Lactose content in kefir
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Lactose Content in Kefir: Key Factors and Variations
Lactose Reduction During Kefir Fermentation
Kefir is a fermented dairy product known for its lower lactose content compared to the milk it is made from. During fermentation, the lactose in milk is broken down by lactic acid bacteria and yeasts, resulting in a significant reduction in lactose levels. Studies consistently show that the lactose content in kefir drops substantially during the fermentation process, making it more suitable for people with lactose intolerance 59.
Influence of Milk Type on Kefir Lactose Content
The type of milk used to make kefir affects its final lactose content. For example, kefir made from cow’s milk, whether fresh, UHT, or skim milk powder, typically has a lactose content ranging from about 2.02% to 3.36% after fermentation. Among these, kefir made from skim milk powder tends to have the highest lactose content at 3.36% . Goat’s milk kefir, depending on the starter culture used, can have lactose levels between 1.48% and 2.67% . Sheep’s milk kefir shows the greatest reduction in lactose during storage, with up to a 52% decrease after 21 days, making it the lowest in lactose among tested fermented milk beverages .
Impact of Starter Cultures and Yeast on Lactose Content
The combination and concentration of starter bacteria and yeast used in kefir production also influence lactose breakdown. Lower concentrations of Lactobacillus acidophilus and Saccharomyces cerevisiae in goat’s milk kefir lead to a greater reduction in lactose content . Additionally, the use of certain yeast species, such as Kluyveromyces spp., can result in kefir drinks with negligible lactose content, especially when ethanol is present, indicating almost complete lactose fermentation .
Storage Time and Further Lactose Reduction
Lactose content in kefir continues to decrease during storage. For sheep’s milk kefir, the lowest lactose levels are observed after 14 to 21 days of refrigeration, with kefir consistently having less lactose than yogurt made from the same milk . This ongoing reduction is due to continued microbial activity during storage.
Lactose-Free Kefir and Sensory Properties
Lactose-free kefir is also available and is produced by either using lactose-free milk or by extensive fermentation that removes almost all lactose. These products tend to have higher levels of glucose and galactose, resulting in a sweeter taste and lower acidity, which are generally well accepted by consumers, especially the elderly .
Water Kefir and Non-Dairy Alternatives
Water kefir, made from demineralized whey or other non-dairy sources, can also be produced with varying lactose content depending on the initial lactose concentration. For example, water kefir made from whey with 2% lactose supports good microbial viability and acceptable sensory properties .
Conclusion
Kefir generally contains much less lactose than the milk it is made from, with final lactose content influenced by the type of milk, starter cultures, yeast species, and storage time. This makes kefir a suitable option for many people with lactose intolerance. The lowest lactose levels are typically found in kefir made from sheep’s milk and in products fermented with specific yeast strains or stored for longer periods. Lactose-free kefir options are also available and are well received for their taste and digestibility.
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