In cooking, a leavening agent (/ˈlɛvənɪŋ/) or raising agent, also called a leaven (/ˈlɛvən/) or leavener, is any one of a number of substances used in doughs and batters that cause a foaming action (gas bubbles) that lightens and softens the mixture. An alternative or supplement to leavening agents is mechanical action by which air is incorporated (i.e. kneading). Leavening agents can be biological or synthetic chemical compounds. The gas produced is often carbon dioxide, or occasionally hydrogen.[1]
When a dough or batter is mixed, the starch in the flour and the water in the dough form a matrix[2] (often supported further by proteins like gluten or polysaccharides, such as pentosans or xanthan gum). The starch then gelatinizes and sets, leaving gas bubbles that remain.
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Transcription
welcome to exploring the 18th century with James Townsend inside today we're starting a series of in-depth episodes are related to leavening and specifically chemical leavening today I'm joined by Kevin Carter he's the guy who's usually behind the camera he does a lot of the research and writing here at James Townsend and son and he also construct the catalog welcome Kevin, thank you, today we're going to be talking about about leavening yes you know I think a great place to start today would be to kind of step back and review the different types of leavening that were used in the 18th century we talked a little bit about this in a previous video that we produced couple years ago and I think it might be just a really good jumping-off point into into our research first of all there's Barm which is yeast that you would get, liquid yeast you would get from the brewer. When you look in the 18th century English cookbooks when they use the word "Yeast" or barm those terms generally interchangeable and and barm is that foam that develops on the top of a batch beer its brewing the krausen and they would sell it in liquid form pints, and that's one of the hint you getting the recipes when they say a pint of yeast today would say "a pint of yeast" what are they talking about they actually mean by barm liquid least it wasn't very concentrated the barm is usually the the foam or the krausen that's off the top of the beer but there's another kind other yeast right right the French would use the spent yeast of the bottom the beer the lees and there is a 1830 reference the talks about how they would actually take that spent yeast put in bags, let the beer drain out then wash it and then dry in into cakes and that's a nineteenth-century resource I would probably say that that was growing in popularity in the nineteenth century eighteenth-century there was more use of "old dough" techniques yes yes the leaven, right what they would call leaven or old dough right, where they would take accually a chunk of the dough from the previous batch, so off made start off with some kind ever a yeast from the brewer right the very first batch and then every subsequent batch they would just use some old dough from last yesterday's batch or two days ago or what ever, the last time they baked. Especially the commercial baker and he wouldn't do take a lump in the dough from the batch of bread, probably a big lump, and then they would put it they would store it either in flour or in salt and it would keep for quite a while. Now in warmer temperatures that leaven would often times go sour and then they would need to refresh with either barm or you start over. You don't see any references to English eighteenth-century wild yeast culture development people didn't say oh you don't have any use just leave this out and it will develop its own that isn't to say that they didn't do that in other cultures German sourdough bread say you know any kind in Northern European Rye breads were sourdough, even in america there is a brand called yankee sour bread likely from other cultural mix is that they'd people in North America had that the British, It's like they are in their own little culture and they're going to do what they think is right and they weren't they were not excited about sour breads They didn't want sour breads. So anyway again in Review we have barm we have leaven we also have mechanical leavening which usually involved eggs or specifically egg whites where they would sit and whip those things up and and until they were infused with air and then they would gently fold that into a cake batter to keep to preserve the air in the batter us so we had mechanical leavening as well Then there's this issue this matter of chemical leavening a matter in great debate has to when that started and we're gonna be looking closer into that. Dig into that here's one here's one little idea I am going to throw this at you. I haven't talked about this before when we did the fritters we added the ale and it was a modern ail of course, it's carbonated and it actually fluffed up the batter well you know it's interesting you say that there are eighteenth-century references to some using carbonated water in bread to improve, they would say improve the fermentation that what was happening was that carbonation was was releasing the gas so you mix up and it froths right up right so there's there's even reference of Sarasoda Springs in New York on that apparently been a carbonated water source and the bakers in that area produce superior bread they also even tried to sort a inject air into dough they were doing weird things in late eighteenth-century saying could we do this does this work right I found one reference to the differences in even in in kneading methods English bakers apparently with thrust their fists into the dough and then open their fingers to try and get as much air into the dough was they kneaded it, moving the bottom dough up to the top and rotating and they would do that for a long time people in the 18th century really didn't know what was happening with yeast and there was this concept called fixed air okay even the earliest mentions the chemical leavenings by the chemists would talk about how these compounds contained fixed air that would be released by the heat They believe that the same thing was happening with yeast that their little pockets of air, compressed air little nodules of compressed air right, you see that idea carried over into mechanical leavening where they're actually injecting air into the eggs you know fixing the air into the eggs for it to be released later on and during the baking process it wasn't until 1830-1840 that it was discovered that the yeast is alive it is an organism, it's a plant it's a mold, and it's actually producing carbolic acid or carbon dioxide as a result They knew what worked, empirically, right and so they came up with all these different processes to to make things work right and we're gonna talk about that in another episode, but how that even applied to the earliest uses a chemical leavening, so the earliest uses of chemical leavening? Is that is the next episode? yes, The next episode we're going to be delving deeper into this the very kernel, the very beginning of the ideas of chemical leavening. If you're new to the channel make sure to subscribe you can also check this link and we'll take you directly to our website and you can request a print catalog thanks so much for watching
Biological leavening agents
- Saccharomyces cerevisiae producing carbon dioxide found in:
- baker's yeast
- Beer barm (unpasteurised—live yeast)
- ginger beer
- kefir
- sourdough starter
- Clostridium perfringens producing hydrogen found in salt-rising bread
Chemical leavening agents
Chemical leavens are mixtures or compounds that release gases when they react with each other, with moisture, or with heat. Most are based on a combination of acid (usually a low molecular weight organic acid) and a salt of bicarbonate (HCO3−). After they act, these compounds leave behind a chemical salt. Chemical leavens are used in quick breads and cakes, as well as cookies and numerous other applications where a long biological fermentation is impractical or undesirable.
