Quality of Greek Yogurts and Optimization of Co-products

Project entitled:

Impact of Production Processes on the Microbiological Quality of Greek Yogurt and the Valorization of By-Products

Gisèle Lapointe, Denis Roy, Claude Champagne, Sylvie Gauthier


  • Greek yogurt has won the favour of consumers and now makes up the largest segment of the yogurt market.
  • The dairy industry is in need of comparative data on the stability and safety of these types of high protein content (HPC) yogurts, produced by centrifugation or ultrafiltration, as well as valorization strategies for by-products.
  • Cold HPC products contain more probiotics, but their subsequent stability is affected by the strain and the HPC process.
  • The survival rate of the sensitive probiotic strain (Bifidobacterium longum ssp. longum R0175) is not higher in HPC yogurt in comparison to traditional yogurt.
  • The centrifugation process concentrates bacteria and curd, furthering survival of the resistant probiotic strain (Lactobacillus helveticus R0052).
  • Mortality of the contaminant E. coli was higher in HPC yogurt produced through ultrafiltration while growth of the yeast Kluyveromyces marxianus was similar in HPC and traditional yogurts.
  • The production of expolysaccharides by lactic acid bacteria increased in the co-cultures of Lactobacillus rhamnosus and the yeast Saccharomyces cerevisiae in comparison to the monoculture, making it possible to obtain a bioingredient that is rich in polysaccharides from the lactic acid bacteria ultrafiltrate.
  • The environmentally friendly design of the new process will provide a simple and cost-effective biological recycling option to produce high value-added polysaccharides.



  • General objective: contribute to the advancement of knowledge of high protein content (HPC) yogurt, as well as enrichment processes and microbial communities that impact the quality and functionality of dairy products. The project aims to increase the energy efficiency of processes with the development of high value-added ingredients using by-products in the production of HPC yogurt.
  • Hypothesis 1: the protein content enrichment method may modify the conditions that are conducive to the stability, survival and activity of the microbial community during the production and storage of high protein content (HPC) “Greek-type” yogurt.
  • Hypothesis 2: the by-products of production may be valorized by obtaining ingredients containing prebiotics.


Results and potential benefits

New knowledge:

  • Effect of the processes on the development of starter cultures, probiotics and contaminants, as well as on sensory characteristics during the storage of HPC yogurts.
    • Better understanding of the growth and stability of probiotics in HPC yogurts.
    • Better understanding of the process on contaminant survival.
  • Development of high value-added ingredients using by-products.
    • Better control of the co-culture of lactic acid bacteria and yeast in the whey permeate.
    • Better understanding of gene expression in microorganisms during fermentation.
  • Eco-friendly design of a process for biological recycling of the whey ultrafiltrate to produce new bioingredients with prebiotic effects.

Potential Benefits:

  • Economic:
    • Increase the value of by-products and dairy products fermented with probiotics.
    • Increase the energy efficiency of milk processing through biological recycling.
    • Better choice of processes depending on the desired product (sensorial or microbiological attributes)
  • Environmental:
    • Decreased energy use and reduced loss of co-products.
  • Social:
    • Improved functionality of dairy products for consumer health.

Professionals trained

  • Andréanne Moineau-Jean, a Master of Science student, has acquired expertise in yogurt production and concentration processes; growth, survival and selective counting in milk, yogurt with lactic acid bacteria, probiotics, and contaminant microorganisms; physico-chemical analyses of milk and yogurt; and the sensory assessment of yogurt.
  • Annalisse Bertsch, a PhD student, has acquired expertise in co-culture fermentation processes, bioingredient production, gene expression through RT-qPCR, the viability of strains through PMA-qPRC, and the valorization of food industry by-products such as whey ultrafiltrate.

Financial contributions

Partnership for innovation in dairy production and dairy processing (EPI2011-2017):

  • Fonds de recherche du Québec – Nature et technologies
  • Ministère de l’Agriculture, des Pêcheries et de l’Alimentation du Québec
  • Novalait

Contribution to the training course of Myriam Laberge by the Canada Research Chair in Lactic Cultures Biotechnology for Dairy and Probiotic Industries