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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.
1

Effects of Controlled Atmosphere Storage on Specific Biochemical Changes in Apricot and Peach Fruits

Wankier, Bartley Norman 01 May 1970 (has links)
The effects of controlled atmosphere storage vs conventional refrigerated storage on the metabolism of Moorpark and Large Early Montgamet apricot and Elberta peach fruits were studied. The controlled atmospheres studied were 0.0 percent CO2-5.0 percent O2; 2.5 percent CO2-5.0 percent O2; 5.0 percent CO2-2.5 percent O2; 7.5 percent CO2-5.0 percent O2; as compared to conventional refrigerated storage. Nitrogen percent was assumed to be the difference between the total CO2 and O2 content minus 100. Fruits were periodically removed from the storage and analyzed for firmness, fleshy pericarp color, total pectins, pH, titratable acidity, total and free reducing sugars, tannins, organic acids, and amino acids. Controlled atmosphere storage had both beneficial and detrimenta1 effects on stored apricot and peach fruits. The general retardation of the respiration rate and consequent delay of the climateric rise due to controlled atmosphere are important in prolonging the storage life of the fruit. Apricot fruits stored in 2.5 to 5.0 percent CO2 and 2.5 to 5.0 percent O2 maintained superior quality for 15 to 30 days longer than did conventionally refrigerated fruit. Moorpark fruit could be stored longer than Large Early Montgamet fruit, mainly because of mesocarp browning in the latter variety of fruit. The results indicated that the storage life of Elberta peach fruits were not substantially increased in controlled atmosphere storage. Apricot fruit stored in controlled atmosphere treatments ripened at a reduced rate and produced less yellow pigments of the fleshy pericarp tissue than the conventional refrigerated fruit. There was a retardation of the de-greening processes of the fruit stored in CO2 concentrations higher than atmospheric air. It appeared that high concentrations of CO2 had an inhibitory effect on chlorophyll degradation. Succinic acid coupled with high tannin concentrations, induced by CO2, apparently caused browning of the mesocarp tissue of the fruit in controlled atmosphere storage at a more rapid rate than conventional refrigerated stored fruit. The organic and amino acids of peach and apricot fruits had a variable response to control atmosphere treatment. The organic acids, particularly malic acid, were reduced in concentration, while succinic acid accumulated. Succinic acid accumulation was dependent upon the concentration of CO2 in the atmosphere. It was suggested that CO2 had a toxic or inhibitory effect on the succinic oxidase enzyme system which resulted in succinic acid accumulation. The accumulated succinic acid, thereby, may have had a toxic effect on the mesocarp tissue of the fruit and caused part of the browning. Aspartic acid decreased in concentration under higher CO2 treat-ments, while alanine and glutamic acid increased. Total sugar concen-tration was generally not effected by controlled atmosphere storage. The metabolism of free reducing sugars in higher CO2 treatments was markedly reduced in the apricot fruit.The beneficial aspects of controlled atmosphere on stored fruit appeared to be the increased length of the storage period for apricot fruit, as well as a reduced rate of metabolism. The storage life of apricot fruit was extended 15 to 30 days in the appropriate atmosphere. The adverse effects of controlled atmosphere storage of apricot and peach fruit appeared to be: the inhibitory or toxic effect of CO2 on certain enzyme systems; the accumulation of certain metabolites, which may have been toxic to the fruit tissue; the increased rate of tissue browning, the inhibitory effect of CO2 on the de-greening and color development mechanisms.
2

Thermal Degradation of Pigments and Relative Biochemical Changes in Cherries and Apricots

Dalal, K. B. 01 May 1963 (has links)
The extent and nature of biochemical changes that take place in canned fruits during storage temperatures above freezing have been reviewed and discussed by Pederson, et al. (1947). These changes include loss in nutritive value, e.g. ascorbic acid, thiamine (Brenner, et al., 1948) and deterioration of color (Tressler, et al., 1955). Bauernfeind (1953) reported that canned peaches, apricots, and sweet cherries, after a few months of storage at 70° F, frequently undergo changes such as destruction of anthocyanin and carotenoid pigments with the subsequent formation of brown colored compounds. Darkening of fruit-color eventually results in their unacceptability at consumer level. Preference for fruit is mainly based upon the attractive appearance of the products. Thus, color is an important factor governing the quality of fruits and fruit products. In earlier studies, conducted elsewhere, emphasis was placed on effects of low storage temperatures on the quality of canned apricots and cherries. Paucity of scientific literature on the stability of processed apricots and cherries gave impetus to a study of the comparative influence of high storage temperatures and their duration, as such tests will have considerable economic bearing upon storing and shipping processed products to tropical countries. This thesis presents the effects of storage temperatures (40, 70, 100, and 120° F) and their duration (16 weeks) on colors (anthocyanins and carotenoids), total titratable acidity, pH, viscosity, carbohydrates (total 2 and free reducing sugars, pectins), volatile reducing substances, hydroxymethyl furfural, and organoleptic quality of canned apricots and cherries .
3

