Blanching (cooking)

[1] 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.

[4][6] The blanching process expels air trapped inside plant tissues, which is a vital step before canning.

[4] Blanching prevents the expansion of air during processing, which reduces strain on the containers and the risk of cans having faulty seams.

[4] When almonds or pistachios are blanched, the skin of the nut (botanically the seed coat surrounding the embryo) softens and can be easily removed later.

[4] Other uses of blanching are enhancing drying rate and product quality, decreasing microbial load, removing pesticide and toxic residues, increasing extraction of bioactive compounds, surface cleaning, removing damaged seeds or foreign materials, killing parasites and their eggs, and reducing oil uptake.

[2] This method greatly reduces the leaching of water-soluble compounds from the product and is the preferred technique for smaller foods and those with cut surfaces.

This reduced heat exposure preserves color, flavor, and overall quality of the food; however, evaporation may occur leading to lower masses and product yields.

This method of cooling prevents the leaching of water-soluble nutrients; however, the air causes evaporation and lowers the mass of the vegetable—a monetary disadvantage for industry.

[2] Blanching with reused water can lead to a buildup of water-soluble compounds that are considered pollutants, and therefore must be properly treated before being discharged.

[4] This can increase capital costs at the industrial level and has been a main reason for the development of newer blanching technologies.