Butter

Food Science | Butter | Butter is one of the most highly concentrated forms of fluid milk.Twenty litres of whole milk are needed to produce one kilogram of butter.This process leaves approximately 18 litres of skim milk and buttermilk, which at one time were disposed of as animal feed or waste.Today the skim portion has greatly increased in value and is fully utilized in other products.

Commercial butter is 80–82 percent milk fat, 16–17 percent water, and 1–2 percent milk solids other than fat (sometimes referred to as curd). It may contain salt , added directly to the butter in concentrations of 1 to 2 percent.Unsalted butter is often referred to as “sweet” butter.This should not be confused with “sweet cream” butter, which may or may not be salted. Reduced-fat, or “light,” butter usually contains about 40 percent milk fat. Butter also contains protein, calcium and phosphorous (about 1.2%) and fat-soluble vitamins A, D and E.

Although there are over 120 different compounds that contribute to butter’s unique flavor, the five primary factors responsible for butter’s flavor include: fatty acids, lactones, methyl ketones, diacetyl and dimethyl sulfide.

Chemically butter fat consists essentially of a mixture of triglycerides, particularly those derived from fatty acids, such as palmitic, oleic, myristic, and stearic acids.The fatty acid composition of butter fat varies according to the producing animal's diet.A measure of the amount of these acids, the Reichert-Meissl, or Reichert-Wollny, number is important in the analysis of butter fat.

- Food Processing -

Food

Food | Food Sciences | Food is any substance, composed of carbohydrates, fats, proteins, minerals and water, that can be eaten or drunk by animals, including humans, for nutrition or pleasure. Items considered food may be sourced from plants, animals or other categories such as fungus.

Although many human cultures sought food items through hunting and gathering, today most cultures use farming, ranching, and fishing, with hunting, foraging and other methods of a local nature included but playing a minor role. Most traditions have a recognizable cuisine, a specific set of cooking traditions using various spices or combinations of flavors unique to that culture. Other differences include preferences (hot or cold, spicy etc), and practices, the study of which is known as gastronomy.

Many cultures have diversified their foods by means of preparation, cooking methods and manufacturing. This also includes a complex food trade which helps the cultures to economically survive by-way-of food, not just by consumption. Many cultures study the dietary analysis of food habits. While evolutionarily speaking (as opposed to culturally) humans are omnivores, religion and social constructs such as morality or environmentalism will often affect which foods they will consume. Food safety is also a concern with foodborne illness claiming many lives each year typically due to contaminated or dirty water or undercooked meats. In English, food is often used metaphorically or figuratively, as in "food for thought". [ food sciences ]

Milk

Milk | Food Sciences | Milk is a white liquid produced by the mammary glands of mammals. It is the main source of nutrition for young mammals before they are able to digest other types of food. In early lactation milk contains colostrum, which carries the antibodies from mother to child and can reduce the risk of many diseases of children. The exact composition of raw milk varies by species and a number of other factors, but it contains significant amounts of saturated fat, protein and calcium and vitamin C. Cow's milk has a pH ranging from 6.4 to 6.8, making it slightly acidic.

In almost all mammals, milk is fed to infants through breastfeeding, either directly or by expressing the milk to be stored and consumed later. Some cultures, historically or currently, continue to use breast milk to feed their children until they are seven years old.

Human infants sometimes are fed fresh goat milk. There are known risks in this practice, including those of developing electrolyte imbalances, metabolic acidosis, megaloblastic anemia, and a host of allergic reactions.

In many cultures of the world, especially the Western world, humans continue to consume milk beyond infancy, using the milk of other animals (especially cattle, goats and sheep) as a food product. For millennia, cow's milk has been processed into dairy products such as cream, butter, yogurt, kefir, ice cream, and especially the more durable and easily transportable product, cheese. Modern industrial processes produce casein, whey protein, lactose, condensed milk, powdered milk, and many other food-additive and industrial products.

