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How is "smart yoghurt" digested?

In this study, we examined digestion of yoghurt produced by combining non-thermal innovative processing technologies, in the laboratory.

Main conclusions

  • Improved protein digestibility of "smart yoghurt" compared to traditional yoghurt
  • Heat treatment (85 °C, 20 min) reduces protein solubility during digestion and hence protein digestibility

Purpose of the trial

Yoghurt is rich in vitamins and minerals and is an excellent source of protein. However, conventional heat treatment in dairy processing may influence the nutritional profile and protein digestibility. As an alternative, non-thermal technologies have gained attention, such as high-pressure (HPP), ultrasound (US), and use of carbon dioxide (CO2), either implemented alone or in selected combinations.

In this trial, we investigated whether non-thermal combination technology (CO2, HPP and US) in yoghurt manufacturing could improve protein digestibility.


Fresh samples of

  1. "Smart yoghurt" (CO2, HPP, US)
  2. Traditional yoghurt (85 °C, 20 min)
  3. Yoghurt made with untreated skimmed milk
  4. Untreated skimmed milk

were subjected to a static in vitro digestion model (INFOGEST). Samples were withdrawn from the gastric and intestinal phases, and protein breakdown products (peptides) were analysed using size exclusion chromatography (SEC). The concentration of dissolved proteins (protein solubility) in the intestinal phase was measured using the DUMAS method.

What was investigated

Proteins dissolved during digestion

  • The percentage of dissolved proteins during digestion was significantly higher in Smart Yoghurt compared to traditional yoghurt.
  • There were no differences between Smart Yoghurt, yoghurt made with untreated milk, and untreated milk (i.e. samples that were not heat-treated).

Protein digestibility

  • Smart Yoghurt, yoghurt made with untreated skimmed milk, and untreated skimmed milk showed improved protein digestibility compared to traditional yoghurt.
  • The improved protein digestibility was due to increased protein solubility during digestion. No clear differences were found in the degradation rate of proteins into peptides.
Oversikt over proteinfordøyelse i yoghurtene som var med i testen
Protein digestibility (% small peptides) of untreated milk, yogurt made with untreated milk, traditional yoghurt and "smart yoghurt". Figure: Anne Rieder, Nofima

More about

Title Author(s) Year
Improved estimation of in vitro protein digestibility of different foods using size exclusion chromatography Anne Rieder *, Nils Kristian Afseth , Ulrike B¨ocker , Svein Halvor Knutsen , Bente Kirkhus , Hanne K. Mæhre , Simon Ballance , Sileshi Gizachew Wubshet 2021 Go to publication

Contact persons

Bente Kirkhus

Seniorforsker, Nofima
+47 900 36 851

Anne Rieder

Scientist, Nofima
+47 64 97 01 75