase life of some species and cultivars is considerably shortened by post-harvest leaf blackening. Research has established carbohydrate depletion to be positively correlated with this disorder. Consequently, a study had been made of the carbohydrate status of various species and cultivars, as well as the effect of supplemental glucose (pre and post-storage) on leaf blackening. Glucose, fructose, sucrose and starch concentrations of various Protea species and cultivars held in water were measured at harvest, and again at leaf blackening initiation. All measured carbohydrates declined significantly in 'Carnival', 'Pink Ice' and 'Sheila'. In 'Cardinal' all carbohydrate concentrations decreased significantly, except the sucrose concentration in the inflorescence. 'Susara' and 'Ivy' had very high initial carbohydrate concentrations in the leaves which decreased significantly. The very high initial carbohydrate concentrations in the inflorescence of 'Ivy' declined significantly. 'Brenda' differed from the other cultivars and species in that glucose concentrations increased over time. Carbohydrate concentrations of most of the tested proteas declined significantly from harvest to the initiation of leaf blackening. This highlighted the dependence of the leaves and inflorescence on the carbohydrate reserves, further substantiating the carbohydrate depletion theory. The inflorescences were characterized by high fructose and glucose concentrations and low sucrose concentrations when compared to the leaves. It was hypothesized that glucose pulsing and cold storage at 1°C for three weeks would significantly reduce leaf blackening. 'Brenda', 'Cardinal', 'Carnival', 'Pink Ice', 'Susara ' and 'Sylvia' had significantly less leaf blackening with glucose treatments of 4 and 10%. Leaf blackening of 'Sheila', P. cynaroides and P. grandiceps was not significantly reduced by glucose pulsing. P. magnifica showed a small, but significant, reduction in leaf blackening in response to the 3, 6 and 9% treatments after 10 days only, but despite this, leaf blackening was unacceptably high. 'Pink Ice' harvested at the soft tip stage had less leaf blackening than those harvested open or closed. Toxicity symptoms on the leaves, and in some instances flowers, were observed at higher glucose concentrations (8 and 10%) onP. grandiceps, P. cynaroides, 'Cardinal' and 'Sheila'. All glucose treatments resulted in toxicity symptoms on P. magnifica. A decrease in nonstructural carbohydrates post-harvest apparently occurs in all proteas but it appears that only members of the Ligulatae respond to glucose. Glucose pulsing followed by cold storage at 1°C for three weeks in combination with post-storage glucose vase solutions, significantly reduced leaf blackening of some Protea cultivars. Glucose (1 and 2%), with hypochlorite, significantly delayed leaf blackening in 'Cardinal' and 'Sylvia' after seven days. Leaf blackening of 'Brenda', 'Carnival', 'Pink Ice' and 'Susara' was not significantly reduced by the glucose vase solutions. Other disinfectants, in combination with the sugar treatments, need to be evaluated since the hypochlorite treatment had a dehydrating effect on all the cultivars and resulted in increased leaf blackening. Carbohydrate supplementation of protea flowers with glucose, pre and post-storage, will help meet the post-harvest carbohydrate requirements of certain Protea cultivars and species to an extent. Glucose treatments must be seen in conjunction with maintaining the cold chain and when combined with cold chain maintenance, can extend the storage and vase life. / AFRIKAANSE OPSOMMING: Protea snyblomme word wêreldwyd