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~~FOOD SCIENCE ARCHIVE~~




 


~~Pyrolysis and Thermal Buffers in Pressure Cooking~~

from Dulce de Leche

When achieving caramel flavor and color through cooking, the process is called pyrolysis (heat decomposition) taking a polysaccharide, Sucrose, and reducing it to Fructose and Glucose. Caramel is made of oxidized forms of those two. When cooking sugars inside a sealed vessel, the process is accelerated. Boiling water heats the vessel, creating kinetic energy which causes pressure to build, which in turn causes it to heat further. All the molecules whizzing around and crashing into each other and the sides create a lot of pressure on the vessel but the kinetic energy of the boiling water creates pressure of its own, keeping the vessel's equilibrium intact. As with an egg, if you tried to cook it without any water distributing the heat and pressing from the outside, the heat and pressure inside would build far to quickly, stress cracks would form and it might burst. Fun with food. Dolce de Leche in a blast cooker. It's SCIENCE!

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The Maillard Reactions (named for the chemist Louis-Camille Maillard) are a family of non enzymatic browning reactions. When we heat meats, and more specifically proteins, especially when we sear or broil, the amino acids and certain sugars in the meat form complex mixtures of semi-volatile flavor and scent molecules giving it that great flavor,color, and smell. Each food group and type have their own nucleophilic amino groups, resulting in their own unique flavors and smells. This reaction is responsible for some of our favorite things like barbecue smells and nice grill marks on a quality steak! Maillard Reaction… SCIENCE!

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~~~Autolysis in Bread Dough~~~

from Basic Whole-Wheat Sandwich Bread

Overworked and stretched out gluten chains are the culprit in the case of chewy/bready pie crusts. In the case of breads, we not only want the glutens to form but we often add one extra step that helps the process. That step is called Autolysis or "self splitting." In the world of bread, this means the breakdown of starches and proteins in the flour through the action of its own natural enzymes (amylase and protease respectively.) This results in the formation of less complex (less complex = more flavor) sugars and the reformation of complex protein structures into simpler gluten forming proteins (mostly glutenin.) These processes of deconstruction and reformation are usually expressed during simple kneading but there is a dark side... When you knead, you also expose the bread to oxygen and that can cause problems. Just like in your body, oxygen (normally O2) can become unstable and destructive O1, also known as "free radicals." These free Os can work against you, causing the breakdown of all those helpful and tasty sugar and protein structures you want even as you build them. Dough autoloysis gives you a big head start, reducing kneading and rising times and thus reducing oxygen exposure! A short 15 minutes and you get improved crumb, better bubbles, better crust better flavor... world of difference! Autolysis! It's Science!






~~~Microbial Symbiosis in Sourdough Starters~~~


In creating a strong, flavorful sourdough, temperature control and proper feeding of the Mother and cool ferment of the Barm overnight before use is essential to maintain a microbial equilibrium in the culture. In nature, and especially in flour itself there are hoards of tiny yeast cells (Saccharomyces exiguus) and Bacteria (Lactobacillus Sanfranciscensis) spores. When we add water to them they wake up and start consuming the sugars broken down by natural enzymes in the flour. The yeast acts as natural leavening as most leavened breads, consuming simple sugars and releasing co2, while the bacteria, consuming mostly waste products from the yeast, produces lactic acid: the familiar "sourdoughness" we all love so much. Friends until the end might be anthropomorphizing a tad but with the right care, we get an ideal symbiotic relationship that will last almost forever. Micro-biotic Symbiosis = SanFransisco Sourdough. Deliciously Scientific if I do say so myself!






