RT Journal Article SR Electronic T1 Anaerobic Metabolism of Organic and Amino Acids in Grape. I. A Device for Measuring the Decarboxylating and Ethanol-releasing Kinetics from a Single 14C-labeled Berry JF American Journal of Enology and Viticulture JO Am J Enol Vitic. FD American Society for Enology and Viticulture SP 161 OP 169 DO 10.5344/ajev.1989.40.3.161 VO 40 IS 3 A1 Jean-Pierre Robin A1 Charles G. Romieu A1 FranÇois X. Sauvage YR 1989 UL http://www.ajevonline.org/content/40/3/161.abstract AB This paper describes a radio-isotopic method for studying the anaerobic metabolism of grapes. With the proposed system, one grape berry labeled with 14C-aspartate, malate, or succinate was continuously flushed at 32°C with nitrogen gas, and the diffused CO2 and ethanol were continuously trapped. This allowed the reliable determination of the kinetics of their respective diffusions as a function of the elapsed time under anaerobic conditions. The derived carbon dioxide curves generally showed three steps: a lag phase and a steady-state metabolic period followed by a decreasing phase when the label was completely decarboxylated. The slope of the steady-state period was interpreted as the rate of the in vivo metabolism of the label, and its value was a proportional function of the total number of translocated nmoles (the consumed nmol/min/berry = 7.10-5 x translocated nmol). Stoichiometry of the reaction and relative CO2-ethanol diffusional characteristics were also obtained; one translocated molecule gave two CO2 and one ethanol, and the releasing rate for CO2 was 10-fold higher than for ethanol. The partition coefficient between total diffused ethanol and berry ethanol at the end of the experiment was ca 0.1, showing that ethanol accumulated more slowly inside the berry than under the usual conditions of carbonic maceration. Good interberry reproducibility and high radioactivity recoveries (95.8%) support this method as being a reliable and versatile tool for assessing, through the use of 14C-labeled molecules which undergo decarboxylation, the main pathways and enzymes occurring in the anaerobic metabolism of grapes.