Making flour mixtures

Making flour mixtures

Topics Flour and flour mixture Methods of raising flour mixture Mechanical air Physical steam Chemical carbon dioxide Functions of different ingredients

Flour and flour mixture

Flour What is flour? Flour is the fine powder derived from the endosperm portion of cereal seeds or other starchy foods The most common source of flour is wheat, but any cereal grain can provide flour, e.g. oat, rye, barley, rice, corn, etc. Non-cereal sources such as soybeans, potatoes, sweet potatoes, taro, arrowroot, etc. can also be made into flour Germ Endosperm Bran

Flour mixture What is flour mixture? The simplest flour mixture is one made from flour and water Other ingredients that may be added include: Sugar Salt Milk Fat Eggs Leavening agents Flavouring Additives (in the case of commercial manufacturers)

Flour mixture The ingredients of a flour mixture may be divided into categories as: Dry: flour, sugar, salt, and leavening agents Liquid: water, milk, fat, and eggs The types and proportions of these ingredients determine the structure, volume, taste, texture, appearance, and nutritive value of the finished baked product

Products made from flour and flour mixture There is a huge variety of baked goods that are made from flour, examples include: Yeast breads (e.g. loaf breads, rolls, pita bread, bagels, English muffin, pizzas crust, pretzels, raised doughnuts, etc.) Quick breads (e.g. pancakes, crepes, waffles, popovers, muffins, unleavened breads, scones, etc.) Cakes Cookies Pastries

Methods of raising flour mixture

Raising flour mixture Raising agents, also known as leavening agents, cause baked goods to rise Providing lightness and volume to baked goods Leavened baked goods are more porous and tender During baking, heat causes matter to change from one physical form to another Solid to liquid (butter melts) Liquid to gas (water to vapour) Molecules move faster and spread farther apart This expansion is the basis for leavening

Raising agent There are three main leavening gases in baked goods: Air Steam Carbon dioxide

Raising agent - air A physical leavener added into batters or doughs Air is gas in the atmosphere that is composed of a mixture of gases, primarily nitrogen Air is incorporated by mechanical means such as: Creaming Whipping Sifting Folding Kneading Stirring

Raising agent - air Sponge cake and angel cake contain eggs that are whipped, and this adds volume of air to the batter. Air is incorporated into batter of sponge cake by whipping.

Raising agent - air When heated, air expands a little, not as much as water does, because it is already a gas Air is added to batters and doughs as small air bubbles, and will be distributed uniformly during mixing During baking, no new air bubbles will be formed, but steam and carbon dioxide that is generated will move into the air bubbles, enlarging them Therefore, under-mixed batter with less air bubbles results in coarse texture and low volume, the size of each bubble is larger Over-mixed batters and doughs will contain many air bubbles. Surface of air bubbles becomes overstretched, thin, and weak. During baking, the thin surface stretches further and collapses, and finally causing poor volume

Raising agent - air Muffins made with same ingredients but at different level of mixing. Under-mixed batter (left) produces muffins that are coarse in texture. The surface is pebbly. In the control (middle), air bubbles are distributed evenly. Over-mixed batter (right) causes some loss of carbon dioxide and a strong gluten formation. During baking, gas follows gluten strands and forms tunnels and a peak.

Raising agent - steam A physical leavener present in batters or doughs Steam is water vapour, gaseous form of water Forms when water, milk, eggs, syrups, or any other moisturecontaining ingredient is heated e.g. choux pastry is leavened almost exclusively by steam

Raising agent - steam Hollow space inside choux pastry Theory behind choux paste Choux paste contains a large amount of liquid from water or milk, and eggs It is baked in a very hot oven, which allows the liquid to evaporate to steam quickly during the first 10 minutes of baking Egg protein and gelatinised starch granules play very important roles As steam expands in oven, egg proteins uncoil and stretch, paste puffs up, pressure breaks the egg protein structure, creating a cavity in the baked choux paste The outside shell of choux pastry is dried by the high heat, gelatinised starch and coagulated egg proteins hardened and set, defining the shell s final volume and shape

Raising agent - carbon dioxide Although it is present in air, in trace amounts only There are two sources: Yeast fermentation, which is a biological leavener Chemical leavening agents Baking powder Baking soda When carbon dioxide is warmed by the heat of the oven, it moves into existing air bubbles, causing them to expand. Breads and cookies are examples of baked products that rely on carbon dioxide to raise

