No description available.

Numerous Escherichia coli O157:H7 outbreaks have been associated with fast food restaurants. This research created a computer model and simulation with the Micrografx computer software program Process™ for the safe handling of ground beef patties and lettuce in a typical fast food restaurant. A reference facility was visited to obtain a text description of the flow of food. To create the model, a process diagram was made that graphically represented the series of steps that were taken from the arrival of products to the delivery of the cooked and assembled product to the consumer. A process model was created when the steps in the process diagram was assigned behaviors. The final phase was process simulation. The simulation results indicated the model was representative of a typical fast-food restaurant. The model was then used successfully to simulate three potential breakdowns of the food safety system that could lead to a foodborne illness outbreak.

Vertical farming has been proposed as a solution for providing food security for an increasing, urbanized human population. Light-emitting diode (LED) technology has become increasingly affordable and efficient, making it an ideal choice as artificial lighting for indoor farms. Still largely undiscovered parameters are the optimal plant varieties and types of production systems for plant growth, profit, and human nutrition. Aquaponics may be able to provide sustainable animal protein for vertical farms, increasing their ability to provide more substantial nutrition to consumers. This research aimed to better understand vertical farming as a food production system, and to determine if aquaponics can be an appropriate and applicable fit for it. The experiment was a randomized, factorial design with three independent variables: (1) LED photoperiod interval (2) LED-plant distance, and (3) nutrient solution, as well as several dependent variables to assess both plant yield and quality. A 4-tiered shelving unit was constructed for nutrient film technique (NFT) plant production, and treatments were assigned to each row: (1) LED experiment: Row A, 12/12hr reduced photoperiod with adjustable LEDs 4in. above plant surface; Row B, 2/1hr altered photoperiod interval relative to the control; Row C (control), 16/8hr “standard” photoperiod. (2) Nutrient experiment: Row C, aquaponic nutrient solution; Row H, hydroponic nutrient solution. Rows C and H had matched photoperiod and light intensity. Kale from Row A had significantly lower fresh and dry plant yield relative to the control, Row C (p<0.05). Hydroponic romaine, Row H, had significantly higher plant yield relative to aquaponics, Row C (p<0.05). Butterhead yields were not significantly different in any treatments (p>0.05). Future research may implement a larger sample size of only one plant variety, harvest plants earlier, limit light intensity variation, effectively “balance” the aquaponics system, and have more measures of plant “quality.”

<p dir="ltr">Romaine lettuce is a vegetable crop that is frequently contaminated with and often implicated in mass outbreaks of human-pathogenic <i>Escherichia coli</i>. To date, research has focused on the specific pathogens responsible for those outbreaks and consumer- and retail-level interventions to eliminate those pathogens or to mitigate their spread. However, in many cases, no singular food source can be identified. Food microbiomes, particularly those associated phylloplanes, are a growing interest area and may be key in identifying the conditions that allow for proliferation of pathogenic organisms like <i>E. coli</i> O157:H7. Further, examination of dominant components of the lettuce microbiome may reveal suitable candidates that can be encouraged or engineered to outcompete or indicate the presence of pathogens. Until recently, most microbiome studies focused on bacteria; less understood are the fungi of these microbiomes. Many fungi have myriad applications in the prevention and mitigation of both human and plant diseases. Thus, to effectively prevent pathogenic <i>E. coli </i>outbreaks, a fundamental understanding about the fungi that cohabit the lettuce microbiome is paramount. The most frequently isolated yeast in the romaine lettuce microbiome is an undescribed yeast, revealing the dearth of information regarding nonpathogenic fungi in food systems. First, the novel yeast <i>Sporobolomyces lactucae</i> is described using a multi-locus phylogeny through genealogical gene concordance, with a discussion on the potential ecological range. Second, the genome of <i>S. lactucae </i>strain HU9244 is assembled and annotated with transcriptomic information to help guide target gene selection for biotechnology, particularly in identifying candidates for reporter genes that may assist in the detection of <i>E. coli </i>O157:H7 via olfactory or visual cues. Third, the distribution of the yeast <i>S. lactucae</i> is determined, finding the organism in various climate types and potentially on other leafy greens as well, indicating its suitability for <i>in situ</i> detection of foodborne pathogens such as <i>E. coli</i> O157:H7 commonly found on romaine lettuce and other leafy greens.</p>

No description available.

