The Impact of Beta-Casein Genetic Variant on the Physicochemical Properties of Various Fermented Milk Types

Dorota Najgebauer-Lejko; Iwona Radkowska; Magda Filipczak-Fiutak

doi:10.2478/aoas-2025-0113

The Impact of Beta-Casein Genetic Variant on the Physicochemical Properties of Various Fermented Milk Types

Annals of Animal Science

AHEAD OF PRINT

By: Dorota Najgebauer-Lejko, Iwona Radkowska and Magda Filipczak-Fiutak

Open Access

|Feb 2026

Figures & Tables

Fermented milk types with the most popular examples (Tamime et al., 2007)

Table 1.

Basic chemical composition of A1 and A2 fermented milks (g/100 g; x ±SD, n=4)

Component	β-CN variant in milk
Component	A1	A2
TS	11.00^a ± 0.28	11.12^a ± 0.26
MSNF	9.13^a ± 0.20	9.23^a ± 0.19
Protein	3.63^a ± 0.28	3.66^a ± 0.20
Fat	1.87^a ± 0.13	1.89^a ± 0.16
Ash	0.8002^a ± 0.0081	0.7910^a ± 0.0233
Carbohydrates	4.68^a ± 0.25*	4.80^a ± 0.23*

TS – total solids; MSNF – milk solids non-fat;

* Carbohydrates = MSNF - protein - ash

a – values in rows with the same letter do not differ significantly (P>0.05).

Table 2.

Acidity and antioxidant characteristics of the fresh (0w) and stored (3w) A1 and A2 fermented milks (x ±SD, n=4)

Characteristic		ABT-yoghurt		Kefir		Cultured milk
Characteristic		0w	3w	0w	3w	0w	3w
pH	A1	4.75^b ± 0.15	4.41^a ± 0.09	4.58^a ± 0.03	4.54^a ± 0.03	4.49^a ± 0.01	4.47^a ± 0.04
pH	A2	4.72^b ± 0.08	4.40^a ± 0.08	4.58^a ± 0.03	4.54^a ± 0.04	4.50^a ± 0.02	4.45^a ± 0.03
acidity (% lactic acid)	A1	0.70^a ± 0.06	0.83^b ± 0.03	0.92^a ± 0.03	0.89^a ± 0.02	0.98^a ± 0.03	0.95^a ± 0.03
acidity (% lactic acid)	A2	0.70^a ± 0.03	0.81^b ± 0.05	0.90^a ± 0.02	0.90^a ± 0.01	0.94^a ± 0.03	0.96^a ± 0.02
FRAP (mMFe²⁺/kg)	A1	0.97^a± 0.36	0.83^a ± 0.11	0.72^a ± 0.01	0.74^a ± 0.03	0.92^a ± 0.10	0.88^a ± 0.22
FRAP (mMFe²⁺/kg)	A2	0.96^a ± 0.28	0.76^a ± 0.05	0.67^a ± 0.09	0.66^a ± 0.08	0.87^a ± 0.12	0.81^a ± 0.10
ARP (mMTE/kg)	A1	0.32^a ± 0.27	0.25^a ± 0.09	0.23^a ± 0.19	0.26^a ± 0.13	0.29^a ± 0.25	0.29^a ± 0.14
ARP (mMTE/kg)	A2	0.29^a ± 0.16	0.30^a ± 0.15	0.23^a ± 0.16	0.27^a ± 0.11	0.31^a ± 0.26	0.31^a ± 0.17

FRAP – ferric reducing antioxidant power; ARP – anti-radical power, TE – trolox equivalents.

a, b – different letters denote statistically significant differences between average values within the specific type of fermented milk (P≤0.05).

Table 3.

