thumb|The first step: green beans in boiling water
thumb|Broccoli being shocked in cold water to complete the blanching
Blanching is a process in which a food, usually a vegetable or fruit, is partially cooked by first scalding in boiling water, then removing after a brief timed interval, and finally plunging into iced water or placing under cold running water (known as shocking or refreshing) to halt the cooking process. Blanching foods helps reduce quality loss over time. Blanching is often used as a treatment prior to freezing, dehydrating, or canning vegetables or fruits to deactivate enzymes, modify texture, remove the peel and wilt tissue. The inactivation of enzymes preserves colour, flavour, and nutritional value. Other benefits of blanching include removing pesticide residues and decreasing microbial load. Catalase and peroxidase are commonly used to determine blanching success, since they are the most thermal-resistant enzymes of concern.
The blanching process expels air trapped inside plant tissues, which is a vital step before canning.
thumb|Blanched almonds
Fruit, vegetable, and nut peeling is also important in food processing.
A limitation to hot water blanching is the leaching of water-soluble nutrients and the degradation of thermal sensitive compounds.