P3-98 Dynamics of Bacterial Community on Spinach during Processing and Storage

Wednesday, July 12, 2017
Exhibit Hall (Tampa Convention Center)
Ganyu Gu , U.S. Department of Agriculture–ARS , Beltsville , MD
Samantha Bolten , U.S. Department of Agriculture–ARS , Beltsville , MD
Lan Wang , U.S. Department of Agriculture–ARS , Beltsville , MD
Steve Rideout , Virginia Tech - Eastern Shore AREC , Painter , VA
Xiangwu Nou , U.S. Department of Agriculture–ARS , Beltsville , MD
Introduction:  Fresh produce, like spinach, is a known vehicle for a number of recent foodborne outbreaks. Fresh produce harbors large and diverse bacterial communities, potentially including pathogenic bacteria, and the survival and proliferation of bacterial pathogens are strongly influenced by the produce microbiota. However, the microbial ecology of the diverse community on vegetables during processing and storage periods is not well studied.

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.