PLAIN WHITE FLOUR Also known as all-purpose flour, this is the standard choice for making roux-based sauces and gravies. Its fine, smooth texture combines easily with melted fat for a sauce with a roux base, so that when heated, the starch grains burst and cook, thickening the sauce liquid. White flour usually contains 70-75 per cent of the wheatgrain. Most of the bran and wheatgerm have been removed during milling, leaving it almost white, so it is excellent for thickening white sauces. White flour is chemically bleached, making it pale in colour and therefore more suitable for white sauces than unbleached, stone ground flours.