Gluten and Flour

Gluten
The seeds of most flowering plants have endosperms with stored protein to nourish embryonic plants during germination. Gluten 麵筋 (from Latin gluten, "glue") is a protein composite found in foods processed from wheat and related grain species. The prolamin and glutelin from wheat constitute about 80% of the protein contained in wheat seed. Gluten content has been implicated as a factor in the staling of bread, possibly because it binds water through hydration.

Gluten forms when glutenin ( only soluble in dilute acids or alkalis) molecules cross-link to form a sub-microscopic network attached to gliadin (alcohol-soluble). It gives elasticity to dough, helping it rise and keep its shape and often gives the final product a chewy texture. True gluten, with gliadin and glutenin, is limited to certain members of the grass family. The stored proteins of maize and rice are sometimes called glutens, but their proteins differ from true gluten.

Flour
Flour is a powder which is made by grinding cereal grains, other seeds or roots. Flour contains a high proportion of starches, which are a subset of complex carbohydrates also known as polysaccharides. Baking coagulates the gluten, which, along with starch, stabilizes the shape of the final product. The higher the protein content the harder and stronger the flour, and the more it will produce crusty or chewy breads. The lower the protein the softer the flour, which is better for cakes, cookies, and pie crusts.

Starch or amylum is a carbohydrate consisting of a large number of glucose units joined by glycosidic bonds. It consists of two types of molecules: the linear and helical amylose and the branched amylopectin. Depending on the plant, starch generally contains 20 to 25% amylose and 75 to 80% amylopectin by weight.

Starch molecules arrange themselves in the plant in semi-crystalline granules. Each plant species has a unique starch granular size: rice starch is relatively small (about 2μm) while potato starches have larger granules (up to 100μm). Pure starch is a white, tasteless and odourless powder that is insoluble in cold water or alcohol. "Oobleck" or "ooze", suspension of starch (e.g. cornstarch) in water, is a non-Newtonian fluid. In a Newtonian fluid, the relation between the shear stress and the shear rate is linear, passing through the origin, the constant of proportionality being the coefficient of viscosity. In a non-Newtonian fluid, the relation between the shear stress and the shear rate is different, and can even be time-dependent. Therefore, a constant coefficient of viscosity cannot be defined.

Starch becomes soluble in water when heated. The granules swell and burst, the semi-crystalline structure is lost and the smaller amylose molecules start leaching out of the granule, forming a network that holds water and increasing the mixture's viscosity. This process is called starch gelatinization. During cooking, the starch becomes a paste and increases further in viscosity. During cooling or prolonged storage of the paste, the semi-crystalline structure partially recovers and the starch paste thickens, expelling water. This is mainly caused by retrogradation of the amylose.

• Plain or all-purpose flour does not have a leavening agent.
• Self-rising (or self-raising) flour is sold premixed with chemical leavening agents. The added ingredients are evenly distributed throughout the flour which aids a consistent rise in baked goods. This flour is generally used for preparing scones, biscuits, muffins, etc.

Corn (maize) flour should never be confused with cornstarch, which is known as "cornflour" in British English. Coarse whole-grain corn flour is usually called corn meal.

Corn starch, cornstarch, cornflour or maize starch is the starch of the corn (maize) grain obtained from the endosperm of the corn kernel. It is used as a thickening agent in soups and liquid-based foods. Corn starch is sometimes preferred over flour because it forms a translucent mixture, rather than an opaque one.

Tapioca Starch/ Tapioca Flour/ Potato Starch (木薯粉/泰國生粉/太白粉) is obtained by grinding the tubers of potato to a pulp and removing the fibre and protein by water-washings. It is very white starch powder used as a thickening agent. Standard potato starch needs boiling, to thicken in water, giving a transparent gel. 食物放涼之後，茨汁會變得較稀，因此一般整蛋糕/做西點多利用粟粉來達到粘稠的特性而不使用太白粉。

Glutinous rice flour (糯米粉) or sticky rice flour, used in east and southeast Asian cuisines for making tangyuan, etc.

Rice flour (粘米粉) is ground kernels of rice. It does not contain gluten. It is distinct from rice starch, which is usually produced by steeping rice in lye.

Wheat flour varieties are called "clean," "white," or "brown" ("strong", "hard") if they have high gluten content, and they are called "soft" or "weak" flour if gluten content is low.

