Graduate Thesis Or Dissertation
 

Banana quality : flavor volatiles under anaerobic and aerobic conditions

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/mg74qp182

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  • Alcoholic off-flavor and accompanying volatile compounds produced by bananas (Cavendishii spp) held at 20°C and subjected to aerobic (air control treatment) or anaerobic conditions (nitrogen treatment) were compared by solid phase micro extraction (SPME), a newly developed method for volatile separation. In general, volatile production was suppressed under anaerobic conditions but resumed, to some extent, after fruits were returned to air. The effects of anaerobic conditions on individual compounds were separated into six groups based on their production trends relative to those of air conditions. It was clear that bananas subjected to anaerobic conditions produced ethanol that could be detected easily by SPME. Anaerobic conditions almost completely blocked the esterification step needed to produced normal volatile profiles of ripening bananas. The effects of anaerobic conditions on banana flavor and off-flavor development were determined by a taste panel quality scaling method. In order to determine the difference between bananas subjected to both conditions (aerobic and anaerobic), the "difference from control" method was used in other experiments. Generally, the bananas subjected to anaerobic conditions had better physical appearance than bananas in the air control group but lacked fruit flavor and firmness. Off-flavor developed to a greater extent in bananas under anaerobic conditions than those under the air control which had almost no off-flavor. The correlation between off-flavor and ethanol was very high (r = 0.87) while for other volatiles was very low. This finding implies that ethanol is probably the only volatile causing anaerobic off-flavor in ripening bananas. In order to confirm this, headspace ethanol was detected by SPME, and tissue ethanol was extracted and assayed enzymaticaily. The result showed that tissue ethanol was correlated with headspace ethanol (r² = 0.66). The threshold for off-flavor development in ripening bananas was 300 mg of tissue ethanol /100 g FW or 0.5 ppm for headspace ethanol. Our results indicate that even three days in anaerobic conditions could injure ripening bananas. Thus unlike other fresh fruits, O₂ levels at or below 1% is not suitable for application as postharvest insect control treatment in ripening bananas.
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