Enhancing high throughput sequencing unveils changes in bacterial communities during ready-to-eat lettuce spoilage

Spoilage flora is critical in vegetal ready to eat (RTE) product shelf-life and selecting efficient spoilage control technologies depends on the microorganisms present. This manuscript describes the evolution of the bacteriome of Batavia RTE lettuce, from fresh lettuce up to completely spoiled (day 14) and correlate these results with the sensorial characteristics. 

The microbiome of vegetal RTE were examined using culture-dependent and culture-independent (16S rRNA metabarcoding) methods. Culture-dependent methods were related with the metagenomic results and sensory analysis to describe the evolution during spoilage and shelf-life.

Our results demonstrated that the RTE lettuce bacteriome during spoilage is dominated by Gram-negative bacteria, mainly Flavobacterium and Pseudomonas. A bacterial population of 22 operational taxonomic units (OTUs) represent up to 96% of total bacterial reads and is maintained during the spoilage, representing the bacterial core of RTE lettuce. A high correlation was detected between culture-independent and culture-dependent results, both in general and selective culture media. Sensorial analysis of lettuce demonstrated that "odor" was the key parameter to determine the sensorial spoilage time and is related to total microbial load and to high concentrations of spoilage-related bacterial genera.

Hereby presented results are limited by the lettuce variety and by the storage conditions (MAP, 6°C, up to 14 days).

This paper describes an overview of the microbial and sensory evolution during spoilage of Batavia lettuce under MAP. A combination of culture-dependent and independent methods and sensorial analysis were used up to 14 days of storage.