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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Analysis of transgenic tomato plants with acc oxidase suppressed by sense constructs

Alphuche-Solis, Angel Gabriel January 1999 (has links)
No description available.
12

Shelf-life: designing and analysing stability trials

Kiermeier, Andreas January 2003 (has links)
All pharmaceutical products are required by law to display an expiry date on the packaging. The period between the date of manufacture and expiry date is known as the label shelf-life. The label shelf-life indicates the period of time during which the consumer can expect the product to be safe and effective. Methods for determining the label shelf-life from stability data are discussed in the guidelines on the evaluation of stability data issued by the International Conference for Harmonization. These methods are limited to data that can be analysed using linear model methods. Furthermore, in the situation where a number of batches are used to determine a label shelf-life, the current regulatory method (unintentionally) penalizes good statistical design. In addition, the label shelf-life obtained this way may not be a reliable guide to the properties of future batches produced under similar conditions. In this thesis it is shown that the current definition of the label shelf-life may not provide the consumer with the desired level of confidence that the product is safe and effective. This is especially the case when the manufacturer has performed a well designed stability study with many assays. Consequently, a new definition for the label shelf-life is proposed, such that the consumer can be confident that a certain percentage of the product will meet the specification by the expiry date. Several methods for obtaining such a label shelf-life under linear model and generalized linear model assumptions are proposed and evaluated using simulation studies. The new definition of label shelf-life is extended to allow a label shelf-life to be obtained from stability studies that make use of many batches, such that a proportion of product over all batches can be assured to meet specifications by the expiry date. Several methods for estimating the label shelf-life in the multi-batch case are proposed and evaluated with the help of simulation studies. / Thesis (Ph.D.)--School of Agriculture and Wine, 2003.
13

Evaluation of Shelf-Life Improvements of Wet Pack Clingstone Peaches Designed for Military Operation Rations by Addition of Calcium Salts

Morse, Lee Charles 01 August 2011 (has links)
When available, wet pack peaches are produced by repackaging sliced and/or diced canned clingstone peaches into a 5-ounce MRE pouch, followed by a thermal process. In this study, wet pack diced peaches were processed in 5-ounce pouches using canned, fresh, and frozen peaches as the raw material. Calcium chloride was added at 0.0 or 0.5% (w/w) to the pouches. The pouches were then stored at 37°C for six months or 50°C for six weeks. The peaches were evaluated for texture, drained weight, pH, brix and sensory evaluations.The canned peaches were not significantly different from wet pack peaches processed using frozen and fresh peaches for overall liking when stored at 37°C for six months. Based on the inability of panelists to differentiate between peach types for overall liking, this study suggests that producers should continue to use canned clingstone peaches as the peach source for wet pack peaches.When calcium chloride was applied to wet pack peaches before thermal processing at 0.5% w/w, a significant increase was seen in the firmness of wet pack peaches after processing. Peaches treated with calcium chloride did not lose firmness as quickly when stored at 50°C for six weeks, but showed no difference in firmness loss rates when stored at 37°C for six months. Sensory analysis of the samples stored at 37°C for six months showed an improvement in firmness scores but a drastic decline in overall acceptance due to the impact of flavor scores.viMultiple levels of calcium chloride showed increased firming effects as the percentage of calcium chloride increased, with negative effects on flavor as the percentage increased. Flavor was not significantly affected by calcium chloride at 0.125% in sensory analysis. This study concludes that to optimize flavor and firmness of wet pack peaches, calcium chloride should only be added at a level up to 0.125%(w/w) that will result in a final pH ≥3.85.
14

Coating of pears (Var. ‘Packhams Triumph’) with kafirin protein and its effect on postharvest physiology and shelf-life

