Determination of volatile organic compounds emission from live plants and food extrusion process tested in NASA's Advanced Life Support Program.

摘要

The types and generation rates of volatile organic compounds (VOC) produced by candidate plants (wheat, tomato, and lettuce) and a potential food processing technique (food extrusion) to be utilized in NASA's Advanced Life Support (ALS) system for space exploration were investigated.; For live plant VOC, a plant-section cuvette (PSC) and a whole-plant vessel system (WPVS) were the enclosure techniques used in the VOC generation rate determination. The WPVS was constructed to study the rate of VOC emissions from small live plants at a high level of CO₂ concentration (1000 ppm). A new approach used in the design of the system provided appropriate controls of plant growth environmental conditions without introducing severe VOC dilution. The VOC was trapped in the solid adsorbents and analyzed by thermal desorption-gas chromatography-mass spectrometry/flame ionization. Our studies showed that ethylene generation rates vary from species to species and their production profiles change with developmental stages. Besides the study of ethylene, this research provided a complete list of VOC and their generation rates of the three plant species as a function of their developmental stages, except for lettuce where only the edible-leaf stage was investigated. The study also included the wound-induced VOC production from a lettuce leaf. The results revealed more types and amounts of VOC than obtained from the healthy plants.; For VOC produced during food extrusion cooking, a technique for collecting VOC released at the extruder die was designed. Our results showed the types and amounts of VOC produced from the extrusion process were flour type and moisture content dependent. The emission rates of VOC were up to 100–1000 times higher than the VOC generation rates by live plants.; Many of identified VOC from both sources currently were not in the list of spacecraft maximum allowable concentrations (SMACs) for trace chemical contaminants and the high emission rates of certain classes of compounds emitted during the extrusion cooking suggested that they should be included and further evaluated in term of toxicity.