FNB News - Applied Chemistry of Baking Powder and Baking Soda

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Applied Chemistry of Baking Powder and Baking Soda

Monday, 23 March, 2015, 08 : 00 AM [IST]

Er Mandeep Singh

Product label of commonly marketed baking powder in the US reads Sodium bicarbonate, Calcium phosphate, Sodium pyrophosphates, Sodium aluminium phosphates, Corn starch and Fibre, whereas famous American Cookery Magazine of 1769 mentions use of Pearl ash or Soda ash as baking ingredient by Amelia Simmons.

“I was never inquisitive to read the product label while purchasing baking powder or considerate enough to choose a branded product for improving quality of cake.”

Simple leavening process
Baking being a simple leavening process in 16th century using sour milk and soda ash carbonate must have required advanced chemical intervention in 19th and 20th century.

Across centuries, scientists have been busy to understand functional and mechanistic details of baking process to reduce off-flavours and chemical precursors used in the food industry. Many potential applications have been generated for other industries (especially cosmetics and toiletries) from simple ingredient available in natural mines of Egypt, France and Europe.

Natural component
Baking soda, also known as cooking soda is common name for Sodium bicarbonate (Bicarbonate of soda). IUPAC name of Sodium bicarbonate is Sodium Hydrogen Carbonate (NaHCO3) which is a natural component of many mineral springs of ancient Egypt. Mineral Natron (Nahcolite) is abundant source of washing soda (Sodium Carbonate – Na2CO3) having salty and alkaline nature.

This natural mineral component was originally used as a cleansing agent or soap and has been a common food ingredient or food additive in baking in Europe and designated with number E 500. Latin Americans mention of Saleratus (Aerated salt) having properties of both sodium bicarbonate and potassium bicarbonate as fish preservative whereas ancient Egyptians adhere to Natron as a natural mixture of Sodium carbonate decahydrate (Na2CO3.10H2O) and sodium bicarbonate (NaHCO3). French chemist – Nicolas Leblanc (1791) produced soda ash (sodium carbonate) and later in 1846, John Dwight and Austin Church (Bakery owners in New York), established the first process of leavening dough through a chemical ingredient and named it Baking soda (Sodium bicarbonate). It was discovered that baking soda evolved carbon dioxide (CO2) that resulted in chemical leavening or rise of dough forming bread. The modern chemical symbol for Sodium (Na) is in fact an abbreviation of Latin Natrium, which is derived from mineral Natron.

Blend of oil
Natron harvested from dry lake beds of ancient Egypt is used historically for regular cleansing of earthen utensils and body bathing. Its blend of oil gave invention to soap. It was used as mouthwash and effective as antiseptic for minor cuts and wounds. Natron salt is a natural preservative of fish and meat and has many other potential industrial applications. With advancement in science in the 19th and 20th century and ability to extract simple compounds from natural mineral ores of earth by scientists showed decline in use of Natron, which was gradually replaced by soda compounds (sodium and related compounds).

Some common products we know today are soda ash (sodium carbonate), baking soda (sodium bicarbonate), caustic soda (sodium hydroxide) and related derivative compounds.

Sodium bicarbonate or baking soda is a white crystalline solid that appears as fine powder. It has a slightly salty and alkaline taste resembling that of washing soda (soda ash). Sodium carbonate is synthetically produced in large quantities from salt (sodium chloride) and limestone by a method known as the Solvay process. Sodium bicarbonate (NaHCO3) is prepared from sodium carbonate (Na2CO3) in Solvay process through reaction of sodium chloride (NaCl), ammonia (NH3), and carbon dioxide (CO2) in water.

Prime source of CO2
Calcium carbonate is the prime source of CO2 and the resultant calcium oxide is used to recover the ammonia from ammonium chloride. Pure product (75% or more) is obtained from sodium carbonate, water and carbon dioxide as shown in one of the following reactions. Usual production scale is about 100,000 tonnes/year according to a report in 2001. Sodium carbonate (washing soda or soda ash, Na2CO3) is the sodium salt of carbonic acid (soluble in water). It occurs as a crystalline decahydrate that readily effervesces to form a monohydrate white powder. Pure sodium carbonate is a white, odourless powder that is hygroscopic (absorbs moisture from the air), has an alkaline taste, and forms strongly alkaline water solution. Sodium carbonate is well known domestically for its everyday use as a water softener. The cooling and fizzing sensation of soft drinks results from the endothermic reaction between sodium carbonate and a weak acid like citric acid, releasing carbon dioxide gas. Sodium carbonate is used by the cotton industry and toothpastes acting as a foaming agent and abrasive to temporarily increase mouth pH. In a solution with common salt, may be used for cleaning silver. Sodium bicarbonate on the other hand is a common food additive (E500), acidity regulator, anti-caking agent, raising agent (leavenizer) and stabilizer when used with common salt. It is one of the components of Kansui salt that gives ramen noodles its characteristic flavor and texture. It is also used in the production of Swedish-style snuff by stabilizing pH of final product. Traditional Cantonese moon cakes and Chinese steamed buns or noodles contain sodium bicarbonate.

Leavening agents or raising agents used in bakery processes commonly include baking powder. Baking powders vary in consistency of sodium bicarbonate (baking soda), weak acid and starch content for dough and batter to rise due to foaming action in breads giving increased volume and lighter density of baked products. Acid-base reaction of baking soda with dilute acids release carbon dioxide into batter causing bubbles in the mixture to expand and leaven. Typical formulation of most commercially available baking powders constitute (by weight) 30% sodium bicarbonate, 5-12% monocalcium phosphate, 21-26% sodium aluminium sulfate and starch. A typical acid in baking formulations is cream of tartar (sour milk), buttermilk, yogurt, vinegar, lemon juice, citrus or honey that constitute to acid-base reaction of baking powders.

