How to make yogurt from raw milk

Last updated on March 7th, 2023 at 09:02 am

5 minutes read.     

Yogurt is an excellent source of protein with a high-quality score, linked to high digestibility and richness in essential amino acids.

Besides, the proteins contained in yogurt are more easily digestible than those in standard milk. This could be the result of the fermentation process, which breaks them into smaller entities (1).

The high-quality proteins of yogurt bring lasting satiety. For instance, a study found that, in the mid-afternoon, women were less hungry after having a high-protein yogurt than after having high-fat crackers or chocolate.

Yogurt contains also a wide range of fatty acids. (2)

Yogurt is a source of vitamins and micronutrients (calcium, and potassium). (3, 4)

It contains also magnesium and the magnesium concentrations in milk are relatively constant, with some variations throughout lactation: around 12mg per 100g. (5)

The nutrient composition of yogurt is based on the nutrient composition of the milk from which it is derived. The final composition is determined by:

• the source and type of milk solids that may be added before fermentation,
• lactic acid fermentation and the strains of bacteria used in the fermentation,
• the temperature,
• the duration of the fermentation process, storage time,
• by ingredients (such as fruits) that may be added to some types of yogurt

How to make yogurt from raw milk

Manufacturers have responded to the growth in yogurt consumption by introducing many different types of yogurt, including Greek yogurt, low-fat and no-fat yogurt, creamy, drinking, bio-yogurt, frozen, etc.

 

However, the basic ingredients and manufacturing are essentially consistent:

Raw milk is first transported from the farm to the manufacturer where it will be processed.

When the milk arrives at the plant, its composition is modified before it is used to make yogurt. The milk is then standardized for its dry matter, pasteurized (176°F or 80°C), and homogenized.

When pasteurization and homogenization are completed, the milk has to cool to 109.4-114.8° F (43-46° C) and the fermentation culture is added in a concentration of about 2%.

Cultures consist of two lactic acid bacteria: Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus.

These are the specific ferments of yogurt, which generate its consistency, flavor, aroma, and health benefits, such as facilitating digestion.

After cooling, fruits, sugar, and other ingredients can be added to obtain a large variety of products, and yogurt is packaged afterward.

Finally, the product is cooled and stored at refrigeration temperatures (40°F or 5° C) to slow down the physical, chemical, and microbiological degradation. (6, 7, 8)

However, in the absence of raw milk, you can make yogurt from milk powder right in your kitchen. Find out here

Different types of yogurt

There are a lot of varieties of yogurt on the market, depending on the manufacturing procedure and ingredients, added to plain yogurt before or after fermentation:

The type of milk used (skimmed, semi-skimmed, or whole), and eventually the addition of cream, will determine the final fat content of yogurt.

For stirred-style yogurt, milk is fermented in the jacketed fermentation tank. After fermentation, the content is stirred.

Fruit and flavor may be incorporated, then the content is cooled and products are packaged and stored at refrigeration temperatures.

For set-style yogurt, also known as French style, the milk is inoculated with ferments and added with other ingredients (fruit preparation, sugar, flavors…) before packaging.

The fermentation process occurs in packages during the incubation period, after which the product is cooled and stored at refrigeration temperatures.

Drinking yogurt is stirred yogurt that has a low total solids content and which has undergone homogenization to further reduce the viscosity.

Sweetener, flavoring, and coloring ingredients may then be added and the product is packed in bottles. (9, 10)

What is Greek yogurt?

Greek yogurt is traditionally obtained by straining normal yogurt, which gives it a thicker texture.

It has concentrated fermented milk as defined by Codex Alimentarius, which specifies that the protein content must be at least 5.6 g per 100 g.

During the draining process, the aqueous part of the milk – the whey or lactose rum – is removed, which explains the low lactose content of Greek yogurt.

During the draining process, the aqueous part of the milk – the whey or lactose rum – is removed, which explains the low lactose content of Greek yogurt. (11,12, 13

However, to date, there is no controlled denomination, either for Greek yogurt or Greek-style yogurt. Only local decrees, varying from one country to another, regulate the names.

So market practices as well as the names vary between countries: Greek yogurt, Greek-style yogurt, strained yogurt, and so on.

Reading the label provides useful clarifications on the real nature of the yogurt.

Greek yogurt infographic

What is lactic acid fermentation?

Lactic acid fermentation is the process, whereby the natural lactose sugar in the milk is converted into lactic acid/lactate through friendly bacteria which give birth to a sour taste product called yogurt.

It results from the action of lactic ferments, which are for yogurt two specific micro-organisms: Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus (14).

Lactic acid fermentation is also used in the production of sauerkraut, sour beer, or numerous

fermented vegetables (tempeh, kimchi). (14)

During the fermentation, the milk sugar (lactose) is first converted into glucose and galactose, after which these simple sugars are converted into lactic acid.

The formation of lactic acid gives some acidity (pH 4.5), which helps to coagulate the proteins (caseins) and set the milk, producing the specific texture of yogurt.

Lactic acid fermentation also produces compounds (carbon dioxide, peptides, amino acids…) that give yogurt its distinctive flavor (15).

History of yogurt infographic

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