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Contents
- What happens when donkey milk is heated?
- Three proteins. Three different reactions.
- Why does heat change a protein?
- From room temperature to intense heating
- What a study on donkey milk actually measured
- Why the results do not apply to all proteins
- What you taste and see when heating
- Using donkey milk at home: What matters?
- What we know – and what remains open
- Frequently Asked Questions
- Scientific Sources
- The science behind a rare food.
Heating donkey milk.
What happens to its proteins?
Lysozyme, lactoferrin and β-lactoglobulin react differently to heat. We examine the biochemical changes, specific study results and how heating affects taste and consistency.
What happens when donkey milk is heated?
Donkey milk contains water, lactose, minerals and fat, as well as various proteins. Some of these are the subject of intensive food science research. Their structure can change when heated.
But heat does not affect all ingredients in the same way. Some proteins change their spatial structure even at relatively moderate temperatures. Others remain detectable longer under certain conditions or retain some of their activity.
The extent of these changes depends not only on the temperature. The heating time, pH value, composition of the milk and the analytical method used also influence the result.
Three proteins. Three different reactions.
Lysozyme
An enzyme that occurs naturally in milk. Donkey milk is known for its comparatively high natural lysozyme content.
In heat treatment studies, lysozyme was found to be more stable than other whey proteins under certain conditions.
Lactoferrin
An iron-binding protein whose structure and properties are being studied in food and basic research.
In a study on donkey milk, it proved to be particularly heat-sensitive.
β-Lactoglobulin
A whey protein that can change its spatial folding due to heat and interact with other proteins.
At high temperatures, a significant decrease was measured in the studied donkey milk.
Why does heat change a protein?
Proteins consist of amino acid chains. Their properties depend not only on the sequence of these building blocks, but also on how the chains fold in three-dimensional space.
Denaturation
Denaturation changes the spatial structure of a protein. Hydrogen bonds and other interactions can be disrupted, for example. This does not necessarily break down the amino acid chain completely.
Aggregation
Partially unfolded proteins can link together. Such aggregates may change the solubility, turbidity and technological properties of the milk.
Loss of measurable activity
In enzymes such as lysozyme, structural changes can also alter catalytic activity. The extent must be measured experimentally.
Presence does not mean unchanged.
If a laboratory can still detect a protein after heat treatment, it does not automatically follow that its original activity has been completely preserved.
From room temperature to intense heating
The following overview describes typical food technology temperature ranges. It is not a universal curve for the preservation of individual proteins nor a preparation guide.Room temperature
No targeted heat treatment. The taste and consistency of the milk remain unchanged. Please follow the storage and consumption instructions on the label.Gentle heating
Some proteins may remain largely preserved under these conditions. The milk is pleasantly warm to drink, and its mild, slightly sweet taste remains largely preserved.Long-time pasteurization range
Industrially established processes use 63 °C for 30 minutes, for example. In this range, particularly heat-sensitive whey proteins such as lactoferrin begin to change.Short-time pasteurization range
A common industrial process operates at at least 72 °C for 15 seconds or an equivalent process. Depending on the duration, the taste and mouthfeel may already change slightly.Significant protein changes
In the study by Ozturkoglu-Budak, substantial losses in the measured lysozyme and β-lactoglobulin levels were observed during this treatment.Boiling range
When boiled, heat-sensitive proteins change significantly. A skin may form, and the taste may seem somewhat "cooked".Note: The temperature specifications are not experimental data points of a joint stability curve. Heating time, process control and milk properties are crucial.
What a study on donkey milk actually measured
A scientific study by Sebnem Ozturkoglu-Budak examined the stability of the whey proteins lysozyme, lactoferrin and β-lactoglobulin in donkey milk after various treatments.
The work was published online in December 2016 in the International Journal of Dairy Technology. It compared, among other things, raw, frozen and heat-treated milk samples.
In the studied treatment, a decrease in measured stability or detected protein was reported.
For β-lactoglobulin, the reported decrease under these conditions was even more pronounced.
During heat treatments above this temperature, lactoferrin was no longer detectable with the analysis method used.
The authors also reported that lysozyme could be detected in similar concentrations in certain untreated, frozen and samples heated below 85 °C. However, this does not allow for a general guarantee of activity retention at 72 °C.
Original publication:
Ozturkoglu-Budak, S.:
Effect of different treatments on the stability
of lysozyme, lactoferrin and β-lactoglobulin
in donkey's milk.
