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Preheating milk : what effects on the drainage of acid-rennet gel?
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Preheating milk : what effects on the drainage of acid-rennet gel?

Preheating milk : what effects on the drainage of acid-rennet gel?

Acid-rennet gels such as « fromage frais », « petit-Suisse », or cream-cheese are highly appreciated by consumers for their high nutritional properties. They are made by coagulation of milk by both rennet and lactic acid bacteria, and then drainage of the acid gel. A better understanding of the mechanism of their drainage is essential to master and control the manufacture and the quality of these cheeses.

In this study, we compared the drainage of acid-rennet gels manufactured from skimmed milk subjected to two different heat treatments:

  • Low heat (LH) (72°C for 20s), that leads to a low whey protein denaturation (around 5%)
  • High heat (HH) (95°C for 120s), that leads to a high whey protein denaturation (around 70%).

Acid-rennet gels were either drained on a lab-scale pilot or stirred and then drained by centrifugation. Composition and structure of drained gels were characterized by rheological and microscopic methods.

We concluded that:

  • HH milk takes longer time and requires more acidification than LH milk to form a gel,
  • HH gel does not show any syneresis while LH gel does,
  • HH gel has a slower and lower drainage than LH one,
  • Although less drained, drained gel from HH milk are firmer than LH ones, but have a more porous structure,
  • These differences are due to the presence of heat-induced protein aggregates that interact with casein and hindered structure rearrangements in the gel during its manufacture.

This study has enabled us to develop methods for analysing drainage and drained curds and to identify a lever for modulating the gel drainage.

Syneresis of acid-rennet gels
© STLO

Acid-rennet gel before drainage made from LH milk (left) with syneresis or HH milk (right) without syneresis.

Collaborations

This work was carried in collaboration with ACTALIA-Produits Laitiers (Romain Richoux, Rennes and Patrice Gaborit, Surgères), ACTALIA-Expertise Analytiques Laitière (Janushan Christy, La Roche-sur-Foron) and l’UMR-OPAALE (Corinne Rondeau-Mouro, INRAE-Rennes). It has been funded by the Centre national interprofessionnel de l’économie laitière Centre (CNIEL). A young scientist, Islem Mtibaa, has been funded for 9 months for this project.

Read more

Drainage of acid-rennet gels: Rheological and microstructural study of milk heat treatment and milk proteins/whey protein aggregates ratio effects MH Famelart, I. Mtibaa, Florence Rousseau, Manon Perrignon, Romain Richoux, Corinne Rondeau-Mouro, Patrice Gaborit, J. Food Eng., 2025, 391,  112457.

Contact

Florence Rousseau

 

Modification date: 19 May 2025 | Publication date: 16 May 2025 | By: STLO-MHFamelart