Once slaughtered or harvested, some initial pre-processing of food commodities must occur to reduce surface contaminants such as dirt and debris and possibly reduce epithelial microflora. Such steps include initial rinsing and trimming but may include peeling for horticultural commodities, de-scaling for fish, and hair removal or evisceration for animal products. Washing in water is an essential step in preparing produce (whole or processed) products for consumption; it reduces cross-contamination by removing dust and soil particles that harbour many micro-organisms. Such cleaning steps are used for a range of raw materials for food production and may include soaking (e.g. potatoes), spraying (e.g. animal carcasses), flotation washing (e.g. apples); dry cleaning procedures include separation by air (e.g. cereal grains), magnetism (for metal removal) or physical methods (e.g. centrifugal clarification of milk). However, wash water harbours residual dirt and microflora and therefore need antimicrobial agents (e.g. chlorine) to be added or water treatment (e.g. filtration) to occur before reuse or dumping.