Usually acid content of baking powder is regulated because if the mixture is too acidic then the acid content will remain unconsumed during the baking process and render an unpleasant smell to the baked product. Alternatively, excess baking soda can be added for baking products that utilise buttermilk, yogurt or honey. Cornstarch or potato starch is another main ingredient of baking powders as starch helps absorb excess moisture of baking soda and acids to render them inactive until used during baking process. This inertness of starch adds bulk to baking powders, flavor and prolongs shelf-life (expiry) of the product by preventing premature reaction between sodium bicarbonate (base) and acid content of baking powder. Calcium phosphate and sodium aluminum sulfate are chemical acid derivatives that do not react easily with baking soda unless introduced in formulation and heated to release carbon dioxide. One teaspoon (5 grams) of baking powder is used for 150 grams (1:30) of flour or batter in minimal volume of batter. Typically, one cup of flour, one egg, and one cup of buttermilk requires only ½ teaspoon of baking powder —the remaining leavening is caused by buttermilk acids. Moisture and heat can cause baking powder to lose its effectiveness over time, and commercial varieties have a somewhat arbitrary expiry printed on the container. Regardless of the expiry date, the effectiveness can be tested by placing a teaspoon of the powder into a small container of hot water. If it bubbles energetically, it is still active and usable.

Typical changes
Some typical changes that take place during the baking process are melting of fats, expulsion of CO2, dissolution and caramelisation of sugars, death of microorganisms, and enzymes, gelatinization of starch, coagulation of proteins, and break down of pectins. Steam and air are also used as leavening agents when dough expands upon heating. To take advantage of this style of leavening, the baking must be done at high enough temperatures to flash the water to steam. Batter that is capable of holding the steam in until starch is set or completely glutenises.

Caramelisation
The dry heat of baking changes the form of starches in the food and causes its outer surfaces to brown giving an attractive appearance and taste of baked product. This browning is caused by caramelisation of sugars - Maillard browning reaction. Maillard browning occurs when "sugars break down in the presence of proteins" giving different flavours. The moisture is sealed over time and baked dry product is obtained in time. During baking dry product is often desired and advantageous. The baking process requires assessment of fat content of food rather dependence of external fats, butter and oils. Baked products are optimal in nutrition content of carbohydrates, proteins and minerals. Baked products rehydrate by consuming moisture of air and prolonged storage in refrigerators and become distaste.

Uses of Baking Soda (Sodium bicarbonate)

Baking soda is prime ingredient of cooking baked products to cause leavening of dough or batter resulting in increased volume of loaf, rich texture and nutrient restoration such as bread, pancakes, quick bread, baked vegetables and so on.
Sodium bicarbonate mixed with water can is used as antacid to treat respiratory acidosis, acid indigestion and heartburn. It is used for treatment of hypokalemia i.e. restore balance of potassium and sodium ions in body cells during periods of metabolic alkalosis.
It can be applied topically, with three parts baking soda to one part water, to relieve inflammations resulting from insect bites and stings. Sodium bicarbonate can be used to treat an allergic reaction to plants such as poison -ivy -oak or -sumac to remove splinters from the skin and associated itching.
Many toothpastes and mouthwash contains sodium bicarbonate to due to its cleansing and abrasive action. It works as a mechanical cleanser on the teeth and gums, neutralises the production of acid in the mouth by increasing pH of mouth.
It acts as mild antiseptic to help prevent infections.
Sodium bicarbonate in combination with flavour ingredients can be used to make a dry or wet deodorant, shampoos and other cosmetic products.
Sodium bicarbonate is used as a buffering agent in table salt.
Sodium bicarbonate and Sodium carbonate are excellent abrasives used for cleaning silver, gold and other inert metals, rust of steel.
Baking soda is commonly added to washing machines as a replacement for softener and to remove odors from clothes. Sodium bicarbonate is also effective in removing heavy tea and coffee stains from cups when diluted with warm water.
Sodium bicarbonate can be used to extinguish small grease or electrical fires by being thrown over the fire. Sodium bicarbonate is used in BC dry chemical fire extinguishers as an alternative to the more corrosive ammonium phosphate in ABC extinguishers.
Sodium bicarbonate is amphoteric, reacting both acids and bases. It reacts violently with acids in an exothermic reaction that forms the basis of acid-base reaction to release carbon dioxide during baking. A wide variety of applications follows from its neutralisation properties that includes reduction in spread of white phosphorus from incendiary bullet wounds.
Sodium bicarbonate is used in a process for removing paint and corrosion called soda blasting. This process is particularly suitable for cleaning aluminum panels which can be distorted by other types of abrasive.
It is administered to pools, spas, and garden ponds to raise pH levels and soften water and weakly disinfect marine microbes.
It is effective fungicide and disodorant in some cases – store terrace furniture, cushions and cotton table cloths, carpets.
It removes residue on earthen pots and pans due to abrasive action.
It can also be used in small quantities in regular cleansing of floors, doors and windows along with other disinfectants. It gives bright and shiny appearance.
Pour in 1 cup baking soda followed by 1 cup hot vinegar to quickly unclog the kitchen drain.
Clean the dishwasher and coffeemaker by running an empty cycle with baking soda.
Add ½ cup baking soda to your bath for an at-home spa treatment.
Fight dandruff by massaging wet scalp with a handful of baking soda followed by mild shampoo treatment.
Clean toothbrushes, comb and other brushes by soaking in a mixture of ¼ cup baking soda and ¼ cup hot water. Let brushes stand overnight for a thorough cleaning.
Make a fluffier omelet by adding ½ teaspoon baking soda for every three eggs.
Use pinch of baking soda in a gallon of freshly-brewed iced tea to take out the bitterness and prevent cloudiness.