Thesis (M.App.Sc.)--University of Adelaide, Dept. of Horticulture, Viticulture and Oenology, 2005. / Includes bibliographical references. Also available in a print form.

This study was aimed at determining the expression and activity of polyphenoloxidase (PPO) during apricot fruit development together with the biochemical characteristics of the enzyme extract at different development stages. Biochemical factors considered include substrate, pH, NaCl level, inhibitor type, high temperature inactivation and sulphur dioxide level. Changes in apricot (Prunus armeniaca L., cv. 'Moorpark') polyphenoloxidase (PPO) were measured during fruit development from a few days after full bloom until over-ripe at 92 days after full bloom. Cold ground amples in McIllvaine's buffer were analysed for PO activity over a range of pH (5.0, 6.0, 6.8 and 7.2); for response to intact fruit sample pre-heating (25, 35, 45, 55 and 65 °C); for sulphite and NaCl inhibition (0.2, 0.5, 2 and 5mM) and other inhibitors (SHAM 0.2mM, cinnamic acid 2.5mM and tropolone 0.5mM). PPO activity was measured at 25°C using a Clark-type oxygen electrode with 4-methyl catechol (20mM) as substrate. As fruit ripened PPO activity increased under all conditions tested. The increase in activity was not even with fruit development. Three common peaks of PPO activity occurred at ages 22-29 days, 57 days and for fully-ripe fruit at 85-92 days. Optimum pH was found to be 6.8 with a wide range for all ages of fruit. PPO activity tended to be higher for more mature fruit at a higher pH of 7.2 to 8.0, whereas activity tended to be higher in less developed fruit at the lower pH of 6.0. Catechol and chlorogenic acid showed reduced PPO activity compared with 4-methyl catechol over all development ages, however, there was a different pattern of response. Both catechol and chlorogenic acid showed greater PPO activity in the fully mature, day 92 fruit and less in the very young day 8 fruit, relative to the control 4-methyl catechol substrate. L-DOPA, as a substrate, showed a reaction lag as previously reported, and quite depressed PPO activity with no particular variation with development age compared to the control. Pre-heating of fruit samples in air for 30 minutes resulted in increased inactivation with holding temperature (35°C - 31%, 45°C - 82%, 55°C - 97%, 65°C - 99%). Sulphite and NaCl acted as inhibitors with increasing effect as concentration increased. Added sulphite depressed PPO activity by about 30% at the level (2mM) used. This was less than the literature would suggest and it appeared that fully-ripe fruit were less inhibited than mature, non-ripe fruit. NaCl has a greater inhibitory effect on apricot PPO activity at the lower pH 5.0 tested. As NaCl added increases PPO activity decreases after an initial small rise. Again, less sensitivity to NaCl inhibition is shown by fruit of greater development age. Sensitivity to inhibition by SHAM, cinnamic acid and tropolone decreased with development age. Tropolone was the most effective inhibitor of apricot PPO. The pattern of change in PPO activity, was consistent with physiological and biochemical changes reported by other workers as fruit develop from hard, green to soft, ripe. Regarding the existence of different PPO isozymes during development, no evidence of a isozyme based differential response with age was found within the constraints of the parameters tested. / Thesis (M.App.Sc.)--School of Agriculture & Wine, 2002.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

Graduation date: 1950

Thesis (PhD (Soil Science))--University of Stellenbosch, 2005. / Approximately 45% of apricot tree plantings in South Africa are centered on Montagu, Koo and Barrydale in the Little Karoo. Below average production in this area could be ascribed to the deteriorating water quality of the Breede River and highly saline groundwater from boreholes which provide this area with irrigation water. Profit margins for farmers are such that decreased yields cannot be tolerated. Correct management of low quality water could improve production and net farm income and could decrease irrigation return flow into the river system. The objective of this work was to establish whether international water quality guidelines for apricot are applicable under a different set of climatic conditions for a locally important cultivar and to revise guidelines if necessary for the management of irrigation with saline water. A drainage lysimeter was used to evaluate the effect of saline irrigation on apricot (Prunus armeniaca cultivar Palsteyn) trees over a period of four years at Stellenbosch (S33° 55’; E18° 53’) in the Western Cape.