Raising agent - carbon dioxide Yeast fermentation Biological or organic production of carbon dioxide results primarily from yeast fermentation Bacterial fermentation also exist in product like sourdough. Lactic acid bacteria (LAB) such as lactobacillus spp. are naturally present in flour and the surrounding, as water is added into flour, a stable culture of LAB is formed. LAB produces lactic acid which contributes flavour Yeast produces gas for leavening, while bacteria produce mostly acids and other flavour molecules Yeast is usually applied in baked goods with the presence of wheat (gluten), so that porous and rigid structure can be formed

Raising agent - carbon dioxide What is yeast? Yeast is very small single-celled microorganism It can break down sugars for energy, this process is called fermentation When energy is released, yeast can survive, grow, and reproduce Human beings have been using yeast in making breads for thousands of years, but it was until mid-1800s when scientist, Louis Pasteur proved that living yeast was necessary for fermentation

Raising agent - carbon dioxide How does yeast produce carbon dioxide? Yeast can break down sugars into smaller simpler molecules Yeast lacks amylase and cannot break down starch into sugar Sometimes, amylase is added as an additive in bread, especially in lean dough where the ingredients are just flour, water, salt, and yeast In the breakdown of sugars to carbon dioxide, many steps are involved, the process is called glycolysis

Raising agent - carbon dioxide Glycolysis yeast sugar CO 2 + alcohol + energy + flavour molecules Alcohol evaporates to a gas and expands during baking Therefore, alcohol also becomes an important leavening gas in yeastraised baked goods

Raising agent - carbon dioxide Adding water to yeast Adding water to yeast and sugar 5 minutes later 5 minutes later Click on the above video to see what happens when water is added. Click on the above video to see what happens when water is added. 1 hour later 1 hour later

Raising agent - carbon dioxide Types and sources of yeast Yeast dough is traditionally made by continual fermentation of old dough a piece of dough saved from one day s production Pure yeast culture can also be obtained, the strain for bread baking is Saccharomyces cerevisiae, usually ferment faster and more consistent The three forms of yeast available to bakers are: Compressed yeast moist, and packed in blocks Active dry yeast dry granules Instant yeast can be used instantaneously without hydrating

Raising agent - carbon dioxide Factors affecting yeast fermentation Temperature of dough Yeast is dormant at 0-1 o C and begins to be quite active starting at about 10 o C. At about 50 o C, fermentation slows down because yeast cells begin to die, the optimum fermentation is at 25-28 o C Amount of salt Salt retards yeast and bacterial fermentation, therefore the higher the amount of salt, the slower the fermentation rate Amount of sugar Sugar favours fermentation, but excess amount of sugar slows down fermentation

Raising agent - carbon dioxide Bread with different amounts of salt: low salt (0%, 0g) (left) medium salt (1%, 5g) (middle) high salt (2%, 10g) (right) 1% salt is the control. Excessive salt will lower the volume of baked product.

Raising agent - carbon dioxide Dough of loaf bread with different amounts of sugar: low sugar (0%) (left) medium sugar (5%) (middle) high sugar (> 15%) (right) 5% sugar is the control. Sugar will affect the volume of bread dough.

Raising agent - carbon dioxide Factors affecting yeast fermentation (cont d) Type of sugar Sucrose, glucose, and fructose favour fermentation Yeast with maltose ferments slowly Yeast with lactose does not ferment at all The ph of dough The optimum ph for yeast fermentation is 4 to 6, rate of fermentation slows down beyond this range Presence of antimicrobial agents Calcium propionate as a preservative to prevent mould growth, will slow down or stop the growth of yeast at the same time

Raising agent - carbon dioxide Factors affecting yeast fermentation (cont d) Presence of spices Most spices, including cinnamon, have strong antimicrobial activity and can slow down yeast fermentation Chlorine content in water Chlorine is an antimicrobial agent. High levels of chlorine in water can inhibit yeast fermentation Addition of yeast foods Ammonium salts and calcium salts provide nitrogen and calcium respectively, which aid yeast fermentation

Raising agent - carbon dioxide Factors affecting yeast fermentation (cont d) Amount of yeast The more yeast, the faster the fermentation. However, a large amount of yeast can add an undesirable yeasty flavour, and yeast can also use up all the sugar Type of yeast Different types of yeast ferment at different rates

