Ketchup

Ketchup (also catsup and catchup) is a sauce that in the United States is made from tomato concentrate or tomato liquid, vinegar, a sweetener and spices. The word comes from a southern Chinese name for a fish brine, and the first English recipes for it contained no tomato. Federal regulations define the product and include a test of how far it runs in 30 seconds.

The usual derivation is from the Hokkien words kê-chiap, kôe-tsap or kôe-chiap. According to the Oxford English Dictionary, kôe is a kind of fish and chiap means "juice, sauce". The sauce was a fermented paste, first made in southern China around 300 BC from fish entrails, meat and soybeans, and it traveled along maritime trade routes. British sailors brought it home in the late 17th century.^[1]

English spellings wandered through kitchup, catchup, katchop and catshup. Catsup had a fashionable air by 1730, when Jonathan Swift listed it among foreign indulgences. A cookbook author of 1831 wrote that the word "can be pronounced by every body but spelled by nobody". In Britain ketchup prevailed around 1850; in the United States catsup stayed ahead until the 1980s.^[1]

Eighteenth-century ketchups were made of oysters, mussels, mushrooms, walnuts and fruit. One, the "Prince of Wales' ketchup", combined elderberries and anchovies.^[1] The first Western recipe, in Eliza Smith's The Compleat Housewife of 1727, spells the word "katchup" and calls for anchovies and white wine vinegar.^[2]

The earliest tomato recipe known is from 1812, by James Mease, a Philadelphia scientist. The H. J. Heinz Company, formed in 1869 to sell horseradish, began selling tomato ketchup in 1876 and was patenting its glass ketchup bottles by 1882.^[2]

Commercial ketchup of the late 19th century was often made from the waste of tomato canning, colored with coal-tar dyes, and it spoiled easily. Manufacturers relied on sodium benzoate to keep it. After the Pure Food and Drug Act of 1906, the chemist Harvey Wiley, who ran the federal Bureau of Chemistry, opposed the preservative, and a trade bulletin of June 24, 1907, dared him to prove his case or show how ketchup could be made without it. He gave the job to a married couple at the Department of Agriculture, Katherine and Arvill Bitting.^[3]

The Bittings examined more than 1,600 bottles of ketchup, visited 40 canneries that made tomato pulp and toured 20 ketchup factories. Homemade ketchup, they found, was thicker than the bottled kind and held more vinegar and sugar. Their report, USDA Bulletin 119 of January 1909, advised ripe tomatoes, more vinegar, a longer boil to thicken the sauce, and sterilizing it after cooking. Heinz and two other makers already made ketchup without preservatives; the bulletin made their methods public. An advisory board of university scientists ruled sodium benzoate safe in small amounts, but most manufacturers dropped it anyway.^[3]

Title 21 of the Code of Federal Regulations, section 155.194, begins: "Catsup, ketchup, or catchup is the food prepared from" one or more of several tomato ingredients, among them tomato concentrate and "the liquid derived from mature tomatoes of the red or reddish varieties". It must contain vinegar, a nutritive carbohydrate sweetener and seasoning, and the label must call it "Catsup", "Ketchup" or "Catchup". It may be preserved "by heat sterilization (canning), refrigeration, or freezing".^[4]

The standard of quality is a measurement of flow. A sample goes into a Bostwick consistometer, a trough closed at one end by a spring-loaded gate, and the gate is released. After 30 seconds at 20 °C the sample may have run no more than 14 centimeters along the trough. A product that runs farther may carry a label saying it is below standard in quality because of low consistency.^[4]

Ketchup is a suspension of tomato particles in a sweet, acid liquid, and it does not obey the simple viscosity law that water does. A 2013 study by Juszczak and colleagues, who added modified starches to ketchup and measured the results, describes it as a shear-thinning fluid with a tendency toward yield stress, together with thixotropy and viscoelasticity.^[5] Yield stress is the push below which a material does not flow at all. A full bottle of ketchup holds still until it is shaken or struck, then gives way, and the thinning that follows is what sends the sauce onto the plate in one rush.

Molecular Reality Corporation has listed a ketchup on the shelf of provisions for its live molecular stream since June 30, 2026. The entry reads "A sample of Safeway signature select ketchup, kept at 4C."^[6] Federal regulations name refrigeration among the permitted ways to preserve ketchup.^[4]

The company's field guide asks "Why ketchup, salsa, and tap water?" and answers that "honest stress tests use ugly samples". For ketchup in particular it says: "The road to the small end runs through the big end, and the big end loves ketchup."^[7] The pore on the stream is 200 micrometers wide, about the scale at which a Coulter counter counts cells. By October 2026 none of the recordings in the company's Streams archive had a condiment as its sample.^[8]

• Condiment trials
• Keltar's Field Guide to Molecular Reality
• 200-micron laser-drilled pore