What is Yogurt?
From a regulatory point of view, Yogurt is a milk product obtained by fermentation of milk specific microorganisms, which shall be viable, active and abundant in the product Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus.
How is yogurt made?
Yogurt is a very ancient food. The first traces of it have been found between 10 000 and 5 000 BCE in the Neolithic period. Today, yogurt is widely recognized as a healthy food. Manufacturers have responded to the growth in yogurt consumption by introducing many different types of yogurt, including low-fat and no-fat, creamy, drinking, bio-yogurt, organic, baby, fruit, and frozen.
However, the basic ingredients and manufacturing are essentially consistent:
- Raw milk is first transported from the farm to the manufacture 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 generates its consistency, flavor, aroma and health benefits, such as a facilitated digestion.
- After cooling, fruits, sugar, and other ingredients can be added to obtain a large variety of products and yogurt is packaged afterwards.
- Finally, the product is cooled and stored at refrigeration temperatures (40°F or 5° C) to slow down the physical, chemical and microbiological degradation.
The different textures and varieties of yogurts
There are a lot of varieties of yogurt on the market, depending of their manufacturing procedure and the 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 into 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.
What is Greek yogurt?
Greek yogurt is traditionally obtained by straining normal yogurt, which gives it a thicker texture. It is a 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 lactoserum – is removed, which explains the low lactose content of Greek yogurt.
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 practises 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.
What is lactic acid fermentation?
Lactic acid fermentation is the process, whereby milk is converted into yogurt. It results from the action of lactic ferments, which are for yogurt two specific micro-organisms: Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus.
Lactic acid fermentation is also used in the production of sauerkraut, sour beer, or numerous fermented vegetables (tempeh, kimchi,…).
During the fermentation, the milk sugar (lactose) is first converted into glucose and galactose, after what 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.
What is the nutrient composition of Yogurt ? Some Nutrition Facts
- 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, and by ingredients (such as fruits) which may be added in some types of yogurt
- Yogurt is an excellent source of protein with a high quality score, linked to high digestibility and richness in essential amino acids.
- Yogurt contains also a wide range of fatty acids.
Source : USDA National Nutrient Database for Standard Reference Legacy Release – Yogurt plain nutrient database.
Does Yogurt contain Magnesium?
Yes, the magnesium concentrations in milk are relatively constant, with some variations throughout lactation: around 12mg per 100g (Haug, et al. 2007).
What are the health benefits of Yogurt?
Regular yogurt intake appears necessary to provide a sustainable benefit on host. Yogurt and dairy products are recognized by most regulatory authorities and scientific institutions as part of a healthy diet (cf. American guidelines or French guidelines).
Yogurt is characterized by its living bacteria, which, in addition to its high nutrient density and its palatability, have been demonstrated to improve lactose digestion (EFSA 2010b).
Recent studies suggest that yogurt could play a valuable role on health. Please discover all the beneficial effects of yogurt on health on each following topics:
- Yogurt and Bone health
- Yogurt and Lactose digestion
- Yogurt and Metabolic diseases
- Yogurt and Nutrient density
- Yogurt and Nutrition economics
- Yogurt and Weight management
What is a healthy snack? Is Yogurt a healthy snack?
The key to healthy snacking is based on the nutrient density and the eating habits. Good eating habits should incorporate eating only while hungry : not only for pleasure or in response to stress or boredom, for example.
The portion size of the snacks is important too. An “ideal” healthy snack should have a high nutrient density. In contrast, an unhealthy snack has a low nutrient content relative to its energy content (also qualified as rich in “empty calories”). For instance, Yogurt can be a healthy snack.
To learn more about healthy snacking, please read our dedicated practical sheets.
What is Lactose intolerance? Can I drink milk/yogurt or should I avoid milk/yogurt when I am lactose intolerant?
Lactose intolerance can result from a natural physiological phenomenon. Lactose is the natural sugar of milk digested by humans thanks to an enzyme called lactase. Lactase activity decreases from infancy until adulthood and may lead to a deficiency. This intolerance affects nearly three quarters of the world’s population with a frequency varying geographically by country and region and by the age of the individual.
Lactase deficiency causes maldigestion of lactose, which often leads to total or partial avoidance of milk and dairy products, which is not always justified. It can entail additional difficulty in satisfying the child’s or adult’s calcium needs and risks their bone health.
Contrary to conventional wisdom, the consumption of dairy products can be maintained, subject to certain hygiene and dietary rules. Incorporating dairy products, including yogurt, improves the quality of the diet, and reduces nutrient deficiencies.
The lactose in yogurt is digested more efficiently than other dairy sources of lactose because the bacteria inherent in yogurt assist with its digestion. Yogurt has the particular characteristic of being well tolerated by individuals who find lactose difficult to digest. It allows them to get all the nutritional benefits of milk. It is therefore a useful alternative to milk to meet daily calcium needs and to help prevent osteoporosis. This is why the regular consumption of at least one serving of yogurt per day is highly recommended. It improves lactose digestion thanks to its specific live cultures (Streptococcus thermophilus and Lactobacillus bulgaricus),which remain active all the way through the digestive tract. Furthermore, its thicker-than-milk consistency leaves more time for the residual lactase to act.
To learn more about lactose intolerance, please visit our dedicated Q&A on lactose intolerance.
Should I avoid yogurt consumption if I have a metabolic syndrome?
Studies have shown that yogurt and dairy product could act on most of the components of Metabolic Symdrome, including weight and waist circumference, blood pressure, dyslipidemia and hyperglycaemia. A systematic review of the evidence suggested a potential benefit of dairy consumption on the risk of having Metabolic Syndrome (Crichton, et al. 2011).
Learn more about the effects and visit our pages on cardiovascular health.
Is it possible to consume yogurt while suffuring from allergy to cow’s milk?
Allergy to cow’s milk protein is an immune response to a minute quantity of cow’s milk protein, and is usually detected in early childhood. It only affects 2% to 6% of infants and disappears in two-thirds of cases around the age of 2 or 3. In France, this affects 0.6% of children under the age of 15 (and is far less prevalent than egg or peanut allergies).
Very few adults (0.1% to 0.5%) are allergic to milk. The symptoms are mainly digestive and, depending on the individual, may be accompanied by, for instance, muscle or joint pain, headaches, nausea, lethargy, acne, sore throat. Often allergy to cow’s milk protein is confused with lactose intolerance.