uitgevoer alhoewel die vaasleeftyd van sommige spesies en kultivars beduidend verkort word deur na-oes loof verbruining. Navorsing het koolhidraatverbruik positief gekorreleer met hierdie probleem. Gevolglik is 'n studie gemaak van die koolhidraatstatus van verskeie spesies en kultivars asook die effek van addisionele glukose (voor en na opberging) op loofverbruining. Glukose, fruktose, sukrose en stysel konsentrasies van verskeie Protea spesies en kultivars wat in water gehou is, is bepaal met oes en weer met die eerste tekens van loofverbruining. Al die gemete koolhidraatkonsentrasies het beduidend afgeneem in 'Carnival', 'Pink Ice' en 'Sheila'. In 'Cardinal' het al die koolhidraatkonsentrasies beduidend afgeneem, behalwe vir die sukrosekonsentrasie in die blom. 'Susara' en 'Ivy' het baie hoë begin koolhidraatkonsentrasies in die blare wat beduidend afneem. Die baie hoë inisiële koolhidraatkonsentrasies in die blom van 'Ivy' neem beduidend af met tyd. 'Brenda' verskil van die ander kultivars en spesies deurdat die glukosekonsentrasies toeneem met tyd. Koolhidraatkonsentrasies van die meeste getoetste proteas neem beduidend af vanaf oes totdat die eerste tekens van loofverbruining verskyn. Dit het die afhanklikheid van die blare en blom op die koolhidraatreserwes beklemtoon en daardeur verder die koolhidraatteorie ondersteun. Die blomme is gekarakteriseer deur hoë fruktose- en glukosekonsentrasies en lae sukrosekonsentrasies wanneer dit met die blare vergelyk is.Die hipotese is gestel dat die voorsiening van glukose, vir 'n aantal ure, gekombineerd met koue opberging by 1°C vir drie weke loofverbruining beduidend sal verminder. 'Brenda', 'Cardinal', 'Carnival', 'Pink lee', 'Susara' en 'Sylvia' het beduidend minder loofverbruining met glukose behandelings tussen 4 en 10%. Loofverbruining van 'Sheila', P. cynaroides en P. grandiceps is nie beduidend verminder deur glukose behandelings nie. P. magnifica het 'n klein, maar beduidende verlaging in loofverbruining getoon met die 3, 6 en 9% behandelings na 10 dae, maar ten spyte hiervan was loofverbruining onaanvaarbaar hoog. 'Pink lee' is geoes by die sagte punt stadium en het minder loofverbruining gehad as blomme wat oop of toe geoes is. Toksisiteitsimptome op die blare, en in sommige gevalle blomme, is waargeneem met hoër glukose konsentrasies (8 en 10%) op P. grandiceps, P. cynaroides, 'Cardinal' en 'Sheila'. Alle glukosebehandelings het toksisiteitsimptome tot gevolg gehad op P. magnifica. 'n Afname in nie-strukturele koolhidrate na oes kom waarskynlik voor in alle proteas maar dit wil voorkom of slegs lede van die Ligulatae positief reageer op glukose. Glukosebehandeling gevolg deur koue opberging by 1°C vir drie weke in kombinasie met na-stoor glukose vaasoplossings het loofverbruining van sommige Protea kultivars beduidend verminder. Glukose (l en 2%), saam met hipoehloriet, het loofverbruining beduidend verminder in 'Cardinal' en 'Sylvia' na sewe dae. Loofverbruining van 'Brenda', 'Carnival', 'Pink lee' en 'Susara' is nie beduidend verminder deur die glukose vaasoplossings nie. Ander ontsmettingsmiddels in kombinasie met die suikerbehandelings moet geëvalueer word aangesien die hipoehlorietbehandeling 'n dehidrerende effek op al die kultivars gehad het en 'n toename in loofverbruining tot gevolg gehad het. Byvoeging van glukose by proteablomme, voor en na opberging, sal tot 'n mate help om in die na-oes koolhidraatbehoeftes van sekere Protea kultivars en spesies te voorsien. Glukosebehandelings moet saam met die beheer van die koueketting gesien word en wanneer gekombineerd met koueketting beheer kan dit opberg en vaasleeftyd verleng.