Buchner, Sonya 24 February 2012 (has links)
In order to reduce postharvest losses of exported Pome fruit and increase export revenue, export quality pears require a reduction in stem-end shrivelling and an extension in shelf-life, regardless of the presence or absence of refrigerated storage. A kafirin coating may fulfil these requirements during export and at the export destination, in retail and at fresh fruit markets. A two-phased approach was followed. During Phase 1, the physiological and biochemical behaviour of ’Packham’s Triumph’ pears were studied under ideal refrigerated (-0.5°C), temperature-abused (10°C) and typical ripening (20°C) conditions. These storage conditions were selected to simulate potential conditions during the export process. Phase 2 involved the development and application of a kafirin-based coating to increase the shelf-life of pears. In Phase 1, two experiments were conducted concurrently on freshly harvested, uncoated pears. In Experiment 1, pears were stored at –0.5, 10 and 20°C and 95 to 98% RH for 42, 42 and 21 d respectively. An increase in storage temperature increased the metabolic activity of the pears and the rate of quality deterioration. Very few quality changes occurred in pears during storage at -0.5°C. Pears stored at 20°C ripened and became senescent in approximately half the time taken by pears at 10°C. However, fully ripe ‘Packham’s’ pears from 10 and 20°C exhibited similar final colour and firmness values. Stem-end shrivelling was exacerbated by storage at 20°C after only 4 days but not observed during storage at -0.5 or 10°C. In Experiment 2, ‘Packham’s Triumph’ pears were stored at -0.5 and 10°C (95 to 98% RH) for 42 and 35 days, respectively before being ripened at 20°C for 7 days. Storage of pears at 10°C prior to ripening accelerated softening and yellowing in the pears, when compared to pears from -0.5°C storage. Storage duration prior to ripening at 20°C also resulted in pears of increasing softness and yellowness by the end of 7 days at 20°C. The effect of storage duration at -0.5°C was less severe on the ripening rate and intensity of softening and yellowing than storage at 10°C. Thus, storage at -0.5°C extended pear shelf-life and resulted in pears of better quality after ripening than storage of pears at 10°C. In Phase 2, pears from Controlled Atmosphere (CA) storage were coated with a kafirin-based coating and stored at 20°C (35 to 45% RH) for 24 days. The ripening rate and the physiological behaviour and physico-chemical changes of pears used in Phase 2 were probably accelerated by 18 weeks under CA conditions and one week under RA conditions prior to the start of the shelf-life study. The kafirin coating did not retard ripening, which was probably already induced during storage before coating, but senescence in the coated pears was delayed by approximately 6 days. The rate of respiration, ethylene production, flesh softening and especially yellowing, was delayed by the coating. Coated and uncoated pears exhibited no growth of coliforms or lactic acid bacteria. Overall, coated pears had lower levels of aerobic mesophiles and yeast and mould growth than uncoated pears. Unfortunately, pear surface-shrivelling was intensified by the coating, probably due to the dehydrating action of the ethanol in the coating solution during dipping. However, the kafirin coating was able to extend pear shelf-life by delaying senescence and microbiological growth. The coating formulation may require a higher concentration of kafirin to increase its hydrophobicity and reduce pear shrivelling. The kafirin coating has possible potential to markedly extend the quality and shelf-life of ‘Packham’s Triumph’ pears, provided that the pears are coated after minimal RA storage when pears are in the pre-climacteric phase. Copyright 2007, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Buchner, S 2007, Coating of pears (Var. ‘Packhams Triumph’) with kafirin protein and its effect on postharvest physiology and shelf-life, MSc(Agric) dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-02242012-113144/ > E549/gm / Dissertation (MSc(Agric))--University of Pretoria, 2012. / Food Science / unrestricted
15

Migration of <I>Penicillium spinulosum</I> from Paperboard Packaging to Extended Shelf Life Milk

Sammons, Laura Dawn 21 October 1999 (has links)
The growth and survival of the psychrotroph Penicillium spinulosum in paperboard was studied along with the wicking characteristics of ultra-pasteurized milk to understand sporadic fungal contamination of ultra-pasteurized, extended shelf life milk products. Previous research has indicated paperboard packaging as a potential source for the fungal contamination. Migration from paperboard to ultra-pasteurized skim milk during a 60-day shelf life, was investigated by inoculating condia (spores) into sterilized paperboard squares (57.2 by 57.2 mm) made from ultra-pasteurized milk cartons. Test-squares were sealed on three sides and inoculated at 3.2, 6.4, 9.5 and 12.7 mm from the uncoated (unskived) edge. The surrounding milk was tested for the presence of the fungus. Penicillium spinulosum was detected in 84% of samples at 3.2, 72% at 6.4, 50% at 9.5, and 28% at 12.7 mm from the uncoated edge. Survival in paperboard was investigated in sealed paperboard test-squares incubated in ultra-pasteurized skim milk at 7&#176;C every 10 days up to 60 days. Penicillium spinulosum survived in the interior of paperboard for the entire incubation period. Survival was also measured on all test-squares for which P. spinulosum was not detected in the surrounding milk in the migration study. Penicillium spinulosum was detected in 94.4% of all negative samples. The wicking characteristics of ultra-pasteurized skim and whole milk were measured in four boards from gable-top cartons for ultra-pasteurized milk products. Test-squares were sealed on 3 sides and incubated in ultra-pasteurized skim or whole milk at 7&#176;C. Wicking distances were measured every 10 days up to 60 days. A significant interaction was seen between the types of paperboard and milk. It is most likely that P. spinulosum at all inoculation distances had access to milk as a source of nutrition by day 40 in the migration study. / Master of Science
16