• Cake flour (低筋麵粉) is a finely milled white flour made from soft wheat. It has very low protein content, between 8% - 10%, making it suitable for soft-textured cakes and cookies. 適合用來做糕點、雪芳蛋糕、笑口棗、鍋餅等
• Pastry flour or cookie flour or cracker flour has slightly higher protein content than cake flour but lower than all-purpose flour. Its protein content ranges between 9% - 10%. It is suitable for pie pastry and tarts, some cookies, muffins, biscuits and other quick breads.
• All-purpose or plain flour (中筋麵粉) is a blended wheat flour with a protein content lower than bread flour, ranging 9% - 12%. The increased protein binds to the flour to entrap carbon dioxide released by the yeast fermentation process, resulting in a stronger rise. 大部分中式點心都是以中筋粉來製作的。
• Bread flour or strong flour (高筋麵粉) is always made from hard wheat, usually hard spring wheat. It has a very high protein content, between 10% - 13%, making it excellent for yeast bread baking. 適合用來做麵包、派皮、鬆餅、餃子皮、麵條等
• Tang flour or wheat starch (澄麵/無筋面粉)) is a type of wheat flour used primarily in Chinese cooking for making the outer layer of dumplings and buns. 澄麵是從小麥萃取澱粉所製成，是一種完全不含蛋白質的麵粉，因此缺乏黏合力，需加入熱水讓部份澄麵中的澱粉糊化，才可和其他澄麵結合起來。澄麵糰成型之後，若用刀將皮拉薄，就是廣式點心常見的澄麵皮，可用來做蝦餃、水晶皮等，蒸熟後餡枓若隱若現，看起來晶瑩剔透。

"The Large" Breaking the Cosmological Principle

Large Quasar Group (LQG)
An international team of astronomers, Using data from the Sloan Digital Sky Survey, has found the largest known structure in the universe - large quasar group (LQG). This LQG is so large that it would take a vehicle travelling at the speed of light some 4 billion years to cross it. For comparison, our own galaxy, the Milky Way, is just a hundred thousand light-years across, while the local supercluster of galaxies in which it's located, the Virgo Cluster, is only a hundred million light-years wide.

Cosmological Principle
The usual models of the Universe in cosmology are built on the assumption of the cosmological principle – assumption of homogeneity after imagined smoothing on some suitably large scale. Models depend on the Robertson–Walker metric assumes the homogeneity of the mass–energy density. Further,  assumes that any property of the Universe ultimately depends on the mass–energy content then homogeneity naturally asserts that any global property of sufficiently large volumes should be the same within the expected statistical variations.

The Milky Way, our galaxy, is separated from its nearest neighbour, the Andromeda Galaxy, by about 0.75 Megaparsecs (Mpc) or 2.5 million light-years. Whole clusters of galaxies can be 2-3 Mpc across but LQGs can be 200 Mpc or more across. Based on the Cosmological Principle and the modern theory of cosmology, calculations suggest that astrophysicists should not be able to find a structure larger than 370 Mpc.

The new discovered LQG has a typical dimension of 500 Mpc, membership of 73 quasars and mean redshift z¯=1.27. In terms of both size and membership, it is the most extreme LQG found in the DR7QSO catalogue for the redshift range 1.0 ≤ z ≤ 1.8. But because it is elongated, its longest dimension is 1240 Mpc (or 4 billion light years) - some 1600 times larger than the distance from the Milky Way to Andromeda.

Implications

1. The occurrence of structure on Gpc-scales from the Huge-LQG and from galaxies implies that the Universe is not homogeneous on these scales. 
2. The Huge-LQG would also indicate that there is more dark matter in some directions than in others. Such mass concentrations could conceivably be associated with the cosmic (dark) flows on the scales of ∼100–1000 Mpc. Of particular interest is the possibility raised by Tsagas (2012) that those living within a large-scale cosmic flow could see local acceleration of the expansion within a Universe that is decelerating overall. 

Soft Chocolate & Chocolate Ice Cream

What we know about milk, cream and chocolate

Milk is an emulsion of butterfat globules within a water-based fluid.

Whipping cream contains 30-36% butterfat.

Butter contains at least 80% butterfat.

Milk chocolate contains cocoa solids, cocoa butter (or other fat), sugar, and milk powder (or condensed milk).

