Poster: Respiratory Pathways

Abs # 266: Fermentative metabolism and ester production of strawberry in response to elevated CO₂ during Storage

Presenter:	Ponce Valadez, Monica , mp239@cornell.edu
Authors	Ponce Valadez, Monica  (A)   Watkins, Chris B. (A)
Affiliations:	(A): Cornell University. Department of Horticulture.

Different cultivars of strawberry respond differently to elevated concentrations of CO₂ (20%) during storage. Some strawberry cultivars, e.g. Jewel, accumulate fermentation products such as acetaldehyde, ethanol and ethyl acetate, while others, e.g. Cavendish, do not accumulate detectable amounts. To determine the difference in the metabolism that result in these cultivar differences, we have measured enzyme activity of alcohol dehydrogenase (ADH), pyruvate decarboxylase (PDC) and alcohol acyltransferase (AAT) in relation to gene expression of the three enzymes. Our results show that PDC and ADH activities in response to CO₂ were affected by strawberry cultivar. However, their activities did not show a positive correlation with accumulation of fermentation products. Different ADH isoenzymes may be important in differential metabolic regulation between the cultivars. Volatile esters, formed by esterification of alcohols and carboxylic acids, catalyzed by AAT, constitute one of the most important group of volatiles that contribute to flavor and aroma of fruit. AAT activity decreased during storage independently of treatment and cultivar. Changes in substrate specificity of AAT during storage with elevated concentration of CO₂ will be discussed. This research was supported by USDA-NRI Grant #99-35503-8165.