Choosing Milk for Making Yogurt

Some of yogurt’s characteristics come from the type of culture that is used. Greek and Bulgarian yogurts are far different from filmjölk and piimä, for instance. But the type of milk you choose will also have a great effect on the way your yogurt turns out.

There are certain qualities, such as fat content, that would make obvious changes in the finished product. But there are additional qualities that make a difference in taste, consistency, texture, and quality.

The Characteristics of Milk

Cow milk is the type most of us in America are familiar with. It is generally the standard against which other milks are compared.

Cow milk contains about 1 gram of protein per ounce, mostly in the form of casein. Casein molecules are bound up into groups called micelles, and the micelles tend to stay apart from each other in fresh milk. In cultured milk, the casein micelles change their chemical structure so that they clump together into curds. The part of the milk that clumps up is called the milk solids, and makes up about 12% of the content of cow milk.

About 20% of the protein in milk is not casein, and when curds form, the other proteins remain in the liquid whey. They are therefore known as whey proteins.

Cow milk also contains lactose, a type of sugar made up of sucrose and galactose. About 40% of the calories in milk come from lactose.

The fat content varies according to the type of cow the milk comes from, the time of year, and other factors. The fat content of raw milk can vary from around 3% to 5%. The fat forms into globules, and each globule is surrounded by a membrane consisting of phospholipids and protein. This membrane keeps the fat from forming into noticeable clumps, and also keeps the fat from being digested by the enzymes in the milk. Vitamins A, E, D, and K are found in milk fat. The fat content of commercial milk is standardized, with “whole milk” containing 3.25% fat.

Raw milk also contains living white blood cells, as well as various bacteria and enzymes.

Cow milk is slightly acidic, with a pH of 6.4 to 6.8.

What Animal Produced the Milk?

Yogurt cultures can thrive in any animal milk, but there are distinct differences between the milks of different animals. Most of our customers use cow or goat milk for their yogurt production.

Milk composition analysis, per 100 grams (average amounts)

 
 
 
 
 
Constituents Unit Cow Goat Sheep Buffalo
Water

g

87.8

88.9

83.0

81.1

Protein

g

3.2

3.1

5.4

4.5

Fat (can vary)

g

3.9

3.5

6.0

8.0

Carbohydrate

g

4.8

4.4

5.1

4.9

Sugars (lactose)

g

4.8

4.4

5.1

4.9

Cholesterol

mg

14

10

11

8

Calcium

mg

120

100

170

195



Goat milk has a taste similar to that of cow milk, although some people find goat milk that is not fresh to have a pungent “goaty” flavor. When a male goat is in a herd of milk-producing female goats, that can affect the flavor also.

In goat milk, the fat globules are extremely small (about one-fifth the size of the globules in cow milk), and stay suspended in the milk rather than rising to the top as in cow milk. This gives the milk a natural homogenization, and a creaminess similar to whole cow milk.

The casein in goat milk is a different kind than what is in cow milk.

Goat milk is more alkaline than cow milk, and tends to be whiter. It contains slightly less lactose, protein, and fat than cow milk, and slightly more water. It contains about 13% milk solids, and the curd that forms is softer than what forms with cow milk. As a result, yogurt made with goat milk tends to be less firm than yogurt made from cow milk. (However, using a chèvre culture with goat milk produces a thick, yogurt-like product that can be strained to make chèvre cheese, or left as is to eat like yogurt.)

Sheep milk is sweeter than cow milk and is used more for making cheese than for making yogurt. It is higher in fat, lactose, and milk solids than cow milk, and makes a very rich yogurt. The fat globules are smaller than those in cow milk, providing natural homogenization. Sheep milk contains over 19% milk solids and makes a firm curd that is more friable (crumbly) than cow milk curd. It has a higher casein content than cow or goat milk, and thus coagulates faster. The type of casein is more similar to that of goat milk than to that of cow milk.

Buffalo milk has about 11% more protein than cow milk, and almost twice as much fat (but only about one-fifth as much cholesterol). Buffalo milk is pretty hard to get, as there are only a few buffalo dairies in the United States. However, buffalo produce around 15% of the world milk supply as they are quite common in Southeast Asia, South America, and India. Buffalo milk is very rich and a little sweeter than cow milk.

Pasteurization

Milk in its natural state is a very friendly environment for bacteria of all sorts. If exposed to pathogenic organisms, milk can become overloaded with bacteria that might cause illness. Milk that is stored badly, or that has to travel long distances, can easily become contaminated and dangerous to consume.

Before methods were developed to protect milk from developing harmful bacteria loads, it was not uncommon for people to become quite ill from contaminated milk, or even die. One method of keeping milk safe to drink is pasteurization, which kills the harmful microorganisms.

