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How does brief heating change the components of donkey milk? An Italian team heated donkey milk in a small continuous-flow system to 75, 85, or 92 °C for 3, 6, or 12 seconds, respectively, and then measured lysozyme, β-lactoglobulin, B vitamins, and several laboratory values. Lysozyme decreased significantly depending on the heating, while the measurable B vitamins showed no significant decrease.
Food technology laboratory study with milk analysis – no statement about an effect in humans. Donkey milk is a food.
Study at a glance
| Feature | Information |
|---|---|
| Original title | Effect of continuous flow HTST treatments on donkey milk nutritional quality |
| Authors | Matera A., Altieri G., Genovese F. et al. |
| Journal | LWT – Food Science and Technology, 153: 112444 |
| Year | 2022 (online 2021) |
| Country | Italy (Basilicata, Marche, Puglia) |
| Study type | Food technology laboratory study with milk analysis |
| Sample | Pooled milk from 120 Martina Franca donkeys (February 2019); 9 heatings plus raw milk |
| DOI | 10.1016/j.lwt.2021.112444 |
What question did the researchers ask?
According to the authors, there are no specific EU-wide guidelines for donkey milk regarding short-time heating (HTST, "high temperature, short time"). The researchers wanted to know how much different combinations of temperature and holding time change sensitive components such as lysozyme, β-lactoglobulin, and B vitamins.
How it was investigated
- Milk: Pooled milk from 120 Martina Franca donkeys from a farm in Laterza (Puglia), delivered chilled at 4 °C.
- System: Small continuous-flow system with a plate heat exchanger, 60 liters per hour, preheating with heat recovery.
- Nine heatings: 75, 85, and 92 °C, each with 3, 6, and 12 seconds holding time; raw milk as a comparison.
- Analyses: Lysozyme and β-lactoglobulin by liquid chromatography, B vitamins, laboratory tests ABTS, FRAP, and free SH groups, polyphenols, and flavonoids.
The results
Lysozyme is an enzyme in whey. In raw milk, it was 1.17 g/L. The hotter and longer it was heated, the less could be detected. The authors report a decrease of between 19.6 and 60.6%.
| Heating | Lysozyme (g/L) | β-lactoglobulin (g/L) |
|---|---|---|
| Raw milk | 1.17 | 3.43 |
| 75 °C, 3 s | 0.94 | 3.33 |
| 85 °C, 6 s | 0.76 | 2.87 |
| 92 °C, 3 s | 0.70 | 3.11 |
| 92 °C, 12 s | 0.46 | 2.66 |
β-lactoglobulin, another whey protein, decreased less; according to the statistics, only three variants differed significantly from raw milk. For B vitamins B2, nicotinic acid (B3), B6, and folic acid (B9), the authors found no significant decrease; B1 and B12 were not detectable in either raw or heated milk. The laboratory tests decreased depending on the heating: ABTS by 20 to 31%, FRAP by 8 to 15%, free SH groups by 11 to 37%.
Lysozyme was the most sensitive measured component, while the measurable B vitamins showed no significant decrease. The variants with 3 seconds and 75 °C/6 s were closest to raw milk in the overall profile.
Critical assessment
- A single batch: Pooled milk from one farm, once in February. Differences across seasons or farms were not captured.
- Small pilot system: 60 liters per hour in a university laboratory. The authors themselves call their results preliminary.
- No process verification: Whether the heatings achieved their technical goal was not checked – no enzyme test, no microbiological examination.
- Minor contradictions: β-lactoglobulin decreases by 2 to 22% according to the abstract, and by 2 to 25% according to the results section. For the polyphenols, the units and percentage figures do not quite match up.
- Laboratory tests: ABTS, FRAP, and SH groups describe chemical properties in a test tube, not an effect in the body.
Funding, conflicts of interest, and level of evidence
No funding is mentioned in the paper. The authors declare no conflicts of interest. One author works for a regional breeders' association (ARA Campania); the breeders' association of Basilicata and the farm that supplied the milk are also thanked.
Level of evidence: Basic research (food technology, milk analysis) – describes changes in components, no statement about effects.
What does this mean for donkey milk as a food?
The study shows that individual components of donkey milk react differently to short-time heating: lysozyme significantly, the measured B vitamins hardly at all. It reports measured values; we do not derive a recommendation for or against a specific heating from this. Our donkey milk was not investigated.
Our research question: Which components – such as lysozyme – should we have measured in our own milk in the laboratory and shown openly?
Frequently asked questions
What does HTST mean?
"High temperature, short time": The milk is brought to a high temperature in a continuous flow for a few seconds and immediately cooled again. In this study, it was 3 to 12 seconds at 75 to 92 °C.
What is lysozyme?
An enzyme that, according to the authors, occurs in donkey milk in a relatively high amount. It is a protein and changes when heated; in this study, its quantity was measured, not its activity.
Were the vitamins destroyed by heating?
For B2, nicotinic acid, B6, and folic acid, the authors found no significant decrease. B1 and B12 were not detectable even in raw milk.
You can find all measured values, interactive graphics, and the full critical assessment on our research page: Study 77: Short-time heating of donkey milk. Further studies in the research archive.
Matera A., Altieri G., Genovese F., Polidori P., Vincenzetti S., Perna A., Simonetti A., Rashvand Avei M., Calbi A., Di Renzo G. C. (2022). Effect of continuous flow HTST treatments on donkey milk nutritional quality. LWT – Food Science and Technology, 153, 112444. DOI: 10.1016/j.lwt.2021.112444
Summarized and reviewed by the DON DONKEY'S editorial team based on the original publication · As of: October 2026. This summary does not replace the original work.
End of the study summary. The study was conducted independently of DON DONKEY'S® and does not refer to our products. Our donkey milk is a food.
