Forms: 1 ʓist, ʓyst, 5 ȝest(e, ȝeest, yeest, 6–9 yest, 7 eyst (?), 8–9 dial. east, 9 dial. yist, 7– yeast. [OE. (late WS.) ȝist, Anglian *ʓest, corresp. to MLG. gest dregs, dirt, MDu. ghist, Du. gist, gest yeast, MHG. jest, gest, gist (G. gischt, gäscht) yeast, froth, ON. jastr yeast, related to OHG. jesan, gesan (MHG. jesen, gesen, gern, G. gähren to ferment), the causative OHG. jerian, gerian to cause to ferment, and ON. gerǒ yeast. The underlying base jes- is found also in Skr. yás(y)ati to seethe, boil, práyastas bubbling over, Zend yah- to boil (intr.), Alb. ǵeš buken I knead bread, Gr. ζέω I boil, ζεστός boiled, W. iās seething.]
1. A yellowish substance produced as a froth or as a sediment during the alcoholic fermentation of malt worts and other saccharine fluids, and used in the manufacture of beer and to leaven bread.
Modern science distinguishes two kinds of yeast, surface or top yeast (G. oberhefe) and under, sediment, or bottom yeast (G. unterhefe), the former propagated by buds, the latter by spores, of the fungus Saccharomyces cerevisiæ. The yeast of beer is used medicinally as an antiseptic and stimulant in low fevers, and as an application to ulcers.
c. 1000. Sax. Leechd., II. 266. Læt þonne hwon ʓestandan, do of þa gaʓellan, do þonne niwne ʓist.
1530. Palsgr., 291/1. Yest or barme for ale, leueton.
1591. A. W., Bk. Cookrye, 8. Put into your broth a spoonfull of yest.
1600. Surflet, Country Farm, V. xxiii. 725. They renewe the force and strength of the yeast or leuen euerie hower with beere already made, so long as till the said leuen or yeast become strong inough of it selfe.
1612. Househ. Bks. Howard of Naworth (Surtees), 41. To Harry Baker to bestow in eyst vs.
1664. Butler, Hud., II. iii. 119. When Yeast, and outward means do fail, And have no pow’r to work on Ale.
1666. G. Harvey, Morb. Angl., viii. (1672), 19. Those sharp scorbutick dregs imitating the nature of yist.
1743. Lond. & Country Brewer, III. (ed. 2), 214. Yeast … consists of a great Quantity of subtile and spirituous Particles, wrapped up in such as are viscid.
1804. Med. Jrnl., XII. 192. An instance of a young gentleman in the last stage of typhus fever, being cured by the use of yeast.
1843. R. J. Graves, Syst. Clin. Med., Introd. Lect. 34. Sugar by presence of yest [is made to resolve itself] into alcohol and carbonic acid.
1858. Lewes, Sea-side Studies, 314. There are two kinds of yeast, or rather two forms of the same plant. The one is called ‘surface’ yeast, the other ‘sediment’ yeast. The former requires a temperature of 70° to 80° Fahrenheit; the latter 32° to 45°.
1877. Huxley, Physiogr., 193. The porous texture of bread is due to the presence of bubbles of gas evolved by the fermentation of the yeast.
b. With qualifying word, as beer-yeast; applied esp. to common yeast drained, pressed dry, and made into a cake in order to be kept for a time: see quots. and cf. yeast-cake, -powder (4).
[1781. T. Henry, Acc. Method Pres. Water, etc. 26. The Process for making artificial Yeast. Boil flour and water together to the consistence of treacle…. In about two days, such a degree of fermentation will have taken place, as to give the mixture the appearance of yeast.]
1858. Simmonds, Dict. Trade, s.v., German yeast is now imported to a considerable extent in a dried form from the Continent.
1878. Chambers’s Encycl., s.v. Yeast, Patent Yeast is exactly similar [to German Yeast], but is raised from a wort made purposely from malt and hops. Artificial Yeast is a dough of wheat or other flour, mixed with a small quantity of common yeast, and made into small cakes, which are dried.
1879. Webster, Suppl., Press-yeast, the yeasty froth from the surface of a fermenting fluid, washed and pressed into cakes for bakers’ use.
1889. Pall Mall Gaz., 1 July, 3/3. Patent yeast is either made by the baker himself or is bought from the yeast merchant. It … leaves an unpleasant smell and taste in the bread.
c. fig. = LEAVEN sb. 2 a.
1760–72. H. Brooke, Fool of Qual. (1809), III. 35. Though liberty has no relation to party…, there is yet a kind of yest observable in its nature, which may be necessary to the fermentation and working up of virtue.