Butterfat is a triglyceride derived from myristic, palmitic, and oleic acids. 

Cocoa butter is a triglyceride (fat) derived from stearic, palmitic, and oleic acids.

Whipping cream is an emulsion of butterfat in water.

Butter is an emulsion of water in butterfat.

In cocoa butter, there are six essential polymorphic forms.

Examples of food emulsifiers are egg yolk (lecithin), mustard, protein, and soy lecithin.

Average milk freezing point is –0.523°C. 

Melting temperature of butter is 28-36 °C (butter is partially solidify at room temperature).

Melting temperature of chocolate: Type V 34 °C, Type VI 36 °C (body temperature 37 °C).

What is an Ice Cream

Ice cream is a smoothly textured semi-solid (frozen) foam that made from milk/cream, and often combined with fruits and flavours. In USA, it may have the following composition:

• at least 10% butterfat.
• 9 - 12% milk solids (not fat) contains: proteins (caseins and whey proteins) and carbohydrates (lactose) found in milk.
• 12 - 16 % glucose-based corn syrup sweeteners
• 0.2 - 0.5% stabilisers and emulsifiers
• 55% - 64% water (from the milk or other ingredients).

The mixture of these ingredients is stirred slowly while cooling, in order to incorporate air and to prevent large ice crystals from forming. 

Gelato, Italian word for ice cream, derived from the Latin word "gelātus." (meaning frozen). In English, gelato is defined as a soft ice cream containing little or no air.  By statute, gelato in Italy must have at least 3.5% butterfat, with no upper limit established.

In order to keep ice cream soft, we have to avoid ice crystals forming. There are tricks to do so:

• Emulsifying fat - sticks fat molecules in between water molecules.
• Sugar - the higher the concentration of sugar (syrup), the lower the freezing point.
• Air - a more aerated ice cream is easier to scoop, and has a fluffier, less dense texture.
• Others - alcohol, starch, protein (in egg and milk), and natural stabilizers like guar gum.

Melting the Chocolate
When melting chocolate, be careful not to allow excess steam to develop, which will interface with the surface of the chocolate, moistening it and increasing the viscosity. The addition of 3% or 4% by weight of water will turn chocolate into a very thick paste. Continuous to increase the amount of water, say above 20%, there is enough water to form continuous streams through the chocolate and so help it flow.

Milk fat has the same effect as cocoa butter on viscosity. Milk fat will slow down the setting rate of chocolate if it is added at temperature 40°C. The effect of an extra 1% of fat upon the viscosity depends upon the amount that is already present. Above a fat contents of 32% there is very little change in viscosity with any further additions. The effect of fat is proportionately much higher for the plastic viscosity then the yield value. The majority of the fat is wetting fat, which is partially tied to the particles surface. This free fat has a large effect on lubricating the flow when it takes place and so the plastic viscosity decreases dramatically. On the other hand, the yield value is more connected with the forces between the solid particles, which in turn are connected with the absolute distance between them.

Cream can be added to chocolate to form a soft mixture, known as ganache, that does not have any snap when broken and does not contract very much upon cooling. This is made by stirring the cream very rigorously as liquid chocolate is added to it. Because there are emulsifiers in both cream and chocolate, the chocolate viscosity is slightly less affected by the moisture.

Chocolate is almost half made up of very tiny sugar particles. Sugar particles are hydrophilic (attract water) but lipophilic (repel fat). Liquid chocolate flow because the sugar and the other solid particles are able to move past one another. In this case, the emulsifier coats the solid surface and forms a boundary layer between the two and is more a surface active agent than a emulsifier. The most common surface active agent used is lecithin which is a naturally occurring substance frequently obtained from soya. Addition of 0.1 - 0.3% soya lecithin are said to reduce the viscosity by more than 10 times their own weight of cocoa butter.

