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Donkey milk research · Study 205
Fermenting donkey milk: two bacterial species working together
Donkey milk beverages with a combination of Streptococcus thermophilus and Lactobacillus plantarum reached a pH below 4.5 after 18 hours of fermentation. Over 35 days of refrigerated storage the culture counts stayed above 7.00 log CFU/mL; with a single species this was not achieved within the intended time.
At a glance · tap the cards
The key figures
Study design
How it was studied
Lab study by the Department of Veterinary Science, University of Pisa (Italy). Isolates of Streptococcus thermophilus and Lactobacillus plantarum were selected on two criteria: resistance to lysozyme and ability to acidify donkey milk (24 hours at 37 °C). Using 4 L. plantarum and 2 S. thermophilus isolates, nine fermented beverages (C1 to C9), each with its own combination, were produced and stored refrigerated for 35 days. pH and viable counts were determined weekly, and a sensory analysis was also carried out. Assessed based on the abstract; the number of isolates screened, origin of the donkey milk, heat treatment and sensory results are not stated there.
Interactive chart · values from the study
Acidification of donkey milk in 24 hours at 37 °C
Source: study abstract, means (± 0.16 and ± 0.66 respectively).
Results
What the study measured
The selected isolates tolerated high lysozyme levels: the minimum bactericidal concentration was above 6.4 mg/mL for 100% of S. thermophilus and 96% of L. plantarum isolates.
Both species acidified donkey milk within 24 hours at 37 °C, S. thermophilus by a mean of 2.91 ± 0.16 pH units, L. plantarum by 1.78 ± 0.66.
The beverages with both species (C1 to C4) reached a pH below 4.5 after 18 hours of fermentation and kept more than 7.00 log CFU/mL until the end of the 35-day refrigerated storage.
Comparing with the beverage containing S. thermophilus alone (C5), the authors observed that L. plantarum stimulated the replication of S. thermophilus.
Beverages with a single species (C5 to C9) did not reach a suitable pH within the intended production time.
Authors’ conclusion: L. plantarum strains are good candidates for a novel fermented donkey milk drink – according to the authors because of their “probiotic potential” and because they enhance the growth of S. thermophilus. The study shows technical feasibility in the lab; any effect of the drink in humans was not examined.
Critical appraisal
Strengths and limitations
Only the abstract assessedClear limitation
Number of isolates, origin and pre-treatment of the milk and the sensory results are missing. Funding and conflicts of interest could not be checked.
Probiotic only according to authorsNote
The “probiotic potential” is the authors’ assessment. Acidification, lysozyme resistance and counts were measured, not any effect in the body.
Lab-scale productionNote
The beverages were made at experimental scale. Whether the values can be reproduced in production remains open.
Sensory results without figuresNote
A sensory evaluation took place, but the abstract does not report its results.
Storage followed over 35 daysStrength
pH and viable counts were tracked weekly over the whole refrigerated storage, and nine combinations were compared directly.
Editorial note: The paper provides practical data on how donkey milk can be fermented despite its high lysozyme content. The interplay of both species is the key technical finding. The study allows no statements about health effects of the drink. To the research archive.
Research question for DON DONKEY’S®
Can thawed donkey milk from our batches be acidified below pH 4.5 with the described culture combinations as reliably as fresh milk, and how long does the product remain stable?
Original publication
Lactobacillus plantarum and Streptococcus thermophilus as starter cultures for a donkey milk fermented beverage.
Original title: Lactobacillus plantarum and Streptococcus thermophilus as starter cultures for a donkey milk fermented beverage.
Turchi B., Pedonese F., Torracca B., Fratini F., Mancini S., Galiero A., Montalbano B., Cerri D., Nuvoloni R.
International Journal of Food Microbiology · 2017 · 256, 54–61
Department of Veterinary Science, University of Pisa, Italy; partly Interdepartmental Research Center Nutrafood (according to the authors)
DOI: 10.1016/j.ijfoodmicro.2017.05.022
Transparency: funding and conflicts of interest could not be checked from the abstract. No product-related statement for DON DONKEY’S®.
Summarised and checked by the DON DONKEY’S editorial team against the original publication · As of: November 2026
The study summarised above was carried out independently of DON DONKEY’S® and does not relate to our products. It serves solely to inform about the state of research.
DON DONKEY’S® donkey milk and donkey milk powder are foods. They are not intended to prevent, treat or cure any disease and do not replace medical advice.
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DON DONKEY’S® donkey milk
100 % donkey milk · raw milk, frozen
On this page we report the findings of a published study. Independently of that, you will find our donkey milk here: 100 % donkey milk, frozen as raw milk.
100 ml bottle / 100ml · Unit price: €249,00 / 1 l · incl. VAT, plus shipping
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Donkey Milk Powder
Donkey milk in powder form
For anyone who prefers a longer shelf life: our donkey milk in powder form – easy to store and portion.
20g · Unit price: €1.245,00 / 1 kg · incl. VAT, plus shipping