Please read the abstract in the section 00front of this document / Dissertation (MSc (Agric) Food Sience and Technology)--University of Pretoria, 2005. / Food Science / unrestricted

Thesis (M.Sc. (Horticulture)) -- University of Limpopo, 2017 / Tomato is popularly consumed as fresh vegetable or processed product due to its nutritional and health benefits. However, due to its high perishability, tomato cannot be stored for longer duration. Therefore, the aim of this study was the determination of appropriate dipping times into different calcium chloride concentrations to preserve the postharvest quality, storage and the shelf-life of tomato fruit. 'Classic round' tomato fruit were harvested at their pink maturity stage. The experiment was carried out as a completely randomized design (CRD), factorial arranged as 4 × 3 × 8. Treatment factors were: 4 × CaCl2 (0, 0.0045, 0.01 and 0.03%), 3 × dipping times (0, 30 and 60 minutes) and 8 × shelf-life (0 - 7 days). Fruit were stored at 15⁰ C for 30 days, thereafter, held under room temperature for 0 - 7 days of shelf-life while collecting data. During shelf-life period, fruit were evaluated for weight loss, firmness, colour, TSS, TA, pH, physiological and pathological disorders. The interaction between the treatments and dipping times showed a significant effect on weight loss, firmness, colour parameters [L*, b*, chroma and hue angle (⁰)], total soluble solids (TSS), titratable acidity (TA), pH, decay and black mould occurrence. However, significant interactive effects were not shown on a* colour component and chilling injury. In conclusion, calcium chloride (CaCl2) improved the quality and shelf-life of 'Classic round' tomato fruit. Calcium chloride concentration 0.01% was effective at 30 minutes dipping time, meanwhile, 0.03% CaCl2 was effective at 60 minutes dipping time. Therefore, 0.01 and 0.03% can be recommended for commercial preservation use for tomato fruit quality and shelf-life. / Agricultural Research Council-Tropical and Subtropical Crops (ARC-TSC) and National Research Foundation (NRF)

Sweet corn is classified among highly perishable horticultural commodities. Thus, it can be deteriorated rapidly after harvest resulting in high loss and poorer produce quality. Sweet corn's sugar loss is about four times higher at 10°C compared to 0°C. Precooling, immediately after harvest, has shown to be an effective method to maintain the quality for a wide range of fresh fruits and vegetables during storage. Further, this method leads to reduction in metabolism and respiration rate of the produce, retardation of its senescence, and inhibition of growth of pathogens. In addition to diminishing postharvest losses of the produce, efficient precooling is required for increasing the length of duration of marketing time for better profitability. / Precooling of sweet corn was accomplished by three main methods including forced-air, water and vacuum cooling. Operating parameters such as temperature, pressure, orientation of corn cobs, air flow rate and water flow pattern were defined and studied for optimization. The assessment and comparison of the performance of precooling systems was achieved by determining the effect of these parameters on half cooling time and quality of the produce during storage for 7 and 21 days at 1°C and 90-95% RH. In addition, room cooling method was also tested and compared to the three precooling systems. The use of three sweet corn cultivars was important to compare their quality response to different cooling methods. / Experiments were performed on a lab-scale vacuum cooler and modified forced-air and water cooler systems. The results showed that changing the cob orientation perpendicular to the direction of flow medium, using higher air flow rate in forced-air cooling and immersed water flow pattern in water cooling, can significantly reduce the half cooling time of the produce. Finally, the best method to be recommended for precooling sweet corn is by using hydrocooling which results in superior quality produce and minimum time.

The market life of many fruits and vegetables can be extended through storage at low temperatures. Chilling injury (CI) is a major postharvest storage problem for tropical commodities. Storing these products at temperatures below their critical temperature may result in severe physiological disorders known as CI symptoms. Mangoes (Mangifera indica. L) are susceptible to CI when stored below 12 °C. Visual CI symptoms include uneven ripening, surface pitting, discoloration, shriveling and scalding. Research has been conducted to overcome these serious problems using various postharvest treatments such as hot water, methyl jasmonate (MJ) or diphenylamine (DPA) with some reduction of the incidence of CI symptoms in fruits and vegetables. / Experiments were performed to assess and compare the potential of the above-mentioned postharvest treatments to reduce the CI symptoms on mango cv. Kent. The obtained results indicated that MJ- and DPA-treatments gave significantly greater percentage of marketable fruits. / Experiments were also conducted with mangoes cv. Tommy Atkins treated with MJ and DPA before storing at low temperatures (1, 4, 7 and 10°C). The chemical treatments were successful at reducing CI symptoms of mangoes. Fruit decay was reduced during subsequent ripening. MJ-treated fruits had lower mass loss and higher total soluble solids (TSS) than the control treatment. The overall quality of MJ- and DPA-treated fruits was good with lower surface pitting and scalding compared with the control treatment. The best results were obtained at storage temperatures of 7 and 10°C. Both MJ and DPA postharvest treatments can reduce CI symptoms in mangoes cvs. Kent and Tommy Atkins when the mangoes are stored at below critical temperature.

