Science of Food chemistryoven

Blended Me with Science! PART II


Cooking is making magic. Without knowing how that is accomplished the process falls under the category of a trick, as in tricks of the trade. The cook, enthusiastic amateur or seasoned professional, can no longer ignore their curiosity as to the science inherent in every recipe, formulation, and transformative activity. The cook makes magic. As with all the arts, the culinary arts requires the bringing together of disparate elements, and forging them in a crucible (of the mind and otherwise) into a new, consumable form.

To boil or braise, sauté or grill? It is as important to be able to predict the expected final result, as it is to know the process of getting there. Once you know how it works the opportunity to creatively expand the applications and outcomes is limitless.

In Part I we examined the mysteries of emulsions, soufflés, caramelization, corn syrup, and Dutch process cocoa. Picking up where we left off let’s look at the magical mysteries of levitation — with baking powder, baking soda, and yeast. While we are at it … just how does the pressure cooker make its magic? And then there are Carbs and GMOs about which everyone speaks freely and often. But shouldn’t we actually know what they are at the molecular level, what they do and why they are good or bad? We should and will.

1. Baking Powder, Baking Soda what are they? How to they work?


Baking powder and baking soda, work by releasing carbon dioxide gas. This gas forms bubbles in the dough, causing it to rise. While the dough is cooking the bubbles harden as the dough bakes.

The release of gas is caused by a chemical reaction. The reaction happens quickly, which is why Irish soda bread, banana bread, zucchini bread and such, all made with baking soda and/or baking powder, are known as “quick breads.”

Baking soda is alkaline, and when you mix in something acidic, like vinegar, it will release gas. The key here is that baking soda needs some sort of acid to activate the reaction — buttermilk, sour cream, lemon juice, yogurt, molasses, chocolate (somewhat), even honey. Any of these ingredients would activate the baking soda. But if you were to try to substitute baking soda for baking powder in a recipe where no acidic ingredient is present, there will be no release of gas, and the dough won’t rise.

Baking powder, on the other hand, is little more than baking soda with an acidic compound already added. The baking soda and the acidic compound won’t react together until they are moistened, which causes the two chemicals to mix.

General rule: One teaspoon of baking powder — or a quarter-teaspoon of baking soda — is enough to leaven one cup of flour.

Double-Acting baking powder releases carbon dioxide twice during the baking process: once when it reacts with liquids during mixing, and again when it’s exposed to the heat in the oven.

NB: Chemical leavening agents like baking powder and baking soda will lose their potency after a while, especially if they are stored in a warm place (like a kitchen!) or if the containers are not sealed tightly.

2. Yeast — what is it? How does it work?


Yeast brings life to bread. Yeast feeds on sugars in dough and oozes a liquid that, when it touches an air pocket, releases carbon dioxide and alcohol (ethanol). The dough traps those tiny carbon-dioxide bubbles like a balloon and a matrix forms and the bread inflates accordingly.

Yeast is a living element. There are wild yeasts all around us. Yeast is the essential ingredient in bread production. It is a one-cell plant that multiplies by a process known as budding. Under the right conditions of water, sugars, warmth, and dissolved minerals, yeast causes fermentation. Carbon dioxide is generated by the yeast as a result of the breakdown of fermentable sugars in the dough. The evolution of carbon dioxide causes expansion of the dough as it is trapped within the protein matrix of the dough. Yeast produces many secondary metabolites such as ketones, higher alcohols, organic acids, aldehydes and esters. Some of these, alcohols for example, escape during baking; that characteristic beery smell of bread baking.

Yeast is available in compressed form as Brewer’s yeast, best kept under refrigeration, as well as active dry, rapid rise (recommended for bread machines), and instant yeast all of which need not be refrigerated. Most larger commercial bread bakeries use compressed yeast in their formulas. When using active dry yeast half as much active dry yeast is required as compared with compressed yeast.

Active Dry Yeast is the most commonly available form for home bakers. It’s available in ¼-oz packets (7g/2 ¼ tsp), enough to leaven 4 cups of flour.

Instant Yeast, a dry yeast, relatively recently developed, are smaller granules than active dry yeast, absorbs liquid rapidly, and doesn’t need to be hydrated or proofed before being mixed into flour.

Rapid Rise Yeast
(Bread machine yeast) is instant yeast that may include ascorbic acid, a dough conditioner.

Fresh Yeast, also known as compressed, brewer’s, baker’s or cake yeast, is active yeast. Fresh yeast does not keep well; it will last about two weeks if refrigerated. Fresh yeast should be proofed in tepid water (80-90 degrees F) without contact with salt or sugar.

3. What is the science of the pressure cooker?

pressure art

The pressure cooker, invented in the 17th century by Denis Papin, has come back into favor. If you love a long, slow braise, get the same or better results with a nifty pressure cooker in a fraction of the time.

Pressure cookers look like other kitchen pots, except their lids are a bit more elaborate. They work by completely (hermetically) sealing the pot. Water boils at 212ºF, and turns into steam. Once water begins to boil, it cannot get any hotter. However, when the boiling liquid is trapped inside the lock-lidded pot the volume of the expanding steam cannot continue to increase so the pressure, and therefore the temperature will rise. The longer the water boils, the more steam pressure builds within the vessel. The pressure of the trapped steam can be measured in pounds of force per square inch or PSI (up to 15 psi inside pressure cooker). Higher cooking temperatures results in shorter cooking times. Sealed environment retains moisture.

