Course:FNH200/Projects/2025/Kefir

Introduction and Background

Homemade Kefir with Grains and Strainer

About: Kefir is a fermented milk drink made by adding kefir grains, which contain proteins, fats, lactic acid bacteria (LAB), and yeasts, into milk. These microbes ferment lactose into lactic acid, ethanol, and carbon dioxide, creating a tangy, slightly fizzy drink with a yogurt-like consistency. Known for its live probiotic cultures, kefir is now popular worldwide as a functional food linked to gut health. Its production reflects key FNH 200 concepts including microbial safety, fermentation, and shelf life extension through pH reduction and microbial competition.

Origins: Kefir originated in the Caucasus Mountains, in regions now part of Russia, Georgia, and Turkey. It was traditionally made by fermenting raw milk in goat-skin bags or clay pots, often hung in doorways and shaken gently. The grains were passed down through families and valued for their health benefits. Though common in Eastern Europe and Central Asia, kefir gained Western attention in the 20th century and is now listed in the Ark of Taste for its cultural and microbial significance.

Nutrition and Functional Properties: Kefir’s microbial composition is about 83-90% LAB (Lactic Acid Bacteria), some acetic acid bacteria, possibly mould, and 10-17% yeasts, which break down lactose and enhance nutrient absorption. A 100g serving of 2% kefir contains:

• 2.0g fat
• 3.4g protein
• 4.6g carbohydrates
• 220mg calcium

It is also a source of:

• Vitamins: B1, B2, B12, K2
• Minerals: phosphorus, magnesium

Probiotics like Lactobacillus and Bifidobacterium may help with digestion and gut health, especially for those sensitive to lactose.

Processing and Industrial Production

Kefir production flowchart.

Commercial kefir production begins with pasteurized milk, which is heated to approximately 90 °C for 2 minutes to eliminate pathogens and ensure safety. After cooling, a liquid or freeze-dried starter culture containing defined strains of lactic acid bacteria and yeast is added to the milk. Industrial manufacture utilizes standardized microbial mixes for uniformity, unlike traditional kefir, which uses grains. Lactose ferments for 18 to 24 hours in stainless steel tanks maintained at 20 to 25 °C. During fermentation, bacteria produce lactic acid, ethanol, and carbon dioxide, resulting in the characteristic low pH, tartness, and carbonation of kefir.

Industrial kefir production relies on pasteurization (pre- and post-fermentation) to ensure safety and shelf life, while controlled fermentation (20–26°C, pH ~4.6) maintains consistency using freeze-dried cultures instead of traditional grains. HACCP protocols enforce critical controls, including raw milk screening, pasteurization validation, and aseptic packaging, to eliminate pathogens like Listeria and Salmonella.

Shelf life extends to 3–6 weeks for pasteurized kefir (vs. 1–2 weeks for raw), though storage alters acidity, CO₂, and nutrient content. Innovations like micro-encapsulation and non-dairy adaptations (e.g., coconut, soy) address scalability challenges, while pasteurization enhances post-biotic benefits (e.g., anti-inflammatory metabolites).

Differences in Kefir Production

Aspect	Industrial Methodology	Traditional Methodology
Starter	Freeze-dried cultures	Kefir grains
Scalability	High (large batches)	Low (small batches)
Food Safety	HACCP-compliant	Viarable microbial risks

Future advancements include AI-driven fermentation and CRISPR-engineered strains for improved safety and functionality. Regulatory compliance (e.g., Codex Alimentarius STAN 243-2003) remains critical for global standards.

Variations and Innovations

Advances in food technology and evolving customer preferences are evident in modern kefir products. Accessible fruit-flavoured kefirs—such as those featuring passion fruit, mango, strawberry, and grape—increase sensory appeal and mitigate the harsh, sour flavour of regular kefir. These flavourings are added after fermentation, which enables producers to maintain the probiotic content of the beverage while enhancing its flavour and commercial viability (Magalhães et al., 2011; Kresova et al., 2006).

Producers have developed high-protein kefirs that contain additional milk protein concentrates to enhance nutritional value and maintain microbial viability (Londoño-Hernández et al., 2023). These products are marketed explicitly toward fitness-oriented consumers. Additionally, plant-based kefirs made from oat, almond, or coconut milk offer dairy-free alternatives. Since plant-based milks do not contain lactose, manufacturers add fermentable sugars or prebiotics to support fermentation and sustain microbial activity.