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Dissertation (PhD (Agric))--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Leaf blackening is a particular problem limiting vase life and marketability of Protea cut flowers. This research investigated suppression of Protea leaf blackening with a specific focus on Protea cv. Sylvia (P. eximia x P. susannae) cut flowers. Leaf blackening decreased significantly with decreasing storage temperatures m 'Sylvia' proteas and this was attributed to lower respiration rate and conservation of carbohydrate. Low storage temperatures were beneficial in short term handling procedures encountered during airfreight. However, use of low temperatures alone during the longer sea freight period was unsatisfactory in either maintaining or extending 'Sylvia' protea vase life. Cooling of 'Sylvia' proteas under vacuum significantly suppressed leaf blackening and was of greater benefit than forced air cooling. Although removal of the uppermost leaves delayed leaf blackening in short term storage no significant benefit was found for longer storage periods. Girdling directly beneath the 'Sylvia' protea flowerhead significantly reduced leaf blackening and in combination with low storage temperatures (O°C) enabled a significant extension in both storage and vase life of 'Sylvia' proteas. 'Sylvia' proteas did not exhibit a climacteric respiration peak during 96 h storage at O°C. Exposure to ethylene did not increase Protea leaf blackening or have a detrimental effect on vase life of either proteas or pincushions evaluated. No beneficial response to sucrose supplementation was found in 'Sylvia' proteas. Analysis of the sugar content of both flowerhead and leaves indicated that glucose supplementation might be of benefit and was investigated. Holding solutions of 2.5 % glucose significantly extended vase life due to a significant reduction in leaf blackening. Vase life was terminated due to flowerhead collapse instead of leaf blackening for the first time in 'Sylvia' protea cut flowers. Vase life was significantly extended by 2:3% glucose pulse solutions and leaf blackening significantly suppressed with increasing glucose pulse concentration. Solution uptake was facilitated by use of high intensity PAR lights in the early morning and was attributed to increased stomata opening and a consequent increase in both transpiration and glucose solution uptake. The faster uptake of glucose solutions in shoots harvested in the afternoon was attributed to higher shoot temperatures and consequent transpiration rate to those harvested in the morning. There was a significant reduction in uptake time with increasing pulse temperature, which enabled vacuum cooling to be performed earlier further benefiting storage and vase life extension. Enclosure of 'Sylvia' proteas in polyethylene (PE) lined cartons did suppress leaf blackening in non-pulsed shoots. However, this had no practical significance on useful vase life, which was terminated at this point due to excessive leaf blackening. Water loss appears to have a minimal influence on 'Sylvia' protea leaf blackening. Shading at four and three weeks prior to harvest coincided with a period of significant flowerhead dry mass increase. It is thought that shading at this point, concurrent with an increased carbohydrate demand by the developing flower head resulted in a temporary limitation in carbohydrate supply resulting in the appearance of preharvest leaf blackening. It would appear that proteas do not store large quantities of carbohydrate. Although accentuating winter light conditions by shading did result in a decrease in carbohydrate content the fact that carbohydrate content was already low precluded shading from having a significant impact on postharvest leaf blackening. The finding that glucose was beneficial in extension of both storage and vase life of 'Sylvia' proteas directed research into its use for other Protea and Leucospermum cut flowers. Significant differences in the response to glucose supplementation were found in