Modern pressure cookers have at least three valves for safety and will automatically release pressure should it build too high.


Nutritional Boost – Due to the shorter cooking time and the fact that food is cooked in less liquid that gets boiled away, more vitamins and minerals are retained than with conventional cooking methods.

Saves Time – Food cooks up to 70% faster.

Energy Efficient – As less cooking time is needed, less energy is used.

Cooler Kitchen – As all the steam and heat stays in the pot, the kitchen stays cooler.

General Pressure Cooking Guidelines

    Never fill your pressure cooker more than half full with foods or two-thirds full of liquid. Foods have a tendency to increase in volume under pressure. Most pressure cookers have a mark stamped on the inside that lets you know when you’ve put in the maximum amount.
    For extra flavor, brown or sauté foods first just like you would when cooking with conventional methods.
    Use less liquids than with conventional cooking methods. When cooking under pressure, less liquid evaporates than with conventional or stove top methods.
    Be ready to adjust the stove heat. Once ideal pressure is reached (the toggle hisses or you hear a tea kettle like humming) lower temperature to a minimum for the duration.
    Begin counting cooking time when the pressure cooker has reached the full pressure, or PSI, called for in the recipe.
    Estimate cooking times on the low side. Because foods cook rapidly in the pressure cooker, a few extra minutes and they can overcook

Releasing Pressure
You cannot open today’s pressure cookers until the pressure inside the pot has been completely released – a significant safety feature. Release steam, and therefore pressure, from your pressure cooker via the natural release or quick release methods.

The Natural Release Method – Remove the pressure cooker form the heat and wait for the pressure to slowly decrease as the temperature of the pot naturally lowers.

Quick Release Method – Some pressure cookers have an automatic release method (check the instructions). If so simply follow the instructions to release steam and pressure. If your pressure cooker does not have an automatic release method move the cooker from the stove to the sink and run cold water over the top and sides until all the pressure is release It should take a about five minutes. Never attempt to force open the lid.

Tips for Safe Pressure Cooking

    Too much pressure is created in one of three ways: the heat is too high; the pressure cooker is overfilled, the pressure regulator valve is obstructed or malfunctioning.
    Use enough liquid in order to build pressure. Usually at least 2 cups for larger pressure cookers.
    Inspect the gasket or ring, making sure it is still flexible and not dried out.
    Remove the rubber gasket or ring and wash this separately by hand.
    Inspect the valves to make sure they are free of debris and food residue.
    Never immerse the cover in water as it can clog and damage the safety valves.
    Hand-wash the pot. Do not store the pressure cooker with the lid locked in place; store the pressure cooker pot with the lid placed upside down on top of it.

4. Carbohydrates — what are they, where are they?

bread science

In the food trendy world they are longer desirable except to runners who still (one hears) carbo-load before marathons.

A carbohydrate is a biological molecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water). In biochemical terms a carbohydrate is synonymous with a saccharide, — that group that includes sugars, starch, and cellulose. That “carbs,” as they are often referred to with a sneer, are essential to living organisms is often overlooked. To many the term conjures foods rich in the complex carbohydrate starch (bread, pasta, boxed cereals, and some grains), as well as simple carbohydrates, especially sugar found in preserves, confections, candy and a variety of desserts. The appeal for the aforementioned runners is that carbohydrates are the storehouses of energy. Energy is calculated in calories and simple sugars contain about four calories per gram; while complex carbohydrates can be a tad higher. Higher levels of carbohydrates occur in “refined” or processed foods; lower in the ”unrefined” such as beans, rice, tubers, and such. Although carbohydrates are a common source of energy, they are not essential. One can get all of their energy needs met with proteins and fats. Lists abound of good vs bad carbohydrates. The lingering question is — Why is everything so bad, so good?

5. What exactly is GMO (genetically modified wheat, corn, etc.)?


The initialization stands for genetically modified organism. The legal term is “living modified organism” that emerged from the Cartagena Protocol of Biosafety that regulated international trade in living GMOs. Another definition, closer to the food chain, is that GMOs are organisms whose genetic makeup has been altered without the addition of genetic material from an unrelated organism.

As far back as 12,000 BCE genetic make up had been cleverly fiddled with by the means of selective breeding and hybridization. Promoting the desirable traits by selecting the best examples of say, corn or sheep. Genetic engineering, or the manipulation of the gene sequence by biotechnology, began in 1973 by Herbert Boyer and Stanley Cohen. Boyer, a Pennsylvanian, was a co-founder of Genentech
GM foods are those food items that have been produced from organisms that have had changes introduced into the DNA by means of genetic engineering. The first of these was the Flavr Savr® tomato created in 1994 by Calgene (acquired by Monsanto 1996). Monsanto is an industry leader in genetically modified organisms and patented seed. In 2014 France banned the sale, use or cultivation of Monsanto’s, MON 810 GMO corn. Currently twenty-one regions in France are declared GMO free. According to the Center for Food Safety, up to 92% of corn grown in America is genetically modified.•
Feature image courtesy of Fondo Antiguo de la Biblioteca de La Universidad de Seville  via Flickr (Creative Commons). Other images courtesy of Boston Public LibraryMathias Beugnon, Isaac Kohane,  and David Goehring via Flickr (Creative Commons). 


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