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The physiological response of cut carnation flowers to ethanol and acetaldehyde post-harvest treatments.Podd, Lindsey Alice. 19 December 2013 (has links)
A replacement for silver thiosulphate as a commercial post-harvest treatment
needs to be found. The longevity of cut carnation flowers is extended by all
concentrations of ethanol tested. Compared to a water control, the vase-life of
ethanol-treated flowers is between 150 and 250% longer. The greatest longevity
increases are recorded with 3% ethanol. The use of ethanol as a post-harvest
treatment was tested. The longevity increase as a result of ethanol application only
occurs if the ethanol is applied as a holding solution. Pulse treatments are not
effective at delaying the senescence of the flowers. The sooner the ethanol is
applied, the greater the increase in vase life. If ethanol treatment is halted at any
point during the experiment, the longevity of the flowers is reduced. It was observed
that the longer the stems of ethanol-treated flowers, the greater the longevity
increases. The ethanol holding solution does not prevent the action of external
ethylene, thereby restricting the potential of ethanol as a commercial post-harvest treatment.
Physiologically, flowers treated with ethanol exhibit a different senescence
process to control flowers. The typical in-rolling of the petals of carnation flowers is
not seen, instead the petals appear burnt. The ovaries are also notably effected by
ethanol, being smaller and more yellow in colour. Ethanol treatment results in
longevity increases by inhibiting the formation of ethylene, the plant hormone
responsible for senescence. The concentration of the direct precursor to ethylene,
ACC, as well as the activity of the enzyme that converts ACC to ethylene, ACC oxidase, is reduced to almost zero in the tissues of treated flowers. Another physiological factor affected by ethanol treatment is the carbohydrate status of the
flowers. The normal sink activity of the ovary is inhibited by ethanol treatment.
Although the carbohydrate content of the petals is found to decrease sharply in
ethanol-treated flowers, these carbohydrates are not relocated to the ovary. The
ovary does not increase in dry matter or chlorophyll content. The carbohydrate
content decreases as a result of ethanol treatment, and when ¹⁴C sucrose was
applied to petals, no radioactivity was recovered in the ovary. The petals and ovary
are the organs most effect by ethanol activity, as when ¹⁴C ethanol was applied to
cut carnation flowers as a pulse, the majority of the radioactivity was discovered
here. The protein content of cells of both organs decreases significantly compared
to control flowers. This is a total protein loss, rather than the destruction of specific systems.
If the activity of alcohol dehydrogenase is prevented in ethanol-treated
flowers, inhibiting the conversion of ethanol to acetaldehyde, no longevity increases
are seen. The airspace surrounding treated flowers was found to contain ethanol
and small amounts of acetaldehyde. The tissues of flowers treated with ethanol
show an increase in the acetaldehyde content, as well as the ethanol content,
especially in the ovary. The application of acetaldehyde directly to cut carnation
flowers as a holding solution resulted in the vase life of the flowers increased by 150%.
To determine the effectiveness of acetaldehyde as a post-harvest treatment,
various concentrations of acetaldehyde were applied to cut carnation ftowers as a
pulse treatment and a holding solution. Pulse treatments did not increase the vase life of flowers, and resulted in a number of negative effects in the flower. A holding
solution of acetaldehyde does increase the longevity of cut carnation flowers,
provided it is above a certain concentration. Treatments at concentrations below 1%
acetaldehyde appear to promote flower senescence. The use of acetaldehyde as a
post-harvest treatment has many of the same disadvantages as ethanol treatment.
Acetaldehyde must also be applied as a holding solution for as long as possible. If
removed from this solution, death of the organ occurred quickly. Acetaldehyde is
also ineffective against external ethylene. A negative effect of acetaldehyde not
found in ethanol-treated flowers, is that the longer the stem of cut carnation flowers, the shorter the resultant vase life.
Physiologically the responses in cut carnation flowers were very similar to
those seen in ethanol-treated flowers. Acetaldehyde inhibited the formation of
ethylene completely. Almost no ACC can be found in treated tissues, and the action
of ACC oxidase is completely reduced. The petals of acetaldehyde-treated flowers
suffer from severe petal browning, rather than in rolling. The ovaries are particularly
badly effected by treatment. There are large scale losses in fresh weight and
chlorophyll content. The latter results in the ovaries appearing yellow in colour.
They also show a loss in structure. The sink activity of these ovaries is destroyed.