Raising agent - carbon dioxide Chemical leavening agents Chemical leaveners break down in the presence of moisture or heat, and give off gases Chemical leavener: Baking soda Baking powder (baking soda combined with one or more acids) Baking ammonia, used in European and Chinese cuisine

Raising agent - carbon dioxide Baking soda Also known as sodium bicarbonate or bicarbonate of soda Gives off gas in the presence of moisture and heat However, a great amount of baking soda is needed to produce sufficient carbon dioxide for leavening High amount of baking soda produce yellow or green discolouration and a strong salty, chemical bite from sodium carbonate residue When baking soda is used for leavening, it is used with acid

Raising agent - carbon dioxide Acid-base reaction moisture baking soda + acid CO 2 + water + salt residue Acids react with baking soda in the presence of moisture, carbon dioxide is released as leavening gas When a lot of baking soda is added to baked goods, both the unreacted baking soda and the remaining salt residue contribute to off-flavours, and in some circumstances, more browning due to more Maillard reactions

Raising agent - carbon dioxide From below clockwise: almond cookies, soda bread, and muffin. Products made with baking powder (A), baking soda (B), yeast (C), and no raising agent (D) (from left to right). A B C D Yoghurt as an acidic ingredient is added to soda bread to react with baking soda. A B C D Baking soda in B causes more browning reaction. A B C D D did not rise because no raising agent is added.

Raising agent - carbon dioxide Acid-base reaction (cont d) Acidic ingredients commonly used with baking soda: Buttermilk Yoghurt Sour cream Fruits and fruit juices Vinegar Most syrups, including molasses and honey Brown sugar Unsweetened chocolate and natural cocoa

Raising agent - carbon dioxide Disadvantages of using different acids in baked goods The acid content of ingredients can vary, hence the quality of baked goods will be inconsistent Buttermilk, sour cream, and yoghurt increase in acidity as they age These ingredients tend to react with baking soda almost immediately, especially in thin batters The batter has poor bench tolerance and must be baked immediately upon mixing Bench tolerance is a measure of how well batters and doughs withstand (tolerate) being held before baking, without risking a large loss in leavening gases. Bench tolerance is affected by the thickness of the batter or dough, and the leavening agent used.

Raising agent - carbon dioxide Baking Powders All baking powders contain: Baking soda One or more acids (in the form of acid salts) Starch or filler, to absorb moisture Acid salts release acid once they are dissolved in water E.g. cream of tartar, also called potassium acid tartrate, is an acid salt When cream of tartar dissolves in batter or dough, tartaric acid is released Tartaric acid reacts with baking soda to release carbon dioxide

Raising agent - carbon dioxide Adding water to baking powder Reaction between baking soda and acid occurs when moisture is present. Adding water to baking soda Baking soda do not release carbon dioxide in water without heating. When water is added When water is added Click on the above video to see what happens when water is added. 5 minutes later Click on the above video to see what happens 5 minutes later when water is added.

Raising agent - carbon dioxide Types of baking powder Single-acting baking powder Contains one acid that dissolves quickly in room temperature water Poor bench tolerance Double-acting baking powder Contains two (or more) acids One dissolves and react with baking soda at room temperature Another acid requires heat to dissolve and react, allowing time for mixing ingredients Nowadays, double-acting baking powder is being used

Raising agent - carbon dioxide Types of baking powder (cont d) Another way to classify baking powder is based on the amount of carbon dioxide released at room temperature and with heat Fast-acting baking powder more carbon dioxide is released in the first few minutes of mixing and less of it in the oven Slow-acting baking powder less carbon dioxide is released in the first few minutes of mixing and more of it in the oven Different acids differ in reaction rates and flavours

Raising agent - carbon dioxide Types of baking powder (cont d) Acid salt Cream of tartar MCP (monocalcium phosphate) SAS (sodium aluminium sulfate) SALP (sodium aluminium phosphate) SAPP (sodium acid pyrophospate) Rate of reaction Fast-acting Fast-acting Slow-acting Slow-acting Slow-acting

Raising agent - carbon dioxide Baking ammonia Also known as ammonium bicarbonate When it is exposed to heat (~38 o C) in the presence of moisture, it quickly decomposes into ammonia, carbon dioxide, and water, so it is considered relatively fast-acting When properly used, baking ammonia leaves no chemical residue Baking ammonia is not very reactive at room temperature, therefore batters and doughs containing baking ammonia have good bench tolerance