Thesis (MBA)--Stellenbosch University, 2002. / Some digitised pages may appear illegible due to the condition of the original hard copy / ENGLISH ABSTRACT: The Fruit Unit of Tiger Brands is annually responsible for the canning of 75 000 tons of fruit of which apricots constitutes approximately twenty percent. The canning of apricots is subject to a few unique challenges with regard to production planning. The challenges are the unpredictable fruit sizes, unpredictable fruit quality, unpredictable fruit degradation in cold storage, unknown starting date for production and the uncompromisable end of production before Christmas day. These uncertainties led to the fact that no formal production planning for apricots had been done in the previous years of operation. The primary aim of this study is to reduce the risks with regard to production, apricot size and apricot quality by effectively forecasting the expected nett result thereof. This will quantify the resultant products available to marketing personnel and give a measure to evaluate and control production performance. The problem is addressed by organising and presenting historical data such that forecasts of future outcomes would become possible. Clear trends are present on throughput and fruit degradation over time, making forecasting of these two uncertainties quite simple. The forecasting of fruit size is however more problematic, especially because of the lack of sufficient data. It was proposed that the four main fruit size categories be described by using probability distributions fitted over the actual data of the last four years. The large variation on these distributions, probably caused by the lack of sufficient data, rendered this method unsuitable. It was decided that the best estimate of the percentage of each fruit size to be expected, was the average of the derived distributions. The model constructed of the above forecasts is suitable for the estimating of the quantities of specific products that would be available as output from the production process. The model is however not suitable for the evaluation and control of production processes. It is proposed that evaluation and control of production be achieved by using control charts derived from the same historical data. The production control charts are constructed from actual, cumulative production output from the last four years. Linear regression was done on this data to establish a trend line with two sigma limits plotted on the same chart. These charts could be used effectively to monitor daily production output to establish if the commitment towards marketing would be achieved. The lack of data for analysis puts a question mark on the statistical significance of the model. The model is viewed to be a first step in the elimination of uncertainties of raw materials and production variances by making use of historical performance data. The model and control charts will become more and more statistically significant if future actual performance data is incorporated. The model could also be drastically improved if detailed agricultural models for the prediction of apricot size and quality, based on climatic and soil conditions during the growing period were available. The development of such models could be the subject of future studies. / AFRIKAANSE OPSOMMING: Die Vrugte eenheid van Tiger Brands is jaarliks verantwoordelik vir die inmaak van naastenby 75 000 ton vrugte. Appelkose maak twintig persent van hierdie volume uit. Die inmaak van appelkose is onderhewig aan unieke uitdagings ten opsigte van produksiebeplanning. Die uniekheid is gesetel in die onvoorspelbaarheid van vruggrootte, die jaarlikse verskille in vrugdegradering tydens opberging, die onvoorspelbaarheid van die begindatum van produksie en die absolute vereiste om voor Kersdag produksie te voltooi. Hierdie onvoorspelbaarhede het tot gevolg dat daar tot op hede geen formele produksiebeplanning vir appelkose gedoen is nie. Die primêre doelwit van die studie is om die risiko's ten opsigte van produksie, appelkoosgehalte en appelkoosgrootte te verminder, deur die impak daarvan vooruit te skat. Sodoende sal die produkte wat vir bemarking beskikbaar gestel behoort te word ook beter bekend en beheerbaar wees. Die probleem word aangespreek deur geskiedkundige data sodanig te verwerk en te organiseer dat vooruitskattings daarmee gedoen kan word. Baie duidelike tendense ten opsigte van deurset en vrugdegradering oor tyd is deur middel van die geskiedkundige data waarneembaar, wat vooruitskatting van die twee faktore redelik vergemaklik. Die vooruitskatting van vruggrootte bly egter problematies, veral as gevolg van die gebrekkige geskiedkundige data wat beskikbaar is. Daar is gepoog om die vier gespesifiseerde vruggrootte kategorieë deur middel van waarskynlikheidsverdelings te beskryf, maar die gebrekkige data en groot variasie van die data en verdelings maak die tegniek ongeskik. Gevolglik is daar besluit om slegs die gemiddeld van hierdie verdelings as 'n beste raming te gebruik van die verwagte hoeveelheid van elke vruggrootte. Die model wat uit bogenoemde manipulering van data afgelei word, word gereken geskik te wees vir die raming van hoeveelhede van spesifieke produkte wat vir verkope beskikbaar sal wees. Die model is egter onvoldoende vir produksiebeheer en evaluasie. Produksie evaluasie sal egter met behulp van produksiebeheer kaarte wat ook van geskiedkundige prestasie afgelei is, gedoen word. Die produksiebeheer kaarte is kumulatiewe werklike fabrieksprestasie waardeur 'n regressielyn gepas is, met twee sigma afwykingslyne weerskante van die regressielyn geplot. Hierdie kaarte sal gebruik word om daaglikse produksie prestasie te plot en te interpreteer of die kommitment teenoor bemarkingspersoneel steeds haalbaar sou wees. Die model en die produksiebeheer kaarte is afgelei van slegs vier vorige seisoene se produksiedata. Die tekort aan relevante data plaas die betekenisvolheid van die afleidings dus onder verdenking. Die model en kaarte word beskou as 'n eerste poging om die risiko van grondstof- en produksievariasies te verminder deur die vooruitskatting van die uitsette met behulp van geskiedkundige prestasie. Die model en kaarte sal met die inkorporering van toekomstige seisoenale data meer statisties beduidend word. Die model sou ook verbeter kon word deur detail landboukundige modelle wat appelkoos gehalte en grootte verbind met klimatologiese en grondkundige kondisies tydens die verbouingsproses van die vrugte. Hierdie verbetering word egter voorgestel vir 'n verdere studie onderwerp.

