• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 63
  • 35
  • 9
  • 8
  • 3
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 132
  • 132
  • 20
  • 19
  • 18
  • 15
  • 15
  • 15
  • 14
  • 14
  • 14
  • 13
  • 13
  • 12
  • 12
  • 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.
21

Physiology of Chilling-Related Postharvest Rind Breakdown of Navel Oranges (Citrus Sinensis (L.) Osbeck)

Lindhout, Katina, Lynette.Brown@latrobe.edu.au January 2007 (has links)
Chilling-related postharvest rind breakdown of navel oranges is a significant economic problem worldwide. Chilling injury (CI) symptoms on navel orange fruit vary, and descriptive classification is generally ad hoc, making inter-study comparisons difficult. In this study, external symptoms of CI were related to patterns of cellular collapse in affected flavedo tissue, and a classification system developed to aid consistent symptom identification and improve communication within the supply chain. Potential markers of senescence were evaluated because older fruit were found to be more susceptible to CI. Electrolyte leakage, moisture content and protein content of flavedo tissue were ineffective indicators of both senescence and chilling stress. Rind colour and internal maturity were generally good indicators of fruit age, but lacked sensitivity over short time periods to be of use. Although there was a strong seasonal effect on CI incidence, pre-storage treatments, including hot water and methyl jasmonate, generally reduced the incidence of CI. Because these treatments elicit defence responses that protect tissue from chilling stress, the response and efficiency of plant defence systems is probably an important factor in chilling tolerance. The concentration of lipid hydroperoxides (LOOH) in flavedo tissue was lower in fruit that were stored at a chilling temperature (1�C) compared to fruit that were stored at a non-chilling temperature (12�C) and lipid peroxidation did not increase during storage at 1�C. There was also a lower concentration of LOOH in the chilling sensitive variety than in the chilling tolerant variety. Therefore, increased lipid peroxidation is not related to chilling stress and subsequent injury but the results do suggest a role for LOOH in stress signalling. Antioxidant activity in the lipophilic fraction of flavedo tissue extracts increased as fruit senesced and was strongly correlated with carotenoid content. LOOH concentrations in flavedo tissue also increased as fruit senesced. The antioxidant activity of both the lipophilic and hydrophilic fractions of flavedo tissue extracts was higher in fruit stored at 12�C than in fruit stored at 1�C.
22

A study of microbial spoilage of beef stored at chill temperatures /

Farber, Jeffrey Mark. January 1982 (has links)
Initial experiments were conducted to determine the microbial development in blocks of ground beef. In the top layers of the meat, Pseudomonas spp. predominated. Attempts were made, as well, to measure the microenvironmental changes occurring in ground beef using pH, oxygen, and redox potential micro-electrodes. / Some of the extrinsic (relative humidity, O(,2)), as well as intrinsic factors (pH, redox potential, ions, nutrients) affecting microbial development in aerobically stored meats, were examined. The decrease in glucose levels observed during the aerobic storage of longissimus dorsi (l. dorsi) muscle at 4(DEGREES)C, was accompanied by an increase in the activity of glucose dehydrogenase, and by the appearance of gluconate and 2-ketogluconate on the meat surface. / The attachment of various meat spoilage organisms to l. dorsi muscle was studied. Generally, the pseudomonads attached in higher numbers than the other bacteria, but possessed lower attachment strengths. Investigations on the attachment of two competing organisms to l. dorsi muscle demonstrated that limited competition occurs between the organisms. / A model of the microbial ecology of aerobically stored fresh beef was developed, based on existing evidence. / Various chemicals were added to minced or whole meat to evaluate their effectiveness as food preservatives. As a single compound, potassium sorbate appeared to have the greatest potential as a meat preservative. Meats > into solutions of 5.0% potassium sorbate for 1 min had their shelf-life substantially increased as compared with control samples > into water.
23

RIPENING AND POSTHARVEST MANAGEMENT OF PAWPAW FRUIT

Galli, Federica 01 January 2007 (has links)
Pawpaw (Asimina triloba (L.) Dunal) has significant potential as a new fruit crop. During ripening, loss of firmness is extremely rapid, and this trait may be the biggest obstacle to the development of a broader market as handling without injury is difficult. Cold storage of pawpaw seems limited to 4 weeks at 4 C. A study of several cultivars with commercial appeal showed that ripening traits such as ethylene production, respiration and loss of firmness were similar in all genotypes, and that no cultivar showed superior responses to cold storage. Cold storage for longer than 4 weeks caused the development of cold injury symptoms such as black discoloration, rapid loss of firmness, impaired respiration, tissue acidification, decrease in antioxidant content, decrease in volatile ester production and development of off-flavor volatile compounds. Overall cold storage injury symptoms observed in pawpaw may be due to oxidative damage linked to the failure of the two major antioxidant systems that could protect against such damage: phenolics and the ascorbateglutamate system. With the aim of enhancing pawpaw low temperature tolerance and prolonging cold storage length, different techniques such as hot air exposure and hot water dips of fruit prior to beginning cold storage, and intermittent warming periods during cold storage, were evaluated. Despite positive results with these techniques for other commodities, all the strategies failed to appreciably alter fruit ripening, loss of firmness or maintain fruit quality during and/or after cold storage.
24