Raising agent - carbon dioxide Baking ammonia (cont d) Baking ammonia has certain unique features that make it particularly suited for use in small, dry baked goods and unsuitable for use in large or moist products Reacts rapidly in the presence of water and heat Increases uniformity and spread in cookies (cookies expand in size) Increases browning Produces a crisp, porous crumb Adds an ammonia-like off-flavour to baked goods

Raising agent - carbon dioxide Baking ammonia (cont d) To be used in products that contain low moisture, as the ammonia gas can fully bake out, otherwise, baked goods will have an ammonia offflavour Examples of products that use baking ammonia as leavener: Chinese fried dough Chinese walnut cookies Chinese walnut cookies made with baking ammonia

Functions of different ingredients

Sugar Different types of sugars have different density, hence weight When making substitution, sweetness and amount of sugar must be considered Sucrose is a kind of sugar that is commonly used in bakery Types of sucrose include: Raw sugar White sugar (granulated sugar, and castor sugar) Powdered sugar (confectioners sugar or icing sugar) Brown sugar

Sugar Natural Sweetener Sweetener Nonnutritive Sweetener Other Sweeteners Sugars Sucrose Syrups Corn syrup Sugar alcohols Sorbitol Saccharin Aspartame E.g. Stevia (steveoside) Glucose Honey Mannitol Acesulfame-K Fructose Molasses Xylitol Sucralose Lactose Maple syrup Neotame Maltose Invert sugar Cyclamates

Sugar Functions of sugar Sugar does not only contribute to sweetness, it also influences the volume, moistness, tenderness, colour, appearance, and caloric content of baked products Increases the volume of cakes and cookies Incorporation of air into the fat during creaming (especially with granulated sugars) Contributes to the volume by providing food for the yeast The more food for yeast, the more fermentation, hence the more carbon dioxide produced

Sugar Functions of sugar (cont d) Increases the volume of the baked product and contributes to a finer and more even texture Sugar raises the temperature at which gelatinisation and coagulation occur, starch granules have more time to swell before they gelatinise, and thus giving the gluten more time to stretch Increases moistness and tenderness and also helps delay staling Sugar has water-retaining nature, this will improve the shelf life of baked product Contributes to the tenderness Crust of baked product becomes softer as sugar attracts moisture

Sugar Functions of sugar (cont d) Helps brown the crust of baked product Caramelisation and Maillard reaction take place with the presence of sugar

Sugar Sponge cake with varied amounts of sugar: 0g, 16g, 32g, 48g, and 64g (from left to right). 32g sugar is the standard amount for making sponge cake in this recipe.

Sugar Too much sugar Baked product may fall A lower volume Coarse texture Gummy texture Excessively browned crust Too sweet Too little sugar Dryness Reduced browning Lower volume Less tenderness

Salt Salt is a compound commonly used in food preservation. It provides flavour to foods Types of salt include: Fortified table salt (iodine is usually added in salt fortification) Unrefined sea salt Light salt (potassium chloride) for reducing sodium levels Gourmet salt (e.g. truffle salt)

Salt Functions of salt A small amount of salt is added to flour mixtures for flavouring, for producing a firmer dough, for improving the volume, texture, and evenness of bread crumb structure, and to prolong shelf life Adds flavour to baked product Baked product made without salt tend to be bland Plays an important role in forming the dough Salt adjusts the solubility and swelling capacity of the gluten, making the dough more pliable, and aiding gluten formation

Salt Functions of salt (cont d) In the production of yeast bread, salt helps control yeast growth Without salt, fermentation would be too rapid and result in a sticky dough Too much salt would inhibit yeast activity, reducing the amount of carbon dioxide gas produced and decreasing the volume of the loaf

Salt Salt influences dough firmness. Bread dough with varied amounts of salt: 0g, 5g, and 10g, (from left to right). 5g salt is the standard amount for making bread loaf in this recipe.

