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- All Subjects: Degradation
- Creators: Cahill, Thomas
Description
Capsaicin and dihydrocapsaicin account for 90% of capsaicinoids when it comes to the pungency of peppers. Capsaicin stability was investigated through a cooking and storage parameter where three different tests were done; cooking duration, cooking temperature, and storage stability. The concentration of capsaicinoids was quantified through gas chromatography-mass spectrometry where those values were then used to determine the total Scoville heat units (SHU). Furthermore, half-life was determined by finding the decay rate during cooking and storage. Results showed that there was an increase in degradation of capsaicinoids concentration when peppers were cooked for a long period of time. Degradation rate increases with increasing temperatures as would be expected by the Arrhenius equation. Hence, if a maximum pungency is wanted, it is best to cook the least time as possible or add the peppers towards the end of the culinary technique. This would help by cooking the peppers for a short period of time while not being exposed to the high temperature long enough before significant degradation occurs. Lastly, the storage stability results interpreted that a maximum potency of the peppers can be retained in a freezer or refrigerator opposed to an open room temperature environment or exposure from the sun. Furthermore, the stability of peppers has a long shelf life with even that the worse storage condition's half-life value was 113.5 months (9.5 years). Thus, peppers do not need to be bought frequently because its potency will last for several years.
ContributorsBustamante, Krista Gisselle (Author) / Cahill, Thomas (Thesis director) / Sweat, Ken (Committee member) / Armendariz Guajardo, Jose (Committee member) / School of Mathematical and Natural Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2017-12
Description
Composite insulators on overhead lines are frequently subjected to corona discharges due to increased electric field intensities under various conditions. These discharges can cause localized heating on the surface and affect the hydrophobicity of the insulator. A study has been undertaken to quantify and evaluate the thermal degradation that composite insulation is subjected to from corona discharges. This has been conducted primarily at the power frequency (60 Hz) and at the low frequency range (37 kHz). Point to plane corona discharge experiments have been performed in the laboratory at both the frequencies and varying levels of thermal degradation has been observed. The amplitude and the frequency of current spikes have been recorded at different voltage levels. A temperature model based on the amplitude and the frequency of current data has been formulated to calculate the maximum temperature attained due to these discharges. Visual thermal degradation has been found to set in at a low frequency range while there is no visual degradation observed at power frequency even when exposed to discharges for relatively much longer periods of time. However, microscopic experiments have been conducted which revealed degradation on the surface at 60 Hz. It has also been found that temperatures in excess of 300 Celsius have been obtained at 37 kHz. This corroborates the thermo gravimetric analysis data that proves thermal degradation in silicone rubber samples at temperatures greater than 300 Celsius. Using the above model, the maximum temperature rise can be evaluated due to discharges occurring on high voltage insulation. This model has also been used to calculate the temperature rise on medium voltage distribution equipment such as composite bushings and stand-off plugs. The samples were subjected to standard partial discharge tests and the corresponding discharge magnitudes have been recorded. The samples passed the tests and the corresponding temperatures plotted have been found to be within thermal limits of the respective insulation used on the samples. The experimental results concur with the theoretical model. A knowledge of the maximum temperatures attained due to these discharges can help in design of insulation with better thermal properties.
ContributorsSangaraju Venkateshwara, Pradeep Varma (Author) / Gorur, Ravi S (Thesis advisor) / Farmer, Richard (Committee member) / Vittal, Vijay (Committee member) / Arizona State University (Publisher)
Created2010