Abstract
This study aims to characterize the microbial and peptidomic composition of raw milk kefir, and to address the potential anti-allergic effects of raw milk kefir using validated research models for food allergy. Raw milk kefir was produced after incubation with a defined freeze-dried starter culture. Kefir was sampled during fermentation at seven-time intervals. For comparison, kefir was also prepared from boiled milk (100 °C; 5 sec). Peptide compositions were determined for the raw and heated milk, plus kefir end products made from these milks. In a murine food allergy model, the two kefir end products were investigated on their allergy modulating effects. In both kefirs, we identified amplicon sequence variants identical to those in the starter, matching the bacteria Lactococcus lactis, Streptococcus thermophilus, Leuconostoc and the yeast Debaromyces. In raw milk kefir, additional sequence variants of Lactococcus lactis and the yeasts Pichia and Galactomyces could be identified, which were absent in heated milk kefir. Analysis of peptide compositions in kefirs indicated that the number and intensity of peptides drastically increased after fermentation. Heating of milk negatively affected the diversity of the peptide composition in kefir. Only raw milk kefir suppressed the acute allergic skin response to the food allergen ovalbumin in sensitised mice. These effects coincided with differences in the T-cell compartment, with lower percentages of activated Th1 cells and IFNg production after treatment with kefir made from heated milk. The results of this study indicate specific properties of raw milk kefir that may contribute to its additional health benefits.
Competing Interest Statement
TB is partly sponsored for his research activity by the Raw Milk Company. J.G. and B.v.E. are partly employed at Danone Nutricia Research. All other authors report no conflict of interest.
Footnotes
↵§ Shared first authors
This version contains a minor revision of the abstract and an updated conflict of interest statement.
Abbreviations
- ASV
- Amplicon Sequence Variant
- cat
- Concatenated
- CFU
- Colony Forming Unit
- Ct
- Cycle threshold
- SC
- Defined Starter Culture eXact® 2 kefir, Hansen
- EV
- Extracellular Vesicles
- ITS
- Internal Transcribed Spacer
- NCBI
- National Centre for Biotechnology Information
- PBS
- Phosphate Buffered Saline solution
- HM
- Heated Milk (shortly boiled)
- HMK
- Heated Milk Kefir based on SC
- qPCR
- Quantitative real-time polymerase chain reaction
- RA
- Relative Abundance
- RM
- Raw Milk
- RMK
- Raw Milk Kefir based on SC