Humans are an exception in the natural world for young children consume milk past, despite the fact that many people have some degree (some as little as 5%) of lactose intolerance, a feature that is more common among people of African or Asian descent. The sugar lactose is found only in milk, forsythia flowers and a few tropical shrubs. The enzyme needed to digest lactose, lactase, reaches its highest level in the small intestine after birth and then begins a slow decline unless milk is consumed regularly. On the other hand, are often the groups that continue to tolerate milk have exercised great creativity in using the milk of domestic ungulates, not only cattle but also sheep, goats, yaks, water buffalo, the horses, reindeer and camels. The largest producer and consumer of cattle and buffaloes in the world is India. [ agriculture commodities ]

Margarine

Margarine | agriculture commodities - food sciences | Margarine was first invented in France by a chemical expert named Hippolyte Mege-Mouries in 1869. The discovery of margarine is actually triggered by the situation in France at the time where the price of butter is very expensive so many people who can not afford it. This happens as a result of the influence of industrial revolution where a lot of farmers who left the farm and go for the city and work in industries. Consequently, there is a shortage of production so the price of butter became expensive because of high demand. To overcome this situation then in 1869 Napoleon III as ruler of France at that time held a contest and will give prizes to anyone who can find a cheap butter substitute, a replacement would have properties such as butter. Hippolyte Mege-Mouries won the competition because he was able to find what is desired by Napoleon III is a cheap substitute for butter. Mege-Mouries named his invention with margarine, the name is derived from Greek words "margarites" that have meaning "pearl". Named the pearl because the fat of margarine when forming dense granules shaped like a shiny crystal of pearls.

The characteristics of margarine that stands out is more plastic, solid at room temperature, a bit hard at low temperature, texture is easily applied, and quick to melt in mouth.

Margarine divided into table margarine and kitchen margarine . For the kitchen margarine is not required the addition of vitamins A and D. Margarine is an emulsion-shaped food products in the oil-water mixture, which is about 16 percent of water in at least 80 percent vegetable oil or fat. Fat phase is generally composed of vegetable oils, some of which have been compacted in order to obtain the desired plastic properties of the final product.

Margarine was originally made from animal fat but now exclusively made only from plant oils. Margarine practically have a calorific value equivalent to the butter, easy to digest, usually equipped with vitamins A and D. Margarine vegetable has long been recommended as a substitute for butter because they contain unsaturated fat and less cholesterol. According to one study published in the Journal of the American Medical Association, replacing butter with margarine in the diet significantly lowers blood cholesterol levels.

Margarine was originally created by converting the unsaturated fats (hydrocarbon double bond) becomes saturated (single bond) through the process of hydrogenated. Saturated fats are fats that form the crystal plays an important role in determining the texture of margarine and make it stay solid at room temperature. However, the incomplete hydrogenation process are not resulting the formation of trans fatty acids which can raise the level of LDL cholesterol and depress HDL .[ agriculture commodities | food sciences ]

Meat Consumption Pattern of Urban Domestic | Study

Meat Consumption Pattern of Urban Domestic | Study | Food Sciences | Agriculture Commodities | Abstract: Animal products are an important part of the diet of urban households in different income classes. However, the concerns of consumers' receive little attention to design has a low profile issues such as lack of credibility and consumer advocacy or pressure groups. The situation is further complicated by the fact that studies on patterns of urban or rural meat consumption information.

The study used information on the cities in the metropolitan area of ​​Nairobi consumer survey by the Institute Tegemeo with the Office of Statistics (CBS), the frame appears at the end of 2003. The survey data is complimented with slaughter numbers and prices of VSF-Suisse, and several slaughterhouses in Nairobi.

This study characterizes household meat consumption in Nairobi and compares per adult equivalent consumption across income quintiles. It further examines the factors influencing domestic consumption including meat prices, channels of acquisition and the traits of the household head for instance education, gender and age.

The results indicate that meat is consumed by a large proportion of the sample but essentially remains a luxury good whose consumption increases with increasing income.

Middle and high-income households consume significantly large amounts of beef, chicken and eggs within the home compared to low-income households. This phenomenon reveals that health concerns especially for red meat do not necessarily influence consumption levels for both low and high-income groups. However, the consumption of chicken and eggs by high-income and educated groups appear to be responding to health concerns. Chevron (goat meat) and mutton (sheep) are hardly consumed at home. Channels of acquisition influence price and ultimately consumption patterns especially for chicken and eggs where there exists some form of product

differentiation.

