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Milk lipolysis, a real issue for the milk sector

Spontaneous lipolysis corresponds to the enzymatic hydrolysis of milk triglycerides by the lipoprotein lipase which is naturally secreted by the mammary gland. This degradation of triglycerides increases milk free fatty acid (FFA) content and leads to the development of a rancid flavor, unacceptable for consumers, in milk and milk products.
Lipolysis is quantified by the measure of FFA. Spontaneous lipolysis is known to vary considerably according to each cow. The rate can vary from 0.2 to 2.5 mmol for 100g of fat content.
Since the 2000s, an increase of lipolysis has been observed in farms by the professionals of milk sector. The reasons are not clearly known. Besides, lipolysis is a factor used in determination of the level of price paid in some French regions such as Brittany. Lipolysis rate should be under 0.89 mmol of FFA for 100 g of fat content. Beyond this value, the penalty point is -3.049€ per 1000L of milk. Lipolysis affects milk quality, milk ability to be processed and the breeder income at the same time.

Zootechnical factors which modulate lipolysis  

In the 1980s, the intensification of milk production led to an increase of lipolysis in milk. This topic had been widely studied in those days. Some zootechnical factors had been identified to enhance spontaneous lipolysis such as lactation stage, milk yield, diet, milk interval, herd’s health status (mastitis, cysts). Nowadays, the increase of milk lipolysis occurs mostly in summer, which also implies an effect of the season. Farms changed since the 1980s so it’s obviously necessary to study and rank all these factors (individual, breed, diets, season, milk yield, lactation stage) in actual farms.

Biochemical factors linked to milk lipolysis are badly known

Three biochemical factors had been shown to determine milk susceptibility to lipolysis:

• Lipoprotein lipase activity.
• Milk fat membrane integrity. Weaker membrane leads to an increase of milk FFA.
• Balance between some lipase activators and inhibitors.

Aim of the PhD

The PhD will deal with the study and rank of the zootechnical factors supposed to modulate lipolysis rate in cow milk.  The biochemical mechanisms of spontaneous lipolysis will also be studied in connection with the zootechnical factors.

Elise Vanbergue has been working on this subject of thesis since the 1st February of 2014 for 3 years. She is supervised by Catherine Hurtaud in the team Alimentation and nutrition.

Most relevant bibliography

Chilliard, Y. 1982. Physiological variations of lipase activities and spontaneous lipolysis in bovine, caprine and human milks - a review. Lait 62 : 1-31. (PDF)
Chilliard, Y., Chazal, M.P., Cartier, P. 1986. Données récentes sur la lipolyse du lait de vache. Revue des ENIL 112 : 12-19
Chilliard, Y., Lamberet, G. 1984. Milk lipolysis - various types, mechanisms, factors of variation, practical significance. Lait 64 : 544-578. (DOI)
Deeth, H.C. 2006.  Lipoprotein lipase and lipolysis in milk.  International Dairy Journal. 16 (6) : 555-562. (DOI)
Olivecrona T. 1980. Biochemical aspects of lipolysis in bovine milk. Bull. Int. Dairy Fed. Doc. 118 : 19.
Sundheim, G. 1988. Spontaneous lipolysis in bovine-milk - combined effects of cream, skim milk, and lipoprotein-lipase activity. J. Dairy Sci. 71 : 620-626. (PDF)

Contacts

Elise Vanbergue elise.vanbergue[at]rennes.inra.fr (PhD student)
Catherine Hurtaud catherine.hurtaud[at]rennes.inra.fr (supervisor)
Jean Louis Peyraud jean-louis.peyraud[at]rennes.inra.fr (manager)
Rouillé Benoit benoit.rouille[at]idele.fr (supervisor, Institut de l'élevage)