Thesis (Ph. D.)--University of Canterbury, 2009. / Typescript (photocopy). "January 2009." Includes bibliographical references (p. 215-236). Also available via the World Wide Web.

The main purpose of this study was to improve the performance of microwave assisted drying. The osmotic treatment was used as pretreatment due to its inherent low energy requirement attributes. The vacuum was applied to microwave drying system to capture low temperature vaporization concepts. The whole process might be called "osmotically dehydrated microwave vacuum drying". Carrots and strawberries were selected to study as a representative of vegetables and fruits, respectively. / The laboratory scale microwave vacuum dryer was setup and the preliminary tests were done with carrots and strawberries. The occurrence of condensation of vapor in vacuum container was found during the drying trials. The location of the open-ended valve which controls the vacuum level was found to have an influence on the condensation. The re-location of valve which allowed air passage to the vacuum container was able to decrease the condensation. The input power for the microwave vacuum drying could not be greater than 1.5 W/g. The continuous use of input power caused the high temperature in the process. The pulse mode (on/off) was recommended for further studies. / Water removal and solid gain of osmotic treatment were considered as factors that affect the dielectric properties dielectric constant (epsilon') and the loss factor (epsilon"). The experiment was set up to investigate the influence of osmotic conditions to dielectric properties. Two osmotic agents, sucrose and salt, were used for carrots; but only sucrose was used for strawberries. The effects of variations in sucrose and salt concentrations, solution temperatures, and length of immersion time on the dielectric properties were studied. The empirical models were generated from response surface methodology (RSM) to predict epsilon' and epsilon" for the various ranges of osmotic conditions considered in this thesis. / As a consideration of the osmotic pre-drying treatment, it was considered appropriate to maximize water loss (WL) and minimize solid gain (SG). The parameter appropriate to study this situation was WL/SG. The optimum conditions of osmotic process to acquire the maximum ratio of WL/SG were investigated. The results of the optimum conditions for carrots were found to be sucrose concentration 50%(w/w), salt concentration 5%(w/w), temperature 20°C and immersion time 3 hours 38 minutes. The optimum conditions for strawberries were found to be sucrose concentration 60%(w/w), temperature 20°C and immersion time 24 hours. / The microwave vacuum drying was then studied as a technique combined with the osmotic pretreatment. The studies were performed on carrots and strawberries. The input power levels 1 and 1.5 W/g with different power modes (continuous, 45s on/15s off and 30s on/30s off) were experimentally studied with a certain condition of osmotic treatment, which was acquired from the previous study. Osmotic treatment prior to microwave vacuum of carrots showed the advantage in most cases; fast drying time, less energy consumption and superior quality aspects except the taste which was affected from the salt. The study of strawberries did not show great advantage of osmotic pretreatment. The drying time and energy consumption of the process with and without osmotic pretreatment were the same but the process with osmotic pre-treatment resulted in better quality of dried strawberries. / The microwave vacuum drying of carrots and strawberries after osmotic pretreatment did not show constant rate period in drying rate curve while the processes without osmotic treatment of strawberries showed longer constant rate period than those observed for carrot drying. According to these phenomena, thin layer models of Lewis and Henderson & Pabis were fitted to the observed data which showed excellent fit for the process without constant rate period, but Page's model was a good fit for both constant rate and falling rate period of microwave vacuum drying.

No description available.

Forecasts for the first fungicide application to manage cercospora blight of carrot (Daucus carota L. subsp. sativus (Hoffim) Arcang) caused by Cercospora carotae (Passerini) Solheim were evaluated during the summers of 1991 and 1992. In the forecast based on infection, the blight severity values (BSV) were calculated for each day using duration of leaf wetness, relative humidity and temperature. The first fungicide was applied when the cumulative blight severity value reached 14 (CBSV 14) and 18 (CBSV 18). The forecasts were compared with the 50% disease incidence threshold method where the first fungicide was applied when the middle leaf of 50% of plants was diseased, and the conventional method where the first fungicide application was made when the plant height reached 15 cm. For the threshold of CBSV 14 and CBSV 18, no loss was observed in yield and fewer fungicides were applied as compared to conventional and 50% disease incidence threshold methods. Three years of weather data from experimental plots and 155 commercial field data were used to study the behaviour of CBSV at 50% disease incidence threshold. Only in 3% of the fields, the disease incidence of 50% was observed before the CBSV reached 11. The increase from CBSV 11 to 20 was rapid. Depending on environmental conditions the first fungicide at a CBSV range of 11 to 20 is proposed rather than a critical threshold since no loss in yield was observed at 18 in the experimental plots. No fungicide is applied until the CBSV reaches 11 and the application must not be delayed after CBSV reaches 20.

Thesis (M.Sc.)--Memorial University of Newfoundland, 1997. / Bibliography: leaves 74-83.

