Cookbook:Gluten
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Gluten is a protein substance formed during the hydration and manipulation of certain grain flours.[1][2][3][4] It contributes important structural properties.
Characteristics
[edit | edit source]Formation
[edit | edit source]Dry flour in itself does not contain gluten, per se.[3] Rather, it contains the two groups of proteins that combine to form gluten: glutenins and gliadins.[2][5] It is only when water is added to the flour that glutenins and gliadins can interact with themselves and each other to form gluten.[1][2][6][7]
When you start with dry flour, the glutenins and gliadins are tightly coiled up and separated from each other.[5][7] When you initially add water, these proteins begin to hydrate and loosen,[5][7] but they are still separated from each other with no significant interaction.[5][8] However, when you begin mixing, the physical agitation of the hydrated proteins stretches them out and forces them to interact with each other.[5][8][9] As they come into contact, the stretched proteins link up with each other[9] and start to form long ordered strands, fibers, and sheets that we know as gluten.[1][5][7] The mixing process also enables the gluten network to interact with water and become more hydrated,[2] which is why dough becomes less wet and sticky as it is kneaded.[2] Interestingly, even if a dough is not kneaded but simply allowed to rest for a very long time (>1 day), a gluten network will still form from the very gradual interaction of the hydrated proteins.[6][9] However, mixing hastens the development for practicality.
Structure and properties
[edit | edit source]Gluten's key characteristic is its viscoelasticity—that is, it has both plasticity (the ability to change shape under pressure) and elasticity (the ability to bounce back afterwards).[2][3][5] This property is a direct result of the glutenin-gliadin interactions in the gluten network, and it is what gives glutenous doughs their stretchy but chewy quality.[5] As long spiraled fibers, the glutenins provide strength and structure to the gluten network, allowing it to maintain and return to a given shape.[2][8][10] On the other hand, the gliadins are more compact and interrupt the strong network wherever they crosslink with the glutenins[2][11]—this interruption prevents the glutenin network from being too strong,[5] which then allows the dough to be plastic and moldable.[5][10] As a result, the degree of viscoelasticity depends on the ratio of glutenin to gliadin in the dough and not just the absolute quantity of gluten.[12]
The gluten network is able to absorb approximately two times its component weights in water.[2][7] Later, when sufficiently heated (such as in baking), the gluten coagulates and solidifies before beginning to dehydrate, all of which provide lasting structure to a dough.[4]
Modulation
[edit | edit source]While we know that hydration and agitation yields gluten, there is still more to the story. The exact characteristics of a gluten network will depend on several factors,[2][3] all of which can be tweaked to yield a different result.
Hydration
[edit | edit source]The degree of hydration in a flour mixture largely governs the strength of the gluten network. Since gluten precursors needs to be well hydrated to form the network, using minimal water in a formula will obviously impede it from forming, allowing the mixture to stay somewhat tender.[2][4][7] However, once you reach full hydration of the gluten network, adding additional water will no longer increase its strength—instead, adding more water after this point will dilute the network, making it harder for them to interact with each other.[2][7][13] Consider, for example, bread dough and crêpe batter. The former has less water but has stronger gluten and is chewier.