Physiology of Chilling-Related Postharvest Rind Breakdown of Navel Oranges (Citrus Sinensis (L.) Osbeck)

Lindhout, Katina, Lynette.Brown@latrobe.edu.au January 2007 (has links)
Chilling-related postharvest rind breakdown of navel oranges is a significant economic problem worldwide. Chilling injury (CI) symptoms on navel orange fruit vary, and descriptive classification is generally ad hoc, making inter-study comparisons difficult. In this study, external symptoms of CI were related to patterns of cellular collapse in affected flavedo tissue, and a classification system developed to aid consistent symptom identification and improve communication within the supply chain. Potential markers of senescence were evaluated because older fruit were found to be more susceptible to CI. Electrolyte leakage, moisture content and protein content of flavedo tissue were ineffective indicators of both senescence and chilling stress. Rind colour and internal maturity were generally good indicators of fruit age, but lacked sensitivity over short time periods to be of use. Although there was a strong seasonal effect on CI incidence, pre-storage treatments, including hot water and methyl jasmonate, generally reduced the incidence of CI. Because these treatments elicit defence responses that protect tissue from chilling stress, the response and efficiency of plant defence systems is probably an important factor in chilling tolerance. The concentration of lipid hydroperoxides (LOOH) in flavedo tissue was lower in fruit that were stored at a chilling temperature (1�C) compared to fruit that were stored at a non-chilling temperature (12�C) and lipid peroxidation did not increase during storage at 1�C. There was also a lower concentration of LOOH in the chilling sensitive variety than in the chilling tolerant variety. Therefore, increased lipid peroxidation is not related to chilling stress and subsequent injury but the results do suggest a role for LOOH in stress signalling. Antioxidant activity in the lipophilic fraction of flavedo tissue extracts increased as fruit senesced and was strongly correlated with carotenoid content. LOOH concentrations in flavedo tissue also increased as fruit senesced. The antioxidant activity of both the lipophilic and hydrophilic fractions of flavedo tissue extracts was higher in fruit stored at 12�C than in fruit stored at 1�C.
25

A FORTRAN 77 simulation of a low temperature storage freezer utilizing a non-azeotropic refrigerant blend

Craddock, David M. January 1995 (has links)
Thesis (M.S.)--Ohio University, March, 1995. / Title from PDF t.p.
26

The composition and nutritive value of fish preserved by cold storage

Almy, Lloyd Huber, January 1938 (has links)
Thesis (Ph. D.)--Columbia University, 1917. / Vita. "Scomber scombrus, was chosen as an ideal fish for an investigation of this sort."--P. 6. Bibliography: p. 22-24.
27

A six-chamber medium-to-high temperature refrigeration system for laboratory purposes

Belaid, Ashur Belaid January 2017 (has links)
Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2017. / Food and water fuel and sustain life on earth. Since ancient times, their sourcing and preservation have been very important issues to humanity. In modern times, experimentation is a major step in analysing how cold storage problems in the medical and food science technology fields can be addressed. For investigating spoilage of new products and/or growth of pathogens in such cases, it is necessary to do experiments at different low temperatures for prolonged periods and check the effects. While this can be undertaken in a conventional two chambers fridge, it takes a long time to investigate a whole range of feasible storage temperatures. This dissertation describes work intended to treble the samples in such investigations and, therefore, significantly reduce the times. Six well- insulated chambers were constructed from plastic and wood and set at different temperatures. An ordinary deep freezer was used as the main heat sink for the chambers. Experiments were done with different methods to get the best result for the cold air flow into the chambers over period of eight months. The chambers temperatures were set between 0 and 15°C. It was finally established that a properly-designed six-chamber system could successfully be added to an ordinary freezer to provide different medium-to-high refrigeration temperatures without the use of a multi-pressure refrigeration cycle.
28

Mejora de la Tecnología de desverdización de cítricos y aptitud a la frigoconservación de nuevas variedades. Estudios sobre parámetros de calidad y composición nutricional

