Donkey Milk Study: Fresh Cheese with Microbial Rennet (Faccia 2020)

With microbial rennet, donkey milk could be curdled in around 9 minutes; the fresh cheese reached a yield of 7.21% with 25.87% protein and 2.90% fat. The control cheese made from cow milk had a yield of 23.52%.

The study in brief

• Original title: Chemical-Sensory Traits of Fresh Cheese Made by Enzymatic Coagulation of Donkey Milk
• Authors: Faccia M., Gambacorta G., Martemucci G. et al.
• Journal: Foods, 9(1), 16 (2020)
• Country: Italy · Study type: Laboratory study

How it was investigated

Pooled milk from ten Martina-Franca donkey mares in mid-lactation (machine-milked, farm in Puglia) was processed into fresh cheese in six laboratory-scale repetitions; pooled cow milk served as a control. For each batch, 5 L of milk were heated in a water bath, treated with calcium chloride (0.3 g/L) and microbial rennet; the curd was cut, heated to 46 °C, shaped, dry-salted after 2 h at 25 °C, and stored overnight at 4 °C. After about 24 hours, the yield, composition (dry matter, protein, fat, ash, pH), fatty acid profile of milk, cheese, and whey (gas chromatography), volatile compounds (headspace-SPME-GC-MS, semi-quantitative), protein fractions (electrophoresis), and sensory profile (Flavour Profile Method, five-member trained panel) were determined.

Key figures

• 10 – Martina-Franca donkey mares provided the pooled milk (mid-lactation)
• 6 – Laboratory-scale cheese productions, 5 L of milk each
• 9.15 min – Time from rennet addition to curd cutting (± 3.10)
• 42.10 vs. 13.20 min – Total processing time donkey milk vs. cow milk
• 7.21 vs. 23.52 % – Cheese yield donkey milk vs. cow milk
• 2.21 % / 0.33 % – Protein and fat content of the donkey milk used

Results

The donkey milk (pH 7.01; 2.21% protein, 0.33% fat, 6.76% lactose) curdled quickly with microbial rennet: 9.15 ± 3.10 minutes elapsed until cutting. However, the curd remained very soft and had to be handled gently; processing until shaping took 42.10 minutes compared to 13.20 minutes for cow milk, which formed a firm curd almost immediately under the same conditions.

After 24 hours, the donkey fresh cheese contained 34.19% dry matter, 25.87% protein, 2.90% fat, and 3.31% ash at pH 5.85; the yield was 7.21%. The control cheese made from cow milk was semi-firm with 49.88% dry matter, 23.76% fat, and a yield of 23.52%. The authors attribute the higher yield compared to the literature primarily to the high protein content of the milk used.

In the donkey milk, oleic acid (24.46%), palmitic acid (19.08%), and linoleic acid (18.27%) were dominant. In the cheese, the proportion of saturated fatty acids was significantly higher at 67.01% than in the milk (48.46%), mainly due to more palmitic, myristic, and stearic acid; polyunsaturated fatty acids dropped from 23.92% to 6.55%. In cow milk, the shifts were weaker and only significant for stearic acid.

Limitations of the study

• Contradictory statement about the milk origin: According to the abstract, the milk came from one Martina-Franca donkey, while the methods section states ten animals. It remains unclear when the milk for the six productions was obtained and whether it was freshly collected each time.
• Control cheese calculation is not consistent: Based on the yield and composition of the cow milk cheese, editorial recalculation shows that around 154% of the milk fat and 122% of the milk protein would be found in the cheese, which is not possible. For the donkey fresh cheese, the values are at plausible 63% and 84% respectively.
• Fatty acid shift unexplained: The sharp decrease of polyunsaturated fatty acids from the milk to the cheese is unusual and is only explained as a hypothesis. According to the table, the whey contained less than 0.1% fat, and its fatty acid profile varied widely.
• Laboratory scale and small panel: Small batches of 5 L of milk were produced. The sensory analysis is based on a consensus profile from five trained testers and is only available as a graphic; no consumer test was conducted.
• Aroma compounds only semi-quantitatively: The volatile compounds were estimated assuming equal response factors against an internal standard. The interpretation of the "egg yolk" aroma based on common compounds with egg yolk is a hypothesis of the authors.

Level of evidence: Basic research (laboratory) – describes the properties of the milk, no statement about effects in humans.

Our assessment

The study is a technological laboratory experiment on cheese production and describes the composition, fatty acids, aroma compounds, and sensory profile of an experimental product. Statements about nutritional effects in humans were not investigated.

Source: Faccia M., Gambacorta G., Martemucci G., Difonzo G., D’Alessandro A.G. (2020). Chemical-Sensory Traits of Fresh Cheese Made by Enzymatic Coagulation of Donkey Milk. Foods. DOI: 10.3390/foods9010016 · Summarized by the DON DONKEY'S editorial team, as of October 2026.

End of the study summary. The study was conducted independently by DON DONKEY'S® and does not refer to our products. Our donkey milk is a food.