What is milk kefir?
Milk kefir is a fermented dairy drink made by adding milk kefir grains to milk. Milk kefir grains are a combination of bacteria and yeast that form into small, jelly-like clumps. When added to milk, these grains ferment the lactose in the milk into lactic acid, which gives the drink its tangy flavor. Milk kefir has been consumed for centuries in various parts of the world, and it is believed to have originated in the Caucasus Mountains of Eastern Europe. Today, it is widely available and has gained popularity due to its probiotic properties and potential health benefits.
What is in milk kefir?
Milk kefir grains are rich in lactic acid bacteria and yeasts in a matrix of proteins, lipids, and sugars, and this symbiotic matrix, or (SCOBY) forms “grains” that resemble cauliflower. For this reason, a complex and highly variable community of lactic acid bacteria and yeasts can be found in these grains although some predominant; Lactobacillus species are always present. Milk kefir is a rich source of probiotics, which are beneficial bacteria that live in your gut and help support a healthy digestive system. The probiotics in milk kefir can also help boost your immune system and improve nutrient absorption. Milk kefir is also a good source of calcium, protein, and other important nutrients.
Kefir grains contain a water-soluble polysaccharide known as kefiran, which imparts a rope-like texture and feeling in the mouth. The grains range in color from white to yellow, and may grow to the size of walnuts.
What are the constituents of milk kefir?
Milk kefir contains a variety of constituents that provide numerous health benefits, including:
- Probiotics: Milk kefir is a rich source of probiotics, which are beneficial bacteria that live in your gut and help support a healthy digestive system. Milk kefir can contain up to 50 different strains of probiotics, including Lactobacillus, Streptococcus, and Bifidobacterium.
- Proteins: Milk kefir contains a variety of proteins, including casein and whey. These proteins are important for muscle growth and repair, and they also help keep you feeling full and satisfied.
- Carbohydrates: they contain carbohydrates in the form of lactose, which is partially fermented during the fermentation process. This makes milk kefir a good option for those who are lactose intolerant, as the lactose is partially broken down.
- Vitamins and minerals: they are a good source of vitamins and minerals, including calcium, magnesium, phosphorus, and vitamin B12. These nutrients are important for bone health, nerve function, and energy production.
- Enzymes: the grains contain a variety of enzymes, including lactase, which helps break down lactose in the milk. This makes milk kefir easier to digest for those who are lactose intolerant.
Micro-organisms found in milk kefir grains:
These can vary depending on the specific strain of kefir grains, the location of cultivation, and other factors. However, some of the common micro-organisms found in milk kefir grains include:
- Lactobacillus: Lactobacillus is a genus of bacteria that is commonly found in fermented dairy products. It helps to convert lactose into lactic acid, which gives milk kefir its tangy flavor. Lactobacillus is also beneficial for digestive health.
- Streptococcus: Streptococcus is a genus of bacteria that is also commonly found in fermented dairy products. It helps to convert lactose into lactic acid, and it also produces carbon dioxide, which helps to create the effervescence in milk kefir.
- Bifidobacterium: Bifidobacterium is a genus of bacteria that is commonly found in the human gut. It helps to support a healthy digestive system and may also have other health benefits, such as boosting the immune system.
- Yeasts: Yeasts are a type of fungus that are also found in milk kefir grains. They help to convert lactose into alcohol and carbon dioxide, which contributes to the unique flavor and effervescence of milk kefir.
Vitamins and pro-vitamins found in milk kefir:
Milk kefir is a rich source of vitamins and minerals, which are essential nutrients that your body needs to function properly. Here are some of the vitamins and pro-vitamins found in milk kefir:
- Vitamin B12: a good source of vitamin B12, a nutrient that is essential for nerve function and the production of red blood cells.
- Vitamin B2 (Riboflavin): also a good source of vitamin B2, which is important for energy production and the metabolism of fats, proteins, and carbohydrates.
