In our latest study we compared metagenomic profiles of different mozzarella cheeses.
Every Italian knows that buffalo mozzarella is much different (and better!) than cow mozzarella. In addition, every Italian is proud of buying mozzarella from a local store, which – of course – is always the best of the whole country. To investigate if metagenomics profile of mozzarella cheese holds traces of this information, we sampled several kinds of mozzarella and profiled their 16s metagenome.
Our samples were classified as follows:
- BDN: Buffalo mozzarella with PDO certification and acidified with Natural Whey Culture (15 samples)
- BDNG: Buffalo mozzarella with PDO certification, acidified with Natural Whey Culture and collected at mass retailers (11 samples)
- BNNG: Buffalo mozzarella without certification, acidified with Natural Whey Culture and collected at mass retailers (3 samples)
- BNCG: Buffalo mozzarella without certification, acidified with commercial starters and collected at mass retailers (2 samples)
- CC: Cow mozzarella acidified with commercial starters and collected at mass retailers (8 samples)
Our first aim was to assess species composition of the different samples. A visual inspection of Figure 1 already shows that CC (and BNCG) samples have different profiles than all the other samples. This is not unexpected. Cow mozzarella has a different profile from Buffalo mozzarella. However, not certified Buffalo mozzarella BNCG, produced by using a commercial starter for acidification has similar composition to CC. This highlights the great importance of the acidification method in determining the composition of mozzarella metagenome.
Figure 1. Abundance of bacterial families represented by at least 0.1% of reads in at least on sample. BDN: Buffalo mozzarella with PDO certification, acidified with Natural Whey Culture; BDNG: Buffalo mozzarella with PDO certification, acidified with Natural Whey Culture and collected at mass retailers; BNNG: Buffalo mozzarella without certification, acidified with Natural Whey Culture and collected at mass retailers; BNCG: Buffalo mozzarella without certification, acidified with commercial starters and collected at mass retailers; CC: Cow mozzarella acidified with commercial starters and collected at mass retailers.
After this first analysis we further caracterized Buffalo mozzarella samples. We removed CC and BNCG from the analysis, and clusterized samples based on the abundance of the 50 most abundant species (Figure 2). While we didn’t observed a full separation between samples, we noticed two different clusters, named Cluster 1 and Cluster 2, enriched respectively in samples retrieved in local stores (BDN) and in stores of mass distribution (BDNG, BNNG). Cluster 1 had in general higher prevalence of lactic species, such Lactococcus spp., Weissella viridescens and Streptococcus vestibularis, while Cluster 2 had overrepresentation of psychrotrophic bacteria (bacteria that grow at low temperature, often associated with spoiling refrigerated foods), and some potential pathogens, such as the genera Plesiomonas and Enterobacter.
Our analysis suggests that shorter delivery chains can result in substantially improved microbial composition of mozzarella cheese.
Figure 2. Clustering of samples obtained by using Natural Whey Culture. BDN: Buffalo mozzarella with PDO certification, acidified with Natural Whey Culture; BDNG: Buffalo mozzarella with PDO certification, acidified with Natural Whey Culture and collected at mass retailers; BNNG: Buffalo mozzarella without certification, acidified with Natural Whey Culture and collected at mass retailers.
We hope that our results will facilitate further studies in the field of food safety. More details on our work can be found here.
Stay tuned for more food microbiome stories. Kefir sequencing is runing next!