Resumo: Com o objetivo de avaliar o crescimento e o acúmulo de macronutrientes em cenoura „Forto‟ e obter equações que melhores os representem, conduziu-se um experimento em São Gotardo (MG), de maio a setembro de 2004. As amostragens de plantas foram realizadas aos 40, 50, 60, 70, 80, 90, 100, 110 e 120 dias após a semeadura (DAS), para determinação da matéria seca e do acúmulo de macronutrientes em folhas e raiz da cenoura. Aos 40 DAS, cinco dias após ter sido realizado o desbaste, a planta de cenoura „Forto‟ apresentava 0,18 g e 0,04 g em matéria seca de folhas (MSF) e de raiz (MSR), respectivamente. A partir de então, até 88 DAS, a partição de matéria seca mostrou-se favorável na parte aérea. A MSR de cenoura foi pequena até dois terços do cultivo, ou seja, 80 DAS. A partir de então, verificou-se que a quantidade de matéria alocada nesta parte da planta teve forte incremento, ultrapassando, aos 88 DAS, a quantidade de MSF. O acúmulo de nutrientes foi pequeno até 60 DAS, coincidindo com o período de menor acúmulo de matéria seca. A ordem decrescente de macronutrientes acumulados pela cultura foi K, N, Ca, P, S e Mg, nas quantidades de 906,7; 438,0; 155,5; 87,4; 58 e 37,6 mg planta-1, respectivamente. A raiz participou com 60,5% do acúmulo de N, 86,1% de P, 58,0% de K, 25,5% de Ca, 55,6% de Mg e 65,5% de S. / Abstract: In order to quantify the growth and accumulation of macronutrients of carrot 'Forto', and obtain equations that best represent them, it was carried out experiment in the São Gotardo (MG), from May to September of 2004. Samples of plants were taken at 40, 50, 60, 70, 80, 90, 100, 110 and 120 days after sowing (DAS) to determine dry matter and accumulation of macronutrients in leaves and roots of carrot. At 40 DAS, five days after thinning, the plants had 0.18 g and 0.04 g of leaves dry mass (LDM) and root dry mass (RDM), respectively. From then, until 88 DAS, the partitioning of dry matter in the aerial part were more pronounced. The RDM was low until 80 DAS, which corresponded to two thirds of the crop cycle, from when the amount of material allocated in this part of the plant had strong growth surpassing at 88 DAS the amount of LDM. The nutrient accumulation was small until 60 DAS, coinciding with the period of lower dry matter accumulation in the plant. The order of decreasing macronutrient accumulation by the plant was K, N, Ca, P, S e Mg, in the amounts of 906.7, 438.0, 155.5, 87.4, 58.0 and 37.6 mg plant-1, respectively. The commercial root participated with 60.5% of the accumulation of N, 86.1% of P, 58.0% of K, 25.5% of Ca, 55.6% of Mg and 65.5% of S. / Mestre

No description available.

No description available.

Our objective is to study the agronomic growth characteristics of two varieties of baby carrots at three planting densities. The study site is in the area of Walipini, town of Lentanias, province of Ingavi, department of La Paz, Bolivia. In this investigation, the two varieties of baby carrots used were ‘Amsterdam Forcing 3-Minicor’ and ‘Thumbelina’ (Daucus carota var. sativus). Both varieties were planted at densities of 333 plants/m2, 166 plants/m2 and 111 plants/m2 with a planting interval of two days. Statistical differences were observed for the following variables: plant height, root length, root diameter, base diameter, leaf yield, and root yield. The density with the highest yield was 333 plants/m2 with a root yield of 32 Tm/hectare, which was higher than the amount reported by MAG/IICA of 30 Tm/hectare. Lower yields were obtained with densities of 166 and 111 plants/m2. The products and their quality at harvest were obtained in trials T1, T2 and T6. These products reached the parameters set by MAC/IICA (2003) and Pimentel (1997) for the baby carrot varieties previously mentioned. Both presented proper development in regard to root diameter, root length and root yield. After a marginal analysis looking at a minimum rate of return of 100%, I determined that trial 1 (‘Amsterdam Forcing 3-Minicor’ planted in Walipini at a density of 333.3 plants/m2) was the most economically profitable with respect to the other trials.

Plant cells resistant to specific amino acid analogs have been reported to accumulate the corresponding free amino acids. The purpose of this study was to determine the concentrations of fifteen free amino acids: alanine, valine, leucine, isoleucine, glutamate, proline, arginine, aspartate, threonine, methionine, lysine, serine, glycine, tryptophan and phenylalanine in Daucus carota cell lines, resistant either to the proline analog azetidine-2 carboxylic acid (A2C), or to the tryptophan analog 5-methyltryptophan (5-MT), or to both the analogs combined. This study also intended to determine if these analogs influence the biosynthesis of the above-mentioned fifteen amino acids in the cell line resistant to A2C and 5-MT. Carrot cell lines resistant to 5-MT, to A2C, or to both the analogs were selected by incubating carrot cells in liquid growth media containing either 0.3 mM 5-MT, or 0.5 mM A2C for 6 to 16 weeks. Free amino acid concentrations were then determined in the extracts of the cells. Resistance to 5-MT resulted in significant increases in the intracellular concentrations of tryptophan, phenylalanine, leucine, valine, isoleucine, and proline. Resistance to A2C resulted in significant increase in proline only. Resistance to both the analogs caused increases in proline, lysine, phenylalanine, and tryptophan concentrations. In the cell line resistant to both the analogs, the treatment with 5-MT caused increases in leucine, proline, aspartate, threonine, lysine, and tryptophan. The treatment with A2C caused increases in isoleucine, arginine, threonine, methionine, lysine, and glycine, whereas treatment with both the analogs caused increases in threonine, lysine, phenylalanine, and tryptophan. These results indicate the possibility of a common biosynthetic control of a number of amino acids in carrot cells, resembling that found in microorganisms. It is also evident from the results that the analogs play an active role in the biosynthesis of amino acids in the resistant cell lines.