Optimization of a method for the extraction and quantification of carotenoids and chlorophylls during ripening in grape berries (Vitis vinifera cv. Merlot).

An extraction method to identify and quantify the carotenoid and chlorophyll profile of lyophilized tissue from unripe (green) to ripe (red) Merlot grape berries was developed. The RP-HPLC method baseline separated all of the carotenoids and chlorophylls and their derivatives. Problems encountered during sample storage and extraction are discussed as well as possible alternative methods. This study confirmed that carotenoids and chlorophylls decreased on a per berry (microg/berry) and concentration (microg/g) basis from veraison to harvest over two growing seasons. The carotenoid 5,8-epoxy-beta-carotene was quantified for the first time in grapes and represents a significant amount of the total carotenoids present at harvest. All the carotenoids and chlorophylls except beta-carotene appeared to be sensitive to seasonal variation in climatic conditions. Lutein and beta-carotene were found to be the most abundant carotenoids present in Merlot grape berries together with chlorophyll a for both seasons studied.