Extending Saleable Shelf Life Of Selected Perishable Specialty Crops

Al-badri, Samir B.Salman 01 May 2019 (has links) (PDF)
Farmers are limited in the amount of specialty crops they can plant, harvest and market without adequate cooling to preserve commodities before sale. A cooler available at a farm would allow the farmer to harvest his produce earlier and take it to market at a later time. Cooling available on the farm will help a farmer to harvest commodities during peak harvest times and store it for future sale at multiple farmers markets or over a period of a week or more at a farm market. A cooler will give a farmer more logistical options. An indirect-direct evaporative pad cooling can provide cooling with high humidity which is sufficient to prolong shelf life. A cool room with window air conditioning (AC) was modified by adding indirect-direct evaporative cooling. The cool room was used for comparative study of produce shelf life under AC (with CoolBot), indirect-direct evaporative cooling (EC), residential AC (RES), and farm building (FB) storage. Results showed that FB had a lower shelf life because of non-conditioned space. RES was a table in an office building with a temperature of about 22°C. For produce with medium temperature requirements such as tomato, cucumber, and green pepper the shelf life was prolonged more in the cooler room. Strawberry and blueberry had a much longer shelf life in a cooler. The shelf life of the blueberry stored at Cooler AC was longer about two and a half fold longer than Cooler EC and RES, and five and half fold longer than FB. The shelf life of the strawberry in Cooler AC was longer one-fold than Cooler EC, two and a half fold longer than RES, and five-fold longer than FB. The shelf life of green pepper stored in Cooler AC was longer fivefold than Cooler EC and nine and a half fold longer than RES and FB. The shelf life of cucumber stored at Cooler AC was longer two fold than Cooler EC and 3.3-fold longer than RES and four fold longer than FB. The shelf life of tomato stored at Cooler AC was longer 1.25-fold than Cooler EC, 1.75 fold longer than RES and two and a half fold longer than FB. Generally stored fruits and vegetables in Cooler AC was maintained quality with minimal weight loss that allows a farmer to store their produce while maintaining shelf life. Cooler EC can be used to store produce for a shorter time with higher weight loss. Finally, FB had a shorter shelf life due to the non-conditioned space.
17

Harvest aids for improved bermudagrass sod shelf-life and transplantation success

Minaev, Nikolay 07 August 2020 (has links)
Shelf-life and transplantation success of sodded and sprigged turfgrasses are negatively affected by disruptive harvest techniques and post-harvest handling/storage conditions. Air and light are limited inside of stacked pallets of sod or masses of sprigs/plugs, which triggers multiple processes that may lead to poor transplant success. Current research looks at the effects of several commercially available turfgrass products and cultural practices on post-harvest bermudagrass storage, its grow-in after transplantation, and harvested area recovery. Ensilation and internal heating sometimes observed in stored, full-sized pallets of sod were difficult to simulate in small-size sod masses. When storage environment and post-harvest conditions were controlled, refrigeration of stored bermudagrass slowed establishment, which is contrary to common knowledge and industry practice. Fluxapyroxad + pyraclostrobin fungicide positively affected turfgrass grow-in during field and greenhouse experiments, and in some instances hastened growth and recovery of bermudagrass.
18

Estudo da viabilidade de tratamentos termicos alternativos para leite pasteurizado e de vida de prateleira estendida / Study of viability of alternatives thermic treatments for pasteurized and extend shelf life milk

Busani, Silvia Fátima Borges, 1954- 28 September 2005 (has links)
Orientador: Salvador Massaguer Roig / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-05T11:20:00Z (GMT). No. of bitstreams: 1 Busani_SilviaFatimaBorges_D.PDF: 12953590 bytes, checksum: f4928b1a7cba5073da7384ea057dda79 (MD5) Previous issue date: 2005 / Doutorado / Doutor em Tecnologia de Alimentos
19

Development and change that occurs in table grape berry composition during growth