Sdiri, Sawsen 25 April 2013 (has links)
RESUMEN Los cítricos son frutos atractivos buscados por los consumidores en todo el mundo por su elevada calidad organoléptica y por los beneficios que tienen para la salud humana. Después de la cosecha, los frutos cítricos para consumo en fresco deben ser sometidos a diferentes tratamientos postcosecha antes de llegar al consumidor. El proceso de desverdizado con exposición al etileno es un tratamiento postcosecha ampliamente utilizado comercialmente para acelerar el cambio de color externo de los cítricos, dado que en las condiciones climáticas del Mediterráneo, las variedades tempranas alcanzan la madurez interna antes que la plena coloración. Sin embargo la aplicación del etileno exógeno puede inducir alteraciones fisiológicas asociadas a la senescencia de la piel y sobre todo del cáliz (ennegrecimiento y caída). Con la finalidad de minimizar estas alteraciones, uno de los objetivos de la presente Tesis fue la optimización del proceso de desverdización así como la evaluación de tratamientos previos a la aplicación del desverdizado en diferentes variedades de mandarinas y naranjas de interés comercial. La aplicación de tratamientos de desverdizado combinando periodos sin exposición al etileno exógeno con periodos con aplicación de etileno, lo que se ha denominado tratamientos combinados, redujo significativamente estas alteraciones sin afectar al cambio de color externo de los frutos. La aplicación del regulador de crecimiento HF-Calibra¿, previamente al desverdizado con etileno, disminuyó el ennegrecimiento y caída del cáliz en las variedades ensayadas, incrementándose este efecto con la dosis de aplicación. Otro objetivo de la presente Tesis fue estudiar el efecto de la aplicación de etileno exógeno, así como del tiempo de exposición al mismo, durante el proceso de desverdizado sobre los componentes bioactivos en diferentes variedades de clementina. La aplicación de etileno durante los diferentes periodos ensayados no afectó al contenido en ácido ascórbico total (TAA), ácido ascórbico (AA) y ácido dehidroascórbico (DHAA) y tampoco a la capacidad antioxidante. Además se evaluó el efecto del tratamiento de desverdizado en condiciones comerciales seguido de un tratamiento de cuarentena por frío en el contenido de vitamina C, compuestos fenólicos y capacidad antioxidante, así como en los compuestos volátiles de diferentes variedades de cítricos. El tratamiento de desverdización seguido del almacenamiento en cuarentena por frío no provocó cambios relevantes en la capacidad antioxidante determinada por DPPH y FRAP ni en el contenido del AA, TAA, DHAA, fenoles totales, flavanonas y flavonas de las variedades ensayadas. Además, estas condiciones postcosecha no afectaron los componentes aromáticos-activos. Por otra parte, la introducción de nuevas variedades de cítricos exige el estudio de su calidad fisico-química y nutricional, así como de su comportamiento durante el periodo postcosecha. Esta evaluación ha sido llevada a cabo en la presente Tesis sobre nuevas variedades triploides de mandarina de recolección tardía, obtenidas en el Departamento de Biotecnología y Protección Vegetal del Instituto Valenciano de Investigaciones Agrarias. Los resultados obtenidos mostraron que las variedades objeto de estudio presentan elevada calidad organoléptica, con altos contenidos en azúcares y ácidos orgánicos, que las hacen altamente atractivas para su consumo en fresco. Además estas variedades muestran alta calidad nutricional, por lo que pueden considerarse como una importante fuente de componentes bioactivos en la dieta humana. La condición de recolección tardía de las nuevas variedades triploides, hace necesario el estudio de su aptitud a la conservación frigorífica. Además de los cambios en la calidad interna que sufren los frutos durante la conservación a baja temperatura hay que tener en cuenta que algunas variedades de cítricos son susceptibles de presentar alteraciones denominadas daño por frío cuando son expuestas a bajas temperaturas. En la presente Tesis, frutos de las nuevas variedades triploides fueron almacenados a 1ºC, 5ºC y 9ºC durante un periodo máximo de 30 días. Todas las variedades ensayadas mantuvieron una elevada calidad interna durante el almacenamiento prolongado, por lo que ésta no resultó un factor limitante. Sin embargo algunas variedades presentaron síntomas externos de daño por frío que limitaron su conservación por lo que las condiciones de temperatura-tiempo de almacenamiento recomendadas serán diferentes en función de la variedad. / Sdiri, S. (2013). Mejora de la Tecnología de desverdización de cítricos y aptitud a la frigoconservación de nuevas variedades. Estudios sobre parámetros de calidad y composición nutricional [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/28213 / TESIS
29

The Balance of Nitric Oxide and Peroxynitrite in the Heart Suring Organ Preservation

Kozak, Allyson Jill January 2007 (has links)
No description available.
30

Effects of chemical treatment on cucumber lipids and flavor volatiles during cold storage /

Geduspan, Haydee S. (Haydee Sumagaysay) January 1984 (has links)
No description available.

Page generated in 0.1962 seconds