The above represents a potential to increase domestic meat, there are low-income groups, but only to take advantage of lower prices or higher incomes. While the government is focusing on the productivity of livestock on the rise, consumers 'concerns' should be duly taken into account.

Policies for livestock development must adapt to changing consumer behavior and deal with marketing systems that prevent the translation of the productivity gains in fuel economy. By: Paul Gamba [ Food Sciences, Agriculture Commodities ]

Science News: Grape skins prevent metabolic disorders

Science News: Grape skins prevent metabolic disorders | agriculture commodities - commodity prices - food sciences | Guarulhos, Brazil. A new Brazilian study found the grape skin extract protected the offspring of normally fed high fat-fed dams during lactation from the phenotypic and metabolic characteristics of metabolic syndrome (J Cardiovasc doctors. June 8, 2011).

The study examined the effect of Vitis vinifera grape skin extract ACH09 (ACH09) on metabolic disturbances and oxidative stress in adult offspring of rats fed a high fat diet (HF) during lactation. Four groups of female rats were fed: control diet (7 percent fat); ACH09 (7 percent fat and 200 mg / kg / d orally ACH09), HF (24 percent fat ), HF + ACH09 (24 percent fat plus 200 mg / kg / d orally ACH09) during lactation for 90 or 180 days.

Systolic blood pressure was increased in adult offspring of HF-fed dams and ACH09 prevented hypertension. The increased adiposity, plasma triglycerides, blood sugar and insulin resistance were observed in the offspring of middle-aged, and these changes were reversed by ACH09. Plasma oxidative damage and increased levels of nitrite decreased in the HF group of middle-aged, which was reversed by ACH09. In addition, restored ACH09 decreased plasma antioxidant activity and mesenteric arteries of superoxide dismutase (SOD), catalase and glutathione peroxidase in the HF group. @food sciences

Journal - Menthol cigarettes and smoking cessation behaviour: a review of tobacco industry documents

Journal - Menthol cigarettes and smoking cessation behaviour: a review of tobacco industry documents - | agriculture commodities - commodity prices - food sciences | Abstract: Objective: To determine what the tobacco industry knew about menthol's relation to smoking cessation behaviour. 

Methods: A snowball sampling design was used to systematically search the Legacy Tobacco Documents Library (LTDL) (http://legacy.library.ucsf.edu) between 15 May to 1 August 2010. Of the approximately 11 million documents available in the LTDL, the iterative searches returned tens of thousands of results. A final collection of 509 documents relevant to 1 or more of the research questions were qualitatively analysed, as follows: (1) perceived sensory and taste rewards of menthol and potential relation to quitting; and (2) motivation to quit among menthol users.

Results: Menthol's cooling and anaesthetic effects mask the short-term negative physiological effects of smoking such as throat pain, burning and cough. This provides superficial physical relief as well as psychological assurance against concerns about the health dangers of smoking that would otherwise motivate smokers to quit. Menthol smokers, particularly women, perceive the minty aroma of menthol cigarettes to be more socially acceptable than non-menthol cigarettes. 

Discussion: Consumers believe menthol's sensory effects equate to health protections and that menthol cigarettes are more socially acceptable than non-menthol cigarettes. Menthol in cigarettes may encourage experimenters who find non-mentholated cigarettes too harsh, including young or inexperienced users, to progress to regular smoking rather than quitting, and may lessen the motivation to quit among established menthol smokers. The perception of menthol cigarettes as more socially acceptable lessens the impact of smoking denormalisation on quitting motivation. Menthol makes cigarettes easier and more palatable to smoke and less desirable to quit among established smokers. Fewer smokers quitting contributes to the incidence of tobacco-related diseases. 