The incorporation of fat builds off this hydration property due to how fats interact with water. When you work fat into a gluten network, the fat binds to the component proteins and makes it harder for them to interact with each other and with starches,[5][8][14] thus reducing the strength of the network. Moreover, since fat repels water, fully working fat into the flour before adding water makes it much harder for the precursor proteins to become hydrated and form the gluten network in the first place.[2][3] This tenderizing effect of fat on gluten is referred to as "shortening".[4]
Like fat, sugar also reduces the hydration and therefore the strength of the gluten network. However, it does this by binding to water itself, holding onto it and reducing its interactions with the network.[2][5]
Minerals
[edit | edit source]The addition of salt to a dough strengthens the gluten network.[2][4][7] Salted dough becomes stiffer and less plastic, but it is less likely to tear when stretched than the same dough without salt.[2][7] Similarly, the minerals present in potable water also strengthen gluten,[2][7] which makes it necessary to determine whether the water you're working with is "hard" (mineral-rich) or "soft" (mineral-poor). Unless compensated for, hard water can make a dough too stiff and soft water can make a dough too soft.[2]
Protein content
[edit | edit source]Because glutenins and gliadins in flour are what ultimately create a gluten network, and because these make up the bulk of a flour's protein content,[7] the overall protein content of a flour can determine how much gluten with form.[3] For example, bread flour has more protein than all-purpose flour and therefore creates a stronger gluten network at the same proportion.[5]
Additionally, as described previously, the interactions between glutenins and gliadins provide the viscoelastic property of gluten.[13] As a result, the ratios of glutenins to gliadins in a mixture can drastically affect the gluten network.[13] Since glutenins provide strength and elasticity while gliadins provide flexibility and plasticity, having a mixture too rich in glutenins will create a too-strong network that is hard to stretch, shape, and proof;[2][5] conversely having too much gliadin will make a very loose network that will retain neither its shape nor the necessary gases for leavening.[2]
Complex chemistry: pH and redox
[edit | edit source]The pH of a mixture impacts the strength of its gluten network. Generally, the pH window that produces the strongest gluten is between 5 and 6, or mildly acidic[8]—mixtures that are more acidic or more alkaline than this will reduce its strength.[2][7] This pH can be determined directly, such as by directly adding an acidic or alkaline mixture to a dough, or indirectly, such as by allowing a mixture to ferment and produce acid on its own.[2]
Since a good portion of the strengthening crosslinks in the gluten network come from disulfide bonds, oxidation and reduction can play a role in its strength. Reducing agents make it harder for these bonds to form, thus reducing its strength, while oxidizing agents do the exact opposite.[2][5][15] Air itself (among others) is an oxidizing agent, so older flours and more mixed doughs yield stronger gluten networks.[5]
Manipulation
[edit | edit source]As described in the previous section on formation, mixing and manipulation provides the energy needed to align the gluten component proteins and create the fibrous structure. Up to a certain point, more mixing means more and stronger gluten[3]—this is why over-mixing some cake batters can make them tough, as the gluten is over-developed.[4] However, with very strong industrial mixers, gluten can actually be overworked to the extent that it breaks down and gets soft and fragile again.[2][3][4] Once this occurs, recovery is impossible.
Fermentation
[edit | edit source]Interestingly, fermentation can both strengthen and relax a gluten network. As fermentation releases gas that expands the dough, the expanding bubbles stretch and move the gluten strands, promoting interaction and strengthening the network.[2][7] Much how overmixing can end up weakening the network, so too can over-proofing.[2][7] However, fermentation also gives the network a chance to rest and relax, becoming more plastic.[8]
Physical obstacles: Particles and proteases
[edit | edit source]Flours often contain proteases, which break down gluten and physically weaken it if allowed to sit after hydration. This can be a good thing, usually when you want a stretchier dough with open crumb.[2] However, over-digestion of the gluten can ultimately weaken the network too much if allowed to proceed for too long.[2]
Physical obstacles like particles of bran, seeds, spices, etc, will get in the way of gluten proteins and prevent them from interacting with each other.[2] As expected, this weakens the network.
