Smaller berries = better skin to fruit ratio = more tannin.(Warmer years will produce small berries.) Petit Verdot and Cabernet Sauvignon have a thick skin and can extract regarding tannins. Wine Tasting is fun so don't make it a complicated, scientific adventure. https://postheaven.net/fieldpocket58/how-to-taste-wine-4-steps-you-ought-to-know