Author: Stacey J Anderson

• Department of Social and Behavioral Sciences, University of California, San Francisco (UCSF), San Francisco, California, USA
• Center for Tobacco Control Research and Education, University of California, San Francisco (UCSF), San Francisco, California, USA

Keywords: tobacco, cigarettes, Menthol, smoking, cessation, behavior, industry, anaesthetic, effects, sensory, smoker, health protection

Study: Survey on dairy cattle milk production and milk quality problems in peri-urban areas in Burkina Faso

Study: Survey on dairy cattle milk production and milk quality problems in peri-urban areas in Burkina Faso – A survey study was carried out around two large cities in Burkina Faso to contribute to the understanding of the situation of local milk production and milk processing. Twenty-two dairy farms associated with nine dairy processing units were selected for the study.

Two separate questionnaires were used to investigate the prerequisites for animal production and milk processing and the interviews were carried out from August to October 2006. Meanwhile, 110 milk samples from individual cows, 22 farm tank milk samples and nine dairy tank milk samples were analyzed. Results of the survey show that daily milk yield was 1 2 L per cow in sedentary traditional farms and 2 4 L per cow in semi intensive farms. Milk temperature at dairy farm level (32.5 ± 4.6°C) was an important factor reducing milk quality before reaching the collection centre.

According to the survey, the use of cottonseed cake in the diet resulted in higher milk yield per cow, both during the rainy and dry season (Chi-square = 9.32; P = 0.01). The use of crossbred cows was also related to higher daily milk yield per cow (Chi-square = 31.80; P = 0.001). It was concluded that more extensive supplementation of diets and cross-breeding would improve milk production in Burkina Faso. Furthermore, milk cooling systems on farm and at dairy processing level are needed.

Author: V. Millogo¹, G. A. Ouédraogo², S. Agenäs¹ a and K. Svennersten-Sjaunja¹

¹Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, P.O. Box 7024, SE-750 07 Uppsala, Sweden.

²Département d´élevage, Institut du Développement Rural, Université Polytechnique de Bobo-Dioulasso, BP 1091, Bobo-Dioulasso, Burkina Faso.

Keywords: Dairy farm, dairy processing unit, cow, milk, production

Abstract: Impact of cocoa processing technologies in free fatty acids formation in stored raw cocoa beans

Abstract: Impact of cocoa processing technologies in free fatty acids formation in stored raw cocoa beans. The quality of raw cocoa beans depends widely on their free fatty acids (FFA) content. High FFA content is a serious quality defect and reduces the technical and economic value of the cocoa beans. 

The work investigates the influence of cocoa processing technologies on FFA formation during storage of raw cocoa beans. Different samples of ferment dried cocoa beans purchased from Cote d’Ivoire were stored and analysed for FFA content. Very low FFA contents were found in whole healthy cocoa beans generally complied with UE standards (1.75% oleic acid equivalent) throughout storage while high FFA content was found in poor quality and broken healthy beans. The formation of FFA did not depend on the genotype or on cocoa post-harvest processing technologies. However, high and increasing FFA contents were observed in defective cocoa beans and could be attributed probably to the activity of microflora which in turn were associated with initial quality and loss of physical integrity of the cocoa beans.

Author: Simplice Tagro Guehi¹, Michae¹ Dingkuhn², Emile Cros³, Gérard Fourny³, Robert Ratomahenina⁴, Guy Moulin⁴ and Anne Clement Vidal^2
1Laboratoire de Biochimie et de Technologie Alimentaire. UFR Sciences et Technologies des Aliments. Université d’Abobo-Adjamé. 02 Bp 801 Abidjan 02. Côte d’Ivoire.
²CIRAD-AMIS, Equipe Ecotrop, TA 40/01, 34398 Montpellier Cedex 5, France.
³CIRAD-CP/Programme Cacao, Laboratoire de Chimie-Technologie du cacao, TA 80/16, 34398 Montpellier Cedex 5, France.
⁴INRA-Montpellier, Laboratoire de microbiologie industrielle et de génétique des microorganismes, 2 Place Viala, 34000 Montpellier, France.

