Kefir

Kefir is a fermented probiotic beverage based on milk or water. The term "kefir" is of Turkish origin and means "to foam", referring to the beverage’s distinctive frothy texture. Historically, kefir has been produced and consumed for thousands of years in Central Asia, the Caucasus, and Eastern Europe. Traditional kefir production has been passed down from generation to generation through cultural transmission, resulting in regional variations and local production techniques.

The history of kefir constitutes an important heritage both in terms of nutritional culture and microbial ecosystems. The first documented kefir production occurred in the Caucasus among nomadic communities, where kefir served both as a food source and a health-promoting beverage.

Structure and Microbial Composition of Kefir Grains

Kefir grains are irregular, cohesive yet firm granules measuring 5–20 mm in diameter, with a gelatinous structure and off-white color. Their appearance resembles miniature cauliflower florets, popped corn, or cooked rice. Kefir grains consist of a complex microbial ecosystem containing polysaccharides known as kefiran, which form the unique structure of the grains. These grains contain lactic acid bacteria (Lactobacillus, Lactococcus, Leuconostoc etc.), yeasts (Saccharomyces, Kluyveromyces etc.), and acetic acid bacteria. Lactic acid bacteria ferment lactose, the sugar in milk, producing lactic acid, which imparts a sour taste to kefir and maintains microbial balance. Yeasts ferment carbohydrates to produce ethanol and carbon dioxide, giving kefir a slight alcoholic flavor and natural effervescence. Acetic acid bacteria produce organic acids that enhance kefir’s characteristic acidic taste. This microbial diversity creates the basis for kefir’s beneficial effects on the digestive system.

Storage of Kefir Grains

The storage of kefir grains involves procedures designed to preserve the viability and fermentation capacity of the microorganisms within them. Environmental factors such as temperature, humidity, and oxygen play a decisive role in this process. Grains are typically stored for short-term preservation under refrigeration conditions (approximately 4°C) and for long-term storage by freezing or using lyophilization (freeze-drying).

Freezing halts microbial activity and preserves the structure and biological properties of kefir grains. Lyophilization removes water content from the grains, allowing them to be stored for extended periods without spoilage. Dry grains obtained through this method can be stored for months under appropriate humidity and temperature conditions and can be reactivated for fermentation.

Packaging material is also a critical factor in preservation. Oxygen-impermeable, light-resistant, and moisture-proof packaging helps maintain the microbial stability of kefir grains. When these conditions are met, kefir grains retain their fermentation capacity to a large extent even after long-term storage and can be reused in production.

Kefir Production Process

Kefir production depends on factors such as the raw material used, fermentation duration, temperature, and microbial composition. Traditional kefir is generally produced from cow, goat, or sheep milk, but variations using water or plant-based milks also exist. The production process begins with milk preparation.

1. Preparation: Milk is heated to an appropriate temperature for production (20–25°C) and is typically pasteurized. Pasteurization eliminates unwanted microorganisms and prepares the milk’s composition for fermentation. The type of raw material directly affects the flavor profile, nutritional value, and microbial diversity of the kefir.
2. Inoculation: Kefir grains are added to the prepared milk. Kefir grains initiate the fermentation of the natural microorganisms present in the milk. These grains are the source of the rich microbial composition that imparts kefir’s probiotic properties.
3. Fermentation: Kefir is typically fermented at 20–25°C for 18–24 hours. Fermentation duration determines the acidity, aroma, and flavor profile of kefir. Prolonged fermentation results in higher acidity and a more pronounced flavor profile, while also increasing microbial diversity. Temperature control directly affects microbial activity and fermentation speed.
4. Filtration: After fermentation is complete, kefir grains are separated from the liquid. This step allows the grains to be stored for reuse and ensures the kefir has a homogeneous texture.
5. Storage: The resulting kefir is cooled and prepared for consumption or packaging. Temperature control during storage is essential to preserve kefir’s probiotic properties and quality.

Strict control of fermentation conditions throughout these stages directly affects the quality, nutritional value, and probiotic efficacy of kefir.

Chemical and Nutritional Composition of Kefir

Kefir stands out due to its high nutritional value and chemical richness. It is rich in protein; during fermentation, proteins are broken down into peptides, facilitating digestion. Lactose is largely degraded during fermentation, making kefir a suitable food for individuals with lactose intolerance. The fermentation process alters the structure of milk fat and increases its digestibility. Kefir is rich in minerals such as calcium, magnesium, phosphorus, potassium, and zinc. It also contains vitamins including B1, B2, B12, folate, and vitamin K. Kefiran, organic acids, and bioactive peptides present in kefir have potential biological effects beneficial to health. These compounds enhance kefir’s probiotic properties and exert positive effects on the immune and digestive systems. Compounds such as lactic acid, acetic acid, and acetoin contribute to kefir’s protective properties.

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Health Effects of Kefir

Scientific studies have demonstrated that kefir has significant health effects. Thanks to its probiotic microorganisms, kefir regulates the gut microbiota and supports digestive health. These microorganisms can enhance immune responses and inhibit the growth of pathogenic microorganisms. Organic acids, kefiran, and bioactive peptides in kefir possess antioxidant properties and may help combat oxidative stress. The reduction of lactose during fermentation makes kefir more easily digestible for individuals with lactose intolerance. These health benefits elevate kefir from a traditional food to a functional food.