Heating
[edit | edit source]Like it does with other proteins, heating denatures gluten.[6]
Refinement
[edit | edit source]Once it forms, gluten can be separated from the rest of the dough by washing to remove the starch. The residual stretchy material then dried to produce a tan powder of about 75% gliadin and glutenin by weight,[2][3][7] called gluten flour or "vital wheat gluten". When reconstituted with water, the powder will reform the gluten network.[2]
Source
[edit | edit source]Not all grains contain the precursor proteins necessary to form gluten. Wheat has them in high levels, and both rye and barley contain them as well,[5][7] which is especially relevant for allergen reasons (see below). However, the so-called "quality" of the gluten formed from these grains (and even sub-types within these grains) is not identical. In baking, the "quality" of gluten refers to how strong and elastic it is,[7] and the quality of flour from a given grain is often determined by the ratios of the constituent glutenins and gliadins (see above). For example, while rye does contain gluten precursor proteins, the proportions are suboptimal with too little glutenin,[7] and they don't form a strong gluten network.[16][17][18] Rye also contains a lot of pentosans, which inhibit gluten formation.[19][20][21][22]
Among the grains, wheat generates the best-quality gluten.[2] However, even within wheat, there is a range of glutenin/gliadin contents and ratios.[2] For example, soft wheat varieties have lower protein overall, and a lower glutenin-to-gliadin ratio—these flours yield less and weaker gluten. On the other hand, hard wheats have more protein and a higher glutenin-to-gliadin ratio, producing a stronger gluten network.[2][7] Durum wheat forms highly plastic gluten networks, which make it great for pasta.[13] These different varieties of wheat are formulated into flours with different gluten-forming capacities, such as bread flour and cake flour.[1]
Selection and storage
[edit | edit source]Vital wheat gluten powder should be stored in an airtight container away from light, heat, and moisture.
Techniques
[edit | edit source]Several techniques exist to control and manipulate gluten in doughs.
Relaxation
[edit | edit source]Many gluten-containing doughs incorporate one or more relaxation periods. Depending on the stage of the process, resting the dough allows the gluten to fully hydrate[2] and/or adjust to changes in shape, becoming easier to manipulate.[2][7]
Flour blending
[edit | edit source]Because different grains and varieties of flour produce gluten networks of different qualities, selecting and blending different kinds of flour can help a cook achieve very specific gluten development[2]—for example, blending bread flour and cake flour in precise ratios, or adding wheat flour to a rye dough to improve its strength.
Safety and restrictions
[edit | edit source]While most people can eat gluten with no issue, some individuals can become very sick from consuming even small amounts of gluten (or, more specifically, its precursor proteins). One of the more well-known of these conditions is Celiac disease—those with this condition have damage to their intestines after eating gluten-containing foods.[5][7] It can be tricky to avoid foods containing gluten or its precursors;[3] for more details, see the section on the gluten-free diet.
Use
[edit | edit source]Depending on the food in question, gluten development may be either desirable or undesirable. Typically, gluten is considered crucial in leavened-loaf bread-making, since it is what provides the necessary structure and the capacity to hold gases.[2][3][4] However, for more delicate pastries and cakes, gluten development creates an undesirable toughness. For these, it's important to use the correct flour type and to avoid over-working the mixture. Even so, the gluten does still help them maintain necessary structure.[2]
Vital wheat gluten powder can be added to doughs in order to increase the strength and development of their gluten networks[7][14]—when done correctly, it can improve volume and crumb texture,[2][7] especially with weaker-gluten breads made from whole-grain flour,[15] rye, barley, etc. Too much gluten, however, will make the final product dense and tough.[2] Note also that adding gluten will require an increase in the water content of a recipe.[2]
Because of its textural qualities, refined gluten is often used to make imitation meat, such as seitan.
Substitution
[edit | edit source]Because gluten plays such an important structural role when it is used, it can be very difficult to replace or eliminate[15]—leaving it out often leaves foods dry, dense, and/or crumbly.[7] Typically, blends of other flours, starches, and stabilizers are needed to approximate its effect,[5][7][23] especially in breads. For details, see the dedicated section on gluten-free cooking.
Recipes
[edit | edit source]References
[edit | edit source]- ↑ a b c d Field, Simon Quellen (2011-11-01). Culinary Reactions: The Everyday Chemistry of Cooking. Chicago Review Press. ISBN 978-1-56976-960-7.
- ↑ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao ap Figoni, Paula I. (2010-11-09). How Baking Works: Exploring the Fundamentals of Baking Science. John Wiley & Sons. ISBN 978-0-470-39267-6.
- ↑ a b c d e f g h i j k Labensky, Sarah; Martel, Priscilla; Damme, Eddy Van (2015-01-06). On Baking: A Textbook of Baking and Pastry Fundamentals, Updated Edition. Pearson Education. ISBN 978-0-13-388675-7.
- ↑ a b c d e f g h Gisslen, Wayne (2015-03-12). Essentials of Professional Cooking, 2nd Edition. Wiley Global Education. ISBN 978-1-119-03072-0.