~~~Pectin Activation~~~

from Organic Blood Orange/Rhubarb Marmalade

When we add pectin to liquids to thicken, we are counting on a process called Gelatinization. When we add the pectin (in this Case a specialized, "low ester" pectin) in certain low sugar formula like this one it can require small amounts of calcium as a catalyst. The calcium water involved comes into play in ionic form facilitating the creation of weak bonds (calcium ionic bridges) between the molecules of pectin. This creates a semi cohesive (from the word cohere, and from the Latin cohaerere to "stick together") structure like a 3D netting or mesh breaking up and holding the liquids involved in place.






~~~Small Particle Distribution in Thickeners~~~

from Organic Blood Orange/Rhubarb Marmalade

For the second half of this section, I want to talk about why we mix the pectin powder with sugars. When we add any powdered gelling agent with liquids, we want each tiny particle of the powder to absorb the liquids evenly and equally. When we add dry powders to hot liquids, if the dry particles are too close together, clumps can form.

Large liquid-filled particles expand so fast due to the excess heat that they begin pressing and squeezing tiny clusters of dry particles together and surrounding them so no liquid can get in. The moist particles cling to the dry because the dry clumpy cores want to steal water from the surrounding environment through capillary action. All this comes together to form lumpy gravy, pudding, ice creams, and jellies and jams and an all around unpleasant result. When we mix the pectin powder with the sugars, we ensure that the particles are spread out and evenly distributed so that very few are touching and able to bully each other. Other ways to ensure even absorption and dissolution include mixing dry with icy water or a fat like butter or oil. Simple and elegant age old solution to an age old problem! Nice smooth emulsions thanks to dry particle distribution and ionic calcium bridges! Science!!






~~~Boiling Water as a Thermal Buffer in Custard Baking~~~

from Orange Blossom and Vanilla Bean Creme Brulee

Many baked custards require a water bath too cook evenly and not burn because the chemical reactions inside the custards that lead to important creamy internal structure need even even heat. The moisture from the water also keeps the fatty solids from burning.

The temperature of a given conventional oven actually forms a shallow holding sign wave, varying up to 20 degrees in either direction, maintaining the set temp more often than not but varying none the less. This is why a water bath is required. Since the energy required to change the temp of water is high, it has the ability to regulate heat flow between mediums, acting like a thermal buffering system. As the ovens temperature may waver over the cooking time, the waters temperature stays more or less the same, distributing its heat to the custard at a slow, even rate, allowing for uniform, stable formation of protein structures in the setting custard. The same thing is true for using a double boiler to set creme anglaise for ice cream or melt chocolate without burning. Water baths as functional thermal buffers allowing for uniform protein gelling in baked custards! it's SCIENCE!






~~~Tannic Acid Chain Oxidation~~~

from Walnut Banana Bread

When you eat certain unripened fruits and nuts, the dry, gritty "taste" in your mouth is tannic Astringency. This sensation is less of a flavor our tongues or noses can perceive than a sensation caused by physical contact. Ongoing research has suggested that tannin "mouth feel" is at least in some part a product of size and shape of the polymerized tannins interfering with the ability of saliva to lubricate surfaces in the mouth properly. Whatever the many and quite complicated reasons behind the astringent properties of these chains, there is no question about not we wanting them in our sweet baked goods! Either by aging normally in at room temperature or via other means like heat and acid, the goal is to oxidize these long chain macromolecules and thus break them and alter them, rendering them less capable of creating the astringent feel.

When we apply quick, penetrating heat to these large molecules, the thermal energy from the hot oven accelerates these reactions. Often foil is used to trap the heat and further speed the process along. Sweet, smooth flavors and mouth feel via thermally catalyzed oxidation of long-chain tannin macromolecules. Mmmmm boy! SCIENCE!






~~~Oxygen Incorporation into Whipped Fatty Liquids~~~

from Spicy Ginger Pears En Pillowette


When we whip cream or any number of other high fat liquids and semi liquids, the idea is to force air into in a way that keeps it stable. When we reach the stage of mechanical whipping sometimes called the frothing stage, 90% of the air we will add is already inside. Once we start moving toward the "Soft Peak" stage, the bubbles are being broken up, multiplying and being compressed. These bubbles attract the fat globules in the cream as they are compressed via the whipping action. Eventually the bubbles become so small that the partially crystallized fat globules come into contact and cling, trapping the air and linking bubble to bubble, stabilizing the cream.