The most common form of pasteurization is called High Temperature/Short Time (HTST). In this process, the milk is forced under pressure through metal plates or pipes, heated to 161°F for 15 to 20 seconds, then immediately cooled to 39°F for storage and transportation. Pasteurized milk still is perishable, however, and must be stored cold by both suppliers and consumers. Pasteurized milk generally produces good results in culturing.

A newer process, ultra-pasteurization (UP) or ultra-high temperature treatment (UHT), pressurizes the milk, then heats it to 275°F or more for about one second. This extends its shelf life and allows the milk to be stored unrefrigerated because of the longer lasting sterilization effect, but UHT milk is actually cooked, and is thus unsuitable for culturing. If UHT milk is the only variety of milk available, we recommend using a direct-set variety culture such as our Traditional Flavored Yogurt Starter or our Mild Flavored Yogurt Starter. The nature of UHT milk makes it difficult to perpetuate over time, so re-culturing starters such as Bulgarian, Greek, viili, etc., are not the best choice here.

The UHT process can also be called flash pasteurization.

Microfiltration, also called “extended shelf life" pasteurization (ESL), is a process that partially replaces pasteurization and produces milk with fewer microorganisms and longer shelf life without a change in the taste of the milk. In this process, cream is separated from the whey and is pasteurized in the usual way, but the whey is forced through ceramic microfilters that trap 99.9% of microorganisms in the milk (as compared to 95% killing of microorganisms in conventional pasteurization). The whey then is recombined with the pasteurized cream to reconstitute the original milk composition. Microfiltered milk behaves similarly to pasteurized milk in culturing.

Thermization (sometimes called thermalization) is a process where the milk is heated to 140° to 150°F for 15 to 20 seconds, then refrigerated. This reduces the number of microorganisms in the milk, but not to the same degree as pasteurization. The FDA considers thermized milk to be raw, while the European Union considers it to be pasteurized. Vat pasteurization is another way of pasteurizing milk more lightly, by heating it to 145°F for 30 minutes in large vats. The behavior of thermized milk or vat-pasteurized milk in culturing would be between pasteurized and raw milk.

Raw milk is not treated with heat before delivery to the consumer, and contains its original microorganisms. These microorganisms provide some competition with the yogurt organisms, and the milk is sometimes difficult to culture. When making yogurt with raw milk, you must either heat the milk yourself to reduce or eliminate the natural bacteria, or go through some extra steps to establish the strength of the yogurt culture before inoculating the raw milk. Yogurt made with unheated raw milk is often thinner than pasteurized milk yogurt, both because of the competing microorganisms and because the unheated protein molecules are more durable and less likely to coagulate.

Many states place restrictions on the sale of raw milk, or do not allow the commercial sale of raw milk at all. The laws governing the sale of raw milk vary in each state, and raw milk may be available to individuals from their own animals, from neighbors or small farmers, or from grocery stores. The laws may differentiate between cow milk and goat milk. Further, the laws may be subject to change making raw milk either more difficult or less difficult to purchase.

Homogenization

Raw milk in a container separates easily into a rich layer of cream that sits on top of a larger, low-fat milk layer. The fat globules rise to the top of a container of milk because fat is less dense than water. They rise rather quickly because the individual fat globules tend to form into clusters containing about a million globules, held together by a number of minor whey proteins. These clusters rise faster than individual globules can. The fat globules in milk from goats, sheep, and water buffalo do not form clusters so readily and are smaller to begin with, so the cream is very slow to separate from these milks.

Commercially sold milk is usually homogenized, a treatment that prevents the cream from separating out of the milk. In the homogenization process, the milk is pumped at high pressures through very narrow tubes, breaking up the fat globules. Since a greater number of smaller particles possess more total surface area than a smaller number of larger ones, the original fat globule membranes cannot completely cover them. Casein clusters are attracted to the newly exposed fat surfaces, so it is much harder for the fat globules to separate from the milk.

The exposed fat globules are vulnerable to certain of the enzymes present in milk, which could cause the fat to become rancid. To prevent this, the enzymes are inactivated by pasteurizing the milk immediately before or during homogenization.

Homogenized milk tastes blander, but feels creamier in the mouth than non-homogenized; it is whiter and more resistant to developing off flavors. Non-homogenized milk sold commercially may or may not have been pasteurized. Milk which has undergone high-pressure homogenization, sometimes labeled as "ultra-homogenized," has a longer shelf life than milk which has undergone ordinary homogenization at lower pressures.

Non-homogenized milk makes wonderful yogurt. With non-homogenized milk the cream will rise to the top of the yogurt just like it does with the milk, so the top layer of the yogurt will be thicker and more yellow in color.

