Background:
Microbial spoilage and safety of fresh produce remain significant global concerns. Environmental microbiota may interact with fresh produce microbiomes throughout the supply chain, potentially affecting food safety, quality, and shelf-life. The transmission of various food-borne pathogens throughout horticultural supply chains has been extensively characterised. However, few studies have focussed on transmission of microbiomes from environmental sources onto fresh produce, and their persistence over time. Of all horticultural production and processing inputs, water has one of the most significant impacts on fresh produce quality and safety. This preliminary study aimed to evaluate the nature and extent of microbiome transfer and survival in fresh produce due to stormwater contact.
Methods:
Cut spinach was employed as a model system due to its ready-to-eat nature, food safety and spoilage relevance. Briefly, 25 g lots of spinach were soaked for 20 min in one of four water treatments (fresh stormwater; autoclaved stormwater; sterile MilliQ water; or no water/unsoaked). Treated samples were dried, weight-standardised and incubated aerobically for 2, 24 or 72 h at 25oC. Stormwater and incubated spinach samples underwent 16S community profiling.
Results:
Bacterial communities in stormwater-soaked spinach exhibited significant α- and β-diversity differences relative to other treatments, more closely resembling fresh stormwater. Substantial initial community transfer from stormwater onto stormwater-soaked spinach was observed in some cases (up to 42% similarity), although this declined over time (7% by 24 h, 0% by 72 h; Sourcetracker 2.0). Taxonomic analyses identified multiple stormwater-derived taxa in stormwater-soaked spinach, though none persisted to 72 h. A persistent core taxonomic community was identified in spinach samples, irrespective of treatment or incubation time. The role of this resident core microbiome in mediating the persistence of stormwater-derived taxa warrants further investigation.
Conclusions:
This study indicates that water microbiomes can transiently impact fresh produce microbiomes via one-off contact events. These preliminary findings offer initial insight into dynamic relationships between water and fresh produce microbiomes. Ultimately, advancing understanding in this area is predicted to drive microbiome-targeted solutions to address horticultural food safety and spoilage concerns.