No whipped cream will keep forever without deflating unless you go all the way to the butter stage. The liquid water that remains in large particle form will eventually break down the bonds between the fat globules, allowing the air to escape and the cream to flatten and deflate. The higher the saturated fat content, generally the longer the cream will stay whipped. Fatty acid bonds trapping microscopic air and water bubbles. What delicious bonds they are! SCIENCE!!







When we approach the subject of leavening, the number one golden rule is this: Leavening, in almost all cases, simply expands tiny air bubbles present in the dough/batter and doesn't actually create them. Without the different varieties of leavening, we would end up with hard, cracker-like breads and dense or soupy muffins... All basic info but it will lead in I promise. For the most part there are three types of leavening present in some part in all recipes: Mechanical Leavening (via the creaming of the sugar and butter,) Chemical Leavening (vial the Baking powder and soda,) and Heat/Steam leavening (the baking itself.) The 4th kind of leavening is microbial leavening through yeast consuming sugars and producing CO2 gas.

Mechanical - When we beat butter and sugar together in recipes that call for creaming, the sharp sugar crystals cut into the fat, creating thousands of tiny tears and pockets forming air bubbles. These are the bubbles we need to expand via chemical and steam/heat leavening.

Chemical - The chemical leavening comes in to play as components in baking powders begin to react in a liquid filled environment. When the liquid allows the particles to move more freely, these particles interact in an acid/base reaction, releasing CO2 gas expanding the tiny bubbles. In certain cases where the pH of the mixture is too high or too low, different formulations of baking powder can create unpleasant flavor due to left over acid salts and others. In these cases we use some baking soda as a sort of pH buffer, consuming the acids and rendering more CO2.

Heat/Steam - In the final step, the heat from the oven accelerates the expansion of the bubbles through the creation of steam and the thermal catalysis of the chemical leavening reactions.

Once again, given the chance, food can surprise with its relative complexity! Delicious, fluffy breads and pastries all thanks to thermally catalyzed acid/base reactions, microbial metabolic CO2 activity, and mechanical micro bubble formation in fatty compounds and doughs! As always... it is SCIENCE! Delicious!






~~~Vitamin A Content in Carotenoid Pigments~~~

from Sage and Rosemary Chicken Scallopini

Carotenoids, depending directly on bonding structure and shape, are what give us vibrant yellow, orange, red, purple colors and also act as important chemical precursors for many of the flavors and aromas we love. Most of us have been told to eat more red and orange fruits and vegetables as they contain more vitamins but in truth we get vitamins from them BECAUSE they are brightly colored. The Color and the vitamins are very much linked.

When we as animals consume carotenoids, especially β-carotenoids, our metabolic activity actually converts them from long chain molecules into short liked Vitamin A in the form of Retinol and other animal forms such as Retinal and Retinoic acid. So when somebody says "Eat your colorful fruits and veggies because they have lots of vitamins" the reason you get vitamin A actually IS the color! Vitamin A production based on vegetative carotenoid chain pigmentation being broken down and reshaped! Science!!






~~~Dry Particle Ratios in Liquid Environments~~~

from Chocolate Decadence with Fresh Red Raspberry Sauce


When we add the liquid to chocolate and other similar solid emulsions, you are adding liquid to a stable emulsion of dry particles (the cocoa itself.) The physics involved are actually quite similar to adding water to sand or dirt in that you need to add the right amount to reach a stable form. If you add too little liquid you get clumps or moistened particles that cling together tightly mixed into dry powder. This is especially true in chocolate where the particles are suspended in a mixture of stable and unstable fatty acids and crystals, making the particles adhere with greater tenacity. If we add too little water, we get lumps of seized chocolate clinging to each other creating even bigger lumps... the end result is a thick, gloppy and eventually hardening mass of un-useable chocolate.

