Abstract
Berry quality is an important issue in wineprocessing, however evaluating characteristics in a single berry level is very complex. The Phenolic compound analysis is more challenging because of the limited amount of material and a mixture of skin, pulp and seed. No clear protocol exists for evaluating these compounds from single berries. The aim of our investigation was to develop such a protocol. Single whole grape berries samples were homogenized in 20 replicates by 5 different methods. The most effective method was when berry was placed in a mortar and was crushed with a pestle under liquid nitrogen until seeds were clearly visible. Seeds were then taken from the mortar and crushed between two stainless steel plates with a hammer, and returned to the mortar without residues. Homogenization continued until the sample had a powdery appearance. The homogenized samples were taken for further analysis such as total polyphenols, total anthocyanin contents and total antioxidant capacity. Our results demonstrate that single berries could be processed and that the homogenates were suitable for taking chemically uniform subsamples.
Highlights
Variability in fruit size and composition can greatly effect wine quality (Fernandez et al, 2006), and the resulting uneven berry ripening generally results in poor fruit quality
Several authors have examined the variability of vineyards on a vine and cluster basis (Kristic et al, 2002, Trought & Tannoc 1996)
Basic quantitative and qualitative parameters are routinely examined on cluster level in the practice
Summary
Variability in fruit size and composition can greatly effect wine quality (Fernandez et al, 2006), and the resulting uneven berry ripening generally results in poor fruit quality. Several authors have examined the variability of vineyards on a vine and cluster basis (Kristic et al, 2002, Trought & Tannoc 1996). Non-homogeneous populations of berries or clusters can elevate the sample size required for accurate vineyard sampling (Kasimatis & Vilas 1985; Wolpert & Vilas 1992). Single berry measurements are required to determine the effect of viticultural practices on berry variability within clusters and the adequate sample size needed for vineyard sampling. Basic quantitative (berry weight, seed number/berry) and qualitative (soluble solids) parameters are routinely examined on cluster level in the practice. Evaluating the phenolic compounds at the single berry level is more complex, due to the presence of seeds and skins. Sub-samples have to be taken to determine several indices from the same berry, which is challenging because of the limited amount of juice and tissue from a single berry
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