Large microbiota survey reveals how the microbial ecology of cooked ham is shaped by different processing steps

The production of cooked ham involves numerous steps shaping the microbial communities of the final product, with consequences on spoilage metabolites production. To identify the main factors driving the ecology of ham and its spoilage, we designed a study encompassing five variables related to ham production: type of storage during meat transportation, churning speed, drain-off time, slicing line and O2 packaging permeability. We obtained about 200 samples from the same facility and we characterized i) their microbiota based on gyrB amplicon sequencing ii ) their production of spoilage-related metabolites based on E-Nose analysis and enzymatic assays. The slicing was the most critical step, shaping two general types of microbiota according to the slicing line: one dominated by Carnobacterium divergens and another one dominated by Leuconostoc carnosum and Serratia proteamaculans . Regarding metabolites production, L. carnosum was associated to D-lactic acid, ethanol and acetic acid production, whereas Serratia proteamaculans was associated to acetic acid production. This last species prevailed with highly O2-permeable packaging. Within a given slicing line, we observed campaign-based variations, with Lactobacillus sakei , Leuconostoc mesenteroides and Carnobacterium maltaromaticum prevalent in summer. L. sakei was associated with L-lactic acid production and C. maltaromaticum with formic and acetic acid productions.