The simple solution to this is adding enough liquid. Once the right ratio is achieved, you get an evenly distributed solution of dry particles in liquid, allowing the particles to move past, over, and around each other and not cling and set so readily. This same principle is true in many different recipes like when you add water to flour before adding fat like eggs and butter (for better mixing), or mixing corn starch with water to allow for absorption into sauces. Science can be chocolate coated too it seems! Delicious, Delicious SCIENCE!!






~~~Invert Sugars Inhibiting Sugar Crystallization~~~

from Fleur de Sel Soft Caramels

"Sugar" is a catch-all word for many different permutations and combinations of similar molecules called Saccharides. Common table sugar, aka Sucrose, is a disaccharide made up from two monosaccharides Glucose and Fructose (fruit biological sugars.) These molecules in solution, when heated then allowed to cool will tend to form, by nature of their structure, large, stable crystals. In things like caramels, certain cooked creams, and other recipes that contain a mostly sugar base, we often use a syrup or gel sugar. These sugars are called "invert" sugar and are valued for their use in preventing crystallization in high heat baking. Invert sugars are found in many fruits, some vegetables, and things like honey and flower nectar. They are artificially reproduced by splitting Sucrose via hydrolysis into its smaller simple components (fructose+glucose.)

Sucrose molecules, as they are larger, tend to want to form larger crystals from solution, so when we break them down into monosaccharides, the molecular structures formed tend to inhibit this trait. When we make caramels or things like jams and jellies, even marshmallows and fruit sauces, the presence of smaller mono saccharides tends to inhibit the formation of gritty sucrose crystals. In recipes with high acid levels (fruit sauces and jams), the invert sugars are formed during cooking when the acids themselves break down the table sugars into their components. Delicious, soft caramel, fluffy marshmallows, and sweet smooth jellies and jams all thanks to hydrolyzed molecular inversion of sucrose polysaccharides. Sounds delicious... and Sciency after all.







~~~Whole Berries, Berry Juice and Capillary Action in Baked Goods~~~

from Blueberry Citron Buttermilk Scones

Whenever we add whole fruit to a fairly dry recipe, we want to keep them whole for a few important reasons. First and more obviously we usually prefer nice pockets of moist whole berries, but second and in this case more importantly we DON'T want little pockets of undercooked or overcooked dough and dried out patches of sour berry juice. When we bake with whole fruit, the liquid inside begins to heat and form steam. The intact skins are able to hold most of this pressure in where it should remain, giving you little heat sinks that can actually help (in a small way) provide even cooking.

If the berries burst prematurely or go into the heat crushed, the juice escapes into the surrounding drier dough and spreads thin via capillary action (like a paper towel absorbing fluid spills.) Just as with any liquid, the more spread out the juice becomes and the more surface area it presents to its drier environment the faster it evaporates. This can give you dried out pockets with little shriveled up berry husks inside. Crispy! ...wait... (Blueberry + Heat)(steam+deliciousness) = SCIENCE! Good times.






~~~Ice Crystallization in Ice Cream Churning~~~

from Vanilla Bean Gelato

When we make ice cream, more importantly when we freeze and churn the custard, the last thing we want is a "slushy" almost crunchy consistency.When we let an ice cream custard base chill overnight in the fridge, it comes down in temp to facilitate even, slow heat exchange when we toss it in the machine, but maybe more importantly to allow the fat globules to hydrate properly. Similar to whipped cream, the action of the fat globules wanting to cling and bind the water into a semi stable network of tiny particles, inhibits the formation of complex, large ice crystals when we churn later. Bound water networking in high fat liquids yielding smaller ice crystallization and a creamier frozen treat for a hot summer evening! Frosty cold SCIENCE!