DIY kefir kits, which allow users to ferment at home using live or dried grains, have gained popularity. Probiotic content is preserved via packaging advancements, including aseptic filling and opaque containers. Many businesses are now adopting packaging that is recyclable or biodegradable, as maintaining a cold chain is crucial for ensuring microbiological stability (Francis et al., 2024; Grafia et al., 2025).

Regulatory Aspects of Dairy Kefir

Liberté Kefir Packaging labelled "probiotic."

Regulatory Changes and Exemptions for Dairy Kefir

Vitamin D Fortification: As of May 13, 2024, manufacturers are now voluntarily permitted to add Vitamin D to dairy kefir.

• This authorization creates an exemption from certain prohibitions in paragraphs 4(1)(a) and (d) of the FDA (prohibiting harmful or adulterated food) and section D.03.002 of the FDR (listing permitted vitamin/mineral additions), specifically for Vitamin D in these products.
• The permitted levels of Vitamin D fortification for dairy kefir are:
  • Plain kefir: 2.7 μg of Vitamin D per 100 mL.
  • Fruit or flavoured kefir: Not less than 2.3 μg and not more than 2.7 μg of Vitamin D per 100 mL.  

These levels are set to help address insufficient Vitamin D intake among Canadians, leveraging dairy products' inherent calcium content for bone health.

Front-of-Package (FOP) Nutrition Symbol Exemptions: Kefir is  conditionally exempt from displaying the "high in saturated fat" or "high in sugars" nutrition symbol if it contains 5% or more of the daily value (DV) for calcium per serving of stated size or reference amount, whichever is greater.

Labelling Requirements for All Kefir Products

Kefir labelled with "probiotic." (see on labelling, CFU is 2 billion per 188mL, source of Vitamin D, and specified strains are Lactobacillus casei, Lactobacillus acidophilus, Bifidobacterium lactis, Lactobacillus rhaminosus)

Kefir follows the general labelling principles provided by the CFIA (Canadian Food Inspection Agency), however there are further requirements for probiotic claims, as some packaging has the label “probiotic” on it. In Canada, the use of terms like "probiotic," on kefir packaging or in advertising is considered an implied health claim. To be compliant with the Food and Drugs Act, these terms must be accompanied by a specific, validated statement about the benefits of the microorganisms.

Two primary categories of probiotic claims are recognized for food products:

• Non-strain-specific claims: These are general statements about the nature of probiotics, such as "provides live microorganisms that contribute to healthy gut flora."
• Strain-specific claims: These are about the health benefits of specific strains. At this time, no strain-specific claims have been accepted by Health Canada for food.

To make a probiotic claim, the food product, in this case, kefir, must contain at least 1.0 x 10⁹ colony-forming units (CFU) of the microorganism(s) per serving throughout its shelf life. The label must also declare the identity of the microorganism(s) using their scientific name and strain identity, and state the quantity in CFU per serving.

Conclusion

Kefir's value as a functional food lies in its unique blend of probiotic benefits and advanced production techniques that guarantee safety, consistency, and scalability. Modern industrial processing employs controlled fermentation, with precise pH and temperature management alongside standardised starter cultures, as well as strategic pasteurisation. These methods optimise shelf life while preserving bioactive compounds. Such innovations enable kefir to comply with rigorous regulatory standards, including Canada's vitamin D fortification and probiotic viability requirements, all while retaining its traditional health benefits.

The rising global demand for kefir mirrors evolving consumer preferences towards gut-friendly, functional foods, spurring innovation in large-scale fermentation, dairy-free alternatives such as coconut or soy bases, and flavour variety. As a model system, kefir demonstrates fundamental food science principles, from microbial safety achieved through pH control and competitive exclusion to effective shelf-life extension. Its commercial success highlights the careful equilibrium between artisanal fermentation practices and industrial efficiency, securing kefir's role as a leading functional food for the future.

Exam Question (FNH 200)

Question: Why does kefir have a longer shelf life than pasteurized milk?

A. It’s vacuum-sealed

B. It contains synthetic preservatives

C. It’s fermented, lowering pH and adding protective microbes

D. It contains vinegar

Answer: C. It’s fermented, lowering pH and adding protective microbes

(Rationale: This question tests understanding of fermentation, microbial safety, and pH control - core food science concepts in FNH 200.)