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A QUANTITATIVE BIOCHEMICAL APPROACH FOR EVALUATION OF ONION QUALITY AND POTENTIAL VOLATILE EMISSION.   Lisa Harris¹, Jan Bauer², and Lanfang Levine².   ¹ Department of Chemistry, Southeast Missouri State University, Cape Girardeau, MO, ² Dynamac Corporation, Mail Code: DYN-3, Kennedy Space Center, FL 32899.

   Plants are anticipated to play an important role in both short and long term space missions as they provides fresh food to the crew members, and revitalize water and air through transpiration and photosynthesis.   Furthermore, their psychological benefits to the crews in an enclosed abiotic environment cannot be underestimated.   Ideal plant species for space should have the characteristics of low space, power and processing requirements, and high nutritional value as well as low bio-emission of undesirable volatiles.  Currently researchers at Kennedy Space Center are evaluating bunching onions (Allium fistulosum L.­), one of the candidate salad crops, for use in near-term space missions.  As a part of cultivar selection project, we attempted to develop quantitative metrics for onion’s nutritional and sensory value as well as their potential volatile emission.   Onions are known for their characteristic flavor and health benefits due to the presence of organosulfur compounds, thiosulfinates.  Thiosulfinates (flavor indicator) and pyruvic acid (pungency indicator) are formed upon the disruption of onion cells due to the action of alliinase on flavor precursors (alk(en)yl cysteine sulphoxides).  The flavor precursors and pyruvic acid were quantified in pseudobulbs and leaves of eight commercially available onion cultivars.  Results demonstrated significant concentration differences between tissue types.  Concentration differences were also detected between pseudobulbs from different cultivars but not between leaves of different cultivars.  These results provide baseline information for cultivar selection based on their nutritional and sensory value, and potential volatile emission.   They also provide a foundation

for future studies in which the influence of environmental factors on onion quality can be evaluated.