Health Effects of Probiotic Kefir(Bazu Çırpıcı, 2024) 

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Kefir Varieties and Applications

Kefir varieties differ based on raw material and production method. Milk kefir is produced from cow, goat, or sheep milk and is rich in protein, minerals, and vitamins. Water kefir is prepared with sugared water, fruit juice, or coconut water and is suitable for those following a vegan diet. Plant-based kefirs are produced from plant sources such as soy, almond, or coconut milk and cater to diverse dietary needs. Kefir is used in nutrition both as a beverage and as a fermented food ingredient in meals. Additionally, due to its health-promoting properties, kefir is included among functional food products.

Products Made Using Kefir

In addition to being traditionally produced through milk fermentation, kefir is also used in the production of various dairy products. Kefir culture is employed not only in traditional dairy products such as yogurt, ice cream, cheese, and tarhana but also in the production of kefir cream, sour cream, kefir clotted cream, kefir butter, kefir-based sauces (e.g., dill, artichoke), kefir-based beverages, milkshakes, smoothies (apple, banana, orange, mango, etc.), and flavored coffees.

Fruit Kefir(Pixabay)

Kefir Yogurt

Yogurt is a dairy product fermented by lactic acid bacteria, including Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus. Yogurt is easily digestible, as its bacteria partially break down milk proteins, enhancing the activity of digestive enzymes. Over time, research has explored the use of different cultures to improve and diversify yogurt’s nutritional value. As part of this effort, “kefir yogurt” has been developed using kefir culture. In its production, milk is pasteurized at 90°C for 15–20 seconds, then cooled to 43–45°C. Kefir culture is added at a 5% rate and incubated at 41–43°C for 3–4 hours. After fermentation, the product is stored at +4°C for one day before being ready for consumption.

Production of Kefir Yogurt(Anadolu Agency)

Kefir Ice Cream

Ice cream is a dairy product made by processing milk and dairy products with sweeteners, stabilizers, emulsifiers, and various flavoring agents. Ice creams produced using kefir belong to the group of fermented dairy products. Although industrial-scale kefir ice cream production does not exist in Türkiye, varieties such as vanilla, raspberry, and peach are available on the market in Ireland. In the United States, kefir ice creams with different flavors such as chocolate chip-raspberry, lemon-lingonberry, coffee, apple-cinnamon, and others are produced and consumed.

Kefir-Based Whey Beverage

Whey is the liquid remaining after casein separates from milk during cheese production. It constitutes approximately 85–90% of milk and contains a large proportion of its nutrients. Lactose, soluble proteins, fats, and mineral salts are the main components of whey. Due to its high organic matter content, this by-product can cause environmental pollution, making its utilization important. Using whey in kefir production is a method for its valorization. In the production process, whey is pasteurized at 90°C for 25 minutes and cooled to 20°C. After filtration, the mixture is prepared with 50% milk and 50% whey. Kefir culture is added at a 2% rate and incubated at 25°C for 48 hours. The resulting beverage is ready for consumption. Optional flavor enhancers such as honey, fruit syrup, cocoa, or chocolate may be added.

Kefir Tarhana

Tarhana is a food produced by fermenting and drying a mixture of wheat flour, yogurt, yeast, vegetables, and spices. “Kefir tarhana”, prepared using kefir instead of yogurt, is a functional variant with enhanced properties. In its production, flour, onion, tomato paste, pepper, potato, carrot, celery, flaxseed, kefir, and kefir cheese are used. Vegetables are ground and added to the mixture. Flour is then added to form dough. The dough is left to ferment and is stirred daily to prevent rising, with additional flour added as needed. Fermentation lasts approximately one week. After fermentation, the dough is dried and finely ground into flour, then packaged.

Kefir Cheese

Kefir cheese is produced by using kefir culture to coagulate milk. Milk is heated to 60°C, and kefir is added at a constant flow rate. During mixing, curd formation occurs and whey separates. If the whey is cloudy, temperature may be increased or additional kefir added. The curds are strained into cheesecloth and left to drain for 15 minutes. This period may be extended to achieve a firmer consistency. Depending on preference, chili flakes, dill, basil, or dried tomatoes may be added to the resulting soft cheese to create different varieties.

Kefir Sürkü

Sürk is a traditional dairy product native to the Hatay region. It is typically made from clotted cream and matured with added spices. Kefir sürkü is a variant of this product prepared using kefir cheese. In its production, kefir cheese is mixed with various spices (cumin, black pepper, clove, oregano, cumin, caraway, mint, mahlep, cinnamon, allspice, ginger), garlic, and salt. The mixture is shaped into pear-like forms, covered with muslin, and dried in the shade for 3–4 days. The product can be consumed fresh or after aging for 20–25 days with mold development.

Cultural and Industrial Significance

Kefir holds importance not only for its nutritional value but also culturally. In Türkiye, kefir production is regulated by the Turkish Food Code Regulation on Fermented Dairy Products. This regulation defines kefir’s production methods, quality criteria, hygiene conditions, and labeling standards. Traditional kefir production contributes to the preservation of cultural heritage, while industrial production enables kefir to reach wider audiences. Globally, kefir is recognized as a functional food and is the subject of health-related research due to its probiotic properties.

^{Product Characteristics of Kefir According to the Turkish Food Code Regulation on Fermented Dairy Products}(Turkish Food Code Notice on Fermented Dairy Products)^【3】 

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