Take home message

Traditional kefir based on grains (SCOBY) has a different composition depending on whether it is made from cow’s milk or goat’s milk. Results are based on highly pasteurised whole milk. A Turkish-trained taste panel prefers kefir made from goat’s milk due to differences in mouthfeel and viscosity. Numerous ingredients are associated with differences in kefir made from goat’s milk or cow’s milk.

Mixing milk and making kefir

Turkish researchers mixed whole cow’s milk and whole goat’s milk in various ratios (100-0; 75-25; 50-50; 25-75 and 0-100%). Using kefir grains (SCOBY), a kefir drink was produced within 24 hours. This kefir was tested after 1 day and after 10 days. Among other things, the question was how the cow-goat ratio in the milk would affect the structure, mouthfeel and numerous breakdown products, such as alcohol and bioactive substances, that arise during fermentation.

The design of the study is appealing. By creating a series with increasing and decreasing amounts of one type of milk or the other (goat or cow), you can effectively track shifts. The starting milk from goats and cows is different. Goat’s milk has a much higher fat content (5.10% compared to 3.05%) and a slightly higher protein content (4.03% compared to 3.84%). After mixing the milk fractions, each milk mixture was heated to 90^oC for 10 minutes, which is a very thorough pasteurisation. Fermentation with kefir grains was then initiated.

From cow’s milk kefir to goat’s milk kefir

Below, the step-by-step shift from 100% cow’s milk to 100% goat’s milk is referred to as cow-100, cow-75, goat-75 and goat-100 (Table 1). For the sake of clarity, the 50-50% ratio has been omitted. It appears that as the proportion of goat’s milk increases, the number of yeasts decreases, while the total number of mesophilic bacteria (germ count) and the number of Lactobacilli in the kefir increases. Kefir made from 100% cow’s milk contains > 25 million bacteria per ml (log 10 = 7.4), 219 million Lactobacilli (log10 = 8.3) and 363 thousand yeasts per ml (log10 = 5.6). Goat kefir made from 100% goat’s milk has a germ count that is 12% higher (112), contains 5% more Lactobacilli (105), but about 17% less yeast than kefir made from 100% cow’s milk (83).

Two antioxidants have been measured, and these increase as the proportion of goat’s milk rises. Various organic acids are higher in goat’s milk. The acid binding after titration is higher, more lactic acid is formed in kefir made from goat’s milk and the pH is therefore slightly lower.

Table 1. Increase or decrease compared to kefir made from 100% cow’s milk. For cow-100, the absolute value is included; other values are relative to cow-100 (note that the cow-goat 50-50 ratio has been omitted); data derived from Şahingil et al., 2026.

	absolute	Relative (%) to cow-100
Cow-goatmilk	cow-100	cow-75	goat-75	goat-100
Mesophylic germs log 10 (cfu/ml)	7.4	102	113	112
Lactobacilli log 10 (cfu/ml)	8.3	98	102	105
Yeasts log 10 (cfu/ml)	5.6	98	94	83
DPPH *	3.6	153	165	170
ABTS *	38.5	101	102	114
Ethanol on day 10 (μg/100 g)	5.3	119	171	157
Hippuric acid (μg/100 g)	821	104	217	283
Lactic acid (μg/100 g)	2.589	103	114	113
Acidic acid (μg/100 g)	274	140	195	243
Titratable acidity (% lactic acid)	1.31	105	105	108
pH	4.40	4.38	4.36	4.35

* ABTS (3-ethylbenzothiazoline-6-sulfonic acid) en 2,2-diphenyl-1-picrylhydrazyl (DPPH) activity (anti-oxidantia)

During fermentation, numerous volatile degradation products are formed, which contribute to aroma and flavour and may or may not be bioactive. A total of 43 volatile compounds were identified in the kefir samples, including 7 acids, 10 esters, 7 ketones, 4 aldehydes, 9 alcohols and 6 other compounds.

When you look at the shift from kefir made from 100% cow’s milk to 100% goat’s milk, the following picture emerges (Figure 1). The shift from cow’s milk to goat’s milk therefore changes the aroma and flavour profile of volatile compounds in kefir.

The highest positive correlations (between +0.8 and +1.0) were for compounds such as toluene, butyl acetate and alpha-pinene, suggesting that these compounds are the dominant aromatic components unique to goat milk kefir.