Fat Content

Milk is often processed by removing the cream, which is then used (or sold) as a separate product. The cream can be skimmed by hand, or separated from the milk rapidly in centrifugal separators. The amount of fat left in the milk describes the milk: whole milk (standardized to 3.25% fat), reduced-fat (2% fat), low-fat (1% fat), or skim (no fat). Some dairies sell "full-fat" milk with 3.4% fat, which is very close to its original composition.

Yogurt made with reduced-fat milk will be thinner than yogurt made with whole milk. Commercially available low-fat yogurts include additives and stabilizers to make them unnaturally thick, or have been strained of some of their whey.

Many yogurt cultures perform very well in half-and-half or even in cream, producing a rich, thick yogurt that is almost like sour cream. Yogurt can also be made with unhomogenized milk, raw milk, whole milk, reduced-fat milk, skim milk, or even powdered milk. You can also use other creamy substances such as rice milk, nut milk, soy milk, coconut milk, etc.

The choice is up to you!

 

 

 

 

 

 

                                                
   
Yogurt


Related Articles & Recipes:

 

Related Products:

Bulgarian Yogurt Starter Yogurt Starter
Yogurt Maker Yogurt Makers
Cotton Bag for Making Yogurt Cheese Lebneh
Cotton Bag for Making Soft Cheese

 