In response to increasing interest in greenhouse production and difficulties imposed by adverse environmental conditions in the southeastern United States, two studies were conducted with green and red-leaf lettuce cultivars. The first study analyzed effects on yield and quality of green and red-leaf lettuce subjected to increasing nutrient solution electroconductivity (EC) across three growing seasons. Results indicated that the interaction between season and cultivar had the greatest effect on growth, flavonoids and phenolics, and leaf mineral content. The second study analyzed effects on yield and quality of increasing solution potassium (K) in red Lollo lettuce at two temperatures. The results suggested that temperature is a stronger regulatory factor than increasing K in the determination of lettuce yield and quality. However, increasing K concentrations to 234.6 mg·L-1 results in higher concentrations of leaf mineral concentrations without compromising lettuce yield and quality.

No description available.

Nutrient accumulation in vegetable crops is declining. New varieties, selected for high yield, may be subject to a dilution effect of nutrient concentration. Alternatively, soil fertility may be to blame. Here, we investigate how nitrogen fertilization can enhance or suppress calcium and potassium content in two lettuce varieties already known to accumulate high or low amounts of these nutrients. Effects of varying the ammonium:nitrate ratio and effects of calcium carbonate buffering on plant growth by mass and on uptake and accumulation of potassium and calcium in two lettuce (Lactuca sativa L.) cultivars, Two Star and Red Deer Tongue, were investigated in three greenhouse hydroponic experiments in which ammonium supplied none, 6%, 12%, 25%, 50%, 75% or all of the nitrogen. Ammonium, supplied as the sole nitrogen source (15 mM), was toxic under buffered or unbuffered conditions. It limited growth and concentrations of potassium and calcium in lettuce leaves. Proportions of ammonium-N greater than 50% of total N nutrition severely curtailed growth and nutrient accumulation for both cultivars. For both cultivars, optima for all three variables occurred in treatments that contained less than 50% NH4+-N in the total N supply. Application of calcium carbonate buffer did not result in improved maxima for growth and shoot potassium or shoot calcium concentrations compared to the best responses in unbuffered solutions. However, supplying calcium carbonate buffer did raise the minima for growth and shoot potassium and shoot calcium concentration. Both cultivars in buffered solutions compared to unbuffered solutions had significantly greater values for growth and for shoot potassium or shoot calcium concentration in treatments that contained 50% ammonium-N or greater in the total N supply. Although buffering relieved symptoms of ammonium toxicity, it did not eliminate symptoms, confirming the work of other researchers that ammonium toxicity is not due solely to acidification of the root-zone and that buffering has an effect on the capacity of plants to tolerate ammonium nutrition. Supplying nitrogen with ammonium:nitrate ratios in which nitrate predominates enhances yield and accumulation of calcium and potassium in lettuce. Two Star, the modern variety, is more ammonium-sensitive than Red Deer Tongue, the heirloom variety, if calcium carbonate buffering is not provided.

A literature review of rubber-bearing plants in the United States was made, and the essentials of distribution, ecology and rubber content presented in condensed form. Filed lettuce of the specie Lactuca scariola was investigated to determine its place among the other rubber-bearing plants. Nearly pure stands of natural growing wild lettuce were harvested and the weights of plant material determined. Yields up to 2,830 pounds of dry leaves together with 5,760 pounds of dry stems per acre were obtained. The seasonal variation in rubber content and resins of one natural growing wild lettuce stand was studied from the time of the appearance of flower buds to the end of the growth cycle. At this time of maximum rubber content of this stand the calculated yield was between 1.16 and 1.57 pounds of rubber per acre. An experimental planting was undertaken to determine rubber content, resin content, and growth and cultivation characteristics of the earlier stages of growth. Young plants gave up to 0.339 percent rubber and a calculated yield of 13.7 pounds of rubber per acre. Drying temperatures up to the 180°F gave no decreases in rubber content during drying. The rubber content of harvested plants was found to decrease rapidly on exposure to sunlight. At least 10.7 percent of the seeds were found to have the power of germinating soon after ripening. Seeds ripened in the fall were found to have between 49 and 68 percent germinating power. / Master of Science

Two separate greenhouse esperiments were conducted to determine the effects of additions of a blue-green algae (Nostoc muscorum) to nutrient solution cultures with different rates of nitrogen fertilizer on the growth of lettuce (Lactuca sativa L. cv. Buttercrunch). Lettuce yields increased with increased rates of N. Yields were significantly greater in treatments containing 165 ppm N with N. muscorum culture added (at the rate of 33.3% by volume) than in treatments containing the same rate of N without N. muscorum. A similar growth increase was not noted at lower N. muscorum inoculation rates (16.7% by volume). These preliminary data indicate the potential for increased yields of lettuce grown under specific conditions in nutrient culture. Further research of the complex interactions within this biological equilibrium are required before specific application recommendations may be suggested. / Master of Science