From farm to cheese : exploring the bacteria in the dairy value chain

Abstract

This thesis investigated potential flows of bacteria from the field through silage and raw milk to the mature cheese, focusing on lactic acid bacteria (LAB) of importance for flavour development in a Swedish long-ripened hard cheese. First, the herbage microbiota was compared to that of corresponding silages made with three different silage additives in laboratory-scale silos. Silages inoculated with starter culture were found to be dominated by the genera Lactobacillus and Pediococcus, irrespective of harvest location (four sites in Sweden), harvest occasion (first or second cut) or year. The other silage additives resulted in silages with fewer LAB and a more mixed microbiota. Next, silages were made in concrete bunker silos, using the same silage additives as in the laboratory study. The resulting silage microbiota was found to be dominated by the genera Lactobacillus and Prevotella, irrespective of silage additive used. Finally, the silages were fed as partial mixed rations to 67 Swedish Red dairy cows for three weeks per silage, with one of the silages repeated. Analyses revealed that the raw milk microbiota had the highest bacterial diversity but the lowest bacterial load, with Lactobacillus and Pseudomonas being the most abundant genera. An effect of silage additive treatment was evident to a minor extent in the used bedding material, but not in the raw milk. In cheese made from the raw milk, the microbiota mainly resembled that of the starter culture used in production. An effect of silage additives was not observed in the microbiota of the cheese produced, with the main variation arising between batches of cheeses. Overall, the microbiota of the cheese was affected by factors not analysed in this thesis or factors at the dairy, with the starter culture used in the cheese making process acting as the main source of bacteria in the final cheese. However, a limitation of the study was the use of short-read sequencing, the resolution was not sufficient to distinguish bacteria fully.

Keywords

Microbiota; lactic acid bacteria; herbage; silage; milk; cheese; Mikroflora; mjölksyrabakterier; växtmaterial; ensilage; mjölk; ost

Published in

Acta Universitatis Agriculturae Sueciae
2024, number: 2024:74ISBN: 978-91-8046-365-2, eISBN: 978-91-8046-401-7Publisher: Swedish University of Agricultural Sciences

SLU Authors

• Eliasson, Thomas

  • Department of Molecular Sciences, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Animal and Dairy Science
Food Science


Publication identifier

DOI: https://doi.org/10.54612/a.6vge2vot86

Permanent link to this page (URI)

https://res.slu.se/id/publ/130469