- ↑ a b c d e f g h i j k l m n o p q r s Provost, Joseph J.; Colabroy, Keri L.; Kelly, Brenda S.; Wallert, Mark A. (2016-05-02). The Science of Cooking: Understanding the Biology and Chemistry Behind Food and Cooking. John Wiley & Sons. ISBN 978-1-118-67420-8.
- ↑ a b c Gibson, Mark (2018-01-04). Food Science and the Culinary Arts. Academic Press. ISBN 978-0-12-811817-7.
- ↑ a b c d e f g h i j k l m n o p q r s t u v w x y Gisslen, Wayne (2016-09-21). Professional Baking. John Wiley & Sons. ISBN 978-1-119-14844-9.
- ↑ a b c d e f The Chefs of Le Cordon Bleu (2011-12-02). Le Cordon Bleu Patisserie and Baking Foundations. Cengage Learning. ISBN 978-1-4390-5713-1.
- ↑ a b c Potter, Jeff (2010-07-20). Cooking for Geeks: Real Science, Great Hacks, and Good Food. "O'Reilly Media, Inc.". ISBN 978-1-4493-9587-2.
- ↑ a b Rinsky, Glenn; Rinsky, Laura Halpin (2008-02-28). The Pastry Chef's Companion: A Comprehensive Resource Guide for the Baking and Pastry Professional. John Wiley & Sons. ISBN 978-0-470-00955-0.
- ↑ Davidson, Alan (2014-01-01). Jaine, Tom (ed.). The Oxford Companion to Food. Oxford University Press. doi:10.1093/acref/9780199677337.001.0001. ISBN 978-0-19-967733-7.
- ↑ Wong, Dominic W. S. (2017-11-08). Mechanism and Theory in Food Chemistry, Second Edition. Springer. ISBN 978-3-319-50766-8.
- ↑ a b c d El-Waylly, Sohla (2023-11-02). Start Here: Instructions for Becoming a Better Cook. Random House. ISBN 978-1-5299-1408-5.
- ↑ a b Goldstein, Darra (2015-01-01). The Oxford Companion to Sugar and Sweets. Oxford University Press. doi:10.1093/acref/9780199313396.001.0001. ISBN 978-0-19-931339-6.
- ↑ a b c Zhou, Weibiao; Hui, Y. H. (2014-08-11). Bakery Products Science and Technology. John Wiley & Sons. ISBN 978-1-119-96715-6.
- ↑ Amendola, Joseph; Rees, Nicole (2003-01-03). Understanding Baking: The Art and Science of Baking. Wiley. ISBN 978-0-471-44418-3.
- ↑ Committee, The BC Cook Articulation (2015-10-24). "Rye Flour".
{{cite journal}}: Cite journal requires|journal=(help) - ↑ "Rye Flour | Rye Bread | Baking Ingredients | BAKERpedia". 2015-06-13. Retrieved 2024-09-12.
- ↑ Wang, Mingwei; van Vliet, Ton; Hamer, Robert J (2004-05-01). "How gluten properties are affected by pentosans". Journal of Cereal Science. 39 (3): 395–402. doi:10.1016/j.jcs.2004.02.002. ISSN 0733-5210.
- ↑ Shalene (2024-06-25). "How Rye Works". Modernist Cuisine. Retrieved 2024-09-13.
- ↑ Oest, Marie; Bindrich, Ute; Voß, Alexander; Kaiser, Heinz; Rohn, Sascha (2020-12-19). "Rye Bread Defects: Analysis of Composition and Further Influence Factors as Determinants of Dry-Baking". Foods. 9 (12): 1900. doi:10.3390/foods9121900. ISSN 2304-8158. PMC 7765839. PMID 33352657.
- ↑ "Pentosan | Baking Ingredients | BAKERpedia". 2017-01-27. Retrieved 2024-09-13.
- ↑ Research Chefs Association (2016-02-29). Culinology: The Intersection of Culinary Art and Food Science. John Wiley & Sons. ISBN 978-0-470-48134-9.