both Protea and Leucospermum (pincushions). The significant difference in sensitivity to glucose concentration in 'Pink Ice' proteas (phytotoxic at 2:4%) and 'Susara' proteas (no apparent toxicity), in conjunction with a lack of response in 'Cardinal' proteas, a hybrid from the same parents as 'Sylvia' indicates the need to direct future research to individual cultivars. Glucose supplementation had no beneficial effect on vase life of 'Scarlet Ribbon' and 'Tango' pincushions, whilst significantly extending vase life of 'Cordi', 'Gold Dust', 'High Gold' and 'Succession' pincushions. / AFRIKAANSE OPSOMMING: Blaarverswarting is 'n spesifieke probleem wat die vaasleeftyd en die bemarkbaarheid van Protea snyblomme beperk. In hierdie navorsing is ondersoek ingestel na die onderdrukking van Protea blaarverswarting met spesifieke fokus op die snyblomme van die kv. Sylvia (P. eximia x P. susannae). Die voorkoms van blaarverswarting by 'Sylvia' het merkbaar afgeneem tydens die verlaging van bergingstemperature. Hierdie afname is toegeskryf aan 'n laer respirasietempo en die behoud van koolhidrate. Lae bergingstemperature in die korttermyn hantering van die produk tydens lugvrag was voordelig. Die gebruik van lae temperature, slegs tydens die langer verskeepingsperiode, was egter onbevredigend vir vaasleeftyd verlenging en onderhoud van 'Sylvia' protea. Die afkoeling van 'Sylvia' proteas onder vakuum het blaarverswarting in 'n groot mate onderdruk en het beter resultate gelewer as geforseerde lugverkoeling. Alhoewel die verwydering van die heel boonste blare blaarverswarting by korttermynopberging vertraag het, het dit geen merkbare voordele vir langer bergingsperiodes ingehou nie. Ringelering direk onder die blomkop van die 'Sylvia' protea het blaarverswarting aansienlik verminder, en saam met lae bergingstemperature (O°C) het dit 'n merkbare verlenging in beide die bergingstyd en die vaasleeftyd van 'Sylvia' proteas teweeggebring. 'Sylvia' proteas het geen klimakteriese respirasiekruin tydens 'n bergingsperiode van 96 uur teen O°C getoon nie. Blootstelling aan etileen het nie die Protea blaarverswarting laat toeneem of 'n nadelige effek op die vaasleeftyd van die proteas of speldekussings wat geevalueer is, gehad nie. Geen voordelige reaksie op sukrose-byvoeging is in 'Sylvia' proteas gevind nie. 'n Analise van die suikerinhoud van beide die blomkoppe en die blare het aangetoon dat 'n glukose-byvoeging moontlik voordelig kon wees, en hierdie aspek is ondersoek. Met stooroplossings van 2,5 % glukose is die vaasleeftyd aansienlik verleng omdat daar 'n merkbare afname in blaarverswarting was. Vir die eerste keer in die geval van die 'Sylvia' protea, het die vaasleeftyd van die snyblomrne tot 'n einde gekom omdat die blornkoppe uitmekaar gebreek het en nie omdat blaarverswarting ingetree het nie. Die vaasleeftyd is aansienlik verleng met ~ 3% glukose-pulsoplossings, en blaarverswarting is merkbaar onderdruk met die verhoging van hierdie oplossings se glukosekonsentrasie. Die opname van die oplossings is gefasiliteer deur hoe intensiteit PAR (fotosinteties-aktiewe radiasie) ligte vroeg in die oggend, en is toegeskryf daaraan dat meer huidmondjies oopgegaan het. Dit het gelei tot 'n toename in transpirasie en 'n toename in die opname van die glukose-oplossing. Die feit dat glukose-oplossings vinniger opgeneem is deur lote wat in die middag geoes is, is toegeskryf daaraan dat loottemperature dan hoer is as soggens en gevolglik lei tot 'n vinniger transpirasietempo. Daar was 'n merkbare afname in die opnametyd wanneer die temperatuur van die pulsoplossings verhoog is. Vakuumafkoeling kon dus vroeer toegepas word, wat 'n verlenging in bergingstyd en vaasleeftyd tot gevolg gehad het. Verpakking van 'Sylvia' proteas in kartonne wat met poli-etileen uitgevoer is, het blaarverswarting van lote wat nie aan pulsering onderwerp is nie, onderdruk. Hierdie maatreel het egter geen praktiese waarde met betrekking tot vaasleeftyd nie; die vaasleeftyd het tot 'n einde gekom as gevolg van omvangryke blaarverswarting. Dit lyk