Salt Too much salt A firm dough Low volume Dense texture Too salty Too little salt A flowing adnd sticky dough Low volume Uneven texture Lack of colour Bland in taste

Liquid Liquid is required in flour mixtures to hydrate flour and to gelatinise starch Liquid used in flour mixtures: Water Milk

Liquid Functions of water Allows gluten to be formed Acts as a solvent for the dry ingredients Activates the yeast Provides steam for leavening Allows baking powder or soda to react and produce carbon dioxide

Liquid Milk Although it is not necessary to include milk in a flour mixture, it is usually recommended over water, because it improves the overall quality of the baked product Important constituents of milk: Protein Milk fat B vitamins Calcium Lecithin (a natural emulsifier) Lactose

Liquid Milk (cont d) Type of milk used depends on the desired end product Types of milk used in baked goods include: Fluid milk Butter-milk Nonfat dried milk Canned milk Yogurt Sour cream

Liquid Functions of milk Contributes water Adds flavour and nutrients (protein, B vitamins, and calcium) Contains compounds that help produce a velvety texture, a creamy white crumb, and a browner crust Results in higher volume Doughs are easier to shape, less sticky and heavier Doughs can retain gas better These are the result of the presence of milk fat and lecithin Results in a browner crust Lactose in milk participates in the Maillard reaction

Liquid Too much liquid A very moist baked item Low in volume Too little liquid Dry baked product Low in volume Stales quickly

Fat Fat in flour mixture interferes with the development of gluten, creating a more tender crumb The higher the fat content, the shorter the gluten strands, and the softer and more pliable the dough will be Types of fat used in baking include: Shortenings Butter Margarine Oil Lard

Fat Functions of fat Fat acts as a tenderiser and adds volume, structure, flakiness, flavour, colour, and a resistance to staling; it also plays a role in heat transfer Improves volume Fat surrounding air bubbles prevents rupturing of bubbles as bubbles expand in baking Creaming of fat and sugar traps air which acts as a leavening agent during heating

Fat Functions of fat (cont d) Affects strength, crumb and flakiness of dough With less fat, baked products may collapse during handling Low fat baked products have a fine, velvety crumb, whereas high in fat is coarse Flakiness of pie crust and pastry is due to fat incorporated into dough Improves flavour and colour Flavour and colour are affected by the amount and type of fat used Delays staling Fat acts as emulsifier, prevents recrystallisation of starch, hence delays staling

Fat Fat influences the volume and texture of loaf bread Bread loaf made with 3% fat Bread loaf made with 20% fat Expanded during baking, softer and greasier in texture

Fat Cross-section of low fat baked product with a fine, velvety crumb (angel food cake) 0% fat Cross-section of high fat product with coarse crumb (pound cake) 25% fat

Fat Layer of Fat Layer of Dough Steam H 2 O Steam H 2 O Layers of dough are separated by the layers of fat When heating in the oven, water in the dough evaporates as steam and the layers of fat melt Melted fat can prevent the escape of steam while the steam pressure can push apart the dough layer from each other and create the flakiness in pastries

Fat Too much fat Batter becomes too fluid Weakens structure Decreases volume of finished product Too little fat Batter is resistant to expansion during leavening Results in a tougher crumb

Eggs Eggs are added to flour mixtures to create different results Important constituents of eggs: Egg white can be whipped into foam and trap air Supply protein and B vitamins Egg yolk acts as emulsifiers, add flavour, nutrients, and colour Supply fat-soluble vitamins (A, D, E, and K), cholesterol, and fat Whipping egg white

Eggs Functions of eggs Eggs are added to enhance structural integrity, contribute to leavening, colour, flavour, and nutritive value Enhance structural integrity Coagulation of egg proteins during baking increases firmness Contribute to leavening Air is incorporated when beating eggs During baking, trapped air expands Liquid in the egg turns to steam when heated, product expands in volume

Eggs Functions of eggs (cont d) Egg yolks add flavour, nutrients, and colour More yellow crumb and browner crust can be formed Delay staling Emulsifier and fat in egg prevent recrystallisation of starch, hence delay staling Improve appearance of baked product A shiny glaze is resulted from egg-wash

Eggs Buns that are egg-washed with egg white, whole egg, and egg yolk (from left to right); effects are pale, shiny, and dark respectively.

Eggs Too many eggs Dense texture Tough and rubbery texture in baked product Too little egg Insufficient volume Poor structural strength, colour, flavour and nutritive value

Eggs Egg influences structure of pound cake. Pound cake with varied amounts of egg: 50g, 100g, and 150g, (from left to right). 100g egg is the standard amount for making pound cake in this recipe.