Sirloin is one of the most popular steaks offered by butchers and caterers. The muscle is consistent in shape, flavour and tenderness. There is a little fat on one edge of the steak (the bark) that should be creamy with a hint of green (grass fed). Fat is often infused through the muscle (marbling) and is considered a quality mark by some. The real key to a great steak is dry-aging. A minimum of 21 days hanging is needed to mature the steak for the table. It is worth noting that at about 21 days, healthy bacteria begin the putrefaction (tenderising) process and a thin khaki coloured seam appears on the edge of the muscle. This indicates that the steak is 'ripe' and ready to be cooked.