Many plants require exposure to low temperature for a certain period during each year. This was determined more than a century ago. Understanding this phenomenon, known as the rest period, is part of a larger problem of understanding the factors which determine the ability of an organism to grow. The property of rest is ultimately a property of the actively growing cells, rather than that of the cells involved with protection and support.

Molecules of anthocyanins and quinones possess distinctive electrophilic character, which is demonstrated by their facile reactions with nucleophiles such as sulfite, thiols, amines and water. In food systems, one of their likely targets would be nucleophilic centers in the side chains of amino acids. Our experiments revealed that on a short-term exposure (1 72 h) to free amino acids in solutions with pH < 7 glycosides of cyanidin and quinones of phenolic acids did not yield nucleophilic addition products with most of the amino acids. A notable exception was cysteine, which reacted with oxidized phenolic acids and caused anthocyanin bleaching at elevated temperature. Thermodynamic aspects of the nucleophilic addition reactions were investigated with the aid of computational chemistry. We have also found that enzymatic browning in apricot puree does not lead to trans-cis -carotene isomerization, contrary to some previous reports. Increased availability of -carotene for extraction was recorded for browned apple- and pear-apricot purees in comparison with the non-browned purees. / Food Science and Technology

No description available.

Thesis (MEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Peach and apricot shells are agricultural waste products. These waste products accumulate around canneries and food-processing plants in South Africa. No effort is being made to utilise these waste products. This study is the first part of the product development from these products i.e. peach shell activated carbon and apricot shell activated carbon. By producing activated carbon from peach and apricot shells the solid waste problem is addressed, but most of all a profit can be made. But why activated carbon? Activated carbons are unique and versatile adsorbent with a vast amount of adsorption applications. It can be produced via a simple oxidation reaction with steam and the nature of peach and apricot shells are such that it is expected that activated carbons with good adsorption properties can be produced from it. The single largest consumer of activated carbon in South Africa is the gold mining industry that uses imported coconut shell activated carbon for gold adsorption in the gold recovery process. Activated carbon is also used as water purification adsorbents. During this study activated carbons were produced in a fluidized bed reactor at various activation conditions: 700 - 900°C, 0.0425 - 0.0629 g steamlg char.min and 30 - 60 min. This was done in order to find the optimum activation conditions within the activation parameter range. The optimal activated carbons were defined as peach and apricot shell activated carbons that showed good microporous as well as mesoporous character. The optimal activated carbons produced are: peach shell activated at 875°C, 0.0533 g stearnlg char. min, 60 min and apricot shell activated carbon at 850°C, 0.0533 g steamlg char.min, 60min. The possible use of these optimal activated carbons and two other activated carbons produced (Peach shell activated carbon 900°C, 0.0425 g steamlg char. min, 60 min and apricot