History
Chemical leavening using pearl ash as a leavening agent was mentioned by Amelia Simmons in her American Cookery,[3] published in 1796.[4]
Since chemical expertise is required to create a functional chemical leaven without producing off-flavors from the chemical precursors involved, such substances are often mixed into premeasured combinations for maximum results. These are generally referred to as baking powders. Sour milk and carbonates were used in the 1800s. The breakthrough in chemical leavening agents occurred in the 1930s with the introduction of monocalcium phosphates (Ca(H2PO4)2). Other leavening agents developed include sodium aluminium sulfate (NaAl(SO4)2·12H2O), disodium pyrophosphate (Na2H2P2O7), and sodium aluminium phosphates (NaH14Al3(PO4)8·4H2O and Na3H15Al2(PO4)8). These compounds combine with sodium bicarbonate to give carbon dioxide in a predictable manner.[5]
Other leavens
Steam and air are used as leavening agents when they expand upon heating.[6] To take advantage of this style of leavening, the baking must be done at high enough temperatures to flash the water to steam, with a batter that is capable of holding the steam in until set. This effect is typically used in popovers, in Yorkshire puddings, and, to a lesser extent, in tempura.
Mechanical leavening
Using a whisk on certain liquids, notably cream or egg whites, can also create foams through mechanical action. This is the method employed in the making of sponge cakes, where an egg protein matrix produced by vigorous whipping provides almost all the structure of the finished product.
The Chorleywood bread process uses a mix of biological and mechanical leavening to produce bread; while it is considered by food processors[who?] to be an effective way to deal with the soft wheat flours characteristic of British Isles agriculture, it is controversial[according to whom?] due to a perceived lack of quality in the final product. The process has nevertheless been adapted by industrial bakers in other parts of the world.
See also
- Aerated Bread Company, bakeries started in 1862 in the UK that made carbon dioxide leavened bread
- Baking powder
- Chametz
- Parable of the Leaven
- Passover
- Unleavened bread
References
- ^ Jacobs, Morris Boris (1951). The Chemistry and Technology of Food and Food Products. Hoboken, NJ: Interscience Publishers. p. 1932.
- ^ Hanft, Steven L. (2016). Fachenglisch für Laborberufe. Weinheim: John Wiley & Sons. p. 208. ISBN 978-3-527-33512-1.
- ^ Simmons, Amelia; Mary Tolford Wilson (1984) [1958]. The First American Cookbook (1984 reprint ed.). Mineola, NY: Dover. ISBN 0-486-24710-4.
- ^ Smith, Andrew F. (2007-05-01). The Oxford Companion to American Food and Drink. Oxford University Press. ISBN 978-0-19-988576-3.
- ^ John Brodie, John Godber "Bakery Processes, Chemical Leavening Agents" in Kirk-Othmer Encyclopedia of Chemical Technology 2001, John Wiley & Sons. doi:10.1002/0471238961.0308051303082114.a01.pub2
- ^ Ensminger, Marion Eugene; Ensminger, Audrey H. (1993). Foods & Nutrition Encyclopedia, Two Volume Set. Boca Raton, FL: CRC Press. p. 249. ISBN 0-8493-8980-1.
Further reading
- Matz, S (1972). "Bakery Technology and Engineering", AVI Publishing Co.
External links
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- Wikibooks Cookbook has a recipe/module on Leavening agent
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