Purpose: To investigate the shift of bacterial community on spinach during washing/packaging and storage processes.
Methods: Fresh spinach was collected from a commercial fresh produce processor before and after washing/packaging process in the factory. Washed spinach was stored at 4, 10, and 15°C for one week. Bacteria were recovered from unwashed, washed, and stored spinach samples. The population of live bacteria on each sample was evaluated by both plate counting using M9, TSA (with polysorbate 80 and lecithin), and PCA (vegitone) media and quantitative real-time PCR (qPCR) after PMA treatment. The microbiota on spinach samples were analyzed by 16S rRNA sequencing using MiSeq and Qiime2.
Results: Plate-counting results indicated bacterial population on spinach reduced from 6.08±0.13 to 4.91±0.04 log CFU/g after washing process in the tested factory. The population on washed samples increased to 6.74±0.05, 7.1±0.04, and 7.48±0.01 log CFU/g after one week storage at 4, 10, and 15°C, respectively. The estimated bacterial population by qPCR analysis was higher (0.2 to 1 log CFU/g) than plate counting, but followed the same trend. The composition and abundance of bacterial communities on spinach were shifted after washing process and affected by the storage temperature.
Significance: This study provides knowledge on the microbial ecology of diverse bacterial community on spinach during production, which can benefit further studies on the interaction of microbes on produce, and the prevention of foodborne pathogens and spoilage.