(Ref: The Science of Chocolate, P.77
http://books.google.com.hk/books?id=miv82VGPL9cC&pg=PA77&lpg=PA77&dq=chocolate+attract+water&source=bl&ots=J2Ie_Al2eE&sig=mqmws11NP982uQ3xW5xjykuIDFk&hl=en&sa=X&ei=ENn4UM3fDKnAiQfH_oCQAg&redir_esc=y#v=onepage&q=chocolate%20attract%20water&f=false)

Experiments
Values used:
Milk chocolate weigh to volume conversion: 100g = 140.83 ml
Milk chocolate: cocoa solid 26%, milk solid 28%, total fat 29.6%
Cream: butterfat 35%

Cream, ml	Chocolate, g	Butter, g	Refrigerator	Form	Water	Cocoa Solid	Total Fat
10	16		10-14 °C	thick paste	19.43%	18.23%	31.21%
20	21		10-14 °C	thick paste	26.35%	15.46%	31.79%
40	21	5	< 10 °C	icecream (soft)	37.50%	11.00%	32.72%
50	21		freezer	icecream (hard)	40.96%	9.61%	33.00%
60	21	5	freezer	icecream (hard)	43.65%	8.54%	33.23%
Planned Next
30	100		10-14 °C	soft chocolate	11.41%	21.43%	30.55%
400	50		freezer	icecream (hard)	55.27%	3.89%	34.19%

Next:
For soft chocolate, the optimal composition is about 10% water and 30% fat.
For ice cream, the optimal composition is about 55% water and >32% fat. 

Chocolate

Cocoa or dark chocolate may positively affect the circulatory system. Other possible effects under basic research include anticancer, brain stimulator, cough preventor and antidiarrhoeal activities.

Chocolate is a raw or processed food produced from the seed of the tropical Theobroma cacao tree. After fermentation, the beans are dried, then cleaned, and then roasted, and the shell is removed to produce cacao nibs. The nibs are then ground to cocoa mass, pure chocolate in rough form. The mass is melted to become the liquor. Chocolate liquor contains roughly 53 percent cocoa butter (fat), about 17 percent carbohydrates, 11 percent protein, 6 percent tannins, and 1.5 percent theobromine. Chocolate liquor is pressed to separate the cocoa butter from the cocoa solids. White chocolate contains cocoa butter, sugar, and milk but no cocoa solids.

Cocoa Butter
Cocoa butter, also called theobroma oil, is a pale-yellow, pure, edible vegetable fat extracted from the cocoa bean, has a cocoa flavor and aroma. Cocoa butter contains a high proportion of saturated fats, derived from stearic and palmitic acids.  Unlike cocoa solids, it has no more than trace amounts of caffeine and theobromine. It is one of the most stable fats known, a quality that coupled with natural antioxidants that prevent rancidity, grants it a storage life of two to five years. The velvety texture, pleasant fragrance and emollient properties of cocoa butter have made it a popular ingredient in products for the skin, such as cosmetics, soaps and lotions.

Cocoa Solids
Cocoa solids contain alkaloids such as theobromine(可可碱) and phenethylamine(PEA,苯乙胺), which have physiological effects on the body. It has been linked to serotonin levels in the brain. In medicine, theobromine is used as a vasodilator (a blood vessel widener), a diuretic (urination aid), and heart stimulant. The presence of theobromine renders chocolate toxic to some animals, especially dogs and cats. Phenylethylamine functions as a neuromodulator or neurotransmitter in the mammalian central nervous system.  Orally ingested phenethylamine is usually inactive because of extensive first-pass metabolism by monoamine oxidase (MAO) into phenylacetic acid. This prevents significant concentrations from reaching the brain.

Serotonin and tryptophan(色氨酸) have been found in chocolate with varying cocoa contents. The highest serotonin content (2.93 ug g-1) was found in chocolate with 85% cocoa, and the highest tryptophan content (13.27-13.34 ug g-1) was found in 70-85% cocoa.

Serotonin (血清素) or 5-hydroxytryptamine (5-HT) is a monoamine neurotransmitter. Biochemically derived from tryptophan, serotonin is primarily found in the gastrointestinal (GI) tract, platelets, and in the central nervous system (CNS) of animals including humans. Approximately 90% of the human body's total serotonin is located in the enterochromaffin cells in the alimentary canal (gut), where it is used to regulate intestinal movements. The remainder is synthesized in serotonergic neurons of the CNS, where it has various functions. These include the regulation of mood, appetite, and sleep. Serotonin also has some cognitive functions, including memory and learning.

Serotonin taken orally does not pass into the serotonergic pathways of the central nervous system, because it does not cross the blood–brain barrier. However, tryptophan and its metabolite 5-hydroxytryptophan (5-HTP), from which serotonin is synthesized, can and do cross the blood–brain barrier. Several classes of drugs target the 5-HT system, including some antidepressants, antipsychotics, anxiolytics, antiemetics, and antimigraine drugs, as well as the psychedelic drugs and empathogens.