Keywords: Raw cocoa beans, processing technologies, free fatty acids content

Food Sciences: Measurement of Coffee Taste Using Lipid Membrane Taste Sensors

Food Sciences: Measurement of Coffee Taste Using Lipid Membrane Taste Sensors – Instant coffee and the components of coffee were measured by the taste sensing system which used lipid membrane taste sensors. The brands of instant coffee were discriminated easily and the difference of strength of sourness appeared clearly. In the case of measurement of components of coffee, only one-dimensional information was obtained, because all the response patterns are related to pH. Therefore it was difficult to detect a difference of delicate taste other than sourness. Thereupon, the preliminary treatment to coffee was tried to increase the information. The response of ch3 changed by adding milk or skim milk to coffee.

Different output patterns from other channels were obtained. In case of discrimination of brands of instant coffee contribution rate of PC2 improved by 5.8 times and the discriminating resolution was improved. The difference of delicate taste other than sourness was detected as PC2. The preliminary treatment to coffee increases the information and has the effect of improving discriminating resolution.

An improvement of the resolution by the preliminary treatment to coffee will greatly contribute to quality control of coffee and development of new products. Improvements of taste sensors and studies of connection between response of sensor and sensory evaluation are being carried out.

Author: H. KOMAI¹, Y. NAITO¹, K. SATO¹, H. IKEZAKI¹, A. TANIGUCHI¹, K. TOKO²

¹Research Laboratory Anritsu Corporation 1800, Onna, Atsugi-shi, Kanagawa-ken 243, Japan

²Department of Electronics, Faculty of Engineering, Kyushu University @food sciences

Food Sciences: Auto Gas Permeability Testing in Fruit and Vegetable Preservation

Food Sciences: Auto Gas Permeability Testing in Fruit and Vegetable Preservation - Abstract: This article briefs on the methods and mechanisms of preservation and storage for fruits and vegetables, and presents a detail introduction about how to obtain the accurate permeability data of preservative film under lower temperature storage environment.

People often focus their attentions on the guarantee period when buying food. Guarantee period is a term used for the safety of food. Food within this period can be eaten safely. However, with the improvement of living standard, people began to pay close attention to the freshness of food. Therefore, the concept of food preservation came into being. Food preservation, which has a higher requirement than quality guarantee, refers to that on the basis of safety insurance, the nutrition, color, texture and flavor can also be guaranteed.

Summary: Plastic wrap is one of the commonly used methods in fruits and vegetable preservation. And it is always used combining with low temperature storage. Therefore, obtain the permeability data of plastic wrap under low temperature is very important to the research of preservative mechanism and effect.

Author: Labthink Instruments Co.,Ltd.

Keywords: preservation of fruit and vegetable, low temperature, permeability, data fitting

School Projects in Food Sciences

School Projects in Food Sciences - Projects in Food Sciences can be fun for all ages. There are a lot of great ideas related to educational can be found in your kitchen. Food sciences and chemistry in the kitchen can be a big science projects. There are many ideas that can possibly be written in an article, so be sure to see the references and resources for more information.

Elemetary School Projects in Food Sciences

Ideas in Food Sciences for elementary students include to understand the dry food research. Why they can  dry? How to make them dry? How long does drying take? Measure of cutting the fruit before and after drying for the amount of moisture that is lost.

Crystal growing is a nice project of candy. Make identical to the saturated sugar solutions, and to test if the crystals grow faster when planted or when the sugar crystals are added to the string or left to their own different crysttalization process.Will crystallization temperature affects the shape of size of crystal ?

Make your own butter. How changes in finished product when you add an acidification agent, such as sour cream or yogurt? What makes the colors of butter different?

Testing the amount of iron in breakfast cereals with a magnet. Crush grains and suspended in water. Drop of a magnet bar in cereals. The iron would be able to stick to the magnet as a gray and filmy substances. Check cereals adverts that claim to be rich in iron actually contain more iron.

Middle School Projects in Food Sciences

How many times has food spoiled in the refrigerator or in your lunch box? Test that the packaging to keep food fresh longer the most, and save money for your family.

Look for hidden food additives. How foods are most often used as "filler" and sweeteners? You might be surprised to find  wheat  in your hot dogs or soybeans in ice cream.

Research on cookies. What kind of pan to help them cook evenly, without burning more? Try the light and dark cookie tins, pots and foils covered with non-stick cookware.

Flour Gluten is a substance that traps the gas and allow the bread to rise. Examine a variety of flour to see what is the gluten. How to apply for different types of gluten-free level, when the yeast rolls or a pie crust?

