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 associated with tannins. Wine Tasting is fun so don't make it a complicated, scientific adventure. https://zenwriting.net/friendjeans4/new-ideas-for-a-wine-cellar-of-your-home