Effects of Water Hardness on Processed Quality of Carrots, Sweet Cherries, and Apricots

Chiang, Jack C. 01 May 1970 (has links)
The Honey Sweet carrots were canned with Ethyienediamine tetracetic acid (CaNa 2 EDTA) and Sodium hexametaphosphate (Ha-HMP) at five different water hardness (0 , 20, 40, 80, 160 ppm of calcium and 20 of magnesium) , then stored at temperatures of 70 and 100 F. Evaluations were made at sixty-day i intervals for six months. Firmness and color degradation decreased significantly when water hardness or storage time increased. Under storage at 100 F and 0 hardness of water, the decrease of color and firmness was constantly accelerated. When hard water (above 80 ppm or below 40 ppm) was used for canning Van sweet cherries and Large Early Montgament apricots, the firmness , volatile reducing substances, and pH decreased. Sensory acceptability was maximum at 40 and 80 ppm. However, when either CaNa 2 EDTA or Na-HMP was used at the 500 ppm, it was found that they counteracted the effects of hard water and the quality of canned sweet cherries and apricots improved, when compared with control.
4

Impacts of low-water activity food type on inactivation kinetics and models of foodborne pathogens treated with low-temperature, vacuum-assisted steam processing

Acuff, Jennifer Claire 29 April 2020 (has links)
Low water activity foods (LWAF), specifically nuts and dried fruits, have been generally considered safe because they do not support the growth of foodborne pathogens. However, many pathogens have been noted to survive in LWAF for considerable periods of time, and a number of recent outbreaks and recalls have implicated various types of nuts and dried fruits. The Food Safety Modernization Act requires food processors to develop preventive control plans that make ready-to-eat LWAF safer for consumers. The presented research was designed to investigate several aspects of LWAF safety by evaluating a steam process as a strategy to remove pathogen contamination from LWAF, modeling the inactivation of such treatments, and studying the thermal resistances of two E. coli strains in low-water activity solutions. Low-temperature, vacuum-assisted steam (vacuum-steam) was evaluated as a potential intervention and preventive control to remove pathogens from the surface of LWAF without using high-heat treatments that could damage product quality. The presented work examined the efficacy of vacuum-steam (<85°C) as a means to decontaminate the surface of whole macadamia nuts, dried apricot halves, and raisins from Salmonella spp., Listeria monocytogenes, and Shiga toxin-producing Escherichia coli (STEC) contamination. The low-temperature steam treatments successfully reduced all pathogens by >4 log CFU/g from the surfaces of the foods. Additionally, Pediococcus acidilactici, proved to be a surrogate organism for these pathogens and could be used to challenge and validate similar treatments within processing plants. The data were fit to models, which showed that food type significantly impacted the fit, with the Weibull model best describing bacterial inactivation kinetics on raisins and macadamia nuts, and the Gompertz model best describing reductions on the apricot halves. The models were challenged for validation of their abilities to predict times required for 3-log reductions using internal and external datasets, determining the usefulness to industry members who wish to design similar thermal treatments for LWAF. Comparing predicted values from internally constructed models to observed values generated from external data, models were shown to be limited in scope and application and could only be applied to pathogen inactivation on different LWAF or thermal processes in certain circumstances. First-order and Weibull model predictions of bacterial reductions on dried apricots had varied success in predicting times for 3-log reductions on other thermally treated LWAF. However, the models of bacterial reductions on thermally treated macadamia nuts frequently overestimated the times required for 3-log bacterial reductions for other LWAF. In an effort to understand the effect that reduced water activity has specifically on STEC, two strains were investigated for induced thermal resistance due to osmotic stress. Thermal resistance of STEC strains (O121:H19 and O157:H7) were evaluated on the basis of strain variation, culture preparation, and water activity (D- and z-values). At the lowest treatment temperature (56°C), O121 displayed greater heat resistance than O157, and the broth-grown samples exhibited greater heat resistance than the lawn-grown cells, but significant differences were not observed at higher temperatures. Samples in reduced-water activity solutions displayed reduced thermal resistance at 56°C, but the z-values were 29-43% higher than those of high-water activity samples. While water activity has been shown to impact thermal resistance of pathogens, comparisons of STEC thermal resistance according to the D- and z-values