Comparison of analytical methods for the determination of condensed tannins in grape skin

Background and Aims: Condensed tannins extracted from grapes are an important organoleptic component of wine. Assessing tannin level in grapes requires an effective analytical method. This study compared the efficacy of three analytical methods. Methods and Results: Condensed tannin levels were measured in 38 grape skin samples by protein and methylcellulose precipitation and by high-performance liquid chromatography (HPLC)- phloroglucinolysis. Total phenolics were determined by absorbance at 280 nm. Tannin levels by protein and methylcellulose precipitation were of similar magnitude, while levels determined by HPLCphloroglucinolysis were generally higher. No correlation was found between the level of phenolics and tannins by any of the methods employed. Neither was there a correlation between tannin levels determined by HPLC-phloroglucinolysis and by precipitation, although previously a strong correlation had been reported between protein precipitation and HPLC-phloroglucinolysis in wine. Conclusions: The ratio of tannin to non-tannin phenolics is highly variable between cultivars. Each analytical method measures a different fraction of the tannin extracted from grape skin. Significance of the Study: The disparity between analytical methods requires that method selection reflect the decision-making that will utilise the information produced. For example, protein precipitation of tannins by bovine serum albumin (BSA) has been correlated with perceived astringency; consequently this may be the best indicator of potential mouthfeel

How to decide whether to move species threatened by climate change

Introducing species to areas outside their historical range to secure their future under climate change is a controversial strategy for preventing extinction. While the debate over the wisdom of this strategy continues, such introductions are already taking place. Previous frameworks for analysing the decision to introduce have lacked a quantifiable management objective and mathematically rigorous problem formulation. Here we develop the first rigorous quantitative framework for deciding whether or not a particular introduction should go ahead, which species to prioritize for introduction, and where and how to introduce them. It can also be used to compare introduction with alternative management actions, and to prioritise questions for future research. We apply the framework to a case study of tuatara (Sphenodon punctatus) in New Zealand. While simple and accessible, this framework can accommodate uncertainty in predictions and values. It provides essential support for the existing IUCN guidelines by presenting a quantitative process for better decision-making about conservation introductions