Because serotonin is a major gastrointestinal tract modulator, it may be produced by plants in fruits as a way of speeding the passage of seeds through the digestive tract, in the same way as many well-known seed and fruit associated laxatives. Serotonin is found in mushrooms, fruits and vegetables. The highest values of 25–400 mg/kg have been found in nuts of the walnut (Juglans) and hickory (Carya) genera. Serotonin concentrations of 3–30 mg/kg have been found in plantains, pineapples, banana, kiwifruit, plums, and tomatoes.

Tempering

In cocoa butter, there are six essential polymorphic forms. Uncontrolled crystallization of cocoa butter typically results in crystals of varying size. The uniform sheen and crisp bite of properly processed chocolate are the result of consistently small cocoa butter crystals produced by the tempering process. Type V crystals is the best for serving and storing.

Crystal Melting temp.

I         17 °C (63 °F) Soft, crumbly, melts too easily

II        21 °C (70 °F) Soft, crumbly, melts too easily

III       26 °C (79 °F) Firm, poor snap, melts too easily

IV       28 °C (82 °F) Firm, good snap, melts too easily

V        34 °C (93 °F) Glossy, firm, best snap, melts near body temperature (37 °C)

VI       36 °C (97 °F) Hard, takes weeks to form

First, the chocolate is first heated to 45 °C (113 °F) to melt all six forms of crystals. Next, the chocolate is cooled to about 27 °C (81 °F), which will allow crystal types IV and V to form. At this temperature, the chocolate is agitated to create many small crystal "seeds" which will serve as nuclei to create small crystals in the chocolate. The chocolate is then heated to about 31 °C (88 °F) to eliminate any type IV crystals, leaving just type V. After this point, any excessive heating of the chocolate will destroy the temper and this process will have to be repeated.

Type V and VI are the most stable and are triple chain packing, whereas the other forms are all double. 

According to polymorphic transformation theory, bloom occurs through the uncontrolled polymorphic transformation of cocoa butter from a less stable form (form IV or V) to the most stable form (form VI). In well-tempered chocolate, the production of form VI from form V does not always lead to bloom. The onset of transformation from form V to form VI crystals should be considered as an aspect of cocoa butter recrystallization that may result in bloom. 

Handling Chocolate

(http://www.chocolat.bz/All%20about%20chocolate/Use%20and%20handling%20of%20chocolate/Use%20and%20handling%20of%20chocolate%20page%201.htm)

A very small amount of moisture in chocolate will noticeably increase its viscosity, making it unacceptable for dipping or enrobing. When melting chocolate, be careful not to allow excess steam to develop, which will interface with the surface of the chocolate, moistening it and increasing the viscosity. 

Because chocolate contains virtually no moisture, it has very low water activity level, and is not prone to bacterial spoilage during storage, resulting in a long shelf life. The factor limiting shelf life for chocolate is rancidity, the breakdown of fats than can create off flavors. Although cocoa butter is relatively resistant to rancidity, chocolate should be stored protected from exposure to oxygen, light, heat, and moisture (humidity), and when working with chocolate, do not expose it to reactive metals such as copper and iron.

Colloid & Colligative Properties

A colloidal system consists of two separate phases: a dispersed phase (or internal phase) and a continuous phase (or dispersion medium) in which the colloid is dispersed. A colloidal system may be solid, liquid, or gas. The dispersed-phase particles have a diameter of between approximately 1 and 1000 nanometers. They are affected largely by the surface chemistry present in the colloid. Because the size of the dispersed phase may be difficult to measure, and because colloids have the appearance of solutions, colloids are sometimes identified and characterized by their physico-chemical and transport properties.

Many of the forces that govern the structure and behaviour of matter, such as excluded volume interactions or electrostatic forces, govern the structure and behaviour of colloidal suspensions. For example, the same techniques used to model ideal gases can be applied to model the behaviour of a hard sphere colloidal suspension. In addition, phase transitions in colloidal suspensions can be studied in real time using optical techniques, and are analogous to phase transitions in liquids.

A sol (溶胶) is a colloidal suspension of very small solid particles in a continuous liquid medium. They are quite stable and show the Tyndall effect. Examples include blood, pigmented ink, and paint.