~~~Capsaicin Activity in Spicy Dishes~~~

from Spicy Aprium Orange Marmalade

Just some notes on spicy, spicy peppers and including them in recipes! What exactly happens when we eat any number of spicy peppers from the mild bell pepper all the way up to the near gamma radiation level spice of the south asian Ghost Pepper (a Scoville rating of nearly 1 million) is the defining chemical Capsaicin acting to irritate the mucus membranes of our mouthes. This chemical, a hydrophobic long chain hydrocarbon, will by definition repel water and most water containing compounds and mixtures. Just as with a grease fire, the common gut reaction to throw water on it will end badly, the water simply dispersing the capsaicin in tiny particle form and causing the burning to spread acordingly. Often the only cure is a glass of milk, the casein (a phosphoprotein) in milk solids with a detergent effect.Capsaicin is not water soluble bit it is Alcohol soluble. In this case we've added a tiny bit of grand marnier to the plum puree in order to disperse and distribute the capsaicin from the peppers. The alcohol acts to help the chemical spiciness penetrate the jam base, creating a more even, mild heat throughout, in balance with the other flavors. Like-dissolves-like strikes again! Spicy Fiery Science!






~~~Ingredient Type Equilibrium in Sponge Cake~~~

from Chocolate Banana Cupcakes with Honey Peanutbutter Buttercream

When it comes to cakes, especially sponge cakes, we want fluffy, light, flavorful crumb. The true trick to getting what we want is a finely played balancing act between sugars, flour, eggs, fats and liquids. Sugar to fat ratios are important in forming air bubbles for leavening through creaming but uneven ratios can cause the butter to melt too slow or too quickly giving you too much or not enough leavening. Excess sugar, more importantly high sugar to egg/flour ratios, can also interfere with protein structure formation, yielding a crumb that is too tender to hold its own weight after the initial rise in the hot oven and collapses into an undercooked puck.
Fat to egg protein ratios are also integral to proper crumb. As fat acts to tenderize, keeping the eggs (as well as flour) from forming excessively long and complex protein networks, the eggs act to keep the fat emulsified, preventing dougeyness and large air runs/pockets....
As simple as a cake may seem, there are a LOT of factors, all balancing each other and maintaining cakey-delicious equilibrium! Like a delicious chemical equation. Bet you'll never be able to look a cupcake the same way again... and if so, I feel I've done my job!






~~~Temperature Differentials and Heat in Cooking~~~

from Peanut Butter Honey-Butter Butter Cream

Temperature variations are very important in cooking. All the physics of the actual cooking cooking can be boiled down to "Heat" in the thermodynamic sense of the word. Heat is flow of thermal energy between multiple mediums at different temperatures in order to achieve a uniform temperature in both. This rate is also affected by thermal conductivity of the two media. When we cook, its less about how hot something is and more about the difference in temp as cooking occurs when heat flow is greatest not when temperature is greatest. This distinction is most easily made via dry ice: at almost -110f, it is a full 200f different from your skin and can burn just like burning hot skillet.
In recipes that require quick cooking of high-fat and/or high-protein via hot sugar syrup or other hot liquids, this physical science principle comes into play in a big way. If you expose 38f-cold-from-the-fridge ingredients to 212f-240f scalding hot liquid, the extreme differences can cause a number of unpleasant effects including seizing/curdling fat, sugar and protein.
In Italian meringue butter cream this means not soft and creamy with evenly cooked egg ans stable sugar crystallization but lumpy and gloppy with "sweet-scrambled" eggs and hard, potentially sharp sugar beads. Not really what comes to mind when you think of meringue...
So keep in mind that sometimes, you should leave the groceries on the counter! Might help out here and there... Temperature stable ingredients = creamy smooth and sweet results.

~~~Enzyme Inactivation in Blanching~~~

from Vanilla Bean Candied Kumquats

Many, many cooking processes involve blanching the required fruit and or vegetables but what really goes on when we "blanch"?  From a scientific standpoint, blanching is a process of quick immersion in rapidly boiling water then of immersion or rinsing in cold water all in order to inactivate certain enzymes that can harm the color, flavors, smells, and structure of the food.  Often with fruit, blanching also destabilizes and washes out certain complex organic molecules (such as tannic acids) than can yield some fairly unpleasant flavors and mouth-feel.  But lets go with vegetables for now...
Just as in our body, enzymes (highly complex protein catalysts) act to accelerate chemical reactions that break down, restructure and build organic molecules.  In food, we worry less about building and more about damaging and reshaping
Lets take one molecule involved in color of almost all vegetables and its foil: Chlorophyll and Chlorophyllase.  Chlorophyllase is an enzyme common in fruits and vegetables that acts to reshape the Chlorophyll molecule in a way that makes it water soluble.  In this state,  chlorophyll can be more easily affected by pH extremes that dull color or simply be dispersed into the cooking liquid.  In blanching we both wash out certain macromolecules and acids at the same time Denaturing the Chlorophyllase (destroying its functionality) via the boiling heat.
So there we have food trial-by-fire so to speak...  Blanching = heat + water = inactivation/removal via liquid of negatively influential protein macro-molecules = nice, pretty colors, scents, flavors, vitamin profiles in long-term stored food.  SCIENCY!