Textural and rheological characteristics of the analysed fresh (0w) and stored (3w) fermented milks (x ±SD, n=4)

Attribute		ABT-yoghurt		Kefir		Cultured milk
Attribute		0w	3w	0w	3w	0w	3w
Hardness (N)	A1	0.85^a ± 0.09	1.13^b ± 0.16	0.39^a ± 0.01	0.49^bc ± 0.04	0.45^a ± 0.02	0.50^ab ± 0.01
Hardness (N)	A2	0.97^a ± 0.07	1.28^b ± 0.04	0.46^b ± 0.04	0.54^c ± 0.07	0.51^b ± 0.02	0.59^c ± 0.06
Adhesiveness (\|N×s\|)	A1	1.52^a ± 0.19	2.41^a ± 0.37	0.63^a ± 0.05	0.89^a ± 0.17	0.74^a ± 0.14	1.08^b ± 0.09
Adhesiveness (\|N×s\|)	A2	2.25^a ± 0.62	1.63^a ± 0.93	0.92^a ± 0.29	1.39^b ± 0.38	1.12^b ± 0.24	1.21^b ± 0.31
Cohesiveness (−)	A1	0.44^c ± 0.01	0.38^a ± 0.01	0.48^a ± 0.01	0.46^a ± 0.04	0.50^a ± 0.00	0.48^a ± 0.01
Cohesiveness (−)	A2	0.41^b ± 0.01	0.37^a ± 0.03	0.50^a ± 0.02	0.47^a ± 0.02	0.43^a ± 0.12	0.51^a ± 0.01
Gumminess (N)	A1	0.37^a ± 0.04	0.43^ab ± 0.05	0.19^a ± 0.00	0.22^ab ± 0.01	0.22^ab ± 0.01	0.22^a ± 0.01
Gumminess (N)	A2	0.40^a ± 0.03	0.47^b ± 0.02	0.23^b ± 0.01	0.26^c ± 0.04	0.26^b ± 0.02	0.29^c ± 0.02
Hysteresis loop area (kPa · s⁻¹)	A1	4.63^a ± 0.25	4.73^a ± 0.31	1.46^a ± 0.10	1.50^a ± 0.09	1.70^a ± 0.07	1.71^a ± 0.06
Hysteresis loop area (kPa · s⁻¹)	A2	8.54^b ± 0.09	8.61^b ± 0.35	1.93^b ± 0.09	1.78^b ± 0.16	1.91^b ± 0.04	2.10^c ± 0.17
k (Pa sⁿ)	A1	2.89^a ± 0.26	4.17^b ± 0.40	1.55^a ± 0.40	5.19^b ± 0.74	6.73^a ± 0.24	6.58^a ± 0.35
k (Pa sⁿ)	A2	7.90^c ± 0.65	12.23^d ± 0.90	4.42^b ± 0.35	4.92^b± 0.73	7.29^a ± 0.71	7.27^a ± 0.67
n	A1	0.40^c ± 0.01	0.24^b ± 0.01	0.37^c ± 0.02	0.29^b ± 0.05	0.25^a ± 0.01	0.27^a ± 0.01
n	A2	0.26^b ± 0.03	0.16^a ± 0.02	0.23^a ± 0.01	0.32^b ± 0.01	0.24^a ± 0.03	0.26^a ± 0.04
Initial η (Pas)	A1	4.90^a ± 0.28	4.79^a ± 0.06	1.71^a ± 0.11	2.32^b ± 0.38	2.48^a ± 0.11	2.71^a ± 0.22
Initial η (Pas)	A2	6.07^b ± 0.21	6.88^c ± 0.46	2.17^ab± 0.18	2.57^b ± 0.25	2.82^a ± 0.14	2.87^a ± 0.26
Final η (Pas)	A1	0.21^b ± 0.01	0.15^a ± 0.00	0.14^a ± 0.01	0.16^a ± 0.03	0.16^a ± 0.00	0.19^b ± 0.01
Final η (Pas)	A2	0.24^c ± 0.02	0.18^ab ± 0.01	0.16^a ± 0.01	0.17^a ± 0.01	0.18^b ± 0.01	0.21^c ± 0.00
τ₀ (Pa)	A1	23.13^a ± 1.11	25.74^b ± 1.00	12.68^a ± 1.31	12.81^a ± 1.55	11.26^a ± 1.75	13.29^a ± 0.97
τ₀ (Pa)	A2	29.67^c ± 1.16	29.28^c ± 1.01	10.96^a ± 1.30	11.92^a± 0.99	18.03^b± 1.03	17.11^b ± 0.59

a, b, c – different letters denote statistically significant differences between average values within the selected type of fermented milk (P≤0.05).

Colour profiles of fresh (-0w) and stored (-3w) fermented milks, i.e. A1 and A2 ABT-yoghurts (Y_A1, Y_A2, respectively), kefirs (K_A1, K_A2, respectively) and cultured milks (CM_A1, CM_A2, respectively); a, b – different letters denote significant differences between results for a specific colour attribute (P≤0.05)

Table 4.

