The preparation of food for consumption, as well as manufacturing of various products from different raw materials, usually involves the application of several discrete unit operations and processes. Many operations, such as washing, trimming, milling, leaching, disintegrating, mechanical separation, and use of membrane techniques, may decrease the natural toxicity of some raw materials by eliminating specific undesirable components. Examples include the removal of most of the fluorine compounds from Antarctic krill

by peeling early after catch, or flushing pathogenic bacteria and viruses from live oysters by depuration in disinfected water. However, processing operations may also reduce the biological value of the products, by leaching or destroying essential ingredients, especially water-soluble vitamins.