High School Projects in Food Sciences

High school students can explore things a little deeper. Start with the bread. How do you keep the bread the freshest the longest? Investigate this type of storage works best and what kind of bread stays fresh the longest. What can you add to the recipe to keep it fresh longer?

What happens when you add the milk to gravy or sauce and it curdles ? What is the ingredient caused by coagulation of milk, and how can it be prevented? Learning the structure of milk proteins and how to avoid lactic acid accumulates.

Investigate the science of tempering chocolate. What exactly is the hardening and why is it necessary? What is the best method of curing to ensure the best product? White chocolate must be tempered, and the temperature is the same as the black or chocolate milk?

Yet another lovely idea. It's the thickness of the steak and cut meat affects the amount of heat and time can be cooked to a certain extent "doneness". Cook a steak thin and the temperature of the fluid. Double the thickness of the meat to cook double or quadruple the time? Find out correlation between  the thickness and the time.

Fish Protein Hydrolysates Beat Alternatives for Foods

Fish Protein Hydrolysates Beat Alternatives for Foods | agriculture commodities - commodity prices - food sciences | Protein hydrolysates from Pacific whiting, an abundant and under-utilised fish, produced better foams than bovine serum albumin, says new research from Mexico. 

Using the commercial protease Alcalase, researchers from the Centro de Investigacion en Alimentacion y Desarrollo produced hydrolysates from fish muscle that could substitute functional compounds such as bovine serum albumin and sodium caseinate. 

"Results in the present study showed that hydrolysates produced from Pacific whiting (Merluccius productus) muscle can be used as food ingredients or additives to impart a desire characteristic to food products or increase food storage stability, acting as emulsifying, foaming or dispersing agents, in sausages, mayonnaise, salad dressings, beverages, creams, etc., all these in a broad pH range," wrote lead author Ramon Pacheco-Aguilar in the journal Food Chemistry. 

The Mexican researchers used Alcalase to produce hydrolysates from Pacific whiting muscle with degrees of hydrolysis of 10, 15, and 20 per cent. 

The functionality of the hydrolysates was then investigated in terms of solubility, emulsifying and foaming properties over a pH range of 4.0 to 10.0, and compared with bovine serum albumin and sodium caseinate. 

Almost 100 per cent stability was reported in freeze-dried hydrolysates at all pHs studied. Moreover, the degree of hydrolysis did not affect the emulsifying properties, which were higher than sodium caseinate at pH 4. 

Recent figures from Frost & Sullivan reveal emulsifiers, along with fat replacers, are leading growth in the food additive industry: since 2001 the market value of emulsifiers rose by some 5.6 per cent. Emulsifiers are used by food makers to reduce the surface tension between two immiscible phases at their interface - such as two liquids, a liquid and a gas, or a liquid and a solid - allowing them to mix. 

While the hydrolysates did not exhibit a high foaming capacity, it was found to be "equal or even better than bovine serum albumin, except at pH 4.0," stated the researchers. 

"Results suggest that hydrolysates from Pacific whiting muscle can be produced with similar or better functional properties than the food ingredients used as standards," they added. Pacheco-Aguilar and co-workers called for further study to explore the potential of the fish protein hydrolysates in real food systems. 

"The use of commercial enzymes for production of highly functional hydrolysates from marine species of low commercial value can be a feasible technology to make the most of a vast underutilized resource (such as the Pacific whiting) and use it as a food ingredient for direct human consumption," concluded the researchers. 

Meat opportunities 

Protein hydrolysates have many functions in the food industry, but one of the most commonly mentioned is as a water-holding agent in meat products to improve the moisture and succulence of the meat. 

This offers the processed meat industry an alternative to phosphates, currently employed by the processed meat industry to maintain the "juiciness" of meat by binding water to the meat. Additives such as E450 (diphosphates), E451 (triphosphates) and E452 (polyphosphates) are commonly used. 