Like ethanol-treated flowers, the carbohydrate content of both the petals and ovaries
are dramatically reduced. When ¹⁴C sucrose was applied to one of the. petals,
almost no radioactivity was recorded in the ovary. There. is also a major loss in
general protein content, slightly more severe than in ethanol-treated flowers. The conversion of ethanol to acetaldehyde is necessary in order to achieve
longevity increases in ethanol-treated flowers. If the conversion of this acetaldehyde
to ethanol is prevented in acetaldehyde-treated flower there is once again no
longevity increase. Both ethanol and acetaldehyde are required within the system to
result in increased longevity. Although ethanol and acetaldehyde treatments result in
decreases in the total protein content of the flowers, certain enzymes remain active.
Alcohol dehydrogenase is a bi-directional enzyme, capable of converting ethanol to
acetaldehyde and then back to ethanol again. The activity of this enzyme, in both
orientations, is increased in ethanol and acetaldehyde-treated flowers. The activity
of pyruvate decarboxylase, which converts pyruvate to acetaldehyde, is also
increased as a result of both treatments. The similarities of the physiological
response of cut carnation flowers to ethanol and acetaldehyde post-harvest
treatments, and the increased activity of these enzymes, indicate that the effect of both compounds on longevity is closely linked. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2000.
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Effects of postharvest oils on arthropod pests of citrus / by Peter TavernerTaverner, Peter January 1999 (has links)
Bibliography: leaves 204-211. / v, 211 leaves : ill. (chiefly col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This study investigates the effects of a number of petroleum and vegetable oils against citrus pests. / Thesis (Ph.D.)--University of Adelaide, Dept. of Applied and Molecular Ecology, 2000
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Die invloed van verskillende SO2-behandelings by die bewaring van tafeldruiweDe Swardt, G. H. (Guillame Hartmann) 03 1900 (has links)
Thesis (MScAgric)--Stellenbosch University, 1962. / ENGLISH ABSTRACT: no abstract available / AFRIKAANSE OPSOMMING: geen opsomming
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Evaluation of temperature variances found with integral reefer containers during shipment of Japanese plums (Prunus salicina Lindl.) at dual and single temperatureKapp, Anine A. C. 03 1900 (has links)
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.
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Cold storage of Leucospermum cutflowers and Leucadendron greensGraham, Shelly 12 1900 (has links)
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.
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Non-destructive prediction and monitoring of postharvest quality of citrus fruitMagwaza, Lembe Samukelo 12 1900 (has links)
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
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Study of nanofibrous membranes for application in post harvest technologyHarmzen, Elrika 04 1900 (has links)
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.
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Sensors and Portable Instruments for Postharvest AgricultureLerud, Ryan M. 10 June 2019 (has links)
The sensing needs for the fresh produce industry can be split into two primary stages: during maturation in the field, also referred to as Precision Farming, and during storage and transport of the produce, or Postharvest Storage. This work seeks to improve the accuracy and reliability of commercially available electrochemical and spectroscopic sensors tailored to the sensing needs of the fresh produce industry. For electrochemical sensing, this study proposes the use of an inline filter to remove polar organic compounds, which can interfere with the readings of a platinum-based electrochemical sensor. A 50% improvement in measurement accuracy was achieved when monitoring the storage headspace of a container of apples. For portable spectroscopy instruments, this study suggests improvements for the alignment of the optical bench and the spectral collect protocol. Methods to reduce the influence of environmental noise, such as variability of background light (sunlight in the field) and thermal effects on hardware performance, are presented. This study also presents the first report of the calibration transfer of spectral regressions developed with Karl Norris's Derivative Quotient Method. The motivation for this aspect of research was to develop methods to collect stable and accurate data in the field, which can be used to improve the quality of fresh produce reaching the customer and reduce premature food spoilage.
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Effect of different modified atmosphere packaging on quality retention of selected traditional leafy vegetables.Mampholo, Mmakatane Bevly. January 2014 (has links)
M. Tech. Agriculture. / Aims of this study was to select a suitable modified atmosphere packaging that retained the overall quality and bioactive compounds of the traditional leafy vegetables during storage. In this study, three types of biorientated polypropylene packaging namely BOPP04, BOPP05 and BOPP06 with different perforations were tested on retention of quality parameters (weight loss, leaf yellowing, colour L*, C*, hº%x;), decay, chlorophyll a, chlorophyll b, bioactive compounds (carotenoids, ascorbic acid, total phenolic compounds), antioxidant scavenging activity, and sensory properties at 10 º%x;C at 2 day intervals up to 14 days.Films without perforation, with macro perforation and unpacked leaves were included for comparison.
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Investigation of energy savings technologies for cold rooms.Mulobe, Ngoy Jean-Claude. January 2014 (has links)
M. Tech. Engineering: Mechanical. / Determines the highest energy savings which could be achieved by using variable air ventilation (VAV) strategy in cool processing, without affecting the performance of the cold room.
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