Ethanol and 3-methyl-1-butanol were the most common alcohols in all kefir samples. The ethanol content was lowest in kefir made from 100% cow’s milk and increased as the proportion of goat’s milk increased (particularly from 75 and 100% goat’s milk after 10 days of storage). In kefir made from goat’s milk, ethanol production increases on day 10, which may mean that more secondary fermentation (and alcohol production) takes place in goat’s milk kefir.

Fig. 1. The shift in volatile compounds after making kefir expressed as a correlation coefficient: blue = more as the proportion of cow’s milk in the kefir is higher; red = more as the proportion of goat’s milk is higher. The longer the bar, the greater the change in the concentration of the substance; data derived from Şahingil et al., 2026.

The differences found in some substances may have arisen due to the grazing and selection behaviour of goats and cows. The article does not mention anything about the origin of the milk. Substances such as alpha- and beta-pinene originate from herbs and are found in greater quantities in goat kefir. When goats have a choice and the supply is there, they will snack much more, select more, and make more choices for tops, twigs, leaves and flowers, while cows (especially if they are fed for production) are given grass products, maize and concentrates. Goats are “intermediate feeders”, falling between true “browsers” such as deer and elk and true “grazers” such as cows and sheep. The higher concentration of hippuric acid in goat’s milk is also well known and is associated with grazing livestock farming. The reason why toluene (a toxic substance) is elevated in goat’s milk may be coincidental. Perhaps the environment in which the goat’s milk is produced is more polluted (urban or industrial environment).

Fig. 2. Classification of different ruminants based on their foraging behaviour: true grazers, true browsers and intermediate feeders (from Vera, 2000)

Smell, taste and mouthfeel assessment

All these differences together ultimately lead to a final assessment of a product. Typical constituents such as alcohol or certain esters (volatile constituents) contribute to the perception of the product as being refreshing (stimulating mouthfeel due to carbon dioxide formation), cheesy aromas and flavours, or, conversely, a sensation that a product is mild and well-rounded in flavour due to its aromas. These are caused, among other things, by protein breakdown and fat oxidation during fermentation.

A trained panel assessed the kefir on foam formation, appearance, aroma, taste, off-flavours, mouthfeel, viscosity, acidity, sweetness, overall impression and hedonic score, which is essentially a subjective assessment of whether a product will be accepted by consumers (1–10). The differences are shown in Figure 3.

Fig. 3. Spider diagram showing the rating of aroma, taste, mouthfeel, etc. of kefir made from 100% cow’s milk (A-blue) to kefir made from 100% goat’s milk (E-green); taken from Şahingil et al., 2026.

It is striking that the taste panel rates kefir made from goat’s milk (green) highest for most characteristics, while the addition of cow’s milk up to and including kefir made from 100% cow’s milk (blue) is clearly less appreciated. The transitions from 75-25, 50-50 and 25-75% cow’s milk/goat’s milk accurately reflect the transitions between the two extremes in terms of rating.

The overall evaluation (top left of the graph) summarises these findings, as does the hedonic rating. This shows that kefir made from goat’s milk has a significantly higher rating than kefir made from cow’s milk. In particular, the ratings at the bottom right (viscosity and mouthfeel) favour kefir made from goat’s milk and show significant differences. After storage, the assessment on day 10 shows less significant differences, but the overall rating between the starting milk ratios remains unchanged (not shown).

Conclusion

There are differences between kefir made from cow’s milk and goat’s milk. These differences are probably partly due to chance, or partly due to the type of farm that supplies the milk (pasture farming, feed level, environmental pollution). On the other hand, there are also intrinsic differences that are likely to occur in all kefirs and are related to the milk properties of goats and cows.

A Turkish-trained taste panel clearly prefers the characteristics of kefir made from goat’s milk, which is evident in characteristics such as the mouthfeel, the typical kefir taste and the viscosity of kefir made from goat’s milk.

Literature

• Şahingil, D., Gürkan, H., & Hayaloğlu, A. A. (2026). Substituting Cow’s Milk with Goat’s Milk Changed the Nutritional, Rheological, and Volatile Profiles of Kefir Produced by Kefir Grains. Dairy, 7(1), 11.
• Vera, F. W. M. (2000). Grazing ecology and forest history. CAB International.