revealed that other factors also play roles in pathogen thermal resistance on LWAF. Results from the collection of experiments conclude that efficacy of thermal treatments is impacted by the physiological state of the cells, stress experienced in the food matrix, and characteristics of the food, including water activity and composition. / Doctor of Philosophy / Consumers expect foods they purchase to be safe to consume by themselves and family members, particularly those that are ready-to-eat with no additional cooking requirements. Many of these foods are low-water activity foods (LWAF), like nuts and dried fruits, with very little water content that could be used by bacteria. These foods may be preferred snack foods due to their affordability, long shelf lives, and health benefits over other types of snack foods. Until recently, LWAF were generally considered safe because they do not support the growth of foodborne pathogens due to the lack of moisture or water within the food. However, a number of recent outbreaks related to various types of nuts and dried fruits have proven that many pathogens can survive in dried foods, even if not actively growing, for considerable amounts of time. Designed to address these types of food safety issues, the Food Safety Modernization Act recognizes risks associated with foods and responded with regulations requiring food processors to take steps to make ready-to-eat LWAF, like nuts and dried fruits, safer for consumers. A popular strategy is to treat foods with heat to destroy pathogens, however the quality attributes of some nuts and dried fruits could be damaged by high-heat treatments like roasting. An alternative process uses a vacuum to form steam at lower temperatures, allowing for efficient heat transfer through water droplets to the surface of the foods, thus causing less damage to the foods without introducing too much moisture. This research evaluated how this process could be used by food processors to remove harmful bacteria from the surfaces of whole macadamia nuts, dried apricot halves, and raisins. Results indicated that the low-temperature steam treatments successfully reduced Salmonella, Listeria monocytogenes, and Shiga toxin-producing Escherichia coli (STEC) by >4 log CFU/g (>99.99%) from the surfaces of the foods. Additionally, a nonpathogenic lactic acid bacterium, Pediococcus acidilactici, exhibited similar or greater heat tolerance, which would allow food processors to use it as a substitute, or surrogate, for in-plant studies without introducing harmful bacteria into the food processing environment. Mathematical models were used to describe the trends of bacterial death due to the steam treatments, and the results indicated that the type of food significantly impacted the reduction of bacteria. The models were tested using additional data collected within our own laboratory, as well as others. Results indicated that some of the models could be used as predictors of bacterial death for similar LWAF but can only be applied with caution and consideration for the type of food and process. Additionally, two different E. coli strains associated with outbreaks (O121:H19 and O157:H7) were investigated to understand impacts of strain variation, growth method, and water activity on thermal resistance. Some differences in heat resistance were observed between the strains and between the growth methods. Additionally, the reduced water activity seemed to decrease the bacteria's ability to withstand some heat treatments. Overall, thermal resistance studies indicated that several factors, in addition to water activity, impact pathogens' development of resistance to heat treatments. The experiments' results show that there are complex relationships between bacteria and the food they inhabit. Food processors must consider these relationships in order to design the best thermal processes to make LWAF safe for consumers.
5

MORAVSKÉ VINAŘSKÉ CENTRUM / Moravian Wine Center

Fűlőpová, Andrea January 2018 (has links)
Modern winery complex hotel Hrůdek is situated on the north part of village Velké Pavlovice, in the heart of south Moravia the Czech Republic. Its significant placement on the south hillside offers beautiful views to the vineyards and apricot plantations. The architectural form of the building is inspired by the regularity and rhythm of vineyard lines, significant horizontal landscape around and rounded contour lines. Embedding of the building into the slope reacts to the topography of the terrain and refers to the traditional principle of local two-storey wine press houses. From the upper part is the entrance to the accommodation part and from the lover part of the slope is entrance to the wine cellar – the gallery of wine. Hotel offers 4-stars class accommodation, two congress halls, restaurant, wellness and gallery of the wine. Project integrates energetic eco-friendly concepts and its proposed as the self-sufficient building.

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