DOI:
10.1111/1471-0307.12380
Why the results do not apply to all proteins
| Protein | Scientific focus | Observation when heated |
|---|---|---|
| Lysozyme | Enzyme structure and activity | Relatively stable under certain conditions; significant changes when heated more intensely. |
| Lactoferrin | Iron binding and protein structure | Particularly heat-sensitive in the cited study. |
| β-Lactoglobulin | Whey protein and denaturation | Significant losses of measured protein at 85 °C. |
| Caseins | Protein micelles and processing | Different structural properties than globular whey proteins; not an identical temperature response. |
Even within the same milk, proteins can behave very differently. Therefore, the statement "Donkey milk loses its ingredients at temperature X" is scientifically too generalized.
What you taste and see when heating
Protein changes are not just a matter for the laboratory. When heating, you also notice them in the taste, appearance and mouthfeel of the milk.
Donkey milk tastes mild and slightly sweet. When gently heated, this character remains largely preserved. The more and longer the milk is heated, the more likely a slightly "cooked" taste will develop.
A thin skin may form on the surface. It forms when altered whey proteins clump together.
Milk components may adhere more easily to the bottom of the pot. Heating slowly at low heat and stirring helps to avoid this.
Please follow the storage and consumption instructions on the label.
Why heating at home is different from the laboratory
Industrial heat treatment is a controlled process with a fixed temperature, holding time and suitable technology. In a regular cooking pot, however, heat is distributed more unevenly.
Study results on individual proteins therefore cannot be applied directly to preparation in your own kitchen.
Using donkey milk at home: What matters?
Maintain the cold chain
Thaw frozen donkey milk in the refrigerator, not unprotected at room temperature. Follow the product-specific storage instructions – find out more in our Thawing Instructions.
Heat gently
If you want to enjoy warm donkey milk, heat it slowly at low heat and stir. Use suitable, clean cookware.
Process cleanly
Use clean containers and kitchen utensils for subsequent use. Do not leave heated milk warm for unnecessarily long.
Cool leftovers quickly
Cool milk that is not used immediately quickly and store it according to the product instructions.
What we know – and what remains open
What research shows
Different whey proteins in donkey milk react differently to heat treatments. The type of treatment affects their measurable stability.
What does not follow from this
The detection of individual proteins does not allow any health effects in humans to be derived.
Questions further studies should clarify
Standardized studies with different donkey milk samples, precisely documented temperature-time profiles, as well as separate measurements of protein content, structure, and enzyme activity are of interest.
Equally important is the question of how laboratory results can be applied to real food processes.
Frequently Asked Questions
Can donkey milk be heated?
Yes. When heated, heat-sensitive proteins may change. Please follow the storage and consumption instructions on the label.
Is lysozyme still present at 72 °C?
Studies show that lysozyme can remain detectable under certain heat conditions. How much protein and enzyme activity is retained at 72 °C depends, among other things, on the heating duration and the testing conditions.
What happens to lactoferrin when heated?
Lactoferrin is heat-sensitive. In the cited study, after treatments above 65 °C with the method used, it was no longer detectable.
Is heated donkey milk still donkey milk?
Of course. Heating does not change the origin of the food. However, individual ingredients may change structurally or in quantity.
What does warmed donkey milk taste like?
When lightly warmed, donkey milk continues to taste mild and slightly sweet. With stronger heating, a slightly more "cooked" taste may develop, and a skin forms more easily.
Is freezing the same as pasteurizing?
No. Freezing is a cold process without heat input. Pasteurizing, on the other hand, is a heat treatment in which heat-sensitive proteins may change.
Scientific Sources
Effect of different treatments on the stability of lysozyme, lactoferrin and β-lactoglobulin in donkey's milk.
International Journal of Dairy Technology.
DOI: 10.1111/1471-0307.12380
Further studies and scientific classifications regarding donkey milk.
To the research archive
The science behind a rare food.
Discover further research on the composition, processing, and food chemistry of donkey milk – presented in an easy-to-understand way and documented with original sources.
Discover the research archive →About this post
DON DONKEY'S® · Scientific guide. This article explains published research findings on food chemistry. It does not constitute a medical recommendation or a health-related efficacy promise for DON DONKEY'S® products. The described studies were not conducted on our sales batches. Please follow the storage and consumption instructions on the label.
