Oak extract application to grapevines as a plant biostimulant to increase wine polyphenols

Oak extract is a mixture of compounds including phenolics (volatiles and non volatiles), which could act as plant biostimulant if they are able to modulate plant physiological response. It is known that it can modify grape volatile composition after the application over grapevines, impacting on wine aroma, but no studies have been carried out on phenolic composition. So, the aim of this work was to evaluate the phenolic composition of wines elaborated from Monastrell grapevines treated with a commercial oak extract in order to study its biostimulant activity. Several families of polyphenols were studied, including phenolic acids, stilbenes, flavanols, flavonols and anthocyanins, which were analyzed by HPLC-DAD-MS. Results showed oak extract could be considered like an important biostimulant of grape polyphenols, since it affected grape composition, producing less alcoholic and add wines with higher colour intensity, lower shade and so a more stable colour and higher content of polyphenols such as gallic acid, hydroxycynnamoyltartaric acids, acylated anthocyanins, flavanols and stilbenes. (C) 2013 Elsevier Ltd. All rights reserved.