1818. Keats, Lett., Wks. 1889, III. 105. The best of men have but a portion of good in them—a kind of spiritual yeast in their frames, which creates the ferment of existence.
1873. Dixon, Two Queens, VI. iv. I. 324. The Plantagenet yeast being strong within his sons.
d. Path. A fungus of the genus Saccharomyces present in certain skin-diseases.
1899. Allbutt’s Syst. Med., VIII. 76. The common saccharomyces or yeast of the scalp.
† 2. The froth or ‘head’ of new or fermenting beer. Obs.
c. 1430. Two Cookery-bks., 10. Þen take ȝest of New ale an caste þer-to.
c. 1440. Promp. Parv., 537/2. Ȝeest, berme, spuma.
1683. Salmon, Doron Med., I. 241. Let not the Head, or Yest work over at the bungs.
1716. Gay, Trivia, II. 290. When drays bound high, they never cross behind, When bubbling yest is blown by gusts of wind.
3. transf. Foam or froth, as of troubled water.
1611. Shaks., Wint. T., III. iii. 94. The Shippe boaring the Moone with her maine Mast, and anon swallowed with yest and froth.
1818. Byron, Ch. Har., IV. clxxxi. They melt into thy yeast of waves.
1864. Q. Rev., April, 311. The dim headlands of new empires which are already looming darkly up out of the yeast of stormy waves into which the wreck of the old Union is sinking.
4. attrib. and Comb., as yeast-ash, -cell, -culture, dumpling, -fungus, -germ, -poultice, -scum; yeast-like adj. and adv.; yeast-beer, new beer with which a small quantity of fermenting wort has been mixed to make it ‘work’; yeast-bitten a. (see quot.); yeast-budding, a direct budding or germination of spores from other spores as occurring in Saccharomyces and other fungi; yeast-cake (see 1 b); † yeast-fat, a fermenting-vat; yeast-plant, any plant of the genus Saccharomyces, esp. S. cerevisiæ, which produces fermentation in saccharine fluids; yeast-powder, the powder of dried yeast (cf. 1 b), also (U.S.) baking powder.
1875. Huxley & Martin, Elem. Biol. (1877), 6. Pasteur himself used actual *yeast ash.
1829. Art of Brewing (ed. 2), 54/2 (L.U.K.). The gas being too weak to buoy up the now close head of the tun, the yeast might partially or wholly subside, and the ale would become *yeast-bitten; it would receive that disagreeable taste which the head had acquired by too long exposure to the atmospheric air.
1898. Porter, trans. Strasburger’s Bot., 350. Such a method of multiplication of conidia by budding is termed *yeast budding, and the conidia are termed yeast conidia.
1795. Sir J. Dalrymple, Lett. to Admiralty, 4. I put in the Wort-cake and *Yeast-cake at his sight.
1847–9. Todd’s Cycl. Anat., IV. I. 101/2. The importance of *yeast-cells in the phenomena of fermentation.
1899. Cagney, trans. von Jaksch’s Clin. Diagn., v. (ed. 4), 200. Yeast-cells (Saccharomycetes) are the commonest form of parasite in the intestinal discharges.
1898. Allbutt’s Syst. Med., V. 420. Protein or dead cultures of bacteria, filtered *yeast-cultures.
1747. Mrs. Glasse, Cookery, ix. 112. *East Dumplings. First make a light Dough … with Flour, Water, Salt, and Yeast.
1367. Priory of Finchale (Surtees), p. lxxviii. j *yestefatt.
1876. trans. Wagner’s Gen. Pathol., 86. The several fermentation or *yeast-fungi.
1867. Edin. Rev., April, 395. The fermentation occurs only in presence of the *yeast germs.
1868. Rep. U. S. Comm. Agric. (1869), 277. The … *yeast-like appearance of the decomposing brood.
1857. Henfrey, Bot., § 813. What is called the *‘Yeast-plant’ consists of a particular form of the vegetative structure (mycelium) of a Fungus.
1871. Tyndall, Fragm. Sci. (1879), II. xii. 257. The brewer deliberately sows the yeast-plant.
1860. Mayne, Expos. Lex., Cataplasma Fermenti, … the *yeast poultice, for sloughing and mortification; flour mixed with yeast and heated till it rise.
1795. Sir J. Dalrymple, Lett. to Admiralty, 2. Wort-cake and *Yeast-powder made at the King’s breweries.
1888. Encycl. Brit., XXIV. 602/1. After ten to fourteen days the *yeast-scum on the surface disappears.