Sonnekus, Nastassja 03 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Grape quality is important for the producer, exporter and the consumer. Consumers judge table grapes according to their size, colour, taste and shelf life. The consumer’s prerequisites will influence the producer. Therefore, it is essential to know how the table grape berry develops so that it can be manipulated, favouring the postharvest quality and shelf life. This study was performed on Prime and Crimson Seedless, both grafted onto Ramsey, in the Paarl district of South Africa. The aim of this study was to describe and quantify table grape berry development and compositional changes taking place throughout growth and ripening. The effect of sugar:acid ratio on postharvest shelf life was also evaluated. To evaluate whether berry size influenced the measured development parameters, three berry sizes were induced for both cultivars by using plant bioregulators such as gibberellic acid (GA3) and forchlorfenuron – synthetic cytokinin (CPPU) or girdling. The following sizes were obtained for Prime: (i) small berries (<20 mm) with no treatment, which acted as the control; (ii) medium berries (20-24 mm) obtained by 15 ppm GA3 application at 8 mm berry size; (iii) large berries (>24 mm) obtained by combination of 15 ppm GA3 and 1 ppm CPPU application at 8 mm berry size. Crimson Seedless berry sizes were as follows: (i) small berries (<18 mm) with no treatment, which acted as the control; (ii) medium berries (18-22 mm) treated with 10 ppm GA3 at 7 mm berry size; (iii) large berries (>22 mm) treated with 10 ppm GA3 and vines were girdled at 7 mm berry size. To evaluate the effect of sugar:acid ratio on postharvest shelf life, grapes were stored for five weeks at -0.5 ˚C and another week at 7.5˚C. The bunches were evaluated for loose berries, browning, soft tissue breakdown, decay and berry split. The following components were analysed for both cultivars to determine changes in berry composition throughout the season: berry fresh weight, total soluble solids (TSS), glucose, fructose, titratable acidity (TA), tartaric acid, malic acid, abscisic acid (ABA) and total phenols. Total and individual anthocyanins were analysed for Crimson Seedless. Differences were obtained for the three berry sizes for both cultivars. Véraison, representing the start of ripening, started at the same time in successive seasons: 21 days after pea size berry (5 mm berry diameter) for Prime and 28 days after pea size berry (5 mm berry diameter) for Crimson Seedless. A lag stage was not observed, at seven day sampling intervals, for either of the cultivars. Components such as TSS, glucose, fructose and TA content per berry were influenced by berry size in either one or in both seasons for both cultivars. Significant changes in component concentration were detected at the start of, or around véraison. Sugar concentrations (TSS) already started to increase for both cultivars before the start of véraison. At véraison, concentrations of glucose, fructose and ABA increased while concentrations of TA, tartaric acid, malic acid and total phenols decreased. Total anthocyanins in Crimson Seedless started to increase one week after véraison commenced. The main anthocyanin found in Crimson Seedless was peonidin-3-glucoside. During ripening a 1:1 glucose:fructose ratio was detected in both cultivars. Prime tartaric:malic acid ratio was lower than Crimson Seedless tartaric:malic acid ratio in both seasons. Tartaric acid was the main organic acid found in Prime, while malic acid was the main organic acid found in Crimson Seedless. No significant differences were found in the postharvest defects between the different berry sizes. However, tendencies for differences were observed which led to the assumption that medium size berries were more prone to loose berries in both cultivars. Large berries showed a higher percentage berry split for both cultivars. Crimson Seedless second harvest date took place 24 hours after rainfall which could have very likely led to the higher percentages berry defects compared to the first season. Greater berry decay was found with later harvest dates for both cultivars. No significant differences were found for the TSS:TA ratio between the three berry sizes for both cultivars. Postharvest defects were therefore found not only to be influenced by TSS:TA ratio but rather by harvest date and packing procedures. Environmental conditions prior to harvest also had an impact on postharvest shelf life. / AFRIKAANSE OPSOMMING: Druif kwaliteit is belangrik vir die produsent, uitvoerder en verbruiker. Tafeldruiwe word gekeur deur die verbruiker volgens grootte, kleur, smaak en raklewe. Die verbruiker se voorkeure sal dus die produsent beïnvloed. Daarom is dit belangrik om te weet hoe tafeldruiwe ontwikkel ten einde