An emulsion is a mixture of two or more liquids that are normally immiscible (nonmixable or unblendable). The word "emulsion" comes from the Latin word for "to milk", as milk is an emulsion of milk fat and water.

Emulsions do not exhibit a static internal structure. They tend to have a cloudy appearance because the many phase interfaces scatter light as it passes through the emulsion. Emulsions appear white when all light is scattered equally. If the emulsion is dilute enough, higher-frequency and low-wavelength light will be scattered more, and the emulsion will appear bluer - this is called the "Tyndall effect". If the emulsion is concentrated enough, the color will be distorted toward comparatively longer wavelengths, and will appear more yellow. This phenomenon is easily observable when comparing skimmed milk, which contains little fat, to cream, which contains a much higher concentration of milk fat.

Whether an emulsion of oil and water turns into a "water-in-oil" emulsion or an "oil-in-water" emulsion depends on the volume fraction of both phases and the type of emulsifier (surfactant) present. An emulsifier is a substance that stabilizes an emulsion by increasing its kinetic stability. One class of emulsifiers is known as "surface active substances", or surfactants. In general, the Bancroft rule applies. For example, proteins dissolve better in water than in oil, and so tend to form oil-in-water emulsions.

Water-in-oil emulsions are less common in food but still exist:

Butter - an emulsion of water in butterfat

Oil-in-water emulsions are common in food:

Crema (foam) in espresso – coffee oil in water (brewed coffee), unstable emulsion

Mayonnaise and Hollandaise sauce - these are oil-in-water emulsions that are stabilized with egg yolk lecithin. The main emulsifying agent is lecithin. Lecithos is the Greek word for egg yolk. Lecithin (卵磷脂) is a generic term to designate any group of yellow-brownish fatty substances occurring in animal and plant tissues composed of phosphoric acid, choline, fatty acids, glycerol, glycolipids, triglycerides, and phospholipids (e.g., phosphatidylcholine). Phosphatidylcholine (磷脂酰胆碱) occurs in all cellular organisms, being one of the major components of the phospholipid portion of the cell membrane.

• Mayonnaise (蛋黃醬（法语：mayonnaise），音譯美乃滋，有時又稱沙拉醬、白汁) is a stable emulsion of oil, egg yolk and either vinegar or lemon juice, with many options for embellishment with other herbs and spices. 
• Hollandaise sauce (荷蘭醬，又稱荷蘭酸辣醬，是一种蛋黄酱) is a mixture of egg yolk and butter, usually seasoned with lemon juice, salt, and a little white pepper or cayenne pepper. 

Some examples of food emulsifiers :

• Mustard - where a variety of chemicals in the mucilage surrounding the seed hull act as emulsifiers.
• Proteins
• Soy lecithin is another emulsifier and thickener
• DATEM (Diacetyl Tartaric (Acid) Ester of Monoglyceride) - an emulsifier primarily used in baking.

Colligative properties are properties of solutions that depend upon the ratio of the number of solute particles to the number of solvent molecules in a solution. They are independent of the nature of the solute particles, and are due essentially to the dilution of the solvent by the solute. Colligative properties include:

• Relative lowering of vapor pressure
• Elevation of boiling point
• Depression of freezing point
• Osmotic pressure.

Solute molecules do not fit well in the solvent (freezing) crystal, i.e. substituting a solute for a solvent molecule in the crystal has high enthalpy. For low solute concentrations, the freezing point depression depends solely on the concentration of solute molecules. This is explained by the fact that entropy of the solvent decreases from liquid to solid. When the solute present, the randomness increases (entropy increases) so the solid is harder to form at the normal freezing point. 

In ice cream the solute that depresses the freezing point is sugar (sucrose). The graph below shows nearly 20% of the water is still liquid at -25°C. 

(Ref: http://www.chm.bris.ac.uk/webprojects2003/brown/colligative_effect.html.htm)

When the water freezes the amount of liquid water surrounding the sucrose decreases such that the sugar solution becomes more concentrated. As more ice forms, so the solution becomes more concentrated and its freezing point continues to drop. 

Milk freezing point estimates are used by Dairy Farmers of Ontario (DFO) to indicate

milk with water added. Average milk freezing point is –0.540°Hortvet (H) (-0.523°C). If the freezing point estimate is >-0.530°H in a milk sample a warning is provided to the

producer. At a freezing point test >-0.525°H a financial penalty is imposed on the

producer.