asof waterverlies weinig invloed het op die blaarverswarting van' Sylvia' proteas. Die vermoede bestaan dat lae koolhidraatvlakke proteas ontvanklik maak vir blaarverswarting. Alhoewel die beklemtoning van winterligtoestande deur beskaduwing gelei het tot 'n afname in koolhidraatinhoud, was hierdie inhoud reeds laag en blaarverswarting na die oes is nie beinvloed nie. Beskaduwing tydens die vier en drie weke voor oestyd het saamgeval met 'n tydperk van aansienlike toename in die droe massa van die blomkop. Die vermoede bestaan dat beskaduwing tydens hierdie fase, saam met die toename in die ontwikkelende blomkop se behoefte aan koolhidrate, aanleiding gegee het tot 'n tydelike beperking in koolhidraatvoorraad wat die voorkoms van blaarverswarting voor die oes tot gevolg gehad het. Die bevinding dat glukose voordelig is vir die verlenging van beide die bergingstyd en die vaasleeftyd van 'Sylvia' proteas het die navorsing gerig om ook ondersoek in te stel na die gebruik daarvan vir ander Protea en Leucospermum snyblomme. Merkbare veranderinge is gevind in die reaksie op glukosebyvoegings in beide Protea en Leucospermum (speldekussings). Die opmerklike verskil in sensitiwiteit vir glukosekonsentrasie in 'Pink Ice' proteas (fitotoksies by ~ 4%) en 'Susara' proteas (geen klaarblyklike toksisiteit), saam met 'n gebrek aan reaksie by 'Cardinal' proteas, 'n hibried van dieselfde ouers as 'Sylvia', dui aan dat verdere navorsing op individuele kultivars toegespits sal rnoet word. Glukosebyvoegings het geen voordelige uitwerking op die vaasleeftyd van 'Scarlet Ribbon' en 'Tango' speldekussings gehad nie, terwyl dit die vaasleeftyd van 'Cordi', 'Gold Dust', 'High Gold' en 'Succession' speldekussingkultivars merkbaar verIeng het.

The influence of uniformity of heat transfer with respect to the effect of heat treatment was investigated by correlating engineering parameters with the quantified heat treatment effects. Differences in treatment effect in terms of quality, anti-pathogen and chilling injury (CI) control properties among commodities was studied by exposing them to different target temperatures. Similar effects were also evaluated and quantified within an individual commodity by a custom-designed device. This device, whose design parameters were based on a heat transfer simulation, insured that one hemisphere of a tomato was exposed to air at 39°C and 0.24 m s-1; while the other hemisphere was exposed to air at a lower temperature with a velocity of0.24 m s-1 or 0.12 m s-1. / Single-temperature heat treatment was most effective in limiting pathogen development and varied according to the parameter measured: 38°C for hypersensitive response (HR), 36°C for tissue breakdown, 36°C, 38°C or 39°C for mycelium abundance, and 38°C or 39°C for lesion size. Bilateral differences in temperature across the fruit significantly affected disease control: decreasing temperature differences significantly improved the uniformity of disease control. / Some of the effects of heat treatment on tomato quality, such as color development and resistance to CI, appear to be localized. A significant difference in redness was identified between heated parts and unheated parts of tomato fruits immediately after treatment; and the differences persisted during storage. Differences in lightness and chroma were noted on day 4. Delay in ripening caused by heat treatment was confirmed through the higher TA and TSS values of heated tomatoes or heated portion of partially heated tomatoes. / The heated parts of tomatoes showed a stronger resistance to chilling injury. The effective temperature control range for CI was wide, but temperatures higher than 39.5°C for 23 h hot air treatment could lead to adverse effects. / Differences in physiological effects between hemispheres in two chambers was reduced by directly decreasing the temperature difference between upper and lower chambers or relatively increasing the heating air flow rate, highlighting the importance of improving the uniformity of air flow around each individual treated fruit.