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<td><span style="font-family: verdana,geneva; font-size: small;">&nbsp;</span> <br />
<p><span style="font-family: verdana,geneva; font-size: small;">Originally a simple fermented dairy product, yogurt now has many variations and personalities. It can be thin and runny, or thick and firm. It can be made from cow milk, goat milk, sheep milk, nut milk, soy milk, rice milk, and from numerous other creamy substances. In some countries the milk of buffalo, horses, yaks, or camels is used.</span><br /><br /><span style="font-family: verdana,geneva; font-size: small;">For most of this discussion, we&rsquo;ll refer to yogurt in its original form: a fermented dairy milk. This was how yogurt was first developed, and most of the yogurt in the world is made this way.</span><br /><br /><span style="font-family: verdana,geneva; font-size: small;">Essentially yogurt is the product of beneficial bacteria fermenting milk and turning it into a thickened, acidic food that will stay fresh longer than milk itself, and that contains millions of bacteria that are welcomed by the human gut.</span></p>
<h1><br /><strong><span style="font-family: verdana,geneva; font-size: small;">The History of Yogurt</span></strong></h1>
<p><span style="font-family: verdana,geneva; font-size: small;">The word yogurt comes from a Turkish word meaning to curdle or to thicken. Today it is spelled yogurt, yoghurt, or yogourt, with yogurt being the most common American spelling.</span><br /><br /><span style="font-family: verdana,geneva; font-size: small;">It&rsquo;s probable that the earliest yogurt was made by accident in Mesopotamia around 5,000 BC, when milk-producing animals were first domesticated. The milk was likely stored and transported in bags made from the stomachs of these animals, and the digestive juices and bacteria in the stomach linings made the milk coagulate and become acidic. Not only was it a new and interesting food, but the acidity and helped to keep it edible for longer</span> <span style="font-family: verdana,geneva; font-size: small;">than if it had just sat out in a bowl or jar.</span><br /><br /><span style="font-family: verdana,geneva; font-size: small;">There is also some evidence of yogurt being used as a cleaning product and a beauty lotion as early as 2000 BC. The acidity of the yogurt helps clean away dirt and rust, and also helps clear away dead skin and nourish healthy skin cells.</span><br /><br /><span style="font-family: verdana,geneva; font-size: small;">Yogurt was a popular food in the Middle East for thousands of years, and has been a staple of the Eastern European diet. It&rsquo;s now eaten throughout the world, as a main course, a snack, an ingredient in many recipes, and a condiment. It has gained considerable popularity in America in the last forty or fifty years, in keeping with general trends toward organic, cultured, and nutrient-dense foods.</span><br /><br /><span style="font-family: verdana,geneva; font-size: small;">Yogurt can be mildly tart or quite sour, and can be thick enough to stand up on a plate, or thin enough to pour, or anywhere in between. It contains protein and calcium as well as a variety of vitamins. Additionally, the process of yogurt fermentation is very similar to the process of digestion, so it can be easily consumed.</span><br /><br /><span style="font-family: verdana,geneva; font-size: small;">Many people eat yogurt plain, while others prefer to mix it with fruits or vegetables, or to add flavors or sweeteners. It is used in a variety of recipes as a flavor enhancer or leavening, and frequently enjoyed as a refreshing drink.</span></p>
<h1><br /><strong><span style="font-family: verdana,geneva; font-size: small;">Nutritional Content</span></strong></h1>
<p><span style="font-family: verdana,geneva; font-size: small;">Not only does yogurt contain the same amount of protein and fat as the milk from which it is made, it also contains calcium, riboflavin, vitamin B6, and vitamin B12. While numerous claims have been made regarding the health benefits and digestibility of yogurt, we don&rsquo;t comment on medical, health, or nutritional qualities of our products. However, a great deal of research on the subject is readily available on the Internet and in dozens of books.</span></p>
<h1><br /><strong><span style="font-family: verdana,geneva; font-size: small;">How is Yogurt Made?</span></strong></h1>
<p><strong><span style="font-family: verdana,geneva; font-size: small;">&nbsp;</span></strong><span style="font-family: verdana,geneva; font-size: small;">True yogurt is made from animal milk. Theoretically, the milk of any mammal could be used to make yogurt.</span><br /><br /><span style="font-family: verdana,geneva; font-size: small;">With care, yogurt cultures can also be used to ferment and coagulate non-dairy &ldquo;milks&rdquo; such as the creamy liquid obtained from nuts, rice, soy, or coconut. While these products are technically not really yogurt, they can be used and enjoyed just like dairy yogurt, alone or in recipes.</span><br /><br /><span style="font-family: verdana,geneva; font-size: small;">Put very simply, the process of turning milk into yogurt involves fermentation. Certain types of bacteria act on the lactose (milk sugar) that is in milk, and produce lactic acid. The lactic acid lowers the pH of the milk, and causes the milk protein to coagulate and make a firm mass. The acidified milk is an inhospitable environment for destructive bacteria, so the yogurt stays fresh longer than untreated milk.</span><br /><br /><span style="font-family: verdana,geneva; font-size: small;">The bacteria that does this is called beneficial bacteria, because it supports digestion and is nourishing, as opposed to pathogenic (harmful) bacteria that causes disease. The beneficial bacteria is called probiotic. It&nbsp; is similar or identical to the type of bacteria that lives in the human gut and which is responsible for the process of food absorption. When you use live cultures, the probiotics stay in the yogurt, and the yogurt can then be used as a starter to make more yogurt.</span></p>
<h1><br /><strong><span style="font-family: verdana,geneva; font-size: small;">Yogurt and Other Fermented Dairy Products</span></strong></h1>
<p><span style="font-family: verdana,geneva; font-size: small;">There are many different ways that beneficial bacteria can be introduced to milk and make an entirely new food. The main difference between the different fermented dairy products is the bacteria used to make them, resulting in different flavors and consistencies.</span><br /><br /><span style="font-family: verdana,geneva; font-size: small;"><em>Yogurt</em> can be cultured with a variety of different bacteria combinations, each of which gives the yogurt a characteristic taste and consistency. There are typically somewhere between the range of two to six different bacteria strains in yogurt, and they are similar to the bacteria found in the intestines.</span><br /><br /><span style="font-family: verdana,geneva; font-size: small;"><em>Kefir</em> is a thickened milk made from little clumps of yeast, bacteria, and milk proteins that ferment the milk. There are about thirty different bacteria strains present in kefir grains. It has a slightly sour flavor and sometimes a faint effervescence. Koumiss is a similar product, made from mare&rsquo;s milk.</span><br /><br /><span style="font-family: verdana,geneva; font-size: small;"><em>Buttermilk</em> is the name given to the whey that&rsquo;s left over when butter is made, but it more commonly refers to a milk drink made by adding bacteria to low-fat milk, producing a thickened product with a tangy flavor.</span><br /><br /><span style="font-family: verdana,geneva; font-size: small;"><em>Sour cream</em> is cream or high-fat milk that&rsquo;s been cultured and thickened. It&rsquo;s very slightly sour, and usually quite thick. It was originally made by letting fresh cream thicken naturally as a result of fermentation from the bacteria present in the cream. When cream is pasteurized and has no natural bacteria present, it must be fermented with added bacteria.</span><br /><br /><span style="font-family: verdana,geneva; font-size: small;"><em>Cr&egrave;me fraiche</em> is a European-style sour cream, slightly sweeter than what we are used to in America. It&rsquo;s also made by letting raw cream thicken naturally, or by adding buttermilk cultures to cream. Cr&egrave;me fraiche can be heated without curdling, unlike sour cream.</span><br /><br /><span style="font-family: verdana,geneva; font-size: small;">In recipes, you can often substitute one cultured milk product for another and get similar results. In fact, sometimes it is hard to tell the difference between a thin, tart yogurt and a thick, sour kefir or a creamy buttermilk!</span><br /><br /><span style="font-family: verdana,geneva; font-size: small;"><em>Soft and hard cheeses</em> are also made by culturing milk over a longer period of time. Some cheeses can be easily made by straining the moisture out of yogurt or sour cream, while others require additional fermentation and culturing steps.</span></p>
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