Co-Authors:
Lavid, N., Department of Vegetable Crops, Agricultural Research Organization (ARO), Newe Ya'ar Research Center, P.O. Box 1021, Ramat Yishay 30-095, Israel
Schwab, W., Lehrstuhl für Lebensmittelchemie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
Kafkas, E., Department of Horticulture, Faculty of Agriculture, University of Çukurova, 01330 Adana, Turkey
Koch-Dean, M., Department of Vegetable Crops, Agricultural Research Organization (ARO), The Volcani Center, Bet-Dagan 50250, Israel, Adgen Ltd., Nellies Gate, Auchincruive, Ayr KA6 5HW, Scotland, United Kingdom
Bar, E., Department of Vegetable Crops, Agricultural Research Organization (ARO), Newe Ya'ar Research Center, P.O. Box 1021, Ramat Yishay 30-095, Israel
Larkov, O., Department of Vegetable Crops, Agricultural Research Organization (ARO), Newe Ya'ar Research Center, P.O. Box 1021, Ramat Yishay 30-095, Israel
Ravid, U., Department of Vegetable Crops, Agricultural Research Organization (ARO), Newe Ya'ar Research Center, P.O. Box 1021, Ramat Yishay 30-095, Israel
Lewinsohn, E., Department of Vegetable Crops, Agricultural Research Organization (ARO), Newe Ya'ar Research Center, P.O. Box 1021, Ramat Yishay 30-095, Israel
Abstract:
Among the most important volatile compounds in the aroma of strawberries are 2,5-dimethyl-4-hydroxy-3(2H)-furanone (Furaneol) and its methoxy derivative (methoxyfuraneol, mesifuran). Three strawberry varieties, Malach, Tamar, and Yael, were assessed for total volatiles, Furaneol, and methoxyfuraneol. The content of these compounds sharply increased during fruit ripening, with maximum values at the ripe stage. An enzymatic activity that transfers a methyl group from S-adenosylmethionine (SAM) to Furaneol sharply increases during ripening of strawberry fruits. The in vitro generated methoxyfuraneol was identified by radio-TLC and GC-MS. The partially purified enzyme had a native molecular mass of ∼80 kDa, with optimum activity at pH 8.5 and 37°C. A high apparent Km of 5 mM was calculated for Furaneol, whereas this enzyme preparation apparently accepted as substrates other o-dihydroxyphenol derivatives (such as catechol, caffeic acid, and protocatechuic aldehyde) with much higher affinities (Km ∼ 105, 130, and 20 μM, respectively). A Km for SAM was found to be ∼5 μM, regardless of the acceptor used. Substrates that contained a phenolic group with only one OH group, such as p-coumaric and trans-ferulic acid, as well as trans-anol and coniferyl alcohol, were apparently not accepted by this activity. It is suggested that Furaneol methylation is mediated by an O-methyltransferase activity and that this activity increases during fruit ripening.
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