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Doctor of Philosophy (PhD)
Year Degree Awarded
Month Degree Awarded
Food Processing | Other Food Science
Shelf stable foods that require no refrigeration or freezing are the predominant food source for astronauts. Due to its high impact on astronauts’ health, it is crucial to know if the astronauts are getting all the necessary nutrients from shelf stable foods, specifically vitamins. With limited knowledge on vitamin degradation in spaceflight foods during storage and processing, our team decided to tackle this issue focusing on unstable vitamins, which included vitamin C (ascorbic acid) and vitamin B1 (thiamine); however, this thesis will specifically focus on vitamin C.
A two-year storage and retort processing study was conducted on 5 different foods (i.e. sugar snap peas, strawberries, and rhubarb applesauce at three different pH levels) to determine the vitamin degradation kinetics and this information was used to determine a mathematical model reliability to predict and control vitamin C degradation during long term storage and retort processing using experimental data. Validation and improvement of model was implemented based on experimental data.
For the storage study, each food was retorted and freeze dried to make it shelf stable according to NASA specifications. The foods were stored at five constant temperatures (-20, -80, 4, 20, and 37 °C). Over a two-year period, samples were periodically pulled and HPLC analysis was used to measure vitamin C. With vitamin C measured at two experimental points, degradation parameters, kTref and c, were determined to make predictive degradation curves for each food, process, and positive temperature for vitamin C using the endpoints method model. When the two-year storage study was completed, the predictive degradation curves were compared to experimental data. Additionally, the combined first order kinetics model incorporating all experimental data was used to determine degradation parameters: Casymptote, kTref, and c. With both models and physiochemical properties (i.e. pH and moisture content) of each food, two databases were created to determine degradation parameters for vitamin C with inputting a pH, moisture content, and storage temperature to retrieve estimated degradation parameters. The knowledge obtained during these studies will help ensure that NASA’s astronauts are getting all the necessary nutrients needed at any time to maintain health and wellness in space.
Dixon, William, "PREDICTION AND CONTROL OF VITAMIN C LOSS IN SPACEFLIGHT FOODS" (2019). Doctoral Dissertations. 1479.
Available for download on Thursday, August 01, 2019