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Dishwashing or dish washing, also known as washing up, is the process of cleaning cooking utensils, dishes, cutlery and other items to prevent foodborne illness. This is either achieved by hand in a sink using dishwashing detergent or by using a dishwasher and may take place in a kitchen, utility room, scullery or elsewhere.
Most institutions have a dish-washing machine which sanitizes dishes by a final rinse in either very hot water or a chemical sanitizing solution such as dilute bleach solution (50-100 parts per million chlorine; about 2 ml of 5% bleach per litre of water, approximately one capful of bleach per gallon water). Dishes are placed on large trays and fed onto rollers through the machine. Dishwashers typically exceed 145 °F (63 °C) and kill all germs, while hand-washing reaches temperatures of at most 104 °F (40 °C).
Bleach is less effective in the presence of organic debris, so a small amount of food residue can be enough to permit survival of, e.g., Salmonella bacteria. Scrubbing followed by soaking in bleach is effective at reducing Salmonella contamination, but even this method does not completely eliminate Salmonella bacteria.
In hand-washing, plastic brushes with nylon bristles are preferred to washcloths or sponges, which can spread microorganisms. Use of soap or sanitizer is mandatory in washing by hand in public food facilities.
Use of hot water and or bleach may sanitize the dishes, however, it does not get rid of FOG (fat, oil and grease). In commercial food preparation units, a grease trap is necessary to trap the FOG items, so they cannot enter the sewage system to contribute to the development of a fatberg.