Authors: R. Pacheco-Aguilar, M.A. Mazorra-Manzano, J.C. Ramirez-Suarez 

Source: Food Chemistry August 2008, Volume 109, Issue 4, Pages 782-789 @food sciences

MILK: a Food Source for Humans (1)

MILK: a  Food Source for Humans (1) - Composition and Structure: Overview.  The role of milk in nature is to nourish and provide immunological protection for the mammalian young. Milk has been a food source for humans since prehistoric times; from human, goat, buffalo, sheep, yak, to the focus of this section - domesticated cow milk (genus Bos). Milk and honey are the only articles of diet whose sole function in nature is food. It is not surprising, therefore, that the nutritional value of milk is high. Milk is also a very complex food with over 100,000 different molecular species found. There are many factors that can affect milk composition such as breed variations (see introduction, cow to cow variations, herd to herd variations - including management and feed considerations, seasonal variations, and geographic variations. With all this in mind, only an approximate composition of milk can be given:

• 87.3% water (range of 85.5% - 88.7%)
• 3.9 % milkfat (range of 2.4% - 5.5%)
• 8.8% solids-not-fat (range of 7.9 - 10.0%):
• protein 3.25% (3/4 casein)
• lactose 4.6%
• minerals 0.65% - Ca, P, citrate, Mg, K, Na, Zn, Cl, Fe, Cu, sulfate, bicarbonate, many others
• acids 0.18% - citrate, formate, acetate, lactate, oxalate
• enzymes - peroxidase, catalase, phosphatase, lipase
• gases - oxygen, nitrogen
• vitamins - A, C, D, thiamine, riboflavin, others

The following terms are used to describe milk fractions:

• Plasma = milk - fat (skim milk)
• Serum = plasma - casein micelles (whey)
• solids-not-fat (SNF) = proteins, lactose, minerals, acids, enzymes, vitamins
• Total Milk Solids = fat + SNF

Not only is the composition important in determining the properties of milk, but the physical structure must also be examined. Due to its role in nature, milk is in a liquid form. This may seem curious if one takes into consideration the fact that milk has less water than most fruits and vegetables. Milk can be described as:

• an oil-in-water emulsion with the fat globules dispersed in the continuous serum phase
• a colloid suspension of casein micelles, globular proteins and lipoprotein partilcles
• a solution of lactose, soluble proteins, minerals, vitamins other components.

Looking at milk under a microscope, at low magnification (5X) a uniform but turbid liquid is observed. At 500X magnification, spherical droplets of fat, known as fat globules, can be seen. At even higher magnification (50,000X), the casein micelles can be observed. The main structural components of milk, fat globules and casein micelles, will be examined in more detail later.

Milk Lipids - Chemical Properties

The fat content of milk is of economic importance because milk is sold on the basis of fat. Milk fatty acids originate either from microbial activity in the rumen, and transported to the secretory cells via the blood and lymph, or from synthesis in the secretory cells. The main milk lipids are a class called triglycerides which are comprised of a glycerol backbone binding up to three different fatty acids. The fatty acids are composed of a hydrocarbon chain and a carboxyl group. The major fatty acids found in milk are: 

Long chain

• C14 - myristic 11%
• C16 - palmitic 26%
• C18 - stearic 10%
• C18:1 - oleic 20%

Short chain (11%)

• C4 - butyric*
• C6 - caproic
• C8 - caprylic
• C10 - capric

* butyric fatty acid is specific for milk fat of ruminant animals and is resposible for the rancid flavour when it is cleaved from glycerol by lipase action. 

Saturated fatty acids (no double bonds), such as myristic, palmitic, and stearic make up two thirds of milk fatty acids. Oleic acid is the most abundant unsaturated fatty acid in milk with one double bond. While the cis form of geometric isomer is the most common found in nature, approximately 5% of all unsaturated bonds are in the trans position as a result of rumen hydrogenation.

Triglycerides account for 98.3% of milkfat. The distribution of fatty acids on the triglyceride chain, while there are hundreds of different combinations, is not random. The fatty acid pattern is important when determining the physical properties of the lipids. In general, the SN1 position binds mostly longer carbon length fatty acids, and the SN3 position binds mostly shorter carbon length and unsaturated fatty acids. For example:

• C4 - 97% in SN3
• C6 - 84% in SN3
• C18 - 58% in SN1

The small amounts of mono- , diglycerides, and free fatty acids in fresh milk may be a product of early lipolysis or simply incomplete synthesis. Other classes of lipids include phospholipids (0.8%) which are mainly associated with the fat globule membrane, and cholesterol (0.3%) which is mostly located in the fat globule core.