~~~Gas Expansion in Hot Liquids~~~

from Roasted Tomato Marinara

If you watch enough food network, or if you've had the personal misfortune of first hand experience, you will know that putting hot liquid in a blender is a poor decision at the best of times... Hot liquid explosion and high likelihood of severe facial burns. But why?
When hot liquid is poured into a blender you have the start of a problem. The liquid is high and deep having very little surface area and thus very little heat can escape. Steam and other expanding gasses on the other hand is the far greater problem. When the blender is turned on it creates a perfect storm of high heat and expanding gasses. As the spinning blades pull hot liquid down to the center bottom of the carafe so do they pull down plenty of relatively cool, room temperature air. The cooler air mixes with the nearly boiling liquid and jumps in temperature, expanding rapidly and creating quite a lot of pressure. The rapid agitation also pumps plenty of energy into the liquid, releasing steam and compounding the welling pressure. Quite similar to the reaction caused when you drop a mentos into diet cola, the pressure forming has no where to go but up and out, creating a small but relatively powerful explosion of boiling liquid, powerful enough to blow the lid off most blenders even when held in place with your hand.
The best precaution to avoid this startling series of events is to remember to let any liquid to be blended cool for a short while and to never fill your blender or food processor more than half full.

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~~~Fatty Acid Chains~~~

from Trio of Figs

Without getting too complicated, all fats have both a backbone (usually a glycerol) and a tail or tails (fatty acid chains.) When we refer to hydrogenated, non-hydrogenated, saturated, unsaturated, poly-unsaturated fats, we are referring less to the consistency of the stuff in question and more to the molecular geometry of the chains themselves. In this case saturation refers to the atomic saturation of hydrogen. Saturated fats are full of hydrogen atoms and have a strait, single bonded chain. Unsaturated fats, have double bonded carbon atoms which form "kinks" in the chain. When it comes to physical appearance, its all about the molecular structure. In saturated fats (eg butter, cheese, animal fats) the acid chains can fit together easily like a simple puzzle, forming a stable, solid structure at room temperature. Unsaturated fats (vegetable and seed oils) have bends in their chains, making them much like bent comb tines. Poly-unsaturated fats (seed and nut oils) bend and twist in such a way that they are nearly guaranteed unable to form stable structures, thus remaining liquid even at relatively low temperatures. When it comes to real world application and demonstration, think of a high fat meat. If its left out on the counter or in the sun, it starts to "sweat." Unpleasant but... cool, in a scientific sense of course. With few exceptions (cocoa butter) fatty tissues contain a wide array of fats from saturated to poly-unsaturated. When fatty foods "sweat" its because the varying fats begin to liquefy at different temperatures and begin also to leach out and pool at the surface. The same situation can be seen with all kinds of fatty substances from butter to salad dressings, even certain cosmetic creams!

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