(Ref: http://www.milk.org/Corporate/pdf/Farmers-FreezingPoint.pdf

http://www.nxtbook.com/dawson/gp/milkproducer_201005/index.php?startid=13)

Fats & Milk

"Oils" is usually used to refer to fats that are liquids at normal room temperature.
"Fats" is usually used to refer to fats that are solids at normal room temperature.
"Lipids" is used to refer to both liquid and solid fats, along with other related substances, usually in a medical or biochemical context.

Fats play a vital role in maintaining healthy skin and hair, insulating body organs against shock, maintaining body temperature, and promoting healthy cell function. Fats containing about 37.8 kilojoules (9 calories) per gram of fat. They are broken down in the body to release glycerol and free fatty acids. The glycerol can be converted to glucose by the liver and thus used as a source of energy.

Fats and oils are the fatty acid esters of glycerol. Chemically, they are triglycerides, triesters of glycerol.

• Glycerol has three hydroxyl groups that are responsible for its solubility in water and its hygroscopic nature. Glycerol can be used as a laxative when introduced into the rectum in suppository or small-volume (2–10 ml) (enema) form; it irritates the anal mucosa and induces a hyperosmotic effect.

• Ethers contain an ether group — an oxygen atom connected to two alkyl or aryl groups — R–O–R'. They are formed from the reaction of the carboxylic acid and an organic alcohol. That is, esters are formed by condensing an acid with an alcohol. Esters with low molecular weight are commonly used as fragrances and found in essential oils and pheromones. Phosphoesters form the backbone of DNA molecules. Nitrate esters, such as nitroglycerin, are known for their explosive properties, while polyesters are important plastics, with monomers linked by ester moieties.

As a simple visual illustration, if the fatty acids each seen as a horizontal line; the glycerol "backbone" would be the vertical line that joins the horizontal lines - "ester" bonds. Fatty acids with long chains are more susceptible to intermolecular forces of attraction (in this case, van der Waals forces), raising its melting point. Long chains also yield more energy per molecule when metabolized.

Milk is an emulsion or colloid of butterfat globules within a water-based fluid that contains dissolved carbohydrates and protein aggregates with minerals. The fat-soluble vitamins A, D, E, and K along with essential fatty acids such as linoleic and linolenic acid are found within the milk fat portion of the milk. 

Butterfat, the fatty portion of milk, is a triglyceride derived from fatty acids such as myristic, palmitic, and oleic acids. Each fat globule is surrounded by a membrane consisting of complex lipids such as phospholipids, along with proteins. These act as emulsifiers which keep the individual globules from coalescing and protect the contents of these globules from various enzymes in the fluid portion of the milk. 

The fatty acids of butterfat are typically composed as follows (by mass fraction):

Saturated fatty acids:

• Palmitic acid: 31%
• Myristic acid: 12%
• Stearic acid: 11%
• Lower (at most 12 carbon atoms) saturated fatty acids: 11%
• pentadecanoic acid and heptadecanoic acid: traces

Unsaturated fatty acids:

• Oleic acid: 24%
• Palmitoleic acid: 4%
• Linoleic acid: 3%
• Linolenic acid: 1%

Milk and cream are sold according to the amount of butterfat they contain. In U.S., the federal standards for butterfat content of dairy products are:

• Low fat milk contains between 0.5–2%; 1% and 2% varieties are widely marketed
• Whole milk contains at least 3.25%
• Sherbet contains 1–2%
• Ice cream contains at least 10%
• Half and half contains 10.5–18%
• Light whipping cream (often called simply "whipping cream") contains 30–36%
• Swiss cheese contains at least 43% relative to the total solids
• Cheddar cheese contains at least 50% relative to the total solids
• Butter (including whipped butter) contains at least 80%

Melting point, is 82.4-96.8°F (28-36°C), measures the temperature range at which a solid becomes a liquid. Solid Fat Index (SFI) is an empirical measure of solid fat content at standardized temperature check points. Butter's SFI curve illustrates that butter will only partially solidify at room temperature.

(Ref:

1.http://www.eatwisconsincheese.com/wisconsin/other_dairy/butter/butter_basics/physical_chemical_characteristics.aspx

2.http://hypertextbook.com/facts/2003/JessicaCheung.shtml)