shell activated carbon 900°C, 0.0425 g steamlg char.min, 60min) were tested in gold recovery and water purification. The gold adsorption properties of peach and apricot shell activated carbons were found to be better than two commercial coconut shell activated carbons (Chemquest 650 and GRC 22). No definite conclusions could, however, be drawn about the replacement of coconut shell activated carbon with peach or apricot shell activated carbon, because abrasion test work and thermal regeneration of the experimental carbons still have to be performed. The experimental activated carbons displayed good phenol adsorption characteristic, although further test work is required. / AFRIKAANSE OPSOMMING: Perske- en appelkoospitte is landbouafvalprodukte. Hierdie afvalprodukte versamel rondom inmaakfabrieke en voedselververkingsaanlegte. Tans word daar geen poging in Suid-Afrika aangewend om hierdie afvalprodukte te benut nie. Hierdie studie is die eerste deel van die ontwikkeling van die produkte: Perskepitdop-geaktiveerde koolstof en appelkoospitdop-geaktiveerde koolstof. Deur geaktiveerde koolstof van die perske- en appelkoospitdoppe te maak, word nie net 'n antwoord op die vastestofafvalsprobleem gevind nie, maar daar kan ook geld gemaak word. Hoekom geaktiveerde koolstof? Aktiveerde koolstowwe is veelsydige en unieke adsorbente met 'n groot verskeidenheid adsorpsie toepassings. Dit kan vervaardig word via 'n eenvoudige oksidasie reaksie met stoom en die aard van die perske- en appelkoospitdoppe is sodanig, dat verwag kan word om geaktiveerde koolstowwe met goeie adsorpsie eienskappe daarvan te kry. Die grootste enkelverbruiker van geaktiveerde koolstof in Suid-Afrika is die goudmynbedryf, wat kokosneutdop geaktiveerde koolstof invoer om goud te herwin. Geaktiveerde koolstof word ook gebruik vir watersuiwering. Tydens hierdie studie IS geaktiveerde koolstowwe by verskillende aktiveeringskondisies in 'n gevloeïdiseerde bed vervaardig: 700 - 900oe, 0.0425 - 0.0629g stoornlg gepiroliseerde pitdoppe.min en 30 - 60 mm. Die aktiveringskondisies is gevarieer om sodoende die optimale aktiveringskondisies binne die aktiveringsparameterreeks te kry. 'n Geaktiveerde koolstof is as optimaal geklassifiseer as dit 'n goeie mikro- sowel as mesostruktuur getoon het. Die optimaal geaktiveerde koolstowwe is: geaktiveerde koolstof vervaardig van perskepitdoppe by 875°e, 0.0533 g stoornlg gepiroliseerde pitdoppe.min, 60 mm en geaktiveerde koolstof vervaardig van appelkoospitdoppe by 850oe, 0.0533 g stoornlg gepiroliseerde pitdoppe.min, 60min. Die gebruik van die twee optimale geaktiveerde koolstowwe sowel as twee ander geaktiveerde koolstowwe (perskepitdop-geaktiveerde koolstof, 900oe, 0.0425 g stoornlg gepiroliseerde pitdoppe.min, 60 min en appelkoospitdop-geaktiveerde koolstof, 850°C, 0.0533 g stoom/g gepiroliseerde pitdoppe.min, 60min) is VIr goudadsorpsie en watersuiwering ondersoek. Die goudadsorpsie eienskappe van die perske-en appelkoospitdop-geaktiveerde koolstowwe was beter as die van twee kommersiële kokosneutdop-geaktiveerde koolstowwe (Chemquest 650 and GRC 22). Daar kan egter geen definitiewe gevolgtrekkings gemaak word oor die vervanging van kokosneutdop geaktiveerde koolstowwe met dié van perske of appelkoospitdoppe nie, aangesien daar nog toetsresultate oor die slytweerstand en reaktiverings eienskappe van die eksperimentele geaktiveerde koolstowwe uitstaande is. Die eksperimentele geaktiveerde koolstowwe toon goeie adsorpie ten opsigte van fenol, maar verdere toetswerk is egter nodig.