Microbial profiles of commercially packaged baby spinach from hydroponic controlled environment agriculture and soil-based open field production

Abstract

Packaged “ready-to-eat” (RTE) fresh leafy greens grown hydroponically (GH) in controlled environment has becoming an important food choice for consumers. However, a significant data gap exists regarding the microbial profile of these products on the markets. In this study, commercially packaged GH baby spinach products were sampled from different retail stores in the Mid-Atlantic region and were compared with the packaged RTE baby spinach grown from soil-based (GS) open field production available in the same stores. Aerobic bacteria and yeast and mold populations were determined by culture-based method, and microbiome was analyzed via high-throughput 16S rRNA gene and ITS amplicon sequencing. While no major differences in microbial population were seen, distinctive patterns on microbial community between GH and GS products were observed. The dominant microbes on GS baby spinach were bacterial genus Pseudomonas (average relative abundance: 70%) and fungal genus Cystofilobasidium (53%). The most abundant bacteria identified on GH baby spinach was a Cyanobacteria genus Synechocystis (25%), and the major fungal genera were Penicillium (22%) and Cladosporium (15%). The abundance of Pseudomonas in RTE leafy greens is well documented; but there have been no reports regarding Synechocystis presence in RTE baby spinach. Further investigations are warranted to investigate the interactions of the microbiome (bacteria, fungi, and Synechocystis), food safety, and quality of RTE GH products.