Sensory properties of A1 and A2 fermented milks (x ±SD, n=14)

Sensory characteristic	ABT-yoghurt		Kefir		Cultured milk
Sensory characteristic	A1	A2	A1	A2	A1	A2
Colour	4.82^a ± 0.37	4.82^a ± 0.54	4.93^a ± 0.27	4.93^a ± 0.27	4.86^a ± 0.36	5.00^a ± 0.00
Appearance	3.64^a ± 0.66	3.29^a ± 0.75	4.32^a ± 0.42	4.29^a ± 0.80	4.00^a ± 0.55	4.61^b ± 0.59
Consistency	4.43^a ± 0.58	4.29^a ± 0.67	4.89^b ± 0.29	4.39^a ± 0.71	4.32^a ± 0.64	4.86^b ± 0.53
Odour	4.57^a ± 0.42	4.54^a ± 0.37	4.89^a ± 0.29	4.61^a ± 0.49	4.54^a ± 0.66	4.57^a ± 0.51
Taste	4.46^a ± 0.57	4.29^a ± 0.58	4.50^a ± 0.48	4.64^a ± 0.57	4.50^a ± 0.73	4.71^a ± 0.38
Total score	4.38^a ± 0.35	4.23^a ± 0.41	4.67^a ± 0.26	4.55^a ± 0.43	4.42^a ± 0.50	4.74^b ± 0.21

a, b – values in rows with different letters differ significantly within the specific fermented milk type (P≤0.05).

Table 5.

Microbiological characteristics of the analysed fermented milks (x ±SD, n=4)

Count of starter microorganism [log CFU/g]	Storage time [week]	Genetic variant of β-CN
Count of starter microorganism [log CFU/g]	Storage time [week]	A1A1	A2A2
ABT-yoghurt
Lb. acidophilus LA-5	0	8.47^a ± 0.04	8.39^a ± 0.07
Lb. acidophilus LA-5	3	8.20^a ± 0.01	8.42^a ± 0.15
Bifidobacterium BB-12	0	6.42^a ± 0.66	6.65^a ± 0.95
Bifidobacterium BB-12	3	5.48^a ± 0.54	5.45^a ± 0.85
Str. thermophilus	0	9.16^a ± 0.74	9.13^a ± 0.81
Str. thermophilus	3	8.51^a ± 0.14	8.52^a ± 0.02
Kefir
Lactobacillus spp.	0	9.16^a ± 0.69	8.93^a ± 0.88
Lactobacillus spp.	3	6.76^b ± 0.31	6.73^b ± 1.03
Lactococcus spp.	0	9.16^a ± 0.04	9.19^a ± 0.05
Lactococcus spp.	3	8.20^b ± 0.40	8.01^b ± 0.30
Yeasts	0	2.99^a ± 0.65	3.13^a ± 0.57
Yeasts	3	4.33^a ± 0.22	3.59^a ± 1.28
Cultured milk
Lactococcus spp.	0	8.98^a ± 0.37	8.92^a ± 0.19
	3	7.45^b ± 0.05	7.44^b ± 0.16

a,b – different letters denote statistically significant differences between average values for a specific type of fermented milk and microorganism (P≤0.05).

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DOI: https://doi.org/10.2478/aoas-2025-0113 | Journal eISSN: 2300-8733 (formerly 1642-3402) | Journal ISSN: 1642-3402

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Language: English

Submitted on: Jun 9, 2025

Accepted on: Oct 2, 2025

Published on: Feb 18, 2026

Published by: National Research Institute of Animal Production

In partnership with: Paradigm Publishing Services

Publication frequency: 4 issues per year

Keywords:

β-casein polymorphism,

A2 milk,

quality,

Related subjects:

© 2026 Dorota Najgebauer-Lejko, Iwona Radkowska, Magda Filipczak-Fiutak, published by National Research Institute of Animal Production
This work is licensed under the Creative Commons Attribution 3.0 License.

AHEAD OF PRINT

The Impact of Beta-Casein Genetic Variant on the Physicochemical Properties of Various Fermented Milk Types

Figures & Tables

Diagram 1.

Diagram 2.

Table 1.

Table 2.

Table 3.

Figure 1.

Table 4.

Table 5.

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