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J Agric Food Chem. 2016 Jun 8;64(22):4487-96. doi: 10.1021/acs.jafc.6b01013. Epub 2016 May 27.

Impact of Leaf Removal, Applied Before and After Flowering, on Anthocyanin, Tannin, and Methoxypyrazine Concentrations in 'Merlot' (Vitis vinifera L.) Grapes and Wines.

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Wine Research Centre, University of Nova Gorica , Lanthieri Palace, Glavni trg 8, SI-5271 Vipava, Slovenia.
Department of Agricultural, Food, Environmental and Animal Sciences, University of Udine , via delle Scienze 206, 33100 Udine, Italy.
Central Laboratories, Agricultural Institute of Slovenia , Hacquetova ulica 17, SI- 1000 Ljubljana, Slovenia.
Department of Horticulture, Michigan State University , 1066 Bogue Street, East Lansing, Michigan 48824, United States.
Wine Research Centre, The University of British Columbia , 2205 East Mall, Vancouver British Columbia, V6T 1Z4 Canada.


The development and accumulation of secondary metabolites in grapes determine wine color, taste, and aroma. This study aimed to investigate the effect of leaf removal before flowering, a practice recently introduced to reduce cluster compactness and Botrytis rot, on anthocyanin, tannin, and methoxypyrazine concentrations in 'Merlot' grapes and wines. Leaf removal before flowering was compared with leaf removal after flowering and an untreated control. No effects on tannin and anthocyanin concentrations in grapes were observed. Both treatments reduced levels of 3-isobutyl-2-methoxypyrazine (IBMP) in the grapes and the derived wines, although the after-flowering treatment did so to a greater degree in the fruit specifically. Leaf removal before flowering can be used to reduce cluster compactness, Botrytis rot, and grape and wine IBMP concentration and to improve wine color intensity but at the expense of cluster weight and vine yield. Leaf removal after flowering accomplishes essentially the same results without loss of yield.


Botrytis; IBMP; antioxidants; aroma; flavonoids; fruit ripening; metabolites; polyphenols

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