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Sanitizer efficacy in reducing microbial load on commercially grown hydroponic lettuce
Author(s) -
Dankwa Adwoa S,
Machado Robson M,
Perry Jennifer J
Publication year - 2020
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.10753
Subject(s) - hand sanitizer , microorganism , food science , listeria monocytogenes , chemistry , peat , chlorine , substrate (aquarium) , shelf life , horticulture , contamination , bacteria , biology , ecology , genetics , organic chemistry
BACKGROUND Most hydroponic lettuce growers harvest and package their marketable‐size lettuces with an intact root ball. With a high microbial load on the peat moss substrate, there is a risk of microbial transfer onto the edible portion during packaging and throughout the product's shelf life. Since the produce is believed to have no contact with the substrate, no sanitizer wash is performed before packaging and storage. RESULTS Aerobic plate count (APC) results suggested that reduction in count was influenced by both sanitizer application and storage time. Peroxyacetic acid significantly reduced APC count on leaves, roots, and substrate, with a 1.8 log CFU g −1 initial reduction on the leaf. Fungi and APC levels increased with storage time, with the greatest APC increase in the roots. Leaves had the lowest coliform bacteria (CB), with chlorine slightly reducing CB count. Unlike APC, CB levels decreased during storage on the substrate and root samples. No Listeria positive was confirmed by agglutination test. Further evaluation of different commercial substrates reveals that Com4, a drier‐compacted plug, had the least ability to support growth/survival of all microbial populations enumerated relative to the spongy, wet black plugs. CONCLUSION The ability of peat moss substrates to host microorganisms is influenced by the physical properties of the product. Sanitizer wash efficacy is dependent on the initial microbial load and the length of storage. Chlorine and peroxyacetic acid are effective in reducing microbial populations on the leaves of hydroponically grown lettuce without affecting visual quality during shelf life. © 2020 Society of Chemical Industry