Milk Lipids - Physical Properties

The physical properties of milkfat can be summerized as follows:

• density at 20° C is 915 kg m(-3)*
• refractive index (589 nm) is 1.462 which decreases with increasing temperature
• solubility of water in fat is 0.14% (w/w) at 20° C and increases with increasing temperature
• thermal conductivity is about 0.17 J m(-1) s(-1) K(-1) at 20° C
• specific heat at 40° C is about 2.1kJ kg(-1) K(-1)
• electrical conductivity is <10(-12) ohm(-1) cm(-1)
• dielectric constant is about 3.1

*the brackets around numbers denote superscript

At room temperature, the lipids are solid, therefore, are correctly referred to as "fat" as opposed to "oil" which is liquid at room temperature. The melting points of individual triglycerides ranges from -75° C for tributyric glycerol to 72° C for tristearin. However, the final melting point of milkfat is at 37° C because higher melting triglycerides dissolve in the liquid fat. This temperature is significant because 37° C is the body temperature of the cow and the milk would need to be liquid at this temperature. The melting curves of milkfat are complicated by the diverse lipid composition:

• trans unsaturation increases melting points
• odd-numbered and branched chains decrease melting points

Crystallization of milkfat largely determines the physical stability of the fat globule and the consistency of high-fat dairy products, but crystal behaviour is also complicated by the wide range of different triglycerides. There are four forms that milkfat crystals can occur in; alpha, ß , ß ' 1, and ß ' 2, however, the alpha form is the least stable and is rarely observed in slowly cooled fat.

Milkfat Structure - Fat Globules

More than 95% of the total milk lipid is in the form of a globule ranging in size from 0.1 to 15 um in diameter. These liquid fat droplets are covered by a thin membrane, 8 to 10 nm in thickness, whose properties are completely different from both milkfat and plasma. The native fat globule membrane (FGM) is comprised of apical plasma membrane of the secretory cell which continually envelopes the lipid droplets as they pass into the lumen. The major components of the native FGM, therefore, is protein and phospholipids. The phospholipids are involved in the oxidation of milk. There may be some rearrangement of the membrane after release into the lumen as amphiphilic substances from the plasma adsorb onto the fat globule and parts of the membrane dissolve into either the globule core or the serum. The FGM decreases the lipid-serum interface to very low values, 1 to 2.5 mN/m, preventing the globules from immediate flocculation and coalescence, as well as protecting them from enzymatic action. 

It is well known that if raw milk or cream is left to stand, it will separate. Stokes' Law predicts that fat globules will cream due to the differences in densities between the fat and plasma phases of milk. However, in cold raw milk, creaming takes place faster than is predicted from this fact alone. IgM, an immunoglobulin in milk, forms a complex with lipoproteins. This complex, known as cryoglobulin precipitates onto the fat globules and causes flocculation. This is known as cold agglutination. As fat globules cluster, the speed of rising increases and sweeps up the smaller globules with them. The cream layer forms very rapidly, within 20 to 30 min., in cold milk. 

Homogenization of milk prevents this creaming by decreasing the diameter and size distribution of the fat globules, causing the speed of rise to be similar for the majority of globules. As well, homogenization causes the formation of a recombined membrane which is much similar in density to the continuous phase.

Recombined membranes are very different than native FGM. Processing steps such as homogenization, decreases the average diameter of fat globule and significantly increases the surface area. Some of the native FGM will remain adsorbed but there is no longer enough of it to cover all of the newly created surface area. Immediately after disruption of the fat globule, the surface tension raises to a high level of 15 mN/m and amphiphilic molecules in the plasma quickly adsorb to the lipid droplet to lower this value. The adsorbed layers consist mainly of serum proteins and casein micelles.

Retrieved from : Dairy Chemistry and Physics of Milk

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