korrelsamestelling te manipuleer om na-oes kwaliteit en raklewe te kan bevoordeel. Hierdie studie is uitgevoer op Prime en Crimson Seedless, beide geënt op Ramsey, in die Paarl distrik van Suid Afrika. Die doel van die studie is om vas te stel hoe korrelsamestelling gedurende groei en rypwording verander. Die effek van suiker:suurverhouding op na-oes raklewe is ook geëvalueer. Om te kan meet of korrel grootte die gemete parameter beïnvloed is drie korrelgroottes verkry vir albei kultivars deur die gebruik van plant bioreguleerders, te wete gibbereliensuur (GA3) en sintetiese sitokiniene (CPPU), of ringelering. Die volgende korrelgroottes is verkry vir Prime: (i) klein korrels (<20 mm) d.m.v. geen behandeling, geklassifiseerd as kontrole; (ii) medium korrels (20-24 mm) d.m.v. ‘n 15 dpm GA3 behandeling by 8 mm korrelgrootte; (iii) groot korrels (>24 mm) d.m.v. ‘n kombinasie van 15 dpm GA3 en 1 dpm CPPU by 8 mm korrelgrootte. Crimson Seedless korrelgroottes was soos volg: (i) klein korrels (<18 mm) d.m.v. geen behandeling, wat as kontrole gedien het; (ii) medium korrels (18-22 mm) d.m.v. ‘n 10 dpm GA3 behandeling by 7 mm korrelgrootte; (iii) groot korrels (>22 mm) d.m.v. ‘n 10 dpm GA3 behandeling en gelyktydige ringelering by 7 mm korrelgrootte. Om die effek van suiker:suur verhouding op na-oes houvermoë te kon evalueer was druiwe gestoor vir vyf weke by -0.5˚C en ‘n verdere week by 7˚C. Die trosse is geëvalueer vir loskorrels, verbruining, sagte weefsel afbreek, verval en korrelbars. Die volgende komponente is geanaliseer vir albei kultivars om veranderinge in korrelsamestelling gedurende die seisoen te bepaal: vars korrelgewig, totale oplosbare vaste stowwe (suikerinhoud), glukose, fruktose, titreerbare sure, wynsteensuur, appelsuur, absisiensuur en totale fenole. Die totale en individuele antosianiene is ook vir Crimson Seedless gemeet. Beduidende verskille tussen die drie korrelgroottes vir albei kultivars is verkry. Deurslaan, naamlik die begin van rypwording, het op dieselfde dag in opeenvolgende seisoene plaasgevind: 21 dae na ertjiekorrel grootte (5 mm korrel deursnee) vir Prime en 28 dae na ertjiekorrel grootte (5 mm korrel deursnee) vir Crimson Seedless. In teenstelling met die tipiese korrel ontwikkelingspatroon is ‘n rusfase nie waargeneem by beide kultivars nie. Komponente soos suikerinhoud, glukose, fruktose en titreerbare suur inhoud per korrel is deur korrelgrootte beïnvloed in een of albei seisoene vir beide kultivars. Suiker konsentrasie van albei kultivars het reeds voor deurslaan begin toeneem. By deurslaan het die konsentrasies van glukose, fruktose en absisiensuur inhoud toegeneem, terwyl die konsentraies van titreerbare sure, wynsteensuur, appelsuur en totale fenole gedaal het. Totale antosianiene in Crimson Seedless het ‘n week na deurslaan begin toeneem. Die hoof antosianien in Crimson Seedless is peonidien-3-glukosied. Gedurende rypwording was daar ‘n 1:1 glukose:fruktose verhouding gevind vir beide kultivars. In terme van sure is Prime se wynsteensuur:appelsuur verhouding laer as in Crimson Seedless vir albei seisoene. Wynsteensuur is die hoof organiese suur in Prime terwyl appelsuur die hoof organiese suur in Crimson Seedless is. Geen betekenisvolle verskille vir na-oes houvermoë tussen korrelgroottes is waargeneem vir beide kultivars nie. Daar was egter tendense wat aanleiding gegee het in die aanname dat medium grootte korrels geneig is tot loskorrels in albei kultivars. Groot korrels het ‘n hoër korrelbars persentasie getoon vir beide kultivars. Crimson Seedless se tweede oes het plaasgevind 24 uur na reënval, wat aanleiding gegee het tot hoër persentasies korrelbederf. Hoër persentasie korrelbederf was ook gevind met later oesdatums. Geen beduidende verskille is gevind vir suiker:suur verhouding tussen die drie korrelgroottes vir beide kultivars nie. Dus word na-oes houvermoë nie net deur suiker:suur verhouding beïnvloed nie, maar ook deur oestyd en verpakkingsprodsedures. Omgewingsomstandighede voor oes kan ook na-oes houvermoë beïnvloed.
20

Determination of the Shelf Life of Aluminum Electrolytic Capacitors.

Wynne, Edward McFaddin 05 1900 (has links)
The aluminum electrolytic capacitor is used extensively in the electric utility industry. A factor limiting the storage of spare capacitors is the integrity of the aluminum oxide dielectric, which over time breaks down contributing to a shelf life currently estimated at one nuclear power electric generating station to be approximately five years. This project examined the electrical characteristics of naturally aged capacitors of several different styles to determine if design parameters were still within limits. Additionally, the effectiveness of a technique known as “Reforming” was examined to determine its impact on those characteristics.

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