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Understanding how plants respond to stress is of importance, considering the increasing need to feed a growing population and supply its energy. Plants have complex systems for detecting, and responding to stresses. One stress-responsive system involves myo-inositol (Ins). Ins is a precursor for cell wall components, inositol trisphosphate (Ins(1,4,5)P3) and phosphatidylinositol phosphate signaling molecules, and an alternate ascorbic acid (AsA) synthesis pathway. The enzyme, myo-inositol oxygenase (MIOX) is encoded by four genes in Arabidopsis and catalyzes the first step of Ins catabolism producing D-glucuronic acid (DGlcA). This research focuses on MIOX metabolism of Ins during plant growth and stress responses. I have examined miox mutants for alterations in metabolism and signaling. MIOX2 and MIOX4 expression patterns correlate with miox mutant root growth in varying nutrient conditions, and changes in flowering time. In miox2 mutants, I found an increase in Ins in most tissues, which was accompanied by cold- and abscisic (ABA)- sensitivity; however, miox4 mutants are ABA- insensitive, and have a small increase of Ins in flowers. MIOX2:GFP fusion protein accumulates in the cytoplasm and MIOX4:GFP accumulates in the cytoplasm and nucleus. Overexpresser MIOX4+ plants provide a model system to examine how directing carbon from Ins into DGlcA impacts Ins levels and Ins signaling. I have examined MIOX4+ plants for alterations in MIOX4 RNA and protein, and measured Ins by gas chromatography (GC). My results indicate that MIOX4+ tissues are impacted differently by the MIOX4 transgene, with decreases in Ins after seed imbibition, and increased Ins levels later in development. Ins depletion in seedlings was correlated with a decrease in Ins(1,4,5)P3. To determine the impact of reducing Ins and Ins(1,4,5)P3 in MIOX4+ seedlings, I examined processes known to involve Ins(1,4,5)P3 signaling. MIOX4+ seed have increased seed dormancy, NaCl-sensitivity, and ABA-insensitivity. These results suggest MIOX affects Ins signaling in response to ABA. Together, these data indicate that transcriptional control of MIOX2 and MIOX4 results in distinct roles in plant growth, and that MIOX2 and MIOX4 function in metabolic and signaling processes critical for growth, nutrient sensing, and stress responses. / Ph. D.

Non-enzymatic browning (NEB) due to ascorbic acid degradation is one of the most common reasons the shelf life of many processed foods is reduced. Different methods to minimize or retard the formation of browning pigments have been studied; however, to date, refrigeration is still the most preferable. Unfortunately, the use of low temperatures to preserve food is not always available in many parts of the world. Indeed, an area of concern due to NEB has been identified in meal-ready-to-eat (MRE) individual military rations, specifically diced peaches with syrup. This product was once part of soldiers' menus; however, it was removed due to browning and textural deterioration that occurred when stored under field conditions. We examined two general approaches to reduce NEB: the replacement of ascorbic acid by a more stable form and the use of flavonoids as antibrowning antioxidants in peach systems. These approaches were studied in three objectives. In our first objective, ascorbyl-2-phosphate showed better stability than ascorbic acid at 40°C in peach puree model systems, but not at 50 or 60°C. In the second objective, after the evaluation of the effect of two forms of vitamin C (ascorbic acid and ascorbyl-2-phosphate) and Pycnogenol (0%, 0.01% and 1%) on the quality of diced peaches in retortable pouches, we concluded that neither ascorbyl-2-phosphate nor pycnogenol resulted in improved color or ascorbic acid stability. Finally, in our third objective, after the evaluation of the effect of peach source (fresh, individually quick frozen and canned), addition of calcium chloride, and the addition of a water soluble flavonoid (°-glucosylrutin, °-GR) in diced peaches packaged in retortable pouches stored at 24, 40 and 51°C, there were no significant effects of °-GR on any of the peach sources at 51°C. However, at 40°C, °-GR improved the quality of diced peaches in pouches made of individually quick frozen and canned peaches, but not for fresh peaches. Quality was assessed by color (CIELAB system), which was measured using a handheld colorimeter, and ascorbic acid levels of peaches, which was determined using high performance liquid chromatography. / Master of Science

The antioxidant properties of various blends of rosemary extract and tocopherols, either alone or with citric and ascorbic acid, were compared in filleted, headed and gutted, and minced rainbow trout (Oncorhynchus mykiss). The filleted and headed and gutted products were stored at -29 degrees C for twelve months, while the minced was stored at the same temperature for 24 weeks. Oxidation was measured by following changes in thiobarbituric reactive substances, conjugated diene hydroperoxides, texture, drip loss, pH, sensory evaluation, and gas chromatographic detection of aldehydes. Natural antioxidants, in particular those that contained citric and ascorbic acids, were effective at retarding the development of conjugated diene hydroperoxides and malonaldehyde (p<0.05). Furthermore, sensory evaluation indicated that treated samples were less oxidized. In subsequent studies, however, it was determined that the herbal flavor notes associated with natural antioxidants complicated the ability of the experienced panel to judge extent of oxidation. Also, using filleted samples, further consumer sensory panels indicated that after 12 months frozen storage, the treated and control samples were equally acceptable. For both the filleted and headed and gutted samples, no texture differences were noted over storage time or between control or variable treatments. When using natural antioxidant products, drip loss and pH were found unreliable predicators of oxidation or muscle degradation. / Master of Science

The effects of packaging treatments, post harvest cooling delay and storage duration on color, texture, ascorbic acid content, weight loss and glucosinolate retention in crown-cut heads of broccoli were studied. Oxygen and CO2 levels inside shrink wrap packages were also monitored. Shrink wrap packaging had a significant positive effect on hue angle (p<0.05). Packaging and post harvest cooling delay had no effect on hue difference and total color difference. While post harvest cooling delay had no effect on texture, crown-cut heads of broccoli stored in shrink wrap packaging retained firmness significantly better than ice packaged heads of broccoli (p<0.05). Ascorbic acid was retained better in broccoli held in shrink wrap packages and cooling delay had a significant negative influence on ascorbic acid content (p<0.05). Packaging and post harvest cooling delay had a significant positive effect on weight loss (p<0.05). Broccoli stored in shrink wrap film lost about 3.7% of original weight while ice packaging resulted in about 17.4% weight loss (p<0.05). No consistent trends were observed in the levels of O2 and CO2 inside shrink wrap packages. An important glucosinolate, glucoraphanin was retained significantly better in shrink wrapped heads (p<0.05). Between two cultivars, shelf life of cv.Gypsy was better than cv.Everest with respect to color, ascorbic acid retention and weight loss. But cv.Everest retained texture (firmness) better after 35 days of storage. Overall results indicate that shrink wrap packaging and shorter post harvest cooling delays protect quality of broccoli. / Master of Science

The present study was undertaken to compare the ascorbic acid content of canned and frozen fruits before and after preparation for quantity use.

The purposes of the present study are to determine the ascorbic acid values of foods served in the lunch room of North Texas State Teachers College Demonstration School at the time food preparation is completed, at the beginning of the serving period, and at the end of the serving period; to ascertain the loss of ascorbic acid during these intervals; and to determine the quantity of ascorbic acid present in the size portions served primary, elementary, and high school students.

The purpose of the present study is to determine the ascorbic acid content of raw cabbage salads as influenced by the method of shredding and by the kind of salad dressing used.

The present study was made in an attempt to determine what contributions the mid-morning feeding and the noon meal served children in a nursery school make toward the day's total intake of vitamin C and vitamin A.