Post-harvest cane deterioration in the South African sugar industry results in significant revenue loss that is estimated to be in the region of ZAR 60 million per annum. Despite these large losses, precise biological data relating to the process of cane deterioration under South African conditions is limited. Severity of deterioration is influenced by a number of factors, including the length of the harvest-to-crush delay (HTCD), ambient temperature and harvesting practices. For example, burning of cane prior to harvest may result in rind splitting, which provides entry for microbes, particularly Leuconostoc mesenteroides that may exacerbate deterioration. The effect of these factors on deterioration was examined by quantifying the biochemical and microbiological changes that occur in sugarcane stalks after harvest, with the influence of length of HTCD, degree of L. mesenteroides infection and ambient temperature receiving attention. The primary novelty of the work resides in the analysis of deterioration under tightly regulated temperatures, which were designed to reflect diurnal variations typically experienced during summer and winter in the South African sugar belt. In addition, inoculation of mature internodes with a consistent titre of L. mesenteroides was used as a means to mimic a consistent level of infection of harvested stalks by the bacterium. Metabolites selected for analysis were those both native to the stalk and produced as by-products of microbial metabolism, viz. sucrose, glucose, fructose, ethanol, lactic acid, dextran and mannitol. Simulated HTCDs under summer temperatures resulted in increasing glucose and fructose levels with time, which contrasted to the approximately constant levels of these hexose sugars under winter conditions. Commonly referred to as ‘purity’ in an industrial context, precise determination of the concentration of these hexoses in cane consignments could potentially indicate the extent of deterioration. Despite the detection of a basal concentration of lactic acid in unspoiled cane, the observed increase in concentration of this organic acid over the simulated summer HTCD suggests that this metabolite could also potentially serve as an indicator for postharvest deterioration. In contrast, the investigation indicated that ethanol was an unsuitable biochemical marker for deterioration of L. mesenteroides infected cane. An inability to detect dextran and mannitol in the samples, combined with consistent sucrose levels and variable mill room data, suggest that extreme proliferation of L. mesenteroides is facilitated primarily by in-field practices, particularly the manner in which cane is prepared prior to harvest and transport to the mill. Bacterial proliferation and infection by L. mesenteroides of inoculated stalks were monitored by standard selective culturing techniques. Despite the limited detection of L. mesenteroides-associated metabolites, culture-based analyses revealed that the bacterium was the dominant bacterial species within the samples. A number of other bacterial species were isolated and identified, however the extent to which the total number of microorganisms proliferated was limited to a maximum of 1 x 105 colony forming units per gram of fresh tissue. In conjunction with these analyses, a molecular approach known as Polymerase Chain Reaction-Mediated Denaturing Gradient Gel Electrophoresis (PCR-DGGE) was undertaken to investigate the bacterial diversity patterns associated with deteriorating sugarcane stalks throughout the delay period. In contrast to the results obtained by means of the culture-based assays, PCR-DGGE revealed that L. mesenteroides was not the dominant bacterial population, and showed that the level of bacterial diversity was relatively consistent across the differing treatments and with time. The use of complimentary culture-dependent and cultureindependent analyses thus permitted the detection of this discrepancy and indicated the utility of PCR-DGGE in the determination of bacterial community structure of postharvest sugarcane tissue. The biology of post-harvest deterioration of green sugarcane stalks is highly complex, even under rigorously controlled temperature and infection regimens. The results of this study emphasize the important effects that harvest method and environmental conditions have on post-harvest sugarcane deterioration. Towards the formulation of industry-relevant recommendations for combating post-harvest deterioration, future work will strive to mimic the effects that harsh harvesting and transport practices have on the severity of the problem. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.