Yogurt and kefir
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Yogurt and Kefir: A Comparative Analysis
Selenium Biotransformation in Yogurt and Kefir
Selenium Species in Fermentation
The biotransformation of inorganic selenium during the fermentation process of yogurt and kefir reveals distinct differences in selenium species produced by the microorganisms involved. In yogurt, which is fermented by Lactobacillus bacteria, the primary selenium species formed are selenocystine (SeCys2) and Se-methylselenocysteine (MeSeCys). Conversely, kefir, fermented by a combination of bacteria and Saccharomyces yeast, predominantly produces selenomethionine (SeMet) . These selenium species remain stable for up to 15 days in yogurt and 10 days in kefir, after which the concentration of selenocystine decreases while Se-methylselenocysteine increases .
Sensory Profiles and Consumer Preferences
Sensory Differences
Yogurt and kefir exhibit distinct sensory profiles. Traditional kefir is more acidic and has a unique flavor profile compared to yogurt. Modified versions of kefir, such as those developed in Poland, are less acidic and have a creamier flavor, which may be more appealing to Western European consumers . Additionally, the incorporation of pequi jam into yogurt and kefir has shown to enhance flavor diversification, with both products meeting physicochemical and microbiological standards and showing good acceptability among consumers .
Nutritional and Health Benefits
Elemental Composition and Digestibility
Kefir and yogurt differ in their elemental composition and digestibility. Kefir products, including Greek yogurt made from kefir grains, are rich in essential elements like calcium, phosphorus, and iron, making them a good dietary source of these nutrients . Moreover, kefir has been shown to improve lactose digestion and tolerance in adults with lactose maldigestion, reducing symptoms such as flatulence and abdominal pain more effectively than milk .
Bioactive Compounds and Antioxidant Potential
The fermentation of hemp press cake using yogurt and kefir cultures results in high-value beverages with significant bioactive compounds, including proteins, amino acids, polyphenols, and flavonoids. These compounds contribute to the antioxidant activity of the products, which remains stable during storage . Additionally, kefir and yogurt made from ewe and camel milk exhibit higher antioxidant potential compared to those made from goat and cow milk, with ewe kefir showing the highest total phenolic content and antioxidant activity .
Microbiological Safety and Probiotic Properties
Pathogen Survival
The microbiological safety of yogurt and kefir, particularly in terms of pathogen survival, has been studied using foodborne pathogens such as Escherichia coli O157:H7, Listeria monocytogenes 4b, and Yersinia enterocolitica O3. Both yogurt and kefir demonstrate effective inhibition of these pathogens, ensuring the safety of these fermented products .
Probiotic Benefits
Yogurt and kefir are rich sources of health-promoting bacteria, including Lactobacillus and Bifidobacterium strains, which contribute to various health benefits. These benefits include improved lactose malabsorption, enhanced immune responses, and reduced risks of metabolic disorders and heart disease 78. The addition of kefir powder to yogurt can further enhance its probiotic properties, maintaining high levels of beneficial bacteria during storage .
Conclusion
Yogurt and kefir, while both fermented dairy products, offer unique benefits and characteristics. From distinct selenium species and sensory profiles to significant health benefits and microbiological safety, these products cater to diverse consumer preferences and nutritional needs. The ongoing research and development in this field continue to enhance the functional properties and acceptability of these fermented foods.
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