- Vitamin D: Some milk kefir is fortified with vitamin D, which is important for bone health and the absorption of calcium.
- Vitamin K: the grains contain small amounts of vitamin K, which is important for blood clotting and bone health.
- Pro-vitamin A: they also contain small amounts of beta-carotene, which is a pro-vitamin A that is important for eye health and immune function.
Minerals found in milk kefir:
Milk kefir is a good source of minerals, which are essential nutrients that your body needs to function properly. Here are some of the minerals found in these grains:
- Calcium: a good source of calcium, which is important for bone health, nerve function, and muscle contraction.
- Magnesium: a good source of magnesium, which is important for nerve function, muscle contraction, and energy production.
- Phosphorus: they contain phosphorus, which is important for bone health, energy production, and DNA synthesis.
- Potassium: a good source of potassium, which is important for nerve function, muscle contraction, and blood pressure regulation.
- Zinc: they also include zinc, which is important for immune function, wound healing, and DNA synthesis.
The effect of the type of milk used:
The composition of kefir depends greatly on the type of milk that was fermented, including the concentration of vitamin B12.
Nutrient changes during the fermentation process:
During the fermentation, changes in composition of nutrients and other ingredients occur:
- Lactose: the sugar present in milk is broken down mostly to Lactic acid (25%) by the lactic acid bacteria.
- Propionibacteria: these bacteria further break down some of the lactic into propionic acid. They also carry out the same fermentation in Swiss Cheese.
- Other substances that contribute to the flavor of kefir are: pyruvic acid, acetic acid, diacetyl and acetoin (of which contribute a “buttery” flavor), citric acid, acetaldehyde and amino acids resulting from protein breakdown.
- Slow-acting yeasts: late in the fermentation process, these break lactose down into ethanol and carbon dioxide. Depending on the process, ethanol concentration can be as high as 1-2% (achieved by small-scale dairies early in the 20th century). The kefir has a bubbly appearance and carbonated taste. Most modern processes, which use shorter fermentation times, result in much lower ethanol concentrations of 0.2-0.3%. Slow-acting yeasts are called “slow-acting” because they take longer to ferment the lactose in milk compared to other types of yeast. However, they are important for the flavor and texture of milk kefir, and they can also contribute to the nutritional value of the drink.
- Minimal lactose as a result of the fermentation: very little lactose remains in kefir. People with lactose intolerance are able to tolerate kefir, providing the number of live bacteria present in this beverage consumed is high enough (i.e. fermentation has proceeded for adequate time). It has also been shown that fermented milk products have a slower transit time than milk, which may further improve lactose digestion.
Traditional kefir – fermentation temperatures:
Traditional kefir is typically fermented at ambient temperatures, which means it is left at room temperature for a period of time to allow the kefir grains to ferment the milk.
The exact temperature and fermentation time can vary depending on factors such as the type of milk used, the kefir grains, and personal preference. However, in general, kefir is typically fermented for around 24 to 48 hours at room temperature, although some people may choose to ferment it for longer or shorter periods of time.
Fermenting kefir at ambient temperatures allows the kefir grains to thrive and ferment the lactose in the milk, producing the characteristic tangy flavor and effervescence of kefir. It also allows the beneficial bacteria and yeasts in the kefir grains to multiply and grow, which contributes to the nutritional value and health benefits of kefir.
While it is possible to ferment kefir at lower temperatures or in the fridge, this may slow down the fermentation process and produce a milder flavor. Conversely, fermenting kefir at higher temperatures may speed up the fermentation process and produce a stronger, more tangy flavor.
How is milk kefir used?
Milk kefir is often used as a base for smoothies or consumed on its own as a refreshing and nutritious drink. It can also be used in recipes as a substitute for yogurt or buttermilk. Some people who are lactose intolerant may find that they can tolerate milk kefir better than regular milk, as the lactose is partially fermented during the fermentation process.
Overall, milk kefir is a healthy